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1

Assessing the RELAPS-3D Heat Conduction Enclosure Model

Three heat conduction problems that have exact solutions are modeled with RELAP5-3D using the conduction enclosure model. These comparisons are designed to be used in the RELAP5-3D development assessment scheduled to be completed in 2009. It is shown that with proper input choices and adequate model detail the exact solutions can be matched. In addition, this analysis identified an error and the required correction in the cylindrical and spherical heat conductor models in RELAP5-3D which will be corrected in a future version of RELAP5-3D.

McCann, Larry D.

2008-09-30

2

RELAP5-3D multidimensional heat conduction enclosure model for RBMK reactor application

A heat conduction enclosure model is conceived and implemented by RELAP5-3D between heat structures. The suggested model uses a lumped parameter model that is generally applicable to multidimensional calculational domain. This new model is applied to calculation of RBMK reactor core graphite blocks and is compared to the commercially available Fluid Dynamics Analysis Package (FIDAP) finite element code. Reasonably good agreement between the results of RELAP5-3D and FIDAP is obtained. The new heat conduction enclosure model gives RELAP5-3D a general multidimensional heat conduction capability. It also provides new routes for temperature cooloff of the RBMK graphite blocks from the ruptured channel to the surrounding ones. This ability to predict graphite temperature cooloff is very important during accidents or for transient simulation, especially concerning long-term coolability of the RBMK reactor core.

Paik, S.

1999-10-01

3

RELAP5-3D multidimensional heat conduction enclosure model for RBMK reactor application

A heat conduction enclosure model is conceived and implemented by RELAP5-3D between heat structures. The suggested model uses a lumped parameter model that is generally applicable to multidimensional calculational domain. This new model is applied to calculation of RBMK reactor core graphite blocks and is compared to the commercially available Fluid Dynamics Analysis Package (FIDAP) finite element code. Reasonably good

Paik

1999-01-01

4

in heat conduction is presented. The present FEM formulation is capable of deter- mining temperatures are presented. KEYWORDS inverse problems, finite element method, inverse heat conduction NOMENCLATURE ¢¡¤£ Damping matrix ¢¥¤¦§£ Stiffness matrix ¨ Fourier coefficient of heat conduction © Heat flux vector Heat

Dennis, Brian

5

Existence and uniqueness results for viscous, heat-conducting 3-D fluid with vacuum

We consider the 3-D full Navier-Stokes equations whose the viscosity coefficients and the thermal conductivity coefficient depend on the density and the temperature. We prove the local existence and uniqueness of the strong solution in a domain $\\Omega\\subset\\mathbb{R}^3$. The initial density may vanish in an open set and $\\Omega$ could be a bounded or unbounded domain. We also prove a blow-up criterion for the solution. Finally, we show the blow-up of the smooth solution to the compressible Navier-Stokes equations in $\\mathbb{R}^n$ ($n\\geq1$) when the initial density has compactly support and the initial total momentum is nonzero.

Ting Zhang; Daoyuan Fang

2007-02-07

6

Conducting Polymer 3D Microelectrodes

Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained showed uniformity and good adhesion to both horizontal and vertical surfaces. Electrodes in combination with metal/conducting polymer materials have been characterized by cyclic voltammetry and the presence of the conducting polymer film has shown to increase the electrochemical activity when compared with electrodes coated with only metal. An electrochemical characterization of gold/polypyrrole electrodes showed exceptional electrochemical behavior and activity. PC12 cells were finally cultured on the investigated materials as a preliminary biocompatibility assessment. These results show that the described electrodes are possibly suitable for future in-vitro neurological measurements. PMID:22163508

Sasso, Luigi; Vazquez, Patricia; Vedarethinam, Indumathi; Castillo-Len, Jaime; Emnus, Jenny; Svendsen, Winnie E.

2010-01-01

7

1D-to-3D transition of phonon heat conduction in polyethylene using molecular dynamics simulations

The thermal conductivity of nanostructures generally decreases with decreasing size because of classical size effects. The axial thermal conductivity of polymer chain lattices, however, can exhibit the opposite trend, ...

Henry, Asegun

8

1D-to-3D transition of photon heat conduction in polyethylene using molecular dynamics simulations

Experiments have demonstrated that the mechanical stretching of bulk polyethylene can increase its thermal conductivity by more than two orders of magnitude, from 0.35 W/mK to over 40W/mK, which is comparable to steel. ...

Henry, Asegun Sekou Famake

2009-01-01

9

The material used in this study was a carbon-carbon fiber composite manufactured from precursor yarn and petroleum based pitch through a process of repetitive densification of a woven preform. The resultant high temperature-high strength material exhibits relatively high thermal conductivity and is thus of interest to the fusion energy, plasma materials interactions (PMI) and plasma facing components (PFC) communities. Carbon-carbon

R. B. Dinwiddie; T. D. Burchell; C. F. Baker

1991-01-01

10

Reduction of Thermal Conductivity by Nanoscale 3D Phononic Crystal

We studied how the period length and the mass ratio affect the thermal conductivity of isotopic nanoscale three-dimensional (3D) phononic crystal of Si. Simulation results by equilibrium molecular dynamics show isotopic nanoscale 3D phononic crystals can significantly reduce the thermal conductivity of bulk Si at high temperature (1000?K), which leads to a larger ZT than unity. The thermal conductivity decreases as the period length and mass ratio increases. The phonon dispersion curves show an obvious decrease of group velocities in 3D phononic crystals. The phonon's localization and band gap is also clearly observed in spectra of normalized inverse participation ratio in nanoscale 3D phononic crystal. PMID:23378898

Yang, Lina; Yang, Nuo; Li, Baowen

2013-01-01

11

Conductive interconnections through thick silicon substrates for 3D packaging

We have developed key technologies to form conductive interconnections through a thick silicon substrate, which are potentially applied for 3D device fabrication or packaging of optical MEMS devices. In this paper, we demonstrate to form metal filled Through-Holes (THs) in thick Silicon (Si) substrates (t=~500 ?m) mainly using Photo Assisted Electro-Chemical Etching (PAECE) and Molten Metal Suctioned Method (MMSM). The

Takashi Takizawa; Satoshi Yamamoto; Kazuhisa Itoi; Tatuso Suemasu

2002-01-01

12

Conduction mechanisms in 2D and 3D SIS capacitors

NASA Astrophysics Data System (ADS)

In this paper, we present a study of conduction mechanisms observed in high performance SIS capacitors (semiconductor-insulator-semiconductor) fabricated on bulk silicon. The combination of high aspect ratio 3D patterns and thin dielectric layers enables amazing capacitance density values. Electrical measurement and modeling of leakage currents have been associated with structural analysis in order to characterize different oxide-nitride stacks, and thus, to scale the layers and reach even higher capacitance densities. Conduction mechanisms are relevant of Fowler-Nordheim tunneling and Poole-Frenkel emission.

Jacqueline, Sbastien; Domengs, Bernadette; Voiron, Frdric; Murray, Hugues

2013-04-01

13

3D conductive nanocomposite scaffold for bone tissue engineering

Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D) ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene) poly(4-styrene sulfonate) (PEDOT:PSS), in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent microscope. Increasing the concentration of the conductive polymer in the scaffold enhanced the cell viability, indicating the improved microstructure of the scaffolds or boosted electrical signaling among cells. These results show that these conductive scaffolds are not only structurally more favorable for bone tissue engineering, but also can be a step forward in combining the tissue engineering techniques with the method of enhancing the bone healing by electrical stimuli. PMID:24399874

Shahini, Aref; Yazdimamaghani, Mostafa; Walker, Kenneth J; Eastman, Margaret A; Hatami-Marbini, Hamed; Smith, Brenda J; Ricci, John L; Madihally, Sundar V; Vashaee, Daryoosh; Tayebi, Lobat

2014-01-01

14

It is well known that laminar heat conduction leads to a totally inadequate gas blanket detachment region. Restricting ourselves to 2D mean toroidal flow over toroidal cavities and utilizing the K-{epsilon}, compressible turbulence code ISAAC we have shown how 3D neutral turbulence can lead to a significantly larger detachment region due to an order of magnitude increase in the heat conduction to the toroidal sidewalls. We now extend these results by incorporating the full 3D divertor geometry and consider 3D mean shear flows: Mach 1.2 toroidal flow over the cavities as well as Mach 0.2 poloidal flow towards the divertor plate. The propagation of the heat front towards the divertor plate is considered as an initial value problem. Heat loads to the toroidal sidewalls, divertor walls as well as the divertor plate will be calculated. The turbulence is (and must) be treated 3D.

Vahala, G.; Vahala, L.; Morrison, J. [and others

1996-12-31

15

NASA Technical Reports Server (NTRS)

Heat conduction plays an important role in the efficiency and life span of electronic components. To keep electronic components running efficiently and at a proper temperature, thermal management systems transfer heat generated from the components to thermal surfaces such as heat sinks, heat pipes, radiators, or heat spreaders. Thermal surfaces absorb the heat from the electrical components and dissipate it into the environment, preventing overheating. To ensure the best contact between electrical components and thermal surfaces, thermal interface materials are applied. In addition to having high conductivity, ideal thermal interface materials should be compliant to conform to the components, increasing the surface contact. While many different types of interface materials exist for varying purposes, Energy Science Laboratories, Inc. (ESLI), of San Diego, California, proposed using carbon velvets as thermal interface materials for general aerospace and electronics applications. NASA s Johnson Space Center granted ESLI a Small Business Innovation Research (SBIR) contract to develop thermal interface materials that are lightweight and compliant, and demonstrate high thermal conductance even for nonflat surfaces. Through Phase II SBIR work, ESLI created Vel-Therm for the commercial market. Vel-Therm is a soft, carbon fiber velvet consisting of numerous high thermal conductivity carbon fibers anchored in a thin layer of adhesive. The velvets are fabricated by precision cutting continuous carbon fiber tows and electrostatically flocking the fibers into uncured adhesive, using proprietary techniques.

2003-01-01

16

Conduction heat transfer solutions

This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. The introduction presents a synopsis on the theory, differential equations, and boundary conditions for conduction heat transfer. Some discussion is given on the use and interpretation of solutions. Supplementary data such as mathematical functions, convection correlations, and thermal properties are included for aiding the user in computing numerical values from the solutions. 155 figs., 92 refs., 9 tabs.

VanSant, J.H.

1983-08-01

17

Conduction heat transfer solutions

This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. This material is useful for engineers, scientists, technologists, and designers of all disciplines, particularly those who design thermal systems or estimate temperatures and heat transfer rates in structures. More than 500 problem solutions and relevant data are tabulated for easy retrieval. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. A case number is assigned to each problem for cross-referencing, and also for future reference. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. At least one source reference is given so that the user can review the methods used to derive the solutions. Problem solutions are given in the form of equations, graphs, and tables of data, all of which are also identified by problem case numbers and source references.

VanSant, J.H.

1980-03-01

18

Heat Transfer Boundary Conditions in the RELAP5-3D Code

The heat transfer boundary conditions used in the RELAP5-3D computer program have evolved over the years. Currently, RELAP5-3D has the following options for the heat transfer boundary conditions: (a) heat transfer correlation package option, (b) non-convective option (from radiation/conduction enclosure model or symmetry/insulated conditions), and (c) other options (setting the surface temperature to a volume fraction averaged fluid temperature of the boundary volume, obtaining the surface temperature from a control variable, obtaining the surface temperature from a time-dependent general table, obtaining the heat flux from a time-dependent general table, or obtaining heat transfer coefficients from either a time- or temperature-dependent general table). These options will be discussed, including the more recent ones.

Richard A. Riemke; Cliff B. Davis; Richard R. Schultz

2008-05-01

19

Hydraulic conductivity imaging from 3-D transient hydraulic tomography at several pumping August 2013; accepted 7 September 2013; published 13 November 2013. [1] 3-D Hydraulic tomography (3-D HT (primarily hydraulic conductivity, K) is estimated by joint inversion of head change data from multiple

Barrash, Warren

20

Coolant side heat transfer with rotation: User manual for 3D-TEACH with rotation

NASA Technical Reports Server (NTRS)

This program solves the governing transport equations in Reynolds average form for the flow of a 3-D, steady state, viscous, heat conducting, multiple species, single phase, Newtonian fluid with combustion. The governing partial differential equations are solved in physical variables in either a Cartesian or cylindrical coordinate system. The effects of rotation on the momentum and enthalpy calculations modeled in Cartesian coordinates are examined. The flow of the fluid should be confined and subsonic with a maximum Mach number no larger than 0.5. This manual describes the operating procedures and input details for executing a 3D-TEACH computation.

Syed, S. A.; James, R. H.

1989-01-01

21

Temperature distributions in the laser-heated diamond anvil cell from 3-D numerical modeling

We present TempDAC, a 3-D numerical model for calculating the steady-state temperature distribution for continuous wave laser-heated experiments in the diamond anvil cell. TempDAC solves the steady heat conduction equation in three dimensions over the sample chamber, gasket, and diamond anvils and includes material-, temperature-, and direction-dependent thermal conductivity, while allowing for flexible sample geometries, laser beam intensity profile, and laser absorption properties. The model has been validated against an axisymmetric analytic solution for the temperature distribution within a laser-heated sample. Example calculations illustrate the importance of considering heat flow in three dimensions for the laser-heated diamond anvil cell. In particular, we show that a flat top input laser beam profile does not lead to a more uniform temperature distribution or flatter temperature gradients than a wide Gaussian laser beam.

Rainey, E. S. G.; Kavner, A. [Department of Earth and Space Sciences, University of California, Los Angeles, California 90095 (United States); Hernlund, J. W. [Department of Earth and Planetary Science, University of California, Berkeley, California 94720 (United States); Earth-Life Science Institute, Megoro, Tokyo 152-8551 (Japan)

2013-11-28

22

On calculation of 3-D eddy currents in conducting and magnetic shells

The impedance type boundary conditions are derived for 3-D eddy currents in conducting and magnetic shells. These boundary conditions are then represented only in terms of magnetic field. This leads to a new magnetic scalar potential formulation for 3-D eddy currents in conducting and magnetic shells. This scalar potential formulation is reduced to weak Galerkin forms. The finite element discretization

I. D. Mayergoyz; G. Bedrosian

1995-01-01

23

NASA Astrophysics Data System (ADS)

A 3D reconstruction solution to ultrasound Joule heat density tomography based on acousto-electric effect by deconvolution is proposed for noninvasive imaging of biological tissue. Compared with ultrasound current source density imaging, ultrasound Joule heat density tomography doesn't require any priori knowledge of conductivity distribution and lead fields, so it can gain better imaging result, more adaptive to environment and with wider application scope. For a general 3D volume conductor with broadly distributed current density field, in the AE equation the ultrasound pressure can't simply be separated from the 3D integration, so it is not a common modulation and basebanding (heterodyning) method is no longer suitable to separate Joule heat density from the AE signals. In the proposed method the measurement signal is viewed as the output of Joule heat density convolving with ultrasound wave. As a result, the internal 3D Joule heat density can be reconstructed by means of Wiener deconvolution. A series of computer simulations set for breast cancer imaging applications, with consideration of ultrasound beam diameter, noise level, conductivity contrast, position dependency and size of simulated tumors, have been conducted to evaluate the feasibility and performance of the proposed reconstruction method. The computer simulation results demonstrate that high spatial resolution 3D ultrasound Joule heat density imaging is feasible using the proposed method, and it has potential applications to breast cancer detection and imaging of other organs.

Yang, R.; Song, A.; Li, X. D.; Lu, Y.; Yan, R.; Xu, B.; Li, X.

2014-10-01

24

Thermal Conduction Path Analysis in 3-D ICs Boris Vaisband1

Thermal Conduction Path Analysis in 3-D ICs Boris Vaisband1 , Ioannis Savidis2 , and Eby G the horizontal and vertical dimensions. The dependence of the thermal conductivity on temperature is integrated, since the thermal conductivity of silicon dioxide is 200 times smaller than the thermal conductivity

Friedman, Eby G.

25

Quantitative three-dimensional prediction of the thermal performance of a vertical borehole heat exchanger (BHE) in a ground-source heat pump installation is sought. As BHE installation exhibits exceptionally disparate characteristic length scales, an alternative formation-fluid-thermal fully coupled algorithm is derived to quickly predict the 3-D temperature distributions. The time scale of the steady prediction is of order minutes. This simulation capability

Allen J. Baker; Cheng-Xian Lin; Joe A. Orzechowski; Cormack Gordon

2011-01-01

26

Variable conductance heat pipe technology

NASA Technical Reports Server (NTRS)

Research and development programs in variable conductance heat pipe technology were conducted. The treatment has been comprehensive, involving theoretical and/or experimental studies in hydrostatics, hydrodynamics, heat transfer into and out of the pipe, fluid selection, and materials compatibility, in addition to the principal subject of variable conductance control techniques. Efforts were not limited to analytical work and laboratory experimentation, but extended to the development, fabrication and test of spacecraft hardware, culminating in the successful flight of the Ames Heat Pipe Experiment on the OAO-C spacecraft.

Marcus, B. D.; Edwards, D. K.; Anderson, W. T.

1973-01-01

27

Thermally induced apoptosis, necrosis, and heat shock protein expression in 3D culture.

This study was conducted to compare the heat shock responses of cells grown in 2D and 3D culture environments as indicated by the level of heat shock protein 70 expression and the incidence of apoptosis and necrosis of prostate cancer cell lines in response to graded hyperthermia. PC3 cells were stably transduced with a dual reporter system composed of two tandem expression cassettes-a conditional heat shock protein promoter driving the expression of green fluorescent protein (HSPp-GFP) and a cytomegalovirus (CMV) promoter controlling the constitutive expression of a "beacon" red fluorescent protein (CMVp-RFP). Two-dimensional and three-dimensional cultures of PC3 prostate cancer cells were grown in 96-well plates for evaluation of their time-dependent response to supraphysiological temperature. To induce controlled hyperthermia, culture plates were placed on a flat copper surface of a circulating water manifold that maintained the specimens within 0.1C of a target temperature. Hyperthermia protocols included various combinations of temperature, ranging from 37C to 57C, and exposure times of up to 2 h. The majority of protocols were focused on temperature and time permutations, where the response gradient was greatest. Post-treatment analysis by flow cytometry analysis was used to measure the incidences of apoptosis (annexin V-FITC stain), necrosis (propidium iodide (PI) stain), and HSP70 transcription (GFP expression). Cells grown in 3D compared with 2D culture showed reduced incidence of apoptosis and necrosis and a higher level of HSP70 expression in response to heat shock at the temperatures tested. Cells responded differently to hyperthermia when grown in 2D and 3D cultures. Three-dimensional culture appears to enhance survival plausibly by activating protective processes related to enhanced-HSP70 expression. These differences highlight the importance of selecting physiologically relevant 3D models in assessing cellular responses to hyperthermia in experimental settings. PMID:24658653

Song, Alfred S; Najjar, Amer M; Diller, Kenneth R

2014-07-01

28

Effects of Heat Loss on the Performance of Micro-Scale 3-D Supersonic Nozzles

NASA Astrophysics Data System (ADS)

The performance optimization of supersonic micro-nozzles is a key element in the design of MEMS-based microthrusters for the next generation of miniaturized satellites ("nanosats"). Owing to the large surface area-to-volume ratio on the microscale and the high conductivity of typical substrate materials, heat transfer effects are expected to be significant. This has been corroborated by thermal measurements performed on microthruster prototypes at NASA/Goddard Space Flight Center. To detail the heat transfer and quantify its impact on thruster performance, 2-D and 3-D numerical simulations of the supersonic micro-nozzle flow with insulated and conductive wall boundaries are performed. Geometry and flow parameters are based on the NASA/Goddard H2O2 monopropellant prototype microthruster. Both steady-state and transient thruster operations are considered. The 3-D steady flow results indicate that heat losses approaching 20enthalpy are possible in comparison to an adiabatic wall assumption, resulting in a 10generation.

Kujawa, Jeffrey; Hitt, Darren

2003-11-01

29

Highly conductive, capacitive and flexible electrodes are fabricated by employing 3D graphene-nanotube-palladium nanostructures and a PEDOT:PSS conducting polymer. The fabricated flexible electrodes, without any additional metallic current collectors, exhibit increased charge mobility and good mechanical properties; they also allow greater access to the electrolyte ions and hence are suitable for flexible energy storage applications. PMID:25142299

Kim, Hyun-Jun; Randriamahazaka, Hyacinthe; Oh, Il-Kwon

2014-12-29

30

Smoothed particle hydrodynamics: Applications to heat conduction

NASA Astrophysics Data System (ADS)

In this paper, we modify the numerical steps involved in a smoothed particle hydrodynamics (SPH) simulation. Specifically, the second order partial differential equation (PDE) is decomposed into two first order PDEs. Using the ghost particle method, consistent estimation of near-boundary corrections for system variables is also accomplished. Here, we focus on SPH equations for heat conduction to verify our numerical scheme. Each particle carries a physical entity (here, this entity is temperature) and transfers it to neighboring particles, thus exhibiting the mesh-less nature of the SPH framework, which is potentially applicable to complex geometries and nanoscale heat transfer. We demonstrate here only 1D and 2D simulations because 3D codes are as simple to generate as 1D codes in the SPH framework. Our methodology can be extended to systems where the governing equations are described by PDEs.

Jeong, J. H.; Jhon, M. S.; Halow, J. S.; van Osdol, J.

2003-06-01

31

Heat conduction in three dimensions

NASA Technical Reports Server (NTRS)

Multidimensional heat conduction program computes transient temperature history and steady state temperatures of complex body geometries in three dimensions. Emphasis is placed on type of problems associated with Space Shuttle thermal protection system, but program could be used in thermal analysis of most three dimensional systems.

Danza, T. M.; Fesler, L. W.; Mongan, R. D.

1980-01-01

32

We define a deterministic ``scattering'' model for heat conduction which is continuous in space, and which has a Boltzmann type flavor, obtained by a closure based on memory loss between collisions. We prove that this model has, for stochastic driving forces at the boundary, close to Maxwellians, a unique non-equilibrium steady state.

Pierre Collet; Jean-Pierre Eckmann

2008-04-18

33

Recent Heat Transfer Improvements to the RELAP5-3D Code

The heat transfer section of the RELAP5-3D computer program has been recently improved. The improvements are as follows: (1) the general cladding rupture model was modified (more than one heat structure segment connected to the hydrodynamic volume and heat structure geometrys internal gap pressure), (2) the cladding rupture model was modified for reflood, and (3) the heat transfer minor edits/plots were extended to include radiation/enclosure heat flux and generation (internal heat source).

Riemke, Richard A; Davis, Cliff B; Oh, Chang

2007-05-01

34

Numerical computation of 3D heat transfer in complex parallel convective exchangers using convective heat exchangers that handles possibly complex input/output con- ditions as well as connection between pipes. It is based on a spectral method that allows to re-cast three-dimensional heat exchangers

Paris-Sud XI, Université de

35

Hybrid Liquid Immersion and Synthetic Jet Heat Sink for Cooling 3-D Stacked Electronics

This paper focuses on the design and parametric numerical study of a hybrid heat sink combining a liquid thermal interface with an array of synthetic jet actuators for 3-D chip stack cooling. The air-side heat sink exploits enhanced localized heat transfer achieved via a central array of synthetic jet actuators. The key focus of this paper is the numerical simulation

Krishna Kota; Pablo Hidalgo; Yogendra Joshi; Ari Glezer

2012-01-01

36

Heat Conduction in a One-Dimensional Harmonic Chain with Three-Dimensional Vibrations

Heat Conduction in a One-Dimensional Harmonic Chain with Three-Dimensional Vibrations Zonghua LIU1 chain connected by three-dimensional (3D) harmonic springs, the coefficient of heat conduction changes where the coefficient is independent of the lattice constant. KEYWORDS: heat conduction, harmonic chain

Li, Baowen

37

HEAT CONDUCTION NETWORKS: DISPOSITION OF HEAT BATHS AND INVARIANT MEASURE

HEAT CONDUCTION NETWORKS: DISPOSITION OF HEAT BATHS AND INVARIANT MEASURE ALAIN CAMANES Abstract. We consider a model of heat conduction networks consisting of oscillators in contact with heat baths the particular geometry of the chain, we work with general networks. These heat conduction networks have been

Paris-Sud XI, Université de

38

Extremal structures of multiphase heat conducting composites

Extremal structures of multiphase heat conducting composites A.V. Cherkaev \\Lambda L.V. Gibiansky y usual properties: their heat conductivity in one direction is equal to the harmonic or arithmetic mean of the phases' heat conductivities and the conductivity in an orthogonal direction does not equal either

Cherkaev, Andrej

39

The 3-D computations of edge induction heating using semi-analytical method and FEM

Contents Both a 3-D semi-analytical method and an approach based on a 3-D FEM are presented to calculate the electromagnetic and thermal fields for edge induction heating. The proposed semi-analytical method is based on the separation of variables and the discrete Fourier transform to solve the eddy current problem. The Fourier components are sinusoidal functions with complex arguments. Boundary conditions

L. Gong; R. Unbehauen

1996-01-01

40

An experimental study was conducted to characterize the heat affected zone produced when laser heating a Ti6Al4V alloy plate workpiece. The emissivity and absorptivity of the Ti6Al4V alloy were determined experimentally. A 3D transient finite element method for a moving Gaussian laser heat source was developed to predict the depth and width of the heat affected zone on the Ti6Al4V

Jihong Yang; Shoujin Sun; Milan Brandt; Wenyi Yan

2010-01-01

41

Methodology for the Assessment of 3D Conduction Effects in an Aerothermal Wind Tunnel Test

NASA Technical Reports Server (NTRS)

This slide presentation reviews a method for the assessment of three-dimensional conduction effects during test in a Aerothermal Wind Tunnel. The test objectives were to duplicate and extend tests that were performed during the 1960's on thermal conduction on proturberance on a flat plate. Slides review the 1D versus 3D conduction data reduction error, the analysis process, CFD-based analysis, loose coupling method that simulates a wind tunnel test run, verification of the CFD solution, Grid convergence, Mach number trend, size trends, and a Sumary of the CFD conduction analysis. Other slides show comparisons to pretest CFD at Mach 1.5 and 2.16 and the geometries of the models and grids.

Oliver, Anthony Brandon

2010-01-01

42

FURN3D: A computer code for radiative heat transfer in pulverized coal furnaces

A computer code FURN3D has been developed for assessing the impact of burning different coals on heat absorption pattern in pulverized coal furnaces. The code is unique in its ability to conduct detailed spectral calculations of radiation transport in furnaces fully accounting for the size distributions of char, soot and ash particles, ash content, and ash composition. The code uses a hybrid technique of solving the three-dimensional radiation transport equation for absorbing, emitting and anisotropically scattering media. The technique achieves an optimal mix of computational speed and accuracy by combining the discrete ordinate method (S{sub 4}), modified differential approximation (MDA) and P, approximation in different range of optical thicknesses. The code uses spectroscopic data for estimating the absorption coefficients of participating gases C0{sub 2}, H{sub 2}0 and CO. It invokes Mie theory for determining the extinction and scattering coefficients of combustion particulates. The optical constants of char, soot and ash are obtained from dispersion relations derived from reflectivity, transmissivity and extinction measurements. A control-volume formulation is adopted for determining the temperature field inside the furnace. A simple char burnout model is employed for estimating heat release and evolution of particle size distribution. The code is written in Fortran 77, has modular form, and is machine-independent. The computer memory required by the code depends upon the number of grid points specified and whether the transport calculations are performed on spectral or gray basis.

Ahluwalia, R.K.; Im, K.H.

1992-08-01

43

FURN3D: A computer code for radiative heat transfer in pulverized coal furnaces

A computer code FURN3D has been developed for assessing the impact of burning different coals on heat absorption pattern in pulverized coal furnaces. The code is unique in its ability to conduct detailed spectral calculations of radiation transport in furnaces fully accounting for the size distributions of char, soot and ash particles, ash content, and ash composition. The code uses a hybrid technique of solving the three-dimensional radiation transport equation for absorbing, emitting and anisotropically scattering media. The technique achieves an optimal mix of computational speed and accuracy by combining the discrete ordinate method (S[sub 4]), modified differential approximation (MDA) and P, approximation in different range of optical thicknesses. The code uses spectroscopic data for estimating the absorption coefficients of participating gases C0[sub 2], H[sub 2]0 and CO. It invokes Mie theory for determining the extinction and scattering coefficients of combustion particulates. The optical constants of char, soot and ash are obtained from dispersion relations derived from reflectivity, transmissivity and extinction measurements. A control-volume formulation is adopted for determining the temperature field inside the furnace. A simple char burnout model is employed for estimating heat release and evolution of particle size distribution. The code is written in Fortran 77, has modular form, and is machine-independent. The computer memory required by the code depends upon the number of grid points specified and whether the transport calculations are performed on spectral or gray basis.

Ahluwalia, R.K.; Im, K.H.

1992-08-01

44

The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce0.8Gd0.2O2 (GDC) oxygen ion conductive phase and a CoFe2O4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered with regards to the design of new material systems which evolve under non-equilibrium operating conditions. PMID:24615571

Harris, William M; Brinkman, Kyle S; Lin, Ye; Su, Dong; Cocco, Alex P; Nakajo, Arata; DeGostin, Matthew B; Chen-Wiegart, Yu-chen Karen; Wang, Jun; Chen, Fanglin; Chu, Yong S; Chiu, Wilson K S

2014-05-01

45

Cellular-structured graphene foam (GF)/epoxy composites are prepared based on a three-step fabrication process involving infiltration of epoxy into the porous GF. The three-dimensional (3D) GF is grown on a Ni foam template via chemical vapor deposition. The 3D interconnected graphene network serves as fast channels for charge carriers, giving rise to a remarkable electrical conductivity of the composite, 3 S/cm, with only 0.2 wt % GF. The corresponding flexural modulus and strength increase by 53 and 38%, respectively, whereas the glass transition temperature increases by a notable 31 C, compared to the solid neat epoxy. The GF/epoxy composites with 0.1 wt % GF also deliver an excellent fracture toughness of 1.78 MPam(1/2), 34 and 70% enhancements against their "porous" epoxy and solid epoxy counterparts, respectively. These observations signify the unrivalled effectiveness of 3D GF relative to 1D carbon nanotubes or 2D functionalized graphene sheets as reinforcement for polymer composites without issues of nanofiller dispersion and functionalization prior to incorporation into the polymer. PMID:24848106

Jia, Jingjing; Sun, Xinying; Lin, Xiuyi; Shen, Xi; Mai, Yiu-Wing; Kim, Jang-Kyo

2014-06-24

46

NASA Astrophysics Data System (ADS)

The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce0.8Gd0.2O2 (GDC) oxygen ion conductive phase and a CoFe2O4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered with regards to the design of new material systems which evolve under non-equilibrium operating conditions.The microstructure and connectivity of the ionic and electronic conductive phases in composite ceramic membranes are directly related to device performance. Transmission electron microscopy (TEM) including chemical mapping combined with X-ray nanotomography (XNT) have been used to characterize the composition and 3-D microstructure of a MIEC composite model system consisting of a Ce0.8Gd0.2O2 (GDC) oxygen ion conductive phase and a CoFe2O4 (CFO) electronic conductive phase. The microstructural data is discussed, including the composition and distribution of an emergent phase which takes the form of isolated and distinct regions. Performance implications are considered with regards to the design of new material systems which evolve under non-equilibrium operating conditions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06684c

Harris, William M.; Brinkman, Kyle S.; Lin, Ye; Su, Dong; Cocco, Alex P.; Nakajo, Arata; Degostin, Matthew B.; Chen-Wiegart, Yu-Chen Karen; Wang, Jun; Chen, Fanglin; Chu, Yong S.; Chiu, Wilson K. S.

2014-04-01

47

Electrical properties of biological tissues are highly sensitive to their physiological and pathological status. Thus it is of importance to image electrical properties of biological tissues. However, spatial resolution of conventional electrical impedance tomography (EIT) is generally poor. Recently, hybrid imaging modalities combining electric conductivity contrast and ultrasonic resolution based on acouto-electric effect has attracted considerable attention. In this study, we propose a novel three-dimensional (3D) noninvasive ultrasound Joule heat tomography (UJHT) approach based on acouto-electric effect using unipolar ultrasound pulses. As the Joule heat density distribution is highly dependent on the conductivity distribution, an accurate and high resolution mapping of the Joule heat density distribution is expected to give important information that is closely related to the conductivity contrast. The advantages of the proposed ultrasound Joule heat tomography using unipolar pulses include its simple inverse solution, better performance than UJHT using common bipolar pulses and its independence of any priori knowledge of the conductivity distribution of the imaging object. Computer simulation results show that using the proposed method, it is feasible to perform a high spatial resolution Joule heat imaging in an inhomogeneous conductive media. Application of this technique on tumor scanning is also investigated by a series of computer simulations. PMID:23123757

Yang, Renhuan; Li, Xu; Song, Aiguo; He, Bin; Yan, Ruqiang

2012-01-01

48

Toward A 3-D Picture of Hydraulic Conductivity With Multilevel Slug Tests

NASA Astrophysics Data System (ADS)

The GEMS (Geohydrologic Experiment and Monitoring Site) field area has been established (in the Kansas River valley near Lawrence, Kansas) for a variety of reasons relating to research and teaching in hydrogeology at the University of Kansas. Over 70 wells have been installed for various purposes. The site overlies an alluvial aquifer with a total thickness of about 70 feet. The water table is typically about 20 feet below the surface, giving a total saturated thickness of about 50 feet. The upper part of the aquifer is finer material consisting of silt and clay. Typically, the lower 35 feet of the aquifer is sand and gravel. A number of wells through out the site are fully screened through the sand and gravel aquifer. Some of these fully screened wells are larger diameters; however, most wells are constructed of 2 inch PVC casing. Slug tests are widely used in hydrogeology to measure hydraulic conductivity. Over the last several years we have been conducting research to improve the slug test method. We have previously reported the detailed structure of hydraulic conductivity that can be seen in a 5 inch well (McElwee and Zemansky, EOS, v. 80, no. 46, p. F397, 1999) at this site, using multilevel slug tests. The existing 2 inch, fully screened wells are spread out over the site and offer the opportunity for developing a 3-D picture of the hydraulic conductivity distribution. However, it is difficult to develop a system that allows multilevel slug tests to be done accurately and efficiently in a 2 inch well. This is especially true in regions of very high hydraulic conductivity, where the water velocity in the casing will be relatively high. The resistance caused by frictional forces in the equipment must be minimized and a model taking account of these forces must be used. We have developed a system (equipment, software, and technique) for performing multilevel slug tests in 2 inch wells. Some equipment configurations work better than others. The data that we have been able to obtain look promising for delineating the spatial change in hydraulic conductivity over the site. The preliminary data definitely indicate significant changes over the area. With improvements in well installation, such as direct push and other techniques, it might be quite feasible to develop a 3-D picture of hydraulic conductivity over an area using multilevel slug tests in fully screened wells.

McElwee, C. D.; McElwee, C. D.; Ross, H. C.

2001-12-01

49

Variable boundary II heat conduction

NASA Technical Reports Server (NTRS)

Computer program for solving both transient and steady-state heat transfer problems is presented. Specific applications of computer program are described. Formulation for individual nodes of solid medium for heat balance is presented. Diffusion equation is solved for all nodes simultaneously at finite increments of time.

Gramer, J.; Oneill, R. F.

1972-01-01

50

3D topographic correction of the BSR heat flow and detection of focused fluid flow

NASA Astrophysics Data System (ADS)

The bottom-simulating reflector (BSR) is a seismic indicator of the bottom of a gas hydrate stability zone. Its depth can be used to calculate the seafloor surface heat flow. The calculated BSR heat flow variations include disturbances from two important factors: (1) seafloor topography, which focuses the heat flow over regions of concave topography and defocuses it over regions of convex topography, and (2) the focused warm fluid flow within the accretionary prism coming from depths deeper than BSR. The focused fluid flow can be detected if the contribution of the topography to the BSR heat flow is removed. However, the analytical equation cannot solve the topographic effect at complex seafloor regions. We prove that 3D finite element method can model the topographic effect on the regional background heat flow with high accuracy, which can then be used to correct the topographic effect and obtain the BSR heat flow under the condition of perfectly flat topography. By comparing the corrected BSR heat flow with the regional background heat flow, focused fluid flow regions can be detected that are originally too small and cannot be detected using present-day equipment. This method was successfully applied to the midslope region of northern Cascadia subducting margin. The results suggest that the Cucumber Ridge and its neighboring area are positive heat flow anomalies, about 10%-20% higher than the background heat flow after 3D topographic correction. Moreover, the seismic imaging associated the positive heat flow anomaly areas with seabed fracture-cavity systems. This suggests flow of warm gas-carrying fluids along these high-permeability pathways, which could result in higher gas hydrate concentrations.

He, Tao; Li, Hong-Lin; Zou, Chang-Chun

2014-06-01

51

New transfer functions for probing 3-D mantle conductivity from ground and sea

NASA Astrophysics Data System (ADS)

The C-response is a conventional transfer function in global electromagnetic induction research and is classically determined from local observations of magnetic variations in the vertical and the horizontal components. Its estimation and interpretation rely on the assumptions that the source of the considered variations is well approximated by a large-scale symmetric (magnetospheric) ring current that can be described by a single spherical harmonic, P10, and that conductivity in the Earth is only a function of depth. However, there is growing evidence for a more complex structure of the magnetospheric source. We investigate the variability of C-responses due to non-P10 contributions to the source. We show that this variability, which we denote as 'source effect' (as opposed to the well-known ocean effect), is significant and persists at all periods. If inverting estimated C-responses for mantle conductivity, this source effect will inevitably be mistaken for conductivity anomalies. To overcome the problem connected with the assumptions for deriving C-responses, we introduce new transfer functions that relate the local vertical component of the magnetic variation to different spherical harmonic coefficients describing the magnetospheric source. The latter are derived from observations of magnetic variations in the horizontal components. The new transfer functions are subsequently estimated with a robust multivariate data analysis tool. By analyzing 16 years of data, collected at the global network of geomagnetic observatories, we demonstrate that the new transfer functions exhibit a significant increase in coherence compared to C-responses, especially at high latitudes. The concept is easily extended to other data types. For example, by relating the voltage variations in abandoned submarine telecommunication cables to spherical harmonic coefficients in the same way as described above, one can define yet another array of transfer functions. In spite of the fact that the newly introduced transfer functions allow for a consistent treatment of a complex spatial structure of the source, the sparse and irregular distribution of geomagnetic observatories and submarine cables impedes a reliable inversion of these data for 3-D mantle conductivity on a global scale. However, in combination with matrix Q-responses estimated from Swarm satellite data, the new transfer functions can be used to probe the 3-D conductivity structure of Earth's mantle.

Pthe, Christoph; Kuvshinov, Alexey; Olsen, Nils

2014-05-01

52

Heat conduction fronts in planetary nebulae

NASA Technical Reports Server (NTRS)

We present arguments which suggest that many of the x-ray, some optical, and some UV observations of planetary nebulae, can be explained by the presence of heat conduction fronts. The heat flows from the hot bubble formed by the shocked fast wind to the cool shell and halo. Heat conduction fronts are likely to account for emission of x rays from plasma at lower temperature than the expected temperature of the hot bubble. In the presence of magnetic fields, only a small fraction of the fast wind luminosity emerges as radiation. Heat conduction fronts can naturally produce some unusual line flux ratios, which are observed in some planetary nebulae. Heat conduction fronts may heat the halo and cause some material at the inner surface of the shell to expand slower than the rest of the shell. In the presence of an asymmetrical magnetic field, this flow, the x-ray intensity, and the emission lines, may acquire asymmetrical structure as well.

Soker, Noam

1994-01-01

53

Entropy and temperature gradients thermomechanics: dissipation, heat conduction

Entropy and temperature gradients thermomechanics: dissipation, heat conduction inequality and heat and heat conduction inequality. The framework of generalized standard materials is then suitable ; second law ; heat conduction inequality ; heat equation Mots-clés : Milieux continus ; thermodynamique

Boyer, Edmond

54

Finite-Difference Algorithm for Simulating 3D Electromagnetic Wavefields in Conductive Media

NASA Astrophysics Data System (ADS)

Electromagnetic (EM) wavefields are routinely used in geophysical exploration for detection and characterization of subsurface geological formations of economic interest. Recorded EM signals depend strongly on the current conductivity of geologic media. Hence, they are particularly useful for inferring fluid content of saturated porous bodies. In order to enhance understanding of field-recorded data, we are developing a numerical algorithm for simulating three-dimensional (3D) EM wave propagation and diffusion in heterogeneous conductive materials. Maxwell's equations are combined with isotropic constitutive relations to obtain a set of six, coupled, first-order partial differential equations governing the electric and magnetic vectors. An advantage of this system is that it does not contain spatial derivatives of the three medium parameters electric permittivity, magnetic permeability, and current conductivity. Numerical solution methodology consists of explicit, time-domain finite-differencing on a 3D staggered rectangular grid. Temporal and spatial FD operators have order 2 and N, where N is user-selectable. We use an artificially-large electric permittivity to maximize the FD timestep, and thus reduce execution time. For the low frequencies typically used in geophysical exploration, accuracy is not unduly compromised. Grid boundary reflections are mitigated via convolutional perfectly matched layers (C-PMLs) imposed at the six grid flanks. A shared-memory-parallel code implementation via OpenMP directives enables rapid algorithm execution on a multi-thread computational platform. Good agreement is obtained in comparisons of numerically-generated data with reference solutions. EM wavefields are sourced via point current density and magnetic dipole vectors. Spatially-extended inductive sources (current carrying wire loops) are under development. We are particularly interested in accurate representation of high-conductivity sub-grid-scale features that are common in industrial environments (borehole casing, pipes, railroad tracks). Present efforts are oriented toward calculating the EM responses of these objects via a First Born Approximation approach. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Aldridge, D. F.; Bartel, L. C.; Knox, H. A.

2013-12-01

55

Heat conductivity in linear mixing systems

We present analytical and numerical results on the heat conduction in a linear mixing system. In particular we consider a quasi one dimensional channel with triangular scatterers with internal angles irrational multiples of pi and we show that the system obeys Fourier law of heat conduction. Therefore deterministic diffusion and normal heat transport which are usually associated to full hyperbolicity, actually take place in systems without exponential instability.

Baowen Li; Giulio Casati; Jiao Wang

2002-08-06

56

Highly conductive, capacitive and flexible electrodes are fabricated by I.-K. Oh and co-workers by employing 3D graphene-nanotube nanostructures and PEDOT:PSS conducting polymer. The 3D graphene-nanotube structures have efficient ionic and electron pathways, and on page 5023 they are shown to greatly enhace charge mobility and mechanical properties that are required for flexible energy storage applications. PMID:25512318

Kim, Hyun-Jun; Randriamahazaka, Hyacinthe; Oh, Il-Kwon

2014-12-01

57

3D volume MR temperature mapping for HIFU heating trajectory comparisons

NASA Astrophysics Data System (ADS)

Many areas of MR-guided thermal therapy research would benefit from temperature maps with high spatial and temporal resolution that cover a large 3-D volume. This paper describes an approach to achieve these goals that is suitable for research applications where retrospective reconstruction of the temperature maps is acceptable. The method acquires undersampled data from a modified 3-D segmented EPI sequence and creates images using a temporally constrained reconstruction algorithm. The 3-D images can be zero-filled to arbitrarily small voxel spacing in all directions and then converted into temperature maps using the standard proton resonance frequency (PRF) shift technique. During HIFU heating experiments, the proposed method was used to obtain temperature maps with 1.51.53.0 mm resolution, 28816278 mm field of view, and 1.7 second temporal resolution. The approach is validated to demonstrate that it can accurately capture the spatial characteristics and time dynamics of rapidly changing HIFU-induced temperature distributions. An example application is presented where the method is used to analyze and compare different HIFU volumetric heating trajectories.

Todd, Nick; Vyas, Urvi; de Bever, Josh; Payne, Allison; Parker, Dennis L.

2012-10-01

58

Heat Transfer Derivation of differential equations for heat transfer conduction

;Collect global force terms. In this example, there is no heat source (Q = 0) or heat flux (q = 0 conducted (heat flux) into the control volume at surface edge x, in units of kW/m2 or Btu/(h-ft2). qx of temperature increase. #12;Similar to The heat flux can be stated as: Expanding this using a two term Taylor

Veress, Alexander

59

3D modelling of coupled mass and heat transfer of a convection-oven roasting process.

A 3D mathematical model of coupled heat and mass transfer describing oven roasting of meat has been developed from first principles. The proposed mechanism for the mass transfer of water is modified and based on a critical literature review of the effect of heat on meat. The model equations are based on a conservation of mass and energy, coupled through Darcy's equations of porous media - the water flow is mainly pressure-driven. The developed model together with theoretical and experimental assessments were used to explain the heat and water transport and the effect of the change in microstructure (permeability, water binding capacity and elastic modulus) that occur during the meat roasting process. The developed coupled partial differential equations were solved by using COMSOL Multiphysics3.5 and state variables are predicted as functions of both position and time. The proposed mechanism was partially validated by experiments in a convection oven where temperatures were measured online. PMID:23305831

Feyissa, Aberham Hailu; Gernaey, Krist V; Adler-Nissen, Jens

2013-04-01

60

Role of 3d-dispersive Alfven waves in coronal heating

NASA Astrophysics Data System (ADS)

Coronal heating is one of the unresolved puzzles in solar physics from decades. In the present paper we have investigated the dynamics of vortices to apprehend coronal heating problem. A three dimensional (3d) model has been developed to study propagation of dispersive Alfvn waves (DAWs) in presence of ion acoustic waves which results in excitation of DAW and evolution of vortices. Taking ponderomotive nonlinearity into account, development of these vortices has been studied. There are observations of such vortices in the chromosphere, transition region and also in the lower solar corona. These structures may play an important role in transferring energy from lower solar atmosphere to corona and result in coronal heating. Nonlinear interaction of these waves is studied in view of recent simulation work and observations of giant magnetic tornadoes in solar corona and lower atmosphere of sun by solar dynamical observatory (SDO).

Sharma, R. P.; Yadav, N.; Pathak, N.

2014-05-01

61

Heat conduction controlled combustion for scramjet applications

NASA Technical Reports Server (NTRS)

The use of heat conduction flame generated in a premixed supersonic stream is discussed. It is shown that the flame is controlled initially by heat conduction and then by chemical reaction. Such a flame is shorter than the diffusion type of flame and therefore it requires a much shorter burner. The mixing is obtained by injecting the hydrogen in the inlet. Then the inlet can be cooled by film cooling.

Ferri, A.; Agnone, A. M.

1974-01-01

62

NASA Astrophysics Data System (ADS)

A heat transfer model of a semi-industrial induction furnace has been build, using a 3D finite element model in order to analyze the entire process cycle, based on the heating, melting, solidification and cooling phases of a multi-crystalline square ingot. In the modeling of the entire process, heat transfer phenomena such as radiation and conduction in the furnace have been taken into account. A PID (Proportional Integral Differential) control algorithm has been implemented into the model for adjusting the power input in the heaters, so that the heater temperature is kept at prescribed time-varying values. The furnace model and the PID control algorithm are validated by temperature measurements from a crystallization experiment. Subsequently the validated model was used to investigate the melt flow field and its impact on the solid-liquid interface shape.

Bellmann, M. P.; Lindholm, D.; Srheim, E. A.; Mortensen, D.; M'Hamdi, M.

2013-11-01

63

Cryogenic regenerator including sarancarbon heat conduction matrix

NASA Technical Reports Server (NTRS)

A saran carbon matrix is employed to conduct heat through the heat storing volume of a cryogenic regenerator. When helium is adsorbed into the saran carbon matrix, the combination exhibits a volumetric specific heat much higher than previously used lead balls. A helium adsorbed saran regenerator should allow much lower refrigerator temperatures than those practically obtainable with lead based regenerators for regenerator type refrigeration systems.

Jones, Jack A. (Inventor); Petrick, S. Walter (Inventor); Britcliffe, Michael J. (Inventor)

1989-01-01

64

ORINC. 1-D Implicit Heat Conduction Solution

ORINC is an inverse computer program which solves a one-dimensional, transient, lumped-parameter, implicit formulation of the conduction equation to determine both the transient surface temperature and the transient surface heat flux of electrically heated rods during a simulated loss-of-coolant accident. The program was developed specifically for analysis of the Thermal-Hydraulic Test Facility Blowdown Heat Transfer (THTF-BDHT) test data as part

Ott

1989-01-01

65

ALE3D Simulation of Heating and Violence in a Fast Cookoff Experiment with LX-10

We performed a computational and experimental analysis of fast cookoff of LX-10 (94.7% HMX, 5.3% Viton A) confined in a 2 kbar steel tube with reinforced end caps. A Scaled-Thermal-Explosion-eXperiment (STEX) was completed in which three radiant heaters were used to heat the vessel until ignition, resulting in a moderately violent explosion after 20.4 minutes. Thermocouple measurements showed tube temperatures as high as 340 C at ignition and LX-10 surface temperatures as high as 279 C, which is near the melting point of HMX. Three micro-power radar systems were used to measure mean fragment velocities of 840 m/s. Photonics Doppler Velocimeters (PDVs) showed a rapid acceleration of fragments over 80 {micro}s. A one-dimensional ALE3D cookoff model at the vessel midplane was used to simulate the heating, thermal expansion, LX-10 decomposition composition, and closing of the gap between the HE (High Explosive) and vessel wall. Although the ALE3D simulation terminated before ignition, the model provided a good representation of heat transfer through the case and across the dynamic gap to the explosive.

McClelland, M A; Maienschein, J L; Howard, W M; Nichols, A L; deHaven, M R; Strand, O T

2006-06-26

66

NASA Astrophysics Data System (ADS)

In the framework of its research on the deep disposal of radioactive waste in shale formations, the French Institute for Radiological Protection and Nuclear Safety (IRSN) has developed a large array of in situ programs concerning the confining properties of shales in their underground research laboratory at Tournemire (SW France). One of its aims is to evaluate the occurrence and processes controlling radionuclide migration through the host rock, from the disposal system to the biosphere. Past research programs carried out at Tournemire covered mechanical, hydro-mechanical and physico-chemical properties of the Tournemire shale as well as water chemistry and long-term behaviour of the host rock. Studies show that fluid circulations in the undisturbed matrix are very slow (hydraulic conductivity of 10-14 to 10-15 m.s-1). However, recent work related to the occurrence of small scale fractures and clay-rich fault gouges indicate that fluid circulations may have been significantly modified in the vicinity of such features. To assess the transport properties associated with such faults, IRSN designed a series of in situ and laboratory experiments to evaluate the contribution of both diffusive and advective process on water and solute flux through a clay-rich fault zone (fault core and damaged zone) and in an undisturbed shale formation. As part of these studies, Modular Mini-Packer System (MMPS) hydraulic testing was conducted in multiple boreholes to characterize hydraulic conductivities within the formation. Pressure data collected during the hydraulic tests were analyzed using the nSIGHTS (n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator) code to estimate hydraulic conductivity and formation pressures of the tested intervals. Preliminary results indicate hydraulic conductivities of 5.10-12 m.s-1 in the fault core and damaged zone and 10-14 m.s-1 in the adjacent undisturbed shale. Furthermore, when compared with neutron porosity data from borehole logging, porosity varies by a factor of 2.5 whilst hydraulic conductivity varies by 2 to 3 orders of magnitude. In addition, a 3D numerical reconstruction of the internal structure of the fault zone inferred from borehole imagery has been built to estimate the permeability tensor variations. First results indicate that hydraulic conductivity values calculated for this structure are 2 to 3 orders of magnitude above those measured in situ. Such high values are due to the imaging method that only takes in to account open fractures of simple geometry (sine waves). Even though improvements are needed to handle more complex geometry, outcomes are promising as the fault damaged zone clearly appears as the highest permeability zone, where stress analysis show that the actual stress state may favor tensile reopening of fractures. Using shale samples cored from the different internal structures of the fault zone, we aim now to characterize the advection and diffusion using laboratory petrophysical tests combined with radial and through-diffusion experiments.

Courbet, C.; DICK, P.; Lefevre, M.; Wittebroodt, C.; Matray, J.; Barnichon, J.

2013-12-01

67

The Conduction of Heat through Cryogenic Regenerative Heat Exchangers

NASA Astrophysics Data System (ADS)

The need for improved regenerative cryocooler efficiency may require the replacement of conventional matrices with ducts. The ducts can not be continuous in the direction of temperature gradient when using conventional materials to prevent unacceptable conduction losses. However, this discontinuity creates a complex geometry to model and determine conduction losses. Chesapeake Cryogenics, Inc. has designed, fabricated and tested an apparatus for measuring the heat conduction through regenerative heat exchangers implementing different matrices. Data is presented for stainless steel photo etched disk, phophorus-bronze embossed ribbon coils and screens made of both stainless steel and phosphorus-bronze. The heat conduction was measured with the regenerators evacuated and pressurized with helium gas. In this test apparatus, helium gas presence increased the heat leak significantly. A description of the test apparatus, instrumentation, experimental methods and data analysis are presented.

Superczynski, W. F.; Green, G. F.

2006-04-01

68

Heat conductivity of the DNA double helix

NASA Astrophysics Data System (ADS)

Thermal conductivity of isolated single molecule DNA fragments is of importance for nanotechnology, but has not yet been measured experimentally. Theoretical estimates based on simplified (1D) models predict anomalously high thermal conductivity. To investigate thermal properties of single molecule DNA we have developed a 3D coarse-grained (CG) model that retains the realism of the full all-atom description, but is significantly more efficient. Within the proposed model each nucleotide is represented by six particles or grains; the grains interact via effective potentials inferred from classical molecular dynamics (MD) trajectories based on a well-established all-atom potential function. Comparisons of 10 ns long MD trajectories between the CG and the corresponding all-atom model show similar root-mean-square deviations from the canonical B-form DNA, and similar structural fluctuations. At the same time, the CG model is 10 to 100 times faster depending on the length of the DNA fragment in the simulation. Analysis of dispersion curves derived from the CG model yields longitudinal sound velocity and torsional stiffness in close agreement with existing experiments. The computational efficiency of the CG model makes it possible to calculate thermal conductivity of a single DNA molecule not yet available experimentally. For homogeneous (polyG-polyC) DNA, the estimated conductivity coefficient is 0.3 W/mK which is half the value of thermal conductivity for water. This result is in stark contrast with estimates of thermal conductivity for simplified, effectively 1D chains (beads on a spring) that predict anomalous (infinite) thermal conductivity. Thus, the full 3D character of DNA double-helix retained in the proposed model appears to be essential for describing thermal properties of DNA at a single molecule level.

Savin, Alexander V.; Mazo, Mikhail A.; Kikot, Irina P.; Manevitch, Leonid I.; Onufriev, Alexey V.

2011-06-01

69

NASA Astrophysics Data System (ADS)

We present a novel 3-D frequency-domain inversion scheme to recover 3-D mantle conductivity from satellite magnetic data, for example, provided by the Swarm mission. The scheme is based on the inversion of a new set of electromagnetic transfer functions, which form an array that we denote as matrix Q-response and which relate external (inducing) and internal (induced) coefficients of the spherical harmonic expansion of the time-varying magnetic field of magnetospheric origin. This concept overcomes the problems associated with source determination inherent to recent schemes based on direct inversion of internal coefficients. Matrix Q-responses are estimated from time-series of external and internal coefficients with a newly elaborated multivariate analysis scheme. An inversion algorithm that deals with matrix Q-responses has been developed. In order to make the inversion tractable, we elaborated an adjoint approach to compute the data misfit gradient and parallelized the numerical code with respect to frequencies and elementary sources, which describe the external part of the magnetic field of magnetospheric origin. Both parts of the scheme have been verified with realistic test data. Special attention is given to the issue of correlated noise due to undescribed sources.

Pthe, Christoph; Kuvshinov, Alexey

2014-05-01

70

ORMDIN. 2-D Nonlinear Inverse Heat Conduction

ORMDIN is a finite-element program developed for two-dimensional nonlinear inverse heat conduction analysis as part of the Oak Ridge National Laboratory Pressurized Water Reactor Blowdown Heat Transfer (BDHT) program. One of the primary objectives of the program was to determine the transient surface temperature and surface heat flux of fuel pin simulators from internal thermocouple signals obtained during a loss-of-coolant accident experiment in the Thermal-Hydraulic Test Facility (THTF). ORMDIN was designed primarily to perform a transient two-dimensional nonlinear inverse heat conduction analysis of the THTF bundle 3 heater rod; however, it can be applied to other cylindrical geometries for which the thermophysical properties are prescribed functions of temperature. The program assumes that discretized temperature histories are provided at three thermocouple locations in the interior of the cylinder. Concurrent with the two-dimensional analysis, ORMDIN also generates one-dimensional solutions for each of the three thermocouple radial planes.

Bass, B.R. [Oak Ridge Gaseous Diffusion Plant, Oak Ridge, TN (United States)

1990-05-01

71

Compact pulsed laser having improved heat conductance

NASA Technical Reports Server (NTRS)

A highly efficient, compact pulsed laser having high energy to weight and volume ratios is provided. The laser utilizes a cavity reflector that operates as a heat sink and is essentially characterized by having a high heat conductivity, by being a good electrical insulator and by being substantially immune to the deleterious effects of ultra-violet radiation. Manual portability is accomplished by eliminating entirely any need for a conventional circulating fluid cooling system.

Yang, L. C. (inventor)

1977-01-01

72

Measurement of heat conduction through stacked screens

NASA Technical Reports Server (NTRS)

This paper describes the experimental apparatus for the measurement of heat conduction through stacked screens as well as some experimental results taken with the apparatus. Screens are stacked in a fiberglass-epoxy cylinder, which is 24.4 mm in diameter and 55 mm in length. The cold end of the stacked screens is cooled by a Gifford-McMahon (GM) cryocooler at cryogenic temperature, and the hot end is maintained at room temperature. Heat conduction through the screens is determined from the temperature gradient in a calibrated heat flow sensor mounted between the cold end of the stacked screens and the GM cryocooler. The samples used for these experiments consisted of 400-mesh stainless steel screens, 400-mesh phosphor bronze screens, and two different porosities of 325-mesh stainless steel screens. The wire diameter of the 400-mesh stainless steel and phosphor bronze screens was 25.4 micrometers and the 325-mesh stainless steel screen wire diameters were 22.9 micrometers and 27.9 micrometers. Standard porosity values were used for the experimental data with additional porosity values used on selected experiments. The experimental results showed that the helium gas between each screen enhanced the heat conduction through the stacked screens by several orders of magnitude compared to that in vacuum. The conduction degradation factor is the ratio of actual heat conduction to the heat conduction where the regenerator material is assumed to be a solid rod of the same cross sectional area as the metal fraction of the screen. This factor was about 0.1 for the stainless steel and 0.022 for the phosphor bronze, and almost constant for the temperature range of 40 to 80 K at the cold end.

Lewis, M. A.; Kuriyama, T.; Kuriyama, F.; Radebaugh, R.

1998-01-01

73

North Cascadia heat flux and fluid flow from gas hydrates: Modeling 3-D topographic effects

NASA Astrophysics Data System (ADS)

bottom-simulating reflector (BSR) of gas hydrate is well imaged from two perpendicular seismic grids in the region of a large carbonate mound, informally called Cucumber Ridge off Vancouver Island. We use a new method to calculate 3-D heat flow map from the BSR depths, in which we incorporate 3-D topographic corrections after calibrated by the drilling results from nearby (Integrated) Ocean Drilling Program Site 889 and Site U1327. We then estimate the associated fluid flow by relating it to the topographically corrected heat flux anomalies. In the midslope region, a heat flux anomaly of 1 mW/m2 can be associated with an approximate focused fluid flow rate of 0.09 mm/yr. Around Cucumber Ridge, high rates of focused fluid flow were observed at steep slopes with values more than double the average regional diffusive fluid discharge rate of 0.56 mm/yr. As well, in some areas of relatively flat seafloor, the focused fluid flow rates still exceeded 0.5 mm/yr. On the seismic lines the regions of focused fluid flow were commonly associated with seismic blanking zones above the BSR and sometimes with strong reflectors below the BSR, indicating that the faults/fractures provide high-permeability pathways for fluids to carry methane from BSR depths to the seafloor. These high fluid flow regions cover mostly the western portion of our area with gas hydrate concentration estimations of ~6% based on empirical correlations from Hydrate Ridge in south off Oregon, significantly higher than previously recognized values of ~2.5% in the eastern portion determined from Site U1327.

Li, Hong-lin; He, Tao; Spence, George D.

2014-01-01

74

Single-mode heat conduction by photons.

The thermal conductance of a single channel is limited by its unique quantum value G(Q), as was shown theoretically in 1983. This result closely resembles the well-known quantization of electrical conductance in ballistic one-dimensional conductors. Interestingly, all particles-irrespective of whether they are bosons or fermions-have the same quantized thermal conductance when they are confined within dimensions that are small compared to their characteristic wavelength. The single-mode heat conductance is particularly relevant in nanostructures. Quantized heat transport through submicrometre dielectric wires by phonons has been observed, and it has been predicted to influence cooling of electrons in metals at very low temperatures due to electromagnetic radiation. Here we report experimental results showing that at low temperatures heat is transferred by photon radiation, when electron-phonon as well as normal electronic heat conduction is frozen out. We study heat exchange between two small pieces of normal metal, connected to each other only via superconducting leads, which are ideal insulators against conventional thermal conduction. Each superconducting lead is interrupted by a switch of electromagnetic (photon) radiation in the form of a DC-SQUID (a superconducting loop with two Josephson tunnel junctions). We find that the thermal conductance between the two metal islands mediated by photons indeed approaches the expected quantum limit of G(Q) at low temperatures. Our observation has practical implications-for example, for the performance and design of ultra-sensitive bolometers (detectors of far-infrared light) and electronic micro-refrigerators, whose operation is largely dependent on weak thermal coupling between the device and its environment. PMID:17093446

Meschke, Matthias; Guichard, Wiebke; Pekola, Jukka P

2006-11-01

75

Single-mode heat conduction by photons

NASA Astrophysics Data System (ADS)

The thermal conductance of a single channel is limited by its unique quantum value GQ, as was shown theoretically in 1983. This result closely resembles the well-known quantization of electrical conductance in ballistic one-dimensional conductors. Interestingly, all particles-irrespective of whether they are bosons or fermions-have the same quantized thermal conductance when they are confined within dimensions that are small compared to their characteristic wavelength. The single-mode heat conductance is particularly relevant in nanostructures. Quantized heat transport through submicrometre dielectric wires by phonons has been observed, and it has been predicted to influence cooling of electrons in metals at very low temperatures due to electromagnetic radiation. Here we report experimental results showing that at low temperatures heat is transferred by photon radiation, when electron-phonon as well as normal electronic heat conduction is frozen out. We study heat exchange between two small pieces of normal metal, connected to each other only via superconducting leads, which are ideal insulators against conventional thermal conduction. Each superconducting lead is interrupted by a switch of electromagnetic (photon) radiation in the form of a DC-SQUID (a superconducting loop with two Josephson tunnel junctions). We find that the thermal conductance between the two metal islands mediated by photons indeed approaches the expected quantum limit of GQ at low temperatures. Our observation has practical implications-for example, for the performance and design of ultra-sensitive bolometers (detectors of far-infrared light) and electronic micro-refrigerators, whose operation is largely dependent on weak thermal coupling between the device and its environment.

Meschke, Matthias; Guichard, Wiebke; Pekola, Jukka P.

2006-11-01

76

Heat conduction model for nanowire applications

NASA Astrophysics Data System (ADS)

A heat conduction model for determining the temperature of a nanowire through which a current is passed is proposed. In the model, the total Joule heating arising in the nanowire due to the current is considered until the system reaches a steady state. It is important to determine the positions of the "cold points" in the system, where the temperature is left unchanged by the current. The current required to cut a nanowire is predicted from the model. The mechanism for Joule heat welding is classified depending on the positions of the cold points in the metallic nanowire system.

Tohmyoh, Hironori

2013-02-01

77

Finite Heat conduction in 2D Lattices

This paper gives a 2D hamonic lattices model with missing bond defects, when the capacity ratio of defects is enough large, the temperature gradient can be formed and the finite heat conduction is found in the model. The defects in the 2D harmonic lattices impede the energy carriers free propagation, by another words, the mean free paths of the energy carrier are relatively short. The microscopic dynamics leads to the finite conduction in the model.

Lei Yang; Yang Kongqing

2001-07-30

78

3D multifields FEM computation of transverse flux induction heating for moving-strips

The numerical and experimental studies on induction heating of continuously moving strips in a transverse field are presented in this paper. The induced eddy current and its coupled thermal field in moving media is computed with FEM. The adopted mathematical model consists of a Fourier thermal conduction equation and a set of differential equations, which describes the steady-state eddy current

Z. Wang; W. Huang; W. Jia; Q. Zhao; Y. Wang; W. Yan; D. Schulze; G. Martin; U. Luedtke

1999-01-01

79

Heat conductivity of a pion gas

We evaluate the heat conductivity of a dilute pion gas employing the Uehling-Uehlenbeck equation and experimental phase-shifts parameterized by means of the SU(2) Inverse Amplitude Method. Our results are consistent with previous evaluations. For comparison we also give results for an (unphysical) hard sphere gas.

Antonio Dobado Gonzalez; Felipe J. Llanes-Estrada; Juan M. Torres Rincon

2007-02-13

80

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

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.

Del-Castillo-Negrete, Diego B [ORNL] [ORNL; Blazevski, D. [University of Texas, Austin] [University of Texas, Austin; Chacon, Luis [ORNL] [ORNL

2012-01-01

81

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

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.

Schlutt, M. G.; Hegna, C. C. [University of Wisconsin-Madison, 1500 Engineering Drive, 510 ERB, Madison, Wisconsin 53706 (United States)

2012-08-15

82

Within the framework of the study of the aircraft structural material lightning, we present a work concerning the heating of metal sheets under the action of a moving electric arc. A 2D and 3D modeling of thermal phenomena occurring in the heated electrodes are used in order to study the influence of the arc root velocity and of the power

Ph. Test; T. Leblanc; F. Uhlig; J.-P. Chabrerie

2000-01-01

83

In this paper, a 3D algorithm for the treatment of radiative heat transfer in emitting, absorbing, and scattering media is developed. The numerical approach is based on the utilization of the unstructured control volume finite element method (CVFEM) which, to the knowledge of the authors, is applied for the first time to simulate radiative heat transfer in participated media confined

H. Grissa; F. Askri; M. Ben Salah; S. Ben Nasrallah

2010-01-01

84

Operating as low as tens of hertz and as high as hundreds of kilohertz, new broadband electromagnetic induction (EMI) sensors have shown promise for classification of unseen buried metallic objects. The three-dimensional (3-D) and bodies-of-revolution (BOR) numerical studies reported here are designed to explain key scattering sensitivities that may either be useful in or may limit object classification capability. The

F. Shubitidze; K. O'Neill; Keli Sun; K. D. Paulsen

2004-01-01

85

Effects of anisotropic heat conduction on solidification

NASA Technical Reports Server (NTRS)

Two-dimensional solidification influenced by anisotropic heat conduction has been considered. The interfacial energy balance was derived to account for the heat transfer in one direction (x or y) depending on the temperature gradient in both the x and y directions. A parametric study was made to determine the effects of the Stefan number, aspect ratio, initial superheat, and thermal conductivity ratios on the solidification rate. Because of the imposed boundary conditions, the interface became skewed and sometimes was not a straight line between the interface position at the upper and lower adiabatic walls (spatially nonlinear along the height). This skewness depends on the thermal conductivity ratio k(yy)/k(yx). The nonlinearity of the interface is influenced by the solidification rate, aspect ratio, and k(yy/k(yx).

Weaver, J. A.; Viskanta, R.

1989-01-01

86

Heat Rejection from a Variable Conductance Heat Pipe Radiator Panel

NASA Technical Reports Server (NTRS)

A titanium-water heat pipe radiator having an innovative proprietary evaporator configuration was evaluated in a large vacuum chamber equipped with liquid nitrogen cooled cold walls. The radiator was manufactured by Advanced Cooling Technologies, Inc. (ACT), Lancaster, PA, and delivered as part of a Small Business Innovative Research effort. The radiator panel consisted of five titanium-water heat pipes operating as thermosyphons, sandwiched between two polymer matrix composite face sheets. The five variable conductance heat pipes were purposely charged with a small amount of non-condensable gas to control heat flow through the condenser. Heat rejection was evaluated over a wide range of inlet water temperature and flow conditions, and heat rejection was calculated in real-time utilizing a data acquisition system programmed with the Stefan-Boltzmann equation. Thermography through an infra-red transparent window identified heat flow across the panel. Under nominal operation, a maximum heat rejection value of over 2200 Watts was identified. The thermal vacuum evaluation of heat rejection provided critical information on understanding the radiator s performance, and in steady state and transient scenarios provided useful information for validating current thermal models in support of the Fission Power Systems Project.

Jaworske, D. A.; Gibson, M. A.; Hervol, D. S.

2012-01-01

87

NASA Astrophysics Data System (ADS)

This paper presents a numerical simulation of the developing flow and heat transfer of a viscoelastic fluid in a rectangular duct. In fully developed flow of a viscoelastic fluid in a non-circular duct, secondary flows normal to the flow direction are expected to enhance the rate of heat and mass transfer. On the other hand, properties such as viscosity, thermal conductivity, specific heat and relaxation time of the fluid are a function of temperature. Therefore, we developed a numerical model which solves the flow and energy equation simultaneously in three dimensional form. We included several equations of state to model the temperature dependency of the fluid parameters. The current paper is one of the first studies which present a 3D numerical simulation for developing viscoelastic duct flow that takes the dependency of flow parameters to the temperature into account. The rheological constitutive equation of the fluid is a common form of the Phan-Thien Tanner (PTT) model, which embodies both influences of elasticity and shear thinning in viscosity. The governing equations are discretized using the FTCS finite difference method on a staggered mesh. The marker-and-cell method is also employed to allocate the parameters on the staggered mesh, and static pressure is calculated using the artificial compressibility approach during the numerical simulation. In addition to report the results of flow and heat transfer in the developing region, the effect of some dimensionless parameters on the flow and heat transfer has also been investigated. The results are in a good agreement with the results reported by others in this field.

Jalali, A.; Hulsen, M. A.; Norouzi, M.; Kayhani, M. H.

2013-05-01

88

NASA Astrophysics Data System (ADS)

This paper documents the 3D modeling and simulation of a three couple thermoelectric module using the Synopsys Technology Computer Aided Design (TCAD) semiconductor simulation software. Simulation results are presented for thermoelectric power generation, cooling and heating, and successfully demonstrate the basic thermoelectric principles. The 3D TCAD simulation model of a three couple thermoelectric module can be used in the future to evaluate different thermoelectric materials, device structures, and improve the efficiency and performance of thermoelectric modules.

Gould, C. A.; Shammas, N. Y. A.; Grainger, S.; Taylor, I.; Simpson, K.

2012-06-01

89

NASA Technical Reports Server (NTRS)

Finite element method applied to heat conduction in solids with temperature dependent thermal conductivity, using nonlinear constitutive equation for heat ABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGH

Aguirre-Ramirez, G.; Oden, J. T.

1969-01-01

90

-dimensional heat conduction. As buildings are exposed to rapid climatic variations (particularly incident solar tools using one-dimensional heat conduction without a sun patch. INTRODUCTION In France, the residential are simplified or neglected, for instance the location of a sun patch, or the treatment of heat conduction

Boyer, Edmond

91

Qualitative aspects in dualphaselag heat conduction Ram on Quintanilla 1

Qualitative aspects in dualphaselag heat conduction Ram?? on Quintanilla 1 Department of Applied.racke@unikonstanz.de Abstract: We consider the system of dualphaselag heat conduction proposed by Tzou [21]. First, we prove of heat conduction based on Fourier's law predicts infinite heat propagation speed. Heat transmission

Racke, Reinhard

92

Measurement of 3-D hydraulic conductivity in aquifer cores at in situ effective stresses.

An innovative and nondestructive method to measure the hydraulic conductivity of drill core samples in horizontal and vertical directions within a triaxial cell has been developed. This has been applied to characterizing anisotropy and heterogeneity of a confined consolidated limestone aquifer. Most of the cores tested were isotropic, but hydraulic conductivity varied considerably and the core samples with lowest values were also the most anisotropic. Hydraulic conductivity decreased with increasing effective stress due to closure of microfractures caused by sampling for all core samples. This demonstrates the importance of replicating in situ effective stresses when measuring hydraulic conductivity of cores of deep aquifers in the laboratory. PMID:12236264

Wright, Martin; Dillon, Peter; Pavelic, Paul; Peter, Paul; Nefiodovas, Andrew

2002-01-01

93

ME 6010 CONDUCTION HEAT TRANSFER 1998 Catalog Data: ME 6010. Conduction Heat Transfer. Lec. 3. Cr. Prerequisite: Math 4510, ME 3710 Textbook: S. Kakac and Y. Yener, Heat Conduction, Taylor & Francis Coordinator. Undergraduate conduction and convection heat transfer, or equivalent 2. Advanced undergraduate mathematics

Panchagnula, Mahesh

94

Long and high conductance helium heat pipe

NASA Astrophysics Data System (ADS)

This paper reports on the development and the thermal tests of two superfluid helium heat pipes. They feature a copper braid located inside a 6 mm outer diameter stainless tube fitted with copper ends for mechanical anchoring. The copper braid is the support of the Rollin superfluid helium film which is essential in the heat transfer. The extremely low thickness of the liquid film allows for a low filling pressure, making the technology very simple without the need for any external hot reservoir and with the possibility to easily bend the tube. We present the design and discuss the thermal performance of two heat pipes tested for several filling pressures, adverse tilt angles and in 1.4-2.0 K temperature range. A minimum filling pressure (0.6 MPa) is needed to get significant transport capacity. A 12 mW transport capacity is achieved for 3.0 MPa filling pressure. It is shown that the long heat pipe (1.2 m) and the short one (0.25 m) have similar thermal performance in adverse tilt. At 1.7 K the long heat pipe, 120 g in weight, reaches a transport capacity of 5.7 mW/4.2 mW for a tilt angle of 0 / 60 and a thermal conductance of 600 mW/K for 4 mW transferred power. When the condenser reaches the super-fluid transition temperature, the Rollin film accelerates the cool down of the evaporator down to 1.7 K with a heating power applied to the evaporator.

Gully, Philippe

2014-11-01

95

NASA Astrophysics Data System (ADS)

In the paper we present implementation of 3D DIC method for in-situ diagnostic measurements of expansion bellows in heating chambers. The simultaneous measurements of a supply and a return pipeline were carried out in a heating chamber in Warsaw at the peak of the heating season in cooperation with Dalkia Warszawa. Results of the measurements enabled assessment of the risk of failure of expansion bellows. In-situ measurements were preceded by feasibility tests carried out in the Institute of Heat Engineering of Warsaw University of Technology. Potential implementations and a direction of future works are discussed in conclusions.

Malesa, M.; Kujawi?ska, M.; Malowany, K.; Siwek, B.

2013-04-01

96

NASA Astrophysics Data System (ADS)

A three-dimensionally integrated microstrip antenna (3DIMA) is a microstrip antenna woven into the three-dimensional woven composite for load bearing while functioning as an antenna. In this study, the effect of weaving direction of conductive yarns on electromagnetic performance of 3DIMAs are investigated by designing, simulating and experimental testing of two microstrip antennas with different weaving directions of conductive yarns: one has the conductive yarns along the antenna feeding direction (3DIMA-Exp1) and the other has the conductive yarns perpendicular the antenna feeding direction (3DIMA-Exp2). The measured voltage standing wave ratio (VSWR) of 3DIMA-Exp1 was 1.4 at the resonant frequencies of 1.39 GHz; while that of 3DIMA-Exp2 was 1.2 at the resonant frequencies of 1.35 GHz. In addition, the measured radiation pattern of the 3DIMA-Exp1 has smaller back lobe and higher gain value than those of the 3DIMA-Exp2. This result indicates that the waving direction of conductive yarns may have a significant impact on electromagnetic performance of textile structural antennas.

Xu, Fujun; Yao, Lan; Zhao, Da; Jiang, Muwen; Qiu, Yipping

2013-10-01

97

SPATIAL STATISTICS MODELS FOR STOCHASTIC INVERSE PROBLEMS IN HEAT CONDUCTION

SPATIAL STATISTICS MODELS FOR STOCHASTIC INVERSE PROBLEMS IN HEAT CONDUCTION J. Wang and N. Zabaras in heat conduction. Spatial statistics models, in particular Markov random fields (MRF), are used to model with the unknown quantities. Introduction Inverse problems in heat conduction, including boundary heat flux

Zabaras, Nicholas J.

98

NON FOURIER HEAT CONDUCTION IN MICROSCOPIC MODELS OF DIELECTRICS

NON FOURIER HEAT CONDUCTION IN MICROSCOPIC MODELS OF DIELECTRICS Oleg Gendelman Faculty equation of heat conduction admits the paradox of infinite velocity of heat propagation. To avoid the microscopic point of view, In order to assess the phenomena of the non-Fourier heat conduction

Adler, Joan

99

NASA Astrophysics Data System (ADS)

The global 3-D electrical conductivity distribution in the mantle (in the depth range between 400 and 1600 km) is imaged by inverting C-responses estimated on a global net of geomagnetic observatories. Very long time-series (up to 51 years; 1957-2007) of hourly means of three components of the geomagnetic field from 281 geomagnetic observatories are collected and analysed. Special attention is given to data processing in order to obtain unbiased C-responses with trustworthy estimates of experimental errors in the period range from 2.9 to 104.2 d. After careful inspection of the obtained C-responses the data from 119 observatories are chosen for the further analysis. Squared coherency is used as a main quality indicator to detect (and then to exclude from consideration) observatories with a large noise-to-signal ratio. During this analysis we found thatalong with the C-responses from high-latitude observatories (geomagnetic latitudes higher than 58)the C-responses from all low-latitude observatories (geomagnetic latitudes below 11) also have very low squared coherencies, and thus cannot be used for global induction studies. We found that the C-responses from the selected 119 mid-latitude observatories show a huge variability both in real and imaginary parts, and we investigated to what extent the ocean effect can explain such a scatter. By performing the systematic model calculations we conclude that: (1) the variability due to the ocean effect is substantial, especially at shorter periods, and it is seen for periods up to 40 d or so; (2) the imaginary part of the C-responses is to a larger extent influenced by the oceans; (3) two types of anomalous C-response behaviour associated with the ocean effect can be distinguished; (4) to accurately reproduce the ocean effect a lateral resolution of 1 1 of the conductance distribution is needed, and (5) the ocean effect alone does not explain the whole variability of the observed C-responses. We also detected that part of the variability in the real part of the C-responses is due to the auroral effect. In addition we discovered that the auroral effect in the C-responses reveals strong longitudinal variability, at least in the Northern Hemisphere. Europe appears to be the region with smallest degree of distortion compared with North America and northern Asia. We found that the imaginary part of the C-responses is weakly affected by the auroral source, thus confirming the fact that in the considered period range the electromagnetic (EM) induction from the auroral electrojet is small. Assuming weak dependence of the auroral signals on the Earth's conductivity at considered periods, and longitudinal variability of the auroral effect, we developed a scheme to correct the experimental C-responses for this effect. With these developments and findings in mind we performed a number of regularized 3-D inversions of our experimental data in order to detect robust features in the recovered 3-D conductivity images. Although differing in details, all our 3-D inversions reveal a substantial level of lateral heterogeneity in the mantle at the depths between 410 and 1600 km. Conductivity values vary laterally by more than one order of magnitude between resistive and conductive regions. The maximum lateral variations of the conductivity have been detected in the layer at depths between 670 and 900 km. By comparing our global 3-D results with the results of independent global and semi-global 3-D conductivity studies, we conclude that 3-D conductivity mantle models produced so far are preliminary as different groups obtain disparate results, thus complicating quantitative comparison with seismic tomography or/and geodynamic models. In spite of this, our 3-D EM study and most other 3-D EM studies reveal at least two robust features: reduced conductivity beneath southern Europe and northern Africa, and enhanced conductivity in northeastern China.

Semenov, Alexey; Kuvshinov, Alexey

2012-12-01

100

Parallelized solvers for heat conduction formulations

NASA Technical Reports Server (NTRS)

Based on multilevel partitioning, this paper develops a structural parallelizable solution methodology that enables a significant reduction in computational effort and memory requirements for very large scale linear and nonlinear steady and transient thermal (heat conduction) models. Due to the generality of the formulation of the scheme, both finite element and finite difference simulations can be treated. Diverse model topologies can thus be handled, including both simply and multiply connected (branched/perforated) geometries. To verify the methodology, analytical and numerical benchmark trends are verified in both sequential and parallel computer environments.

Padovan, Joe; Kwang, Abel

1991-01-01

101

Electromagnetic induction (EMI) instruments provide rapid, noninvasive, and spatially dense data for characterization of soil and groundwater properties. Data from multi-frequency EMI tools can be inverted to provide quantitative electrical conductivity estimates as a function of depth. In this study, multi-frequency EMI data collected across an abandoned uranium mill site near Naturita, Colorado, USA, are inverted to produce vertical distribution of electrical conductivity (EC) across the site. The relation between measured apparent electrical conductivity (ECa) and hydraulic conductivity (K) is weak (correlation coefficient of 0.20), whereas the correlation between the depth dependent EC obtained from the inversions, and K is sufficiently strong to be used for hydrologic estimation (correlation coefficient of -0.62). Depth-specific EC values were correlated with co-located K measurements to develop a site-specific ln(EC)-ln(K) relation. This petrophysical relation was applied to produce a spatially detailed map of K across the study area. A synthetic example based on ECa values at the site was used to assess model resolution and correlation loss given variations in depth and/or measurement error. Results from synthetic modeling indicate that optimum correlation with K occurs at ~0.5m followed by a gradual correlation loss of 90% at 2.3m. These results are consistent with an analysis of depth of investigation (DOI) given the range of frequencies, transmitter-receiver separation, and measurement errors for the field data. DOIs were estimated at 2.0??0.5m depending on the soil conductivities. A 4-layer model, with varying thicknesses, was used to invert the ECa to maximize available information within the aquifer region for improved correlations with K. Results show improved correlation between K and the corresponding inverted EC at similar depths, underscoring the importance of inversion in using multi-frequency EMI data for hydrologic estimation. ?? 2011.

Brosten, T.R.; Day-Lewis, F. D.; Schultz, G.M.; Curtis, G.P.; Lane, J.W.

2011-01-01

102

While the number of man-made nano superstructures realized by self-assembly is growing in recent years, assemblies of conductive polymer nanocrystals, especially for superlattices, are still a significant challenge, not only because of the simplicity of the shape of the nanocrystal building blocks and their interactions, but also because of the poor control over these parameters in the fabrication of more elaborate nanocrystals. Here, we firstly report a facile and general route to a new generation of 3D layered superlattices of polyaniline doped with CSA (PANI-CSA) and show how PANI crystallize and self-assemble, in a suitable single solution environment. In cyclohexane, 1D amorphous nanofibers transformed to 1D nanorods as building blocks, and then to 2D single-crystal nanosheets with a hexagonal phase, and lastly to 3D ordered layered superlattices with the narrowest polydispersity value (M(w)/M(n) = 1.47). Remarkably, all the instructions for the hierarchical self-assembly are encoded in the layered shape in other non-polar solvents (hexane, octane) and their conductivity in the ?-? stacking direction is improved to about 50 S cm(-1), which is even higher than that of the highest previously reported value (16 S cm(-1)). The method used in this study is greatly expected to be readily scalable to produce superlattices of conductive polymers with high quality and low cost. PMID:22609947

Tao, Yulun; Shen, Yuhua; Yang, Liangbao; Han, Bin; Huang, Fangzhi; Li, Shikuo; Chu, Zhuwang; Xie, Anjian

2012-06-21

103

Electromagnetic Scattering From a Rectangular Cavity Recessed in a 3-D Conducting Surface

NASA Technical Reports Server (NTRS)

The problem of electromagnetic (EM) scattering from an aperture backed by a rectangular cavity recessed in a three-dimensional conducting body is analyzed using the coupled field integral equation approach. Using the free-space Green's function, EM fields scattered outside the cavity are determined in terms of (1) an equivalent electric surface current density flowing on the three-dimensional conducting surface of the object including the cavity aperture and (2) an equivalent magnetic surface current density flowing over the aperture only. The EM fields inside the cavity are determined using the waveguide modal expansion functions. Making the total tangential electric and magnetic fields across the aperture continuous and subjecting the total tangential electric field on the outer conducting three-dimensional surface of the object to zero, a set of coupled integral equations is obtained. The equivalent electric and magnetic surface currents are then obtained by solving the coupled integral equation using the Method of Moments. The numerical results on scattering from rectangular cavities embedded in various three-dimensional objects are compared with the results obtained by other numerical techniques.

Deshpande, M. D.; Reddy, C. J.

1995-01-01

104

Heat conduction in X-ray clusters: Spitzer over 3

Effective heat conduction in a random variable magnetic field should be equal to one third of the Spitzer's value. Recent observations indicate that this heat conduction is sufficient to account for the bremsstrahlung in cooling X-ray clusters.

Andrei Gruzinov

2002-03-04

105

A 3D block of radiogenic heat production was constructed from the subsurface total gamma ray logs of Bahariya Formation, Western Desert, Egypt. The studied rocks possess a range of radiogenic heat production varying from 0.21 ?Wm(-3) to 2.2 ?Wm(-3). Sandstone rocks of Bahariya Formation have higher radiogenic heat production than the average for crustal sedimentary rocks. The high values of density log of Bahariya Formation indicate the presence of iron oxides which contribute the uranium radioactive ores that increase the radiogenic heat production of these rocks. The average radiogenic heat production produced from the study area is calculated as 6.3 kW. The histogram and cumulative frequency analyses illustrate that the range from 0.8 to 1.2 ?Wm(-3) is about 45.3% of radiogenic heat production values. The 3D slicing of the reservoir shows that the southeastern and northeastern parts of the study area have higher radiogenic heat production than other parts. PMID:23291561

Al-Alfy, I M; Nabih, M A

2013-03-01

106

Nonintegrability and the Fourier heat conduction law.

We study in momentum-conserving systems, how nonintegrable dynamics may affect thermal transport properties. As illustrating examples, two one-dimensional (1D) diatomic chains, representing 1D fluids and lattices, respectively, are numerically investigated. In both models, the two species of atoms are assigned two different masses and are arranged alternatively. The systems are nonintegrable unless the mass ratio is one. We find that when the mass ratio is slightly different from one, the heat conductivity may keep significantly unchanged over a certain range of the system size and as the mass ratio tends to one, this range may expand rapidly. These results establish a new connection between the macroscopic thermal transport properties and the underlying dynamics. PMID:25314422

Chen, Shunda; Wang, Jiao; Casati, Giulio; Benenti, Giuliano

2014-09-01

107

Heat conduction across molecular junctions between nanoparticles Samy Merabia,1,

Heat conduction across molecular junctions between nanoparticles Samy Merabia,1, Jean-Louis Barrat 27, 2011) We investigate the problem of heat conduction across a molecular junction connecting two, a mini- mal thermal conductivity is required to convert heat in electric current; molecular junctions

Paris-Sud XI, Université de

108

NUMERICAL SIMULATION OF A VISCOELASTIC FLUID WITH ANISOTROPIC HEAT CONDUCTION

NUMERICAL SIMULATION OF A VISCOELASTIC FLUID WITH ANISOTROPIC HEAT CONDUCTION P. WAPPEROM and M contraction. Key words: shift factors, dissipation, anisotropic heat conduction, finite elements, streamline with Fourier's law, where the heat conduction may be anisotropic. In the derivation of a temperature equation

Wapperom, Peter

109

October 2011 SDI FEP Issues Heat Conduction Issues (HC)

October 2011 SDI FEP Issues Heat Conduction Issues (HC) SDI(HC) -1 DOE needs to provide of the run-of-mine salt would conduct less heat away from the heater than that analyzed here, and potentially temperature halite and run-of-mine salt would conduct less heat away from the heater and potentially produce

110

Heat Conduction in Fine Scale Mixtures With Interfacial Contact Resistance

Heat Conduction in Fine Scale Mixtures With Interfacial Contact Resistance Robert Lipton Department. The effective conductivity associated with the overall heat dissipation rate inside a composite cube]. 1 #12; The composite heat conductor occupies the region\\Omega ae R 3 . The conductivity of each

111

A generalization of Beck's method for Inverse Heat Conduction Problems

A generalization of Beck's method for Inverse Heat Conduction Problems H.-J. Reinhardt and Dinh Nho H`ao 1 Introduction Inverse Heat Conduction Problems (abbr.: IHCP) occur whenever surface are used. In this paper we present the Inverse Heat Conduction Problem in a general setting and outline

Reinhardt, Hans-Jürgen

112

CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011

ME 525 CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011 Office: 201C Roberts Hall Lecture Room: 121 Roberts Hall Phone: 994-6295 Lecture Periods: 12:45- 2:00, TR TEXT: Heat Conduction, M. N. Ozisik of conduction heat transfer. Important results which are useful for engineering application will also

Dyer, Bill

113

NASA Astrophysics Data System (ADS)

While the number of man-made nano superstructures realized by self-assembly is growing in recent years, assemblies of conductive polymer nanocrystals, especially for superlattices, are still a significant challenge, not only because of the simplicity of the shape of the nanocrystal building blocks and their interactions, but also because of the poor control over these parameters in the fabrication of more elaborate nanocrystals. Here, we firstly report a facile and general route to a new generation of 3D layered superlattices of polyaniline doped with CSA (PANI-CSA) and show how PANI crystallize and self-assemble, in a suitable single solution environment. In cyclohexane, 1D amorphous nanofibers transformed to 1D nanorods as building blocks, and then to 2D single-crystal nanosheets with a hexagonal phase, and lastly to 3D ordered layered superlattices with the narrowest polydispersity value (Mw/Mn = 1.47). Remarkably, all the instructions for the hierarchical self-assembly are encoded in the layered shape in other non-polar solvents (hexane, octane) and their conductivity in the ?-? stacking direction is improved to about 50 S cm-1, which is even higher than that of the highest previously reported value (16 S cm-1). The method used in this study is greatly expected to be readily scalable to produce superlattices of conductive polymers with high quality and low cost.While the number of man-made nano superstructures realized by self-assembly is growing in recent years, assemblies of conductive polymer nanocrystals, especially for superlattices, are still a significant challenge, not only because of the simplicity of the shape of the nanocrystal building blocks and their interactions, but also because of the poor control over these parameters in the fabrication of more elaborate nanocrystals. Here, we firstly report a facile and general route to a new generation of 3D layered superlattices of polyaniline doped with CSA (PANI-CSA) and show how PANI crystallize and self-assemble, in a suitable single solution environment. In cyclohexane, 1D amorphous nanofibers transformed to 1D nanorods as building blocks, and then to 2D single-crystal nanosheets with a hexagonal phase, and lastly to 3D ordered layered superlattices with the narrowest polydispersity value (Mw/Mn = 1.47). Remarkably, all the instructions for the hierarchical self-assembly are encoded in the layered shape in other non-polar solvents (hexane, octane) and their conductivity in the ?-? stacking direction is improved to about 50 S cm-1, which is even higher than that of the highest previously reported value (16 S cm-1). The method used in this study is greatly expected to be readily scalable to produce superlattices of conductive polymers with high quality and low cost. Electronic supplementary information (ESI) available: SEM, and TEM images. See DOI: 10.1039/c2nr30743j

Tao, Yulun; Shen, Yuhua; Yang, Liangbao; Han, Bin; Huang, Fangzhi; Li, Shikuo; Chu, Zhuwang; Xie, Anjian

2012-05-01

114

Molecular Dynamics Simulations of Heat Conduction in Nanostructures: Effect of Heat Bath

Molecular Dynamics Simulations of Heat Conduction in Nanostructures: Effect of Heat Bath Jie CHEN1 on heat conduction in nanostructures exemplified by silicon nanowires (SiNWs) and silicon/germanium nano produce consistent results with experiment in large heat bath parameter range. KEYWORDS: heat conduction

Li, Baowen

115

Use of 2D and 3D Resistivity Methods to Monitor Dilution of a Conductive Plume in Fractured Basalt

NASA Astrophysics Data System (ADS)

2D cross-borehole and 3D surface electrical resistance tomography (ERT) methods have been shown to be useful in delineating conductive plume migration in porous media. However, their application in fractured basalt, and to monitoring in situ dilution of conductive plumes has been largely uninvestigated. The objective of this study was to monitor the dilution of a conductive plume by more resistive water to delineate the spatial distribution of resistivity changes over time. Eight wells were drilled for the hydrogeophysical experiments. A KCl solution was injected into the partially saturated, fractured basalt via a centrally located injection well for 76 days prior to this dilution experiment. Tap water was then injected into the injection well for 34 days. ERT was used to monitor the dilution and displacement of the KCl plume during tap water injection, and during a subsequent 62-day monitoring period. Data were collected between the wells and at land surface. The ERT data collected during the investigation show the spatial distribution of resistivity changes caused by the influx of diluting water. 3D images of surface ERT results delineate broad areas of increased resistivity due to dilution/displacement of the KCl plume. Cross-borehole ERT data delineate specific locations of water influx. Injection-well resistivities delineate specific locations where tap water seeped from the injection well via preferential flow paths determined by time-dependent resistivity increases at different elevations. Monitoring- well resistivities delineate specific fracture locations and clustered areas of resistivity changes due to the dilution and displacement of the KCl solution. The experimental results presented herein illustrate the application of combined ERT methods to delineate spatially distributed dilution in fractured rock.

Nimmer, R. E.; Osiensky, J. L.; Binley, A. M.; Sprenke, K. F.; Williams, B. C.

2006-12-01

116

NASA Astrophysics Data System (ADS)

As an important factor affecting the accuracy of thermal conductivity measurement, systematic (bias) error in the guarded comparative axial heat flow (cut-bar) method was mostly neglected by previous researches. This bias is primarily due to the thermal conductivity mismatch between sample and meter bars (reference), which is common for a sample of unknown thermal conductivity. A correction scheme, based on finite element simulation of the measurement system, was proposed to reduce the magnitude of the overall measurement uncertainty. This scheme was experimentally validated by applying corrections on four types of sample measurements in which the specimen thermal conductivity is much smaller, slightly smaller, equal and much larger than that of the meter bar. As an alternative to the optimum guarding technique proposed before, the correction scheme can be used to minimize the uncertainty contribution from the measurement system with non-optimal guarding conditions. It is especially necessary for large thermal conductivity mismatches between sample and meter bars.

Xing, Changhu; Folsom, Charles; Jensen, Colby; Ban, Heng; Marshall, Douglas W.

2014-05-01

117

Heat Conduction in Fine Scale Mixtures With Interfacial Contact Resistance

Heat Conduction in Fine Scale Mixtures With Interfacial Contact Resistance Robert Lipton Department of the imperfect heat conduction problem (1.3) - (1.6) is given by Z k1[ k2 k(x)ruk r dx + #12; Z k [uk][ ]ds = Z of Mathematical Sciences Worcester Polytechnic Institute 100 Institute Road Worcester, MA 01609 Abstract Heat

118

Non-conductive heat transfer associated with frozen soils

The assertion that pure conductive heat transfer always dominates in cold climates is at odds with decades of research in soil physics which clearly demonstrate that non-conductive heat transfer by water and water vapor are significant, and frequently are for specific periods the dominant modes of heat transfer near the ground surface. The thermal regime at the surface represents the

Douglas L Kane; Kenneth M Hinkel; Douglas J Goering; Larry D Hinzman; Samuel I Outcalt

2001-01-01

119

Experimental evidence of hyperbolic heat conduction in processed meat

The objective of this paper is to present experimental evidence of the wave nature of heat propagation in processed meat and to demonstrate that the hyperbolic heat conduction model is an accurate representation, on a macroscopic level, of the heat conduction process in such biological material. The value of the characteristic thermal time of a specific material, processed bologna meat,

K. Mitra; S. Kumar; A. Vedavarz; M. K. Moallemi

1995-01-01

120

The Next Generation Nuclear Plant project is aimed at the research and development of a helium-cooled high-temperature gas reactor that could generate both electricity and process heat for the production of hydrogen. The heat from the high-temperature primary loop must be transferred via an intermediate heat exchanger to a secondary loop. Using RELAP5-3D, a model was developed for two of the heat exchanger options a printed-circuit heat exchanger and a helical-coil steam generator. The RELAP5-3D models were used to simulate an exponential decrease in pressure over a 20 second period. The results of this loss of coolant analysis indicate that heat is initially transferred from the primary loop to the secondary loop, but after the decrease in pressure in the primary loop the heat is transferred from the secondary loop to the primary loop. A high-temperature gas reactor model should be developed and connected to the heat transfer component to simulate other transients.

N. A. Anderson; P. Sabharwall

2014-01-01

121

Thermal Conductivity of Composites Under Di erent Heating Scenarios

Thermal Conductivity of Composites Under Di#11;erent Heating Scenarios H.T. Banks #3; , J.H. Hogan: Two dimensional heat transfer model #26;(z), and c p (z) represent the thermal conductivity, density y , R.E. Tirpak y , S. Wynne #3; October 5, 2003 Abstract We study the overall thermal conductivity

122

Extended Development of Variable Conductance Heat Pipes

NASA Technical Reports Server (NTRS)

A high-capacity vapor-modulated heat pipe was designed and tested. In 1977, a program was undertaken to use the aforementioned heat pipe to study protection from freezing-point failure, increase control sensitivity, and transient behavior under a wide range of operating conditions in order to determine the full performance potential of the heat pipe. A new concept, based on the vapor-induced-dry-out principle, was developed for passive feedback temperature control as a heat pipe diode. This report documents this work and describes: (1) the experimental and theoretical investigation of the performance of the vapor-modulated heat pipe; and (2) the design, fabrication and test of the heat pipe diode.

Antoniuk, D.; Edwards, D. K.; Luedke, E. E.

1978-01-01

123

NASA Astrophysics Data System (ADS)

The global three-dimensional (3-D) electrical conductivity distribution in the mantle is imaged by inverting C-responses obtained on a global net of geomagnetic observatories. We processed very long time series (up to 51 years; 1957-2007) of hourly means of three components of the geomagnetic field from 281 observatories. The responses were estimated at 15 periods between 2.9 to 104.2 days. After careful inspection of the obtained responses we selected those from 119 observatories. We investigated in what extent ocean and auroral effects can explain huge variability of the observed responses, and developed schemes to correct the data for these effects. The retrieved 3-D images of mantle conductivity are compared with the results of independent global and semi-global 3-D EM studies, and with the results of 3-D seismic tomography.

Kuvshinov, A. V.; Semenov, A. A.

2011-12-01

124

Superfluid Heat Conduction and the Cooling of Magnetized Neutron Stars

We report on a new mechanism for heat conduction in the neutron star crust. We find that collective modes of superfluid neutron matter, called superfluid phonons, can influence heat conduction in magnetized neutron stars. They can dominate the heat conduction transverse to the magnetic field when the magnetic field B > or approx. 10{sup 13} G. At a density of {rho}{approx_equal}10{sup 12}-10{sup 14} g/cm{sup 3}, the conductivity due to superfluid phonons is significantly larger than that due to lattice phonons and is comparable to electron conductivity when the temperature {approx_equal}10{sup 8} K. This new mode of heat conduction can limit the surface anisotropy in highly magnetized neutron stars. Cooling curves of magnetized neutron stars with and without superfluid heat conduction could show observationally discernible differences.

Aguilera, Deborah N. [Tandar Laboratory, Comision Nacional de Energia Atomica, Avenida Gral. Paz 1499, 1650 San Martin, Buenos Aires (Argentina); Cirigliano, Vincenzo; Reddy, Sanjay; Sharma, Rishi [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Pons, Jose A. [Department of Applied Physics, University of Alicante, Apartado de Correos 99, E-03080 Alicante (Spain)

2009-03-06

125

Superfluid Heat Conduction and the Cooling of Magnetized Neutron Stars

We report on a new mechanism for heat conduction in the neutron star crust. We find that collective modes of superfluid neutron matter, called superfluid phonons (sPhs), can influence heat conduction in magnetized neutron stars. They can dominate the heat conduction transverse to magnetic field when the magnetic field $B \\gsim 10^{13}$ G. At density $\\rho \\simeq 10^{12}-10^{14} $ g/cm$^3$ the conductivity due to sPhs is significantly larger than that due to lattice phonons and is comparable to electron conductivity when temperature $\\simeq 10^8$ K. This new mode of heat conduction can limit the surface anisotropy in highly magnetized neutron stars. Cooling curves of magnetized neutron stars with and without superfluid heat conduction could show observationally discernible differences.

Deborah N. Aguilera; Vincenzo Cirigliano; Jos A. Pons; Sanjay Reddy; Rishi Sharma

2008-07-29

126

Superfluid heat conduction and the cooling of magnetized neutron stars

We report on a new mechanism for heat conduction in the neutron star crust. We find that collective modes of superftuid neutron matter, called superfiuid phonons (sPhs), can influence heat conduction in magnetized neutron stars. They can dominate the heat conduction transverse to magnetic field when the magnetic field B {approx}> 10{sup 13} C. At density p {approx_equal} 10{sup 12}--10{sup 14} g/cm{sup 3} the conductivity due to sPhs is significantly larger than that due to lattice phonons and is comparable to electron conductivity at when temperature {approx_equal} 10{sup 8} K. This new mode of heat conduction can limit the surface anisotropy in highly magnetized neutron stars. Cooling curves of magnetized neutron stars with and without superfluid heat conduction show observationally discernible differences.

Cirigliano, Vincenzo [Los Alamos National Laboratory; Reddy, Sanjay [Los Alamos National Laboratory; Sharma, Rishi [Los Alamos National Laboratory; Aguilera, Deborah N [BUENOS AIRES

2008-01-01

127

Control of heat source in a heat conduction problem

NASA Astrophysics Data System (ADS)

The mathematical model of thermal processes during the heat treatment of a moving axisymmetric environment, for example wire. is considered. The wire is heated by internal constantly or periodically operating heat source. It is presented in the form of initial-boundary value problem for the unsteady heat equation with internal constantly or periodically operating heat source. The purpose of the work is the definition of control parameter of temperature field of a moving area, which is heated by internal heat source. The control parameters are determined by solving a nonlocal problem for the heat equation. The problem of getting an adequate temperature distribution throughout the heating area is considered. Therefore, a problem of heat source control is solved, in particular, control by electric current. Control of the heat source allows to maintain the necessary, from a technological point of view, temperature in the heating area. In this paper, to find additional information about the source of heat. The integral condition is used in the control problem. Integral condition, which is considered in the work, determines the energy balance of the heating zone and connects the desired temperature distribution in the internal points of area with temperatures at the boundaries. Control quality in an extremum formulation of the problem is assessed using the quadratic functional. In function space, from a physical point of view, proposed functional is the absolute difference between the actual emission of energy and absorbed energy in the heating zone. The absorbed energy is calculated by solving of the boundary value problem. Methods of determining the control parameters of temperature field are proposed. The resulting problem is solved by iterative methods. At different physical conditions, numerical calculations are carried out, control parameters of the heat treatment process are obtained.

Lyashenko, V.; Kobilskaya, E.

2014-11-01

128

Theory and design of variable conductance heat pipes

NASA Technical Reports Server (NTRS)

A comprehensive review and analysis of all aspects of heat pipe technology pertinent to the design of self-controlled, variable conductance devices for spacecraft thermal control is presented. Subjects considered include hydrostatics, hydrodynamics, heat transfer into and out of the pipe, fluid selection, materials compatibility and variable conductance control techniques. The report includes a selected bibliography of pertinent literature, analytical formulations of various models and theories describing variable conductance heat pipe behavior, and the results of numerous experiments on the steady state and transient performance of gas controlled variable conductance heat pipes. Also included is a discussion of VCHP design techniques.

Marcus, B. D.

1972-01-01

129

A numerical investigation of the 3-D flow in shell and tube heat exchangers

A three-dimensional computer program for simulation of the flow and heat transfer inside Shell and Tube Heat Exchangers has been developed. The simulation of shell and tube heat exchangers is based on a distributed resistance method that uses a modified two equation {kappa}-{epsilon} turbulence model along with non-equilibrium wall functions. Volume porosities and non-homogeneous surface permeabilities account for the obstructions due to the tubes and arbitrary arrangement of baffles. Sub-models are described for baffle-shell and baffle-tube leakage, shellside and tubeside heat transfer, with geometry generators for tubes, baffles, and nozzle inlets and outlets. The sub-models in HEATX use parameters that have not been altered from their published values. Computed heat transfer and pressure drop are compared with experimental data from the Delaware project (Bell, 1963). Numerically computed pressure drops are also compared for different baffle cuts, and different number of baffles with the experiments of Halle et al. (1984) which were performed in an industrial sized heat exchanger at Argonne National Labs. Discussion of the results is given with particular reference to global and local properties such as pressure drop, temperature variation, and heat transfer coefficients. Good agreement is obtained between the experiments and HEATX computations for the shellside pressure drop and outlet temperatures for the shellside and tubeside streams.

Prithiviraj, M.; Andrews, M.J. [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering

1996-12-31

130

Communications technology satellite - A variable conductance heat pipe application

NASA Technical Reports Server (NTRS)

A variable-conductance heat pipe system (VCHPS) has been designed to provide thermal control for a transmitter experiment package (TEP) to be flown on the Communications Technology Satellite. The VCHPS provides for heat rejection during TEP operation and minimizes the heat leak during power down operations. The VCHPS described features a unique method of aiding priming of arterial heat pipes and a novel approach to balancing heat pipe loads by staggering their control ranges.

Mock, P. R.; Marcus, B. D.; Edelman, E. A.

1974-01-01

131

NASA Astrophysics Data System (ADS)

The three-dimensional hypersonic rarefied gas flow over blunt bodies in the transitional flow regime is studied. The 3D thin viscous shock layer equations are solved by the asymptotic method developed for low Re numbers. The simple analytical solution is obtained for heat transfer and skin friction coefficients as functions of flow parameters and body geometry parameters. The values of these coefficients approach their values in the free molecular flow at unit accommodation coefficient as Reynolds number tends to zero. Comparison with DSMC solutions is carried out.

Brykina, Irina G.

2014-12-01

132

Signatures of small-scale heating events in EUV spectral lines as modeled from 3D MHD simulations

NASA Astrophysics Data System (ADS)

We aim at understanding the implications of small scale heating events in the solar atmosphere for the variations of the solar spectral irradiance. We present a technique for identification and characterization of these events in 3D simulations of the solar atmosphere. An accurate property determination of these events in time and space will help us to understand how spectral lines, in particular in the EUV, respond to them and which kind of spectral signatures one would expect to find in observations as from SOHO/SUMER and eventually from future space missions, as for example observations by SPICE on board Solar Orbiter.

Guerreiro, Nuno; Haberreiter, Margit; Hansteen, Viggo; Curdt, Werner; Schmutz, Werner

2014-05-01

133

Heat conduction in carbon nanotube materials: Strong effect of intrinsic thermal conductivity of the finite thermal conductivity kT of individual nanotubes on the conductivity k of the CNT materials.1063/1.4737903] Experimental measurements of thermal conductivity of individual CNTs, kT, reveal exceptionally high room

Zhigilei, Leonid V.

134

Aerodynamic heating on 3-D bodies including the effects of entropy-layer swallowing

NASA Technical Reports Server (NTRS)

A relatively simple method was developed previously (authors, 1973) for calculating laminar, transitional, and turbulent heating rates on three-dimensional bodies in hypersonic flows. This method was shown to yield reasonably accurate results for laminar heating on blunted circular and elliptical cones and an earlier version of the space shuttle vehicle. As the boundary layer along the surface grows, more and more of the inviscid-flow mass is entrained into the boundary layer, and the streamlines which passed through the nearly normal portion of the bow shock wave are 'swallowed' by the boundary layer. This phenomenon is often referred to as entropy-layer or streamline swallowing, and it can have a significant effect on the calculated heating rates. An approximate, yet simple, method for including the effects of entropy-layer swallowing in the heating-rate calculations is given.

Dejarnette, F. R.; Hamilton, H. H.

1974-01-01

135

The conduction of heat from sliding solids

Ah&act-The large scale restrictions to heat flow from two sliding solids can have a significant effect on the temperature field near the interface. It is shown that a practical system can be approximated to two semi-intinite solids whose temperatures at infinity are related to the heat flow rates through them. A number of existing semi-infinite solid solutions am generalised to

J. R. BARBER

1970-01-01

136

Challenges in microscale conductive and radiative heat transfer

This work addresses challenges in the emerging field of microlength scale radiative and conductive heat transfer in solids and recommends specific directions of future research. Microlength scale heat transfer involves thermal energy transport processes in which heat carrier characteristic lengths become comparable to each other or the characteristic device dimension. Identification of these characteristic lengths leads to the definition of

C. L. Tien; G. Chen

1994-01-01

137

Heat conduction errors and time lag in cryogenic thermometer installations

NASA Technical Reports Server (NTRS)

Installation practices are recommended that will increase rate of heat exchange between the thermometric sensing element and the cryogenic fluid and that will reduce the rate of undesired heat transfer to higher-temperature objects. Formulas and numerical data are given that help to estimate the magnitude of heat-conduction errors and of time lag in response.

Warshawsky, I.

1973-01-01

138

Hierarchical Bayesian models for inverse problems in heat conduction

Stochastic inverse problems in heat conduction with consideration of uncertainties in the measured temperature data, temperature sensor locations and thermophysical properties are addressed using a Bayesian statistical inference method. Both parameter estimation and thermal history reconstruction problems, including boundary heat flux and heat source reconstruction, are studied. Probabilistic specification of the unknown variables is deduced from temperature measurements. Hierarchical Bayesian

Jingbo Wang; Nicholas Zabaras

2005-01-01

139

Efficient Reformulation of HOTFGM: Heat Conduction with Variable Thermal Conductivity

NASA Technical Reports Server (NTRS)

Functionally graded materials (FGMs) have become one of the major research topics in the mechanics of materials community during the past fifteen years. FGMs are heterogeneous materials, characterized by spatially variable microstructure, and thus spatially variable macroscopic properties, introduced to enhance material or structural performance. The spatially variable material properties make FGMs challenging to analyze. The review of the various techniques employed to analyze the thermodynamical response of FGMs reveals two distinct and fundamentally different computational strategies, called uncoupled macromechanical and coupled micromechanical approaches by some investigators. The uncoupled macromechanical approaches ignore the effect of microstructural gradation by employing specific spatial variations of material properties, which are either assumed or obtained by local homogenization, thereby resulting in erroneous results under certain circumstances. In contrast, the coupled approaches explicitly account for the micro-macrostructural interaction, albeit at a significantly higher computational cost. The higher-order theory for functionally graded materials (HOTFGM) developed by Aboudi et al. is representative of the coupled approach. However, despite its demonstrated utility in applications where micro-macrostructural coupling effects are important, the theory's full potential is yet to be realized because the original formulation of HOTFGM is computationally intensive. This, in turn, limits the size of problems that can be solved due to the large number of equations required to mimic realistic material microstructures. Therefore, a basis for an efficient reformulation of HOTFGM, referred to as user-friendly formulation, is developed herein, and subsequently employed in the construction of the efficient reformulation using the local/global conductivity matrix approach. In order to extend HOTFGM's range of applicability, spatially variable thermal conductivity capability at the local level is incorporated into the efficient reformulation. Analytical solutions to validate both the user-friendly and efficient reformulations am also developed. Volume discretization sensitivity and validation studies, as well as a practical application of the developed efficient reformulation are subsequently carried out. The presented results illustrate the accuracy and implementability of both the user-friendly formulation and the efficient reformulation of HOTFGM.

Zhong, Yi; Pindera, Marek-Jerzy; Arnold, Steven M. (Technical Monitor)

2002-01-01

140

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...

141

3D crustal-scale heat-flow regimes at a developing active margin (Taranaki Basin, New Zealand)

NASA Astrophysics Data System (ADS)

The Taranaki Basin in the west of New Zealand's North Island has evolved from a rifted Mesozoic Gondwana margin to a basin straddling the Neogene convergent Australian-Pacific plate margin. However, given its proximity to the modern subduction front, Taranaki Basin is surprisingly cold when compared to other convergent margins. To investigate the effects of active margin evolution on the thermal regime of the Taranaki Basin we developed a 3D crustal-scale forward model using the petroleum industry-standard basin-modelling software Petromod. The crustal structure inherited from Mesozoic Gondwana margin breakup and processes related to modern Hikurangi convergent margin initiation are identified to be the main controls on the thermal regime of the Taranaki Basin. Present-day surface heat flow across Taranaki on average is 59 mW/m2, but varies by as much as 30 mW/m2 due to the difference in crustal heat generation between mafic and felsic basement terranes alone. In addition, changes in mantle heat advection, tectonic subsidence, crustal thickening and basin inversion, together with related sedimentary processes result in variability of up to 10 mW/m2. Modelling suggests that increased heating of the upper crust due to additional mantle heat advection following the onset of subduction is an ongoing process and heating has only recently begun to reach the surface, explaining the relatively low surface heat flow. We propose that the depth of the subducted slab and related mantle convection processes control the thermal and structural regimes in the Taranaki Basin. The thermal effects of the subduction initiation process are modified and overprinted by the thickness, structure and composition of the lithosphere.

Kroeger, K. F.; Funnell, R. H.; Nicol, A.; Fohrmann, M.; Bland, K. J.; King, P. R.

2013-04-01

142

An inverse heat conduction method for simultaneously estimating spatially varying thermal conductivity and heat capacity per unit volume under the conditions of a flash method type of experiment is developed. The unknown thermal properties are assumed to vary only in the space dimension normal to the slab sample and are modeled with piecewise linear representations. Lacking in the literature are

G. P. Flach; M. N. zi?ik

1989-01-01

143

Heat pipe embedded AlSiC plates for high conductivity - low CTE heat spreaders

Heat pipe embedded aluminum silicon carbide (AlSiC) plates are innovative heat spreaders that provide high thermal conductivity and low coefficient of thermal expansion (CTE). Since heat pipes are two phase devices, they demonstrate effective thermal conductivities ranging between 10,000 and 200,000 W\\/m-K, depending on the heat pipe length. Installing heat pipes into an AlSiC plate dramatically increases the plate's effective

J. Weyant; S. Garner; M. Johnson; M. Occhionero

2010-01-01

144

A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in an internally manifolded planar solid oxide electrolysis cell (SOEC) stack. This design is being evaluated at the Idaho National Laboratory for hydrogen production from nuclear power and process heat. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, operating potential, steam-electrode gas composition, oxygen-electrode gas composition, current density and hydrogen production over a range of stack operating conditions. Single-cell and five-cell results will be presented. Flow distribution through both models is discussed. Flow enters from the bottom, distributes through the inlet plenum, flows across the cells, gathers in the outlet plenum and flows downward making an upside-down ''U'' shaped flow pattern. Flow and concentration variations exist downstream of the inlet holes. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, oxygen-electrode and steam-electrode current density, and contact resistance from the base case are presented. Contour plots of local electrolyte temperature, current density, and Nernst potential indicate the effects of heat transfer, reaction cooling/heating, and change in local gas composition. Results are discussed for using this design in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production, cell thermal efficiency, cell electrical efficiency, and Gibbs free energy are discussed and reported herein.

Grant L. Hawkes; James E. O'Brien; Greg Tao

2011-11-01

145

Heat conduction in relativistic neutral gases revisited

The kinetic theory of dilute gases to first order in the gradients yields linear relations between forces and fluxes. The heat flux for the relativistic gas has been shown to be related not only to the temperature gradient but also to the density gradient in the representation where number density, temperature and hydrodynamic velocity are the independent state variables. In this work we show the calculation of the corresponding transport coefficients from the full Boltzmann equation and compare the magnitude of the relativistic correction.

A. L. Garcia-Perciante; A. R. Mendez

2010-09-30

146

A new type of 3D lanthanide(III) metal-organic framework directly constructed by double-chain motifs was synthesized. It shows a proton conductivity of 1.6 10(-5) S cm(-1) at 75 C at 97% RH, and tunable emission including white light. PMID:24407038

Zhu, Min; Hao, Zhao-Min; Song, Xue-Zhi; Meng, Xing; Zhao, Shu-Na; Song, Shu-Yan; Zhang, Hong-Jie

2014-02-21

147

The AP1000 is an 1100 MWe advanced nuclear power plant that uses passive safety features to enhance plant safety and to provide significant and measurable improvements in plant simplification, reliability, investment protection and plant costs. The AP1000 received final design approval from the US-NRC in 2004. The AP1000 design is based on the AP600 design that received final design approval in 1999. Wherever possible, the AP1000 plant configuration and layout was kept the same as AP600 to take advantage of the maturity of the design and to minimize new design efforts. As a result, the two-loop configuration was maintained for AP1000, and the containment vessel diameter was kept the same. It was determined that this significant power up-rate was well within the capability of the passive safety features, and that the safety margins for AP1000 were greater than those of operating PWRs. A key feature of the passive core cooling system is the passive residual heat removal heat exchanger (PRHR HX) that provides decay heat removal for postulated LOCA and non-LOCA events. The PRHR HX is a C-tube heat exchanger located in the in-containment refueling water storage tank (IRWST) above the core promoting natural circulation heat removal between the reactor cooling system and the tank. Component testing was performed for the AP600 PRHR HX to determine the heat transfer characteristics and to develop correlations to be used for the AP1000 safety analysis codes. The data from these tests were confirmed by subsequent integral tests at three separate facilities including the ROSA facility in Japan. Owing to the importance of this component, an independent analysis has been performed using the ATHOS-based computational fluid dynamics computer code PRHRCFD. Two separate models of the PRHR HX and IRWST have been developed representing the ROSA test geometry and the AP1000 plant geometry. Confirmation of the ROSA test results were used to validate PRHRCFD, and the AP1000 plant model was used to confirm the heat removal capacity for the full-sized heat exchanger. The results of these simulations show that the heat removal capacity of the PRHR HX is conservatively represented in the AP1000 safety analyses. (authors)

Schwall, James R.; Karim, Naeem U.; Thakkar, Jivan G.; Taylor, Creed; Schulz, Terry; Wright, Richard F. [Westinghouse Electric Company P.O. Box 355, Pittsburgh, PA 15230-0355 (United States)

2006-07-01

148

Cascade variable-conductance heat pipe (A0076)

NASA Technical Reports Server (NTRS)

The objective is to verify the capability of a cascade variable conductance heat pipe (CVCHP) system to provide precise temperature control of long life spacecraft without the need for a feedback heater or other power sources for temperature adjustment under conditions of widely varying power input and ambient environment. Solar energy is the heat source and space the heat sink for thermally loading two series connected variable conductance heat pipes. Electronics and power supply equipment requirements are minimal. A 7.5 V lithium battery supplies the power for thermistor type temperature sensors for monitoring system performance, and a 28 V lithium battery supplies power for valve actuation.

Grote, M. G.; Calhoun, L. D., II

1984-01-01

149

Three-dimensional (3D) subsurface imaging by using inversion of data obtained from the very early time electromagnetic system (VETEM) was discussed. The study was carried out by using the distorted Born iterative method to match the internal nonlinear property of the 3D inversion problem. The forward solver was based on the total-current formulation bi-conjugate gradient-fast Fourier transform (BCCG-FFT). It was found that the selection of regularization parameter follow a heuristic rule as used in the Levenberg-Marquardt algorithm so that the iteration is stable.

Wang, G.L.; Chew, W.C.; Cui, T.J.; Aydiner, A.A.; Wright, D.L.; Smith, D.V.

2004-01-01

150

NASA Technical Reports Server (NTRS)

A Fourier-Chebyshev pseudospectral method for solving steady 3D Navier-Stokes equations in cylindrical cavities is presented and discussed. The general method is pseudo-unsteady and uses a semi-implicit finite difference scheme for the time discretization. The generalized ADI (Alternating Direction Implicit) procedure is then applied to reduce the problem to a successive solution of one-dimensional problems. The spatial approximation uses a Fourier-Galerkin approximation in the periodic direction and a Chebyshev-collocation approximation in the other directions. Difficulties related to the pressure are surmounted by using the artifical compressibility method. A suitable variable change was chosen to avoid the problem of singularity at the axis generated by cylindrical coordinates. The method is first tested on an advection-diffusion equation and then on the Navier-Stokes equations. Finally, the method is illustrated by a convection problem of a differentially heated fluid.

Pulicani, J. P.; Ouazzani, J.

1991-01-01

151

Electrical conductivity of rocks in the heating and cooling cycle

Summary The values of the electrical conductivity, recorded during the heating and cooling cycle, of eclogites and basalts are compared. The observed difference in the values is explained by reversible and irreversible changes which take place in the samples.

Marcela Lastovickov; F. Jank

1978-01-01

152

Experimental evidence of hyperbolic heat conduction in processed meat

The objective of this paper is to present experimental evidence of the wave nature of heat propagation in processed meat and to demonstrate that the hyperbolic heat conduction model is an accurate representation, on a macroscopic level, of the heat conduction process in such biological material. The value of the characteristic thermal time of a specific material, processed bologna meat, is determined experimentally. As a part of the work different thermophysical properties are also measured. The measured temperature distributions in the samples are compared with the Fourier results and significant deviation between the two is observed, especially during the initial stages of the transient conduction process. The measured values are found to match the theoretical non-Fourier hyperbolic predictions very well. The superposition of waves occurring inside the meat sample due to the hyperbolic nature of heat conduction is also proved experimentally. 14 refs., 7 figs., 2 tabs.

Mitra, K.; Kumar, S.; Vedavarz, A.; Moallemi, M.K. [Polytechnic Univ., Brooklyn, NY (United States)

1995-08-01

153

Hierarchical Bayesian Models for Inverse Problems in Heat Conduction

inverse problems in heat conduction with consideration of uncertainties in the measured temperature data, temperature sensor locations and thermophysical properties are addressed using a Bayesian statistical variables is deduced from temperature measurements. Hierarchical Bayesian models are adopted to relax

Zabaras, Nicholas J.

154

Ballistic heat conduction and mass disorder in one dimension.

It is well-known that in the disordered harmonic chain, heat conduction is subballistic and the thermal conductivity (?) scales asymptotically as lim(L--> ?) ? ? L(0.5) where L is the chain length. However, using the nonequilibrium Green's function (NEGF) method and analytical modelling, we show that there exists a critical crossover length scale (LC) below which ballistic heat conduction (? ? L) can coexist with mass disorder. This ballistic-to-subballistic heat conduction crossover is connected to the exponential attenuation of the phonon transmittance function ? i.e. ?(?, L) = exp[-L/?(?)], where ? is the frequency-dependent attenuation length. The crossover length can be determined from the minimum attenuation length, which depends on the maximum transmitted frequency. We numerically determine the dependence of the transmittance on frequency and mass composition as well as derive a closed form estimate, which agrees closely with the numerical results. For the length-dependent thermal conductance, we also derive a closed form expression which agrees closely with numerical results and reproduces the ballistic to subballistic thermal conduction crossover. This allows us to characterize the crossover in terms of changes in the length, mass composition and temperature dependence, and also to determine the conditions under which heat conduction enters the ballistic regime. We describe how the mass composition can be modified to increase ballistic heat conduction. PMID:25077430

Ong, Zhun-Yong; Zhang, Gang

2014-08-20

155

A study of temperature distributions due to conduction reservoir heating

A STUDY OF TEMPERATURE DISTRIBUTIONS DUE TO CONDUCTION RESERVOIR HEATING A Thesis by CHARLES RICHARD CONNAUGHTON Submitted to the Graduate College of Texas ARM University in partial fulfillment of the requirement for the degree of MASTER... OF SCIENCE January 1969 MAJOR SUBJECT: PETROLEUM ENGINEERING A STUDY OF TEMPERATURE DISTRIBUTIONS DUE TO CONDUCTION RESERVOIR HEATING A Thesis by CHARLES RICHARD CONNAUGHTON Approved as to style and content by: Chairman of Committee (Head of Departm...

Connaughton, Charles Richard

1969-01-01

156

LavaSIM: the effect of heat transfer in 3D on lava flow characteristics (Invited)

NASA Astrophysics Data System (ADS)

Characteristics of lava flow are governed by many parameters like lava viscosity, effusion rate, ground topography, etc. The accuracy and applicability of lava flow simulation code is evaluated whether the numerical simulation can reproduce these features quantitatively, which is important from both strategic and scientific points of views. Many lava flow simulation codes are so far proposed, and they are classified into two categories, i.e., the deterministic and the probabilistic models. LavaSIM is one of the former category models, and has a disadvantage of time consuming. But LavaSIM can solves the equations of continuity, motion, energy by step and has an advantage in the calculation of three-dimensional analysis with solid-liquid two phase flow, including the heat transfer between lava, solidified crust, air, water and ground, and three-dimensional convection in liquid lava. In other word, we can check the detailed structure of lava flow by LavaSIM. Therefore, this code can produce both channeled and fan-dispersive flows. The margin of the flow is solidified by cooling and these solidified crusts control the behavior of successive lava flow. In case of a channel flow, the solidified margin supports the stable central main flow and elongates the lava flow distance. The cross section of lava flow shows that the liquid lava flows between solidified crusts. As for the lava extrusion flow rate, LavaSIM can include the time function as well as the location of the vents. In some cases, some parts of the solidified wall may be broken by the pressure of successive flow and/or re-melting. These mechanisms could characterize complex features of the observed lava flows at many volcanoes in the world. To apply LavaSIM to the benchmark tests organized by V-hub is important to improve the lava flow evaluation technique.

Fujita, E.

2013-12-01

157

Use of Spreadsheets in Solving Heat Conduction Problems in Fins

NSDL National Science Digital Library

Excel is an effective and inexpensive tool available on all computers equipped with Microsoft Office. This software has the necessary functions for solving a large class of engineering problems, including those related to heat transfer. This paper provides several examples to demonstrate the application of Excel in solving problems involving one-dimensional heat conduction in various fin configurations. It provides formulas for the temperature distribution and heat transfer for several different fin profiles.

Karimi, Amir

2011-04-04

158

Weak coupling limits in a stochastic model of heat conduction

We study the Brownian momentum process, a model of heat conduction, weakly coupled to heat baths. In two different settings of weak coupling to the heat baths, we study the non-equilibrium steady state and its proximity to the local equilibrium measure in terms of the strength of coupling. For three and four site systems, we obtain the two-point correlation function and show it is generically not multilinear.

Frank Redig; Kiamars Vafayi

2011-01-14

159

Stationary non-equilibrium properties for a heat conduction model

We consider a stochastic heat conduction model for solids composed by N interacting atoms. The system is in contact with two heat baths at different temperature $T_\\ell$ and $T_r$. The bulk dynamics conserve two quantities: the energy and the deformation between atoms. If $T_\\ell \

Cedric Bernardin

2008-08-05

160

Heat conduction in relativistic systems: alternatives and perspectives

The non-equilibrium thermodynamics of relativistic systems have a rich phenomenology. The simplest phenomenon in the class of dissipative processes is that of heat. This letter presents a brief summary of the efforts made to tackle the problem of relativistic heat conduction. In particular, we focus on the multi-fluid approach to relativistic dissipation.

C. S. Lopez-Monsalvo

2010-11-30

161

Heat conduction models for the transient hot wire technique

In the first part of this paper, we present a transient model of radial heat conduction in infinitely large media to model the hot-wire technique. Pulse and a Heaviside heat sources are investigated. The general instantaneous solution is generated using Green's functions and is computed with a hybrid method. Thus, the estimation of the thermal properties is possible using a

Mohamed B. H. Sassi; Dos Santos; Zaqueu E. Da Silva; Jose M. Gurgel; Jose P. A. Junior

2009-01-01

162

Initial and boundary value problems of hyperbolic heat conduction

This is a study on the initial and boundary value problem of a symmetric hyperbolic system which is related to the conduction\\u000a of heat in solids at low temperatures. The nonlinear system consists of a conservation equation for the energy density e and a balance equation for the heat flux , where e and are the four basic fields

Wolfgang Dreyer; Matthias Kunik

1999-01-01

163

Conductive heat transfer in salt gradient stabilized solar ponds

This paper deals with heat transfer in salt gradient solar ponds. Spatial variations in thermal properties have been considered and the resulting one-dimensional heat conduction equation with a source term is solved explicitly to obtain a closed form mathematical expression for temperature distribution in the non-convecting zone of the solar pond. The present analysis is not restricted to any one

Thakus

1983-01-01

164

Magnonic domain wall heat conductance in ferromagnetic wires.

We present a theoretical study of magnon-mediated heat transport in electrically insulating ferromagnetic wires containing a domain wall (DW). In the regime of validity of continuum micromagnetism, a DW is found to have no effect on the heat conductance. However, spin waves are found to be reflected by DWs with widths of a few lattice spacings, which is associated with emergence of an additional spin wave bound state. The resulting DW heat conductance should be significant for thin films of yttrium iron garnet with sharply defined magnetic domains. PMID:23002771

Yan, Peng; Bauer, Gerrit E W

2012-08-24

165

Single-photon heat conduction in electrical circuits

We study photonic heat conduction between two resistors coupled weakly to a single superconducting microwave cavity. At low enough temperature, the dominating part of the heat exchanged between the resistors is transmitted by single-photon excitations of the fundamental mode of the cavity. This manifestation of single-photon heat conduction should be experimentally observable with the current state of the art. Our scheme can possibly be utilized in remote interference-free temperature control of electric components and environment engineering for superconducting qubits coupled to cavities.

P. J. Jones; J. A. M. Huhtamki; K. Y. Tan; M. Mttnen

2011-07-14

166

An Experiment in Heat Conduction Using Hollow Cylinders

ERIC Educational Resources Information Center

An experimental apparatus was designed and built to allow students to carry out heat conduction experiments in hollow cylinders made of different materials, as well as to determine the thermal conductivity of these materials. The evolution of the temperature difference between the inner and outer walls of the cylinder as a function of time is

Ortuno, M.; Marquez, A.; Gallego, S.; Neipp, C.; Belendez, A.

2011-01-01

167

Fourier analysis of conductive heat transfer for glazed roofing materials

NASA Astrophysics Data System (ADS)

For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.

Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah; Zakaria, Nor Zaini

2014-07-01

168

Heat Pipe Embedded AlSiC Plates for High Conductivity - Low CTE Heat Spreaders

Heat pipe embedded aluminum silicon carbide (AlSiC) plates are innovative heat spreaders that provide high thermal conductivity and low coefficient of thermal expansion (CTE). Since heat pipes are two phase devices, they demonstrate effective thermal conductivities ranging between 50,000 and 200,000 W/m-K, depending on the heat pipe length. Installing heat pipes into an AlSiC plate dramatically increases the plates effective thermal conductivity. AlSiC plates alone have a thermal conductivity of roughly 200 W/m-K and a CTE ranging from 7-12 ppm/ deg C, similar to that of silicon. An equivalent sized heat pipe embedded AlSiC plate has effective thermal conductivity ranging from 400 to 500 W/m-K and retains the CTE of AlSiC.

Johnson, Matthew (DOE/NNSA Kansas City Plant (United States)); Weyant, J.; Garner, S. (Advanced Cooling Technologies, Inc. (Lancaster, PA (United States)); Occhionero, M. (CPS Technologies Corporation, Norton, MA (United States))

2010-01-07

169

NASA Astrophysics Data System (ADS)

Identifying plume-like structures in an utomatic manner in 3-D mantle convection is a challenging technical problem. A successful method can help immensely in shedding light on the relative contributions from various sources to the surface heat budget and also to understand the dynamics of plumes interacting with each other and with the background flow. We have developed a technique based on wavelets for detecting the coherent structures of plumes in 3-D convection. The wavelets used are second-generation discrete bi-orthonormal wavelets which, in contrast to first-generation wavelets, can be constructed in a spatial domain. Collocation wavelets set up a one-to-one correspondence between the points in physical space and the set of wavelet coefficients. Proper identification of the wavelet basis functions that cover the features of interest, both in scale and position, will automatically yield a reduced representation of these coherent features associated with plumes. We have employed simple thresholding technique to identify plumes in mantle convection problems. We have constructed a user interface to Amira, a visualization software, to allow a user to construct Ip, the set of grid points in physical space, corresponding to the set of wavelet coefficients with absolute value greater than a given threshold value, ?. By plotting these set of points as cubes, we can localize the plume structures. We have demonstrated the feasibility by reconstructing the plumes for different threshold values. We find that we can identify the plumes by keeping around 1% of the full set of wavelet coefficients. From identifying the locations of the plumes, we can also calculate the fraction of surface heat flow due to the cylindrical plumes, as compared to the surrounding network of downwellings and the bulk interior. We have investigated this for a range of Rayleigh numbers from 106 to 109. We have found that wavelets can provide a useful tool for extracting coherent features in mantle convection and can be applied to other types of problems in geophysics, such as geodynamo simulations and earthquake deformation.

Yuen, D. A.; Erlebacher, G.; Dubuffet, F. J.; Vasilyev, O. V.

2002-12-01

170

Thermal conductivity of spin-polarized liquid 3 D. Sawkey, L. Puech and P.E. Wolf

Thermal conductivity of spin-polarized liquid 3 He D. Sawkey, L. Puech and P.E. Wolf Centre de measurements of the thermal conductivity of spin-polarized normal liquid 3He. Using the rapid melting technique transport coefficients (thermal conductivity, viscosity, and spin diffusivity) are better accounted

Paris-Sud XI, Université de

171

Heat conductance in nonlinear lattices at small temperature gradients

This paper proposes a new methodological framework within which the heat conductance in 1D lattices can be studied. The total process of heat conductance is separated into two parts where the first one is the equilibrium process at equal temperatures $T$ of both ends and the second one -- non-equilibrium with the temperature $\\Delta T$ of one end and zero temperature of the other. This approach allows significant decrease of computational time at $\\Delta T \\to 0$. The threshold temperature $T_{\\rm thr}$ is found which scales $T_{\\rm thr}(N) \\sim N^{-3}$ with the lattice size $N$ and by convention separates two mechanisms of heat conductance: phonon mechanism dominates at $T T_{\\rm thr}$. Solitons and breathers are directly visualized in numerical experiments. The problem of heat conductance in non-linear lattices in the limit $\\Delta T \\to 0$ can be reduced to the heat conductance of harmonic lattice with time-dependent stochastic rigidities determined by the equilibrium process at temperature $T$. The detailed analysis is done for the $\\beta$-FPU lattice though main results are valid for one-dimensional lattices with arbitrary potentials.

T. Yu. Astakhova; V. N. Likhachev; G. A. Vinogradov

2010-06-09

172

An analysis is presented to predict the heat transfer characteristics of a plane layer of a semitransparent, high-temperature, porous material which is irradiated by an intense solar flux. A transient, combined conduction and radiation heat transfer model, which is based on a two-flux approximation for the radiation, is used to predict the temperature distribution and heat transfer in the material.

L. K. Matthews; F. P. Incropera; R. Viskanta

1985-01-01

173

Variable Conductance Heat Pipe Performance after Extended Periods of Freezing

NASA Astrophysics Data System (ADS)

Radiators operating in lunar or Martian environments must be designed to reject the maximum heat load at the maximum sink temperature, while maintaining acceptable temperatures at lower powers or sink temperatures. Variable Conductance Heat Pipe (VCHP) radiators can passively adjust to these changing conditions. Due to the presence of non-condensable gas (NCG) within each VCHP, the active condensing section adjusts with changes in either thermal load or sink temperature. In a Constant Conductance Heat Pipe (CCHP) without NCG, it is possible for all of the water to freeze in the condenser, by either sublimation or vaporization. With a dry evaporator, startup is difficult or impossible. Several previous studies have shown that adding NCG suppresses evaporator dryout when the condenser is frozen. These tests have been for relatively short durations, with relatively short condensers. This paper describes freeze/thaw experiments involving a VCHP with similar dimensions to the current reactor and cavity cooling radiator heat pipe designs.

Ellis, Michael C.; Anderson, William G.

2009-03-01

174

Thermally conductive cementitious grout for geothermal heat pump systems

A thermally conductive cement-sand grout for use with a geothermal heat pump system. The cement sand grout contains cement, silica sand, a superplasticizer, water and optionally bentonite. The present invention also includes a method of filling boreholes used for geothermal heat pump systems with the thermally conductive cement-sand grout. The cement-sand grout has improved thermal conductivity over neat cement and bentonite grouts, which allows shallower bore holes to be used to provide an equivalent heat transfer capacity. In addition, the cement-sand grouts of the present invention also provide improved bond strengths and decreased permeabilities. The cement-sand grouts can also contain blast furnace slag, fly ash, a thermoplastic air entraining agent, latex, a shrinkage reducing admixture, calcium oxide and combinations thereof.

Allan, Marita (Old Field, NY)

2001-01-01

175

Heat conduction from a sphere to an infinite external region

The cooling of a sphere by heat conduction to an infinite external region is considered. Both regions are considered to have constant physical parameters with the internal sphere initially at temperature V and the external region initially at temperature zero. Conduction takes place across the boundary so that temperature and heat flux are continuous. Three separate cases involving differences in the thermal diffusivities kappa/sub 1/, kappa/sub 2/, and conductivities K/sub 1/, K/sub 2/ are considered: (1) kappa/sub 1/ = kappa/sub 2/ and K/sub 1/ = K/sub 2/ (2) kappa/sub 1/ not equal to kappa/sub 2/ and K/sub 1/ not equal to K/sub 2/ (3) K/sub 1/ = Infinity. In this latter case, the inner sphere has heat capacity, but zero thermal gradient. In each case, the temperature distributions are obtained as well as the short and long time asymtotic behavior.

Amos, D.E.

1979-07-01

176

NASA Astrophysics Data System (ADS)

Conductive adhesives are found favorable in a wide range of applications including a lead-free solder in micro-chips, flexible and printable electronics and enhancing the performance of energy storage devices. Composite materials comprised of metallic fillers and a polymer matrix are of great interest to be implemented as hybrid conductive adhesives. Here we investigated a cost-effective conductive adhesive material consisting of silver-coated copper as micro-fillers using synchrotron-based three-dimensional (3D) X-ray nano-tomography. The key factors affecting the quality and performance of the material were quantitatively studied in 3D on the nanometer scale for the first time. A critical characteristic parameter, defined as a shape-factor, was determined to yield a high-quality silver coating, leading to satisfactory performance. A `stack-and-screen' mechanism was proposed to elaborate such a phenomenon. The findings and the technique developed in this work will facilitate the future advancement of conductive adhesives to have a great impact in micro-electronics and other applications.Conductive adhesives are found favorable in a wide range of applications including a lead-free solder in micro-chips, flexible and printable electronics and enhancing the performance of energy storage devices. Composite materials comprised of metallic fillers and a polymer matrix are of great interest to be implemented as hybrid conductive adhesives. Here we investigated a cost-effective conductive adhesive material consisting of silver-coated copper as micro-fillers using synchrotron-based three-dimensional (3D) X-ray nano-tomography. The key factors affecting the quality and performance of the material were quantitatively studied in 3D on the nanometer scale for the first time. A critical characteristic parameter, defined as a shape-factor, was determined to yield a high-quality silver coating, leading to satisfactory performance. A `stack-and-screen' mechanism was proposed to elaborate such a phenomenon. The findings and the technique developed in this work will facilitate the future advancement of conductive adhesives to have a great impact in micro-electronics and other applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06068g

Chen-Wiegart, Yu-Chen Karen; Figueroa-Santos, Miriam Aileen; Petrash, Stanislas; Garcia-Miralles, Jose; Wang, Jun

2014-12-01

177

Mechanical control of heat conductivity in molecular chains

NASA Astrophysics Data System (ADS)

We discuss a possibility to control heat conductivity in molecular chains by means of external mechanical loads. To illustrate such possibilities we consider first well-studied one-dimensional chain with degenerate double-well potential of the nearest-neighbor interaction. We consider varying lengths of the chain with fixed number of particles. Number of possible energetically degenerate ground states strongly depends on the overall length of the chain, or, in other terms, on average length of the link between neighboring particles. These degenerate states correspond to mechanical equilibria; therefore, one can say that formation of such structures mimics a process of plastic deformation. We demonstrate that such modification of the chain length can lead to quite profound (almost fivefold) reduction of the heat conduction coefficient. Even more profound effect is revealed for a model with a single-well nonconvex potential. It is demonstrated that in a certain range of constant external forcing, this model becomes effectively double-well and has a multitude of possible states of equilibrium for fixed value of the external load. Due to this degeneracy, the heat-conduction coefficient can be reduced by two orders of magnitude. We suggest a mechanical model of a chain with periodic double-well potential, which allows control of the heat transport. The models considered may be useful for description of heat transfer in biological macromolecules and for control of the heat transport in microsystems. The possibility of the heat transport control in more realistic three-dimensional systems is illustrated by simulation of a three-dimensional model of polymer ?-helix. In this model, the mechanical stretching also brings about the structural inhomogeneity and, in turn, to essential reduction of the heat conductivity.

Savin, A. V.; Gendelman, O. V.

2014-01-01

178

Mechanical control of heat conductivity in molecular chains.

We discuss a possibility to control heat conductivity in molecular chains by means of external mechanical loads. To illustrate such possibilities we consider first well-studied one-dimensional chain with degenerate double-well potential of the nearest-neighbor interaction. We consider varying lengths of the chain with fixed number of particles. Number of possible energetically degenerate ground states strongly depends on the overall length of the chain, or, in other terms, on average length of the link between neighboring particles. These degenerate states correspond to mechanical equilibria; therefore, one can say that formation of such structures mimics a process of plastic deformation. We demonstrate that such modification of the chain length can lead to quite profound (almost fivefold) reduction of the heat conduction coefficient. Even more profound effect is revealed for a model with a single-well nonconvex potential. It is demonstrated that in a certain range of constant external forcing, this model becomes effectively double-well and has a multitude of possible states of equilibrium for fixed value of the external load. Due to this degeneracy, the heat-conduction coefficient can be reduced by two orders of magnitude. We suggest a mechanical model of a chain with periodic double-well potential, which allows control of the heat transport. The models considered may be useful for description of heat transfer in biological macromolecules and for control of the heat transport in microsystems. The possibility of the heat transport control in more realistic three-dimensional systems is illustrated by simulation of a three-dimensional model of polymer ?-helix. In this model, the mechanical stretching also brings about the structural inhomogeneity and, in turn, to essential reduction of the heat conductivity. PMID:24580199

Savin, A V; Gendelman, O V

2014-01-01

179

Heat conduction in one-dimensional aperiodic quantum Ising chains.

The heat conductivity of nonperiodic quantum Ising chains whose ends are connected with heat baths at different temperatures are studied numerically by solving the Lindblad master equation. The chains are subjected to a uniform transverse field h, while the exchange coupling J{m} between the nearest-neighbor spins takes the two values J{A} and J{B} arranged in Fibonacci, generalized Fibonacci, Thue-Morse, and period-doubling sequences. We calculate the energy-density profile and energy current of the resulting nonequilibrium steady states to study the heat-conducting behavior of finite but large systems. Although these nonperiodic quantum Ising chains are integrable, it is clearly found that energy gradients exist in all chains and the energy currents appear to scale as the system size ~N{?}. By increasing the ratio of couplings, the exponent ? can be modulated from ? > -1 to ? < -1 corresponding to the nontrivial transition from the abnormal heat transport to the heat insulator. The influences of the temperature gradient and the magnetic field to heat conduction have also been discussed. PMID:21517475

Li, Wenjuan; Tong, Peiqing

2011-03-01

180

Neutrino Heat Conduction and Inhomogeneities in the Early Universe

NASA Technical Reports Server (NTRS)

Constraints on parameters of inhomogeneous nucteosynthesis, namely, the overdensity and size of baryon lumps, are found by calculatig the blackbody neutrino heat conduction into the lumps, which tends to inflate them away. The scale size for efficient heat conduction is determined by the mean free path lambda of the neutrino, and so we compute lambda in our case of a high-temperature plasma with low chemical potential, and find a general result that many-body effects are unimportant, simplifying the calculation. We find that in the region of interest for nucleosynthesis, neutrino inflation is important for overdensities greater than 10(exp 4).

Heckler, A.; Hogan, C. J.

1993-01-01

181

Application of Genetic Algorithms in Nonlinear Heat Conduction Problems

Genetic algorithms are employed to optimize dimensionless temperature in nonlinear heat conduction problems. Three common geometries are selected for the analysis and the concept of minimum entropy generation is used to determine the optimum temperatures under the same constraints. The thermal conductivity is assumed to vary linearly with temperature while internal heat generation is assumed to be uniform. The dimensionless governing equations are obtained for each selected geometry and the dimensionless temperature distributions are obtained using MATLAB. It is observed that GA gives the minimum dimensionless temperature in each selected geometry. PMID:24695517

Khan, Waqar A.

2014-01-01

182

A mechanical model for Fourier's law of heat conduction

Nonequilibrium statistical mechanics close to equilibrium is a physically satisfactory theory centered on the linear response formula of Green-Kubo. This formula results from a formal first order perturbation calculation without rigorous justification. A rigorous derivation of Fourier's law for heat conduction from the laws of mechanics remains thus a major unsolved problem. In this note we present a deterministic mechanical model of a heat-conducting chain with nontrivial interactions, where kinetic energy fluctuations at the nodes of the chain are removed. In this model the derivation of Fourier's law can proceed rigorously.

David Ruelle

2011-02-27

183

A Mechanical Model for Fourier's Law of Heat Conduction

NASA Astrophysics Data System (ADS)

Nonequilibrium statistical mechanics close to equilibrium is a physically satisfactory theory centered on the linear response formula of Green-Kubo. This formula results from a formal first order perturbation calculation without rigorous justification. A rigorous derivation of Fourier's law for heat conduction from the laws of mechanics remains thus a major unsolved problem. In this note we present a deterministic mechanical model of a heat-conducting chain with nontrivial interactions, where kinetic energy fluctuations at the nodes of the chain are removed. In this model the derivation of Fourier's law can proceed rigorously.

Ruelle, David

2012-05-01

184

Numerical experiments using hierarchical finite element method for nonlinear heat conduction hierarchical finite element method for heat conduction problems over two- or three-dimensional plates. Problems considered are nonlinear because the heat conductivity parameter depends upon the temperature itself

Kaneko, Hideaki

185

MOLECULAR DYNAMICS SIMULATION OF QUASI-BALLISTIC HEAT CONDUCTION IN CARBON NANOTUBES

MOLECULAR DYNAMICS SIMULATION OF QUASI-BALLISTIC HEAT CONDUCTION IN CARBON NANOTUBES J Shiomi. While experimental attempts to characterize heat conduction of carbon nanotubes encounter technical difficulties, the classical molecular dynamics (MD) simulations hold an advantage as the heat conduction

Maruyama, Shigeo

186

Federal Register 2010, 2011, 2012, 2013, 2014

...Circuit Packages Provided With Multiple Heat- Conducting Paths and Products Containing...circuit packages provided with multiple heat-conducting paths and products containing...circuit packages provided with multiple heat-conducting paths and products...

2012-07-05

187

Federal Register 2010, 2011, 2012, 2013, 2014

...Circuit Packages Provided With Multiple Heat- Conducting Paths and Products Containing...Circuit Packages Provided With Multiple Heat-Conducting Paths and Products Containing...circuit packages provided with multiple heat-conducting paths and products...

2012-06-06

188

Tunable heat conduction through coupled Fermi-Pasta-Ulam chains

NASA Astrophysics Data System (ADS)

We conduct a study on heat conduction through coupled Fermi-Pasta-Ulam (FPU) chains by using classical molecular dynamics simulations. Our attention is dedicated to showing how the phonon transport is affected by the interchain coupling. It has been well accepted that the heat conduction could be impeded by the interchain interaction due to the interface phonon scattering. However, recent theoretical and experimental studies suggest that the thermal conductivity of nanoscale materials can be counterintuitively enhanced by the interaction with the substrate. In the present paper, by consecutively varying the interchain coupling intensity, we observed both enhancement and suppression of thermal transport through the coupled FPU chains. For weak interchain couplings, it is found that the heat flux increases with the coupling intensity, whereas in the case of strong interchain couplings, the energy transport is found to be suppressed by the interchain interaction. Based on the phonon spectral energy density method, we attribute the enhancement of the energy transport to the excited phonon modes (in addition to the intrinsic phonon modes), while the upward shift of the high-frequency phonon branch and the interface phonon-phonon scattering account for the suppressed heat conduction.

Su, Ruixia; Yuan, Zongqiang; Wang, Jun; Zheng, Zhigang

2015-01-01

189

Using Markov Chain Monte Carlo Simulation for Heat Conduction Problems

NASA Astrophysics Data System (ADS)

In our Damped Heat Wave (DHW) algorithm for calculation of temperature distribution in a one-dimensional finite medium, the space and time is discretized using N nodal points with steps ?x and ?t. Heat propagates through the medium due to temperature differences between divisions. At any instant of time a certain portion (given by the inner heat transfer coefficient) of the excessive heat energy moves from one division to its neighbour division thus lowering temperature difference between those two divisions. We will show that our DHW algorithm represents a special case of time-space Markov Chain Monte Carlo (MCMC) simulation with a simple random number generator for the redistribution sequence. This is a very unique and distinctive feature. All today existing numerical methods used in heat conduction calculations (e.g. explicit or implicit finite differences method, finite elements methods, etc.) are Markov Chains in time, but not simultaneously in space. We will show that in a general case, when we choose a different random number generator for the redistribution sequence, with randomly chosen neighbor, with the inner heat transfer coefficient also a random number drawn from Gaussian distribution, the MCMC simulation is rapidly converging to the analytical solution of transient heat conduction equation.

Gembarovic, Jozef

2011-10-01

190

Projected heat loads onto the divertor plate in ITER-like tokamaks pose a severe problem. Several somewhat different ideas have been proposed to control the energy flux coming into the SOL: (a) impurity radiation, and (b) formation of a cold neutral gas blanket in front of the target. Here we consider 3D neutral fluid turbulence within the gas blanket regime in

George Vahala; Linda Vahala; Joseph Morrison

1996-01-01

191

Conductive adhesives are found favorable in a wide range of applications including a lead-free solder in micro-chips, flexible and printable electronics and enhancing the performance of energy storage devices. Composite materials comprised of metallic fillers and a polymer matrix are of great interest to be implemented as hybrid conductive adhesives. Here we investigated a cost-effective conductive adhesive material consisting of silver-coated copper as micro-fillers using synchrotron-based three-dimensional (3D) X-ray nano-tomography. The key factors affecting the quality and performance of the material were quantitatively studied in 3D on the nanometer scale for the first time. A critical characteristic parameter, defined as a shape-factor, was determined to yield a high-quality silver coating, leading to satisfactory performance. A 'stack-and-screen' mechanism was proposed to elaborate such a phenomenon. The findings and the technique developed in this work will facilitate the future advancement of conductive adhesives to have a great impact in micro-electronics and other applications. PMID:25474162

Chen-Wiegart, Yu-Chen Karen; Figueroa-Santos, Miriam Aileen; Petrash, Stanislas; Garcia-Miralles, Jose; Wang, Jun

2014-12-18

192

A Monte Carlo solution of heat conduction and Poisson equations

A Monte Carlo method is developed for solving the heat conduction, Poisson, and Laplace equations. The method is based on properties of Brownian motion and Ito processes, the Ito formula for differentiable functions of these processes, and the similarities between the generator of Ito processes and the differential operators of these equations. The proposed method is similar to current Monte

M. Grigoriu

2000-01-01

193

Element-by-element factorization algorithms for heat conduction

NASA Technical Reports Server (NTRS)

Element-by-element solution strategies are developed for transient heat conduction problems. Results of numerical tests indicate the effectiveness of the procedures proposed. The small database requirements and attractive architectural features of the algorithms suggest considerable potential for solving large scale problems.

Hughes, T. J. R.; Winget, J. M.; Park, K. C.

1983-01-01

194

Duality and exact correlations for a model of heat conduction

We study a model of heat conduction with stochastic diffusion of energy. We obtain a dual particle process which describes the evolution of all the correlation functions. An exact expression for the covariance of the energy exhibits long-range correlations in the presence of a current. We discuss the formal connection of this model with the simple symmetric exclusion process.

C. Giardin; J. Kurchan; F. Redig

2006-12-07

195

Aluminum variable-conductive heat pipes of the communication satellites

In NPO PM, Zheleznogorsk of Krasnoyarsk region, Russia created the first variable-conductance heat pipes (VCHP) for maintenance of the thermal behavior of the communication satellite of a type ``SMALLSAT'' in whole (four VCHP), and for thermal control of autonomous devices of an attitude control and stabilization system of the communication satellites of a type ``LUCH.'' Due to the presence of

V. Dvirnyi; O. Zagar; Yu. Golovanov; S. Ermilov; K. Smirnov-Vasiliev; V. Khalimanovich; A. Lekanov; G. Panov; G. Ovechkin; A. Kozlov; F. Sinkovsky

1999-01-01

196

Development of variable conductance heat pipe at ISAC

A detailed study has been carried out on the performance of gas loaded nonwicked hot reservoir variable conductance heat pipes employing S.S.-Acetone-Nitrogen as envelope material, working fluid, and noncondensible gas (NCG) respectively. Effect of NCG reservoir to condenser volume ratio and NCG charge quantity on the temperature controllability and sensitivity to operating temperature level is investigated. Results indicate that the

D. Kumar; P. P. Gupta; H. N. Murthy

1984-01-01

197

The Tonga-Vanuatu Subduction Complex -- a Self-Optimized 3D Slab-Slab-Mantle Heat Pump

NASA Astrophysics Data System (ADS)

Recently published geophysical and geochemical data and increasingly actualistic free subduction models prompted a fresh look at 2 classics hinting, in combination, that a coupled 3D slab-slab-upper mantle interaction (Scholz and Campos, 1995; full citations at URL below) might power the prodigious surface heat dissipation (Lagabrielle et al., 1997) characterizing one of Earth's most remarkable tectonomagmatic systems, the Tonga-Vanuatu Subduction Complex (TVSC). The 3D TVSC includes (1) the kinematically, magmatically, and bathymetrically distinct North Tonga (NT, 14-26 S) and South Vanuatu (SV, 16-23 S) trenches and slabs, (2) the shared NT-SV backarc, and (3) entrained mobile upper mantle (MUM). That Earth's greatest convergence, rollback, and spreading rates; most disseminated spreading (the North Fiji Basin (NFB) ridge swarm); and greatest concentration of aggregate active ridge length coincide in a 1,500 km TVSC can't be accidental. To the north and south, the respective active NT and SV trenches swing abruptly 90 counterclockwise into continuity with the Vitiaz and Hunter fossil trenches, both active in the Late Miocene but now sinistral strike-slip loci standing over long exposed PA and AU slab edges. These 2 active-fossil trench pairs bracket a hot, shallow and geophysically and geochemically exceptional TVSC interior consisting of 2 rapidly spreading backarcs set back-to-back in free sublithospheric communication: The Lau-Havre NT backarc on the east and the ridge-infested SV backarc (NFB) on the west. The NFB and adjacent North Fiji Plateau make up the unplatelike New Hebrides-Fiji Orogen (Bird, 2003). As in the western Aleutians, the NT-Vitiaz and SV-Hunter subduction-to-strike-slip transitions (SSSTs) stand above toroidal fluxes of hot, dry PA and AU MUM driven along-trench and around the free NT and SV slab edges from subslab to supraslab regions by dynamic pressure gradients powered by slab free-fall and induced viscous couplings. These edge flows must converge and mix beneath the shared TVSC backarc, which must then shed a huge advected subslab heat load by maximizing ridge length in the area available. Found at both SSSTs are adakites indicative of a TVSC source laced with slab-edge melt and boninites consistent with flux- melting of hot, dry subslab MUM on entry to the supraslab wedge. Isotopics reveal widespread source mixing of Pacific and Indian MOR end-members. Diverging NT and VS trenches rotate clockwise at extremely high rates about pinning points at and Euler poles near trench-floater intercepts: Louisville Ridge on PA, and West Torres Plateau-D'Entrecasteaux Ridge on AU. In this configuration, the spinning, free-falling NT and SV slabs form a highly coupled self-organized gravity-powered pump pulling hot subslab MUM beneath the TVSC with enough left-over head to power severe transition zone buckling of an 80+ Ma NT (PA) slab also actively extending toward its free edge. Several nonlinear couplings (e.g., temperature-dependent viscosity and slab damage at tightening upper hinges) feedback positively to pump efficiency. The TVSC is but one possible slab-mantle pump partaking of the strong self-optimizing tendency characteristic of all natural flow systems (e.g., Bejan and Lorente, 2006). Slab-mantle pump natural history is now under investigation, as such pumps may have allowed a shrinking post-Pangean Pacific with an unrelenting sublithospheric room problem to relieve itself of excess MUM by making efficient use of available circum-Pacific slab curtain porosity -- a commodity that may have been in very short supply through most of the Cretaceous.

McCreary, J. A.

2008-12-01

198

High temperature electrically conducting ceramic heating element and control system

NASA Technical Reports Server (NTRS)

Improvements were made in both electrode technology and ceramic conductor quality to increase significantly the lifetime and thermal cycling capability of electrically conducting ceramic heater elements. These elements were operated in vacuum, inert and reducing environments as well as oxidizing atmospheres adding to the versatility of the conducting ceramic as an ohmic heater. Using stabilized zirconia conducting ceramic heater elements, a furnace was fabricated and demonstrated to have excellent thermal response and cycling capability. The furnace was used to melt platinum-20% rhodium alloy (melting point 1904 C) with an isothermal ceramic heating element having a nominal working cavity size of 2.5 cm diameter by 10.0 cm long. The furnace was operated to 1940 C with the isothermal ceramic heating element. The same furnace structure was fitted with a pair of main heater elements to provide axial gradient temperature control over a working cavity length of 17.8 cm.

Halbach, C. R.; Page, R. J.

1975-01-01

199

Disparate quasiballistic heat conduction regimes from periodic heat sources on a substrate

We report disparate quasiballistic heat conduction trends for periodic nanoscale line heaters deposited on a substrate, depending upon whether measurements are based on the peak temperature of the heaters or the temperature ...

Zeng, Lingping

200

Heat, Light, and Videotapes: Experiments in Heat Conduction Using Liquid Crystal Film.

ERIC Educational Resources Information Center

Presents a range of experiments in heat conduction suitable for upper-level undergraduate laboratories that make use of heat sensitive liquid crystal film to measure temperature contours. Includes experiments mathematically described by Laplace's equation, experiments theoretically described by Poisson's equation, and experiments that involve

Bacon, Michael E.; And Others

1995-01-01

201

Development of a high capacity variable conductance heat pipe.

NASA Technical Reports Server (NTRS)

The high-capacity, pressure-primed, tunnel-artery wick concept was used in a gas-controlled variable conductance heat pipe. A variety of techniques were employed to control the size of gas/vapor bubbles trapped within the artery. Successful operation was attained with a nominal 6-foot long, 1-inch diameter cold reservoir VCHP using ammonia working fluid and nitrogen control gas. The pipe contained a heat exchanger to subcool the liquid in the artery. Maximum transport capacity with a 46-inch effective length was 1200 watts level (more than 50,000 watt-inches) and 800 watts at 0.5-inch adverse tilt.

Kosson, R.; Hembach, R.; Edelstein, F.; Loose, J.

1973-01-01

202

Correlations and scaling in one-dimensional heat conduction.

We examine numerically the full spatiotemporal correlation functions for all hydrodynamic quantities for the random collision model introduced recently. The autocorrelation function of the heat current, through the Kubo formula, gives a thermal conductivity exponent of 1/3 in agreement with the analytical prediction and previous numerical work. Remarkably, this result depends crucially on the choice of boundary conditions: for periodic boundary conditions (as opposed to open boundary conditions with heat baths) the exponent is approximately 1/2. All primitive hydrodynamic quantities scale with the dynamic critical exponent predicted analytically. PMID:14682932

Deutsch, J M; Narayan, Onuttom

2003-10-01

203

We consider three one-dimensional continuous-time Markov processes on a lattice, each of which models the conduction of heat: the family of Brownian Energy Processes with parameter $m$, a Generalized Brownian Energy Process, and the Kipnis-Marchioro-Presutti process. The hydrodynamic limit of each of these three processes is a parabolic equation, the linear heat equation in the case of the BEP$(m)$ and the KMP, and a nonlinear heat equation for the GBEP($a$). We prove the hydrodynamic limit rigorously for the BEP$(m)$, and give a formal derivation for the GBEP($a$). We then formally derive the pathwise large-deviation rate functional for the empirical measure of the three processes. These rate functionals imply gradient-flow structures for the limiting linear and nonlinear heat equations. We contrast these gradient-flow structures with those for processes describing the diffusion of mass, most importantly the class of Wasserstein gradient-flow systems. The linear and nonlinear heat-equation gradient-flow structures are each driven by entropy terms of the form $-\\log \\rho$; they involve dissipation or mobility terms of order $\\rho^2$ for the linear heat equation, and a nonlinear function of $\\rho$ for the nonlinear heat equation.

Mark A. Peletier; Frank Redig; Kiamars Vafayi

2014-03-19

204

Qualitative aspects in dual-phase-lag heat conduction Ramon Quintanilla1

Qualitative aspects in dual-phase-lag heat conduction Ram´on Quintanilla1 Department of Applied.racke@uni-konstanz.de Abstract: We consider the system of dual-phase-lag heat conduction proposed by Tzou [21]. First, we prove of heat conduction based on Fourier's law predicts infinite heat propagation speed. Heat transmission

Racke, Reinhard

205

Until now, few sp2 carbon materials simultaneously exhibit superior performance for specific surface area (SSA) and electrical conductivity at bulk state. Thus, it is extremely important to make such materials at bulk scale with those two outstanding properties combined together. Here, we present a simple and green but very efficient approach using two standard and simple industry steps to make such three-dimensional graphene-based porous materials at the bulk scale, with ultrahigh SSA (3523?m2/g) and excellent bulk conductivity. We conclude that these materials consist of mainly defected/wrinkled single layer graphene sheets in the dimensional size of a few nanometers, with at least some covalent bond between each other. The outstanding properties of these materials are demonstrated by their superior supercapacitor performance in ionic liquid with specific capacitance and energy density of 231 F/g and 98 Wh/kg, respectively, so far the best reported capacitance performance for all bulk carbon materials. PMID:23474952

Zhang, Long; Zhang, Fan; Yang, Xi; Long, Guankui; Wu, Yingpeng; Zhang, Tengfei; Leng, Kai; Huang, Yi; Ma, Yanfeng; Yu, Ao; Chen, Yongsheng

2013-01-01

206

An eigenvalue method for solving transient heat conduction problems

NASA Technical Reports Server (NTRS)

The eigenvalue method, which has been used by researchers in structure mechanics, is applied to problems in heat conduction. Its formulation is decribed in terms of an examination of transient heat conduction in a square slab. Taking advantage of the availability of the exact solution, we compare the accuracy and other numerical properties of the eigenvalue method with those of existing numerical schemes. The comparsion shows that, overall, the eigenvalue method appears to be fairly attractive. Furthermore, only a few dominant eigenvalues and their corresponding eigenvectors need to be computed and retained to yield reasonably high accuracy. Greater savings are attained in the computation time for a transient problem with long time duration and a large computational domain.

Shih, T. M.; Skladany, J. T.

1983-01-01

207

Kinematic Self-Similar Heat Conducting and Charge Solutions

The objective of this paper is to study the plane symmetric kinematic self-similar heat conducting fluid and charge dust solutions of the Einstein field equations. These solutions are classified according to self-similarity of the first, second, zeroth and infinite kinds with different equations of state. We take the self-similar vector to be tilted, orthogonal and parallel to the fluid flow. For heat conducting fluid, it is found that there exist only \\emph{one} solution in parallel case. In all other possibilities, these solutions reduce to the perfect fluid kinematic self-similar solutions. For charge dust case, we also obtain only \\emph{one} kinematic self-similar solution.

M. Sharif; Wajiha Javed

2010-12-01

208

Comparative evaluation of fuel element heat conduction models

Computer codes that predict thermal-hydraulic performance in light water reactors are found to employ a variety of conduction heat transfer models for the determination of the temperature distribution within fuel elements. The objective of this study was to evaluate, in a consistent manner, the relative merits of these various fuel element conduction heat transfer models by comparing accuracy, speed, and computer storage requirements for calculations performed on selected reference or benchmark problems. Methods of particular interest include: (1) implicit finite difference method (FDM) in COBRA-IIIC; (2) weighted residuals method (WRM) in COBRA-IV; (3) nodal integral method (NIM) in TRAC-PF1; and (4) control volume method (CVM) in RELAP5/MOD1.

Panicker, M.; Dugan, E.T.; Anghaie, S.

1986-01-01

209

Non-steady-state heat conduction in composite walls.

The problem of heat conduction in one-dimensional piecewise homogeneous composite materials is examined by providing an explicit solution of the one-dimensional heat equation in each domain. The location of the interfaces is known, but neither temperature nor heat flux is prescribed there. Instead, the physical assumptions of their continuity at the interfaces are the only conditions imposed. The problem of two semi-infinite domains and that of two finite-sized domains are examined in detail. We indicate also how to extend the solution method to the setting of one finite-sized domain surrounded on both sides by semi-infinite domains, and on that of three finite-sized domains. PMID:24808751

Deconinck, Bernard; Pelloni, Beatrice; Sheils, Natalie E

2014-05-01

210

NASA Astrophysics Data System (ADS)

We present evidence of a drastic renormalization of the optical conductivity of graphene on SrTiO 3 resulting in almost full transparency in the ultraviolet region. These findings are attributed to resonant excitonic effects further supported by ab initio Bethe-Salpeter equation and density functional theory calculations. The (? ,? *) orbitals of graphene and Ti-3 d t2 g orbitals of SrTiO 3 are strongly hybridized and the interactions of electron-hole states residing in those orbitals play dominant role in the graphene optical conductivity. These interactions are present much below the optical band gap of bulk SrTiO 3. These results open a possibility of manipulating interaction strengths in graphene via d orbitals, which could be crucial for optical applications.

Gogoi, Pranjal Kumar; Trevisanutto, Paolo E.; Yang, Ming; Santoso, Iman; Asmara, Teguh Citra; Terentjevs, Aleksandrs; Della Sala, Fabio; Breese, Mark B. H.; Venkatesan, T.; Feng, Yuan Ping; Loh, Kian Ping; Neto, Antonio H. Castro; Rusydi, Andrivo

2015-01-01

211

NASA Technical Reports Server (NTRS)

The paper describes the numerical simulation of hyperbolic heat conduction with convection boundary conditions. The effects of a step heat loading, a sudden pulse heat loading, and an internal heat source are considered in conjunction with convection boundary conditions. Two methods of solution are presened for predicting the transient behavior of the propagating thermal disturbances. In the first method, MacCormack's predictor-corrector method is employed for integrating the hyperbolic system of equations. Next, the transfinite element method, which employs specially tailored elements, is used for accurately representing the transient response of the propagating thermal wave fronts. The agreement between the results of various numerical test cases validate the representative behavior of the thermal wave fronts. Both methods represent hyperbolic heat conduction behavior by effectively modeling the sharp discontinuities of the propagating thermal disturbances.

Glass, David E.; Tamma, Kumar K.; Railkar, Sudhir B.

1989-01-01

212

Micro to Nano Scale Heat Conduction in Thermoelectric Materials

NASA Astrophysics Data System (ADS)

Understanding and controlling heat transfer in solids is very important for increasing the efficiency of thermoelectric materials such as skutterudites, clatharates, superlattices, nanowires, and quantum dots. Although the mechanisms governing the thermal conductivity have been understood for years, a comprehensive theoretical method to calculate heat transfer, particularly at small scales, has not been available. This is mainly due to the complexity of anharmonic processes and phonon boundary scattering. We present a comprehensive theoretical model to calculate the thermal conductivity of thermoelectric materials at small length scales. The approach involves an exact calculation of the reduction of the phonon mean free paths due to boundary scattering and removes the need to solve the Boltzmann equation or to use adjustable terms as in the Callaway or Holland models. The analysis is based on the kinetic theory of transport processes and considers general expressions for dispersion relations, phonon mean free paths, and surface specularity parameters. The results show an excellent agreement with experiments for thin films, nanowires, and superlattices over a wide range of temperature and across multiple length scales. The theoretical approach can further be applied to a wide variety of problems involving the conduction of heat in micro/nanostructured thermoelectrics. This research was funded by the MIT Energy Initiative.

Maldovan, Martin

2011-03-01

213

Fuzzy and interval finite element method for heat conduction problem

Traditional finite element method is a well-established method to solve various problems of science and engineering. Different authors have used various methods to solve governing differential equation of heat conduction problem. In this study, heat conduction in a circular rod has been considered which is made up of two different materials viz. aluminum and copper. In earlier studies parameters in the differential equation have been taken as fixed (crisp) numbers which actually may not. Those parameters are found in general by some measurements or experiments. So the material properties are actually uncertain and may be considered to vary in an interval or as fuzzy and in that case complex interval arithmetic or fuzzy arithmetic has to be considered in the analysis. As such the problem is discretized into finite number of elements which depend on interval/fuzzy parameters. Representation of interval/fuzzy numbers may give the clear picture of uncertainty. Hence interval/fuzzy arithmetic is applied in the finite element method to solve a steady state heat conduction problem. Application of fuzzy finite element method in the said problem gives fuzzy system of linear equations in general. Here new methods have also been proposed to handle such type of fuzzy system of linear equations. Corresponding results are computed and has been reported here.

Sarangam Majumdar; Sukanta Nayak; S. Chakraverty

2012-09-26

214

NASA Astrophysics Data System (ADS)

SummaryMajor factors affecting groundwater flow through fractured rocks include the geometry of each fracture, its properties and the fracture-network connectivity together with the porosity and conductivity of the rock matrix. When modelling fractured rocks this is translated into attaining a characterization of the hydraulic conductivity ( K) as adequately as possible, despite its high heterogeneity. This links with the main goal of this paper, which is to present an improvement of a stochastic inverse model, named as Gradual Conditioning (GC) method, to better characterise K in a fractured rock medium by considering different K stochastic structures, belonging to independent K statistical populations (SP) of fracture families and the rock matrix, each one with its own statistical properties. The new methodology is carried out by applying independent deformations to each SP during the conditioning process for constraining stochastic simulations to data. This allows that the statistical properties of each SPs tend to be preserved during the iterative optimization process. It is worthwhile mentioning that so far, no other stochastic inverse modelling technique, with the whole capabilities implemented in the GC method, is able to work with a domain covered by several different stochastic structures taking into account the independence of different populations. The GC method is based on a procedure that gradually changes an initial K field, which is conditioned only to K data, to approximate the reproduction of other types of information, i.e., piezometric head and solute concentration data. The approach is applied to the sp Hard Rock Laboratory (HRL) in Sweden, where, since the middle nineties, many experiments have been carried out to increase confidence in alternative radionuclide transport modelling approaches. Because the description of fracture locations and the distribution of hydrodynamic parameters within them are not accurate enough, we address the domain by using a pseudo porous media approach, in which fractures are represented by high K zones. This approach has already been proven to be successful in real case studies. Results of the K conditional fields have been compared to those obtained in a scenario where the independence of the different stochastic structures was not fully considered. After performing an uncertainty assessment, we have found that when using additional conditioning data (piezometric head data) and multiple SPs the reproduction of the hydraulic head field is significantly improved and uncertainty is reduced. However, honouring the independence of different SPs does not warrant a decrease of uncertainty but in fact due to a more realistic reproduction of the statistical features uncertainty can be increased.

Llopis-Albert, C.; Capilla, J. E.

2010-09-01

215

Continuing advancements in subsurface electrical resistivity tomography (ERT) are giving the method increasing capability for understanding shallow subsurface properties and processes. The inability of ERT imaging data to uniquely resolve subsurface structure and the corresponding need include constraining information remains one of the greatest limitations, and provides one of the greatest opportunities, for further advancing the utility of the method. In this work we describe and demonstrate a method of incorporating constraining information into an ERT imaging algorithm in the form on discontinuous boundaries, known values, and spatial covariance information. We demonstrate the approach by imaging a uranium-contaminated wellfield at the Hanford Site in southwestern Washington State, USA. We incorporate into the algorithm known boundary information and spatial covariance structure derived from the highly resolved near-borehole regions of a regularized ERT inversion. The resulting inversion provides a solution which fits the ERT data (given the estimated noise level), honors the spatial covariance structure throughout the model, and is consistent with known bulk-conductivity discontinuities. The results are validated with core-scale measurements, and display a significant improvement in accuracy over the standard regularized inversion, revealing important subsurface structure known influence flow and transport at the site.

Johnson, Timothy C.; Versteeg, Roelof J.; Rockhold, Mark L.; Slater, Lee D.; Ntarlagiannis, Dimitrios; Greenwood, William J.; Zachara, John M.

2012-09-17

216

As an important factor affecting the accuracy of the thermal conductivity measurement, systematic (bias) error in the guarded comparative axial heat flow (cut-bar) method was mostly neglected by previous researches. This bias is due primarily to the thermal conductivity mismatch between sample and meter bars (reference), which is common for a sample of unknown thermal conductivity. A correction scheme, based on a finite element simulation of the measurement system, was proposed to reduce the magnitude of the overall measurement uncertainty. This scheme was experimentally validated by applying corrections on four types of sample measurements in which the specimen thermal conductivity is much smaller, slightly smaller, equal and much larger than that of the meter bar. As an alternative to the optimum guarding technique proposed before, the correction scheme can be used to minimize uncertainty contribution from the measurement system with non-optimal guarding conditions. It is especially necessary for large thermal conductivity mismatches between sample and meter bars.

Douglas W. Marshall; Changhu Xing; Charles Folsom; Colby Jensen; Heng Ban

2014-05-01

217

NASA Astrophysics Data System (ADS)

Projected heat loads onto the divertor plate in ITER-like tokamaks pose a severe problem. Several somewhat different ideas have been proposed to control the energy flux coming into the SOL: (a) impurity radiation, and (b) formation of a cold neutral gas blanket in front of the target. Here we consider 3D neutral fluid turbulence within the gas blanket regime in front of the divertor plate and determine the heat flux to the toroidal walls and the divertor plate as a heat front propagates towards the plate. The effect of cavities in the toroidal walls are also determined. The turbulent heat fluxes are compared to those arising if the flow was laminar. The neutral toroidal Mach number is 1.2, while the poloidal Mach number = 0.12. Tmax = 1 eV for the heat front with pmax of 1 torr. The simulations are fully 3D and use the K-epsilon turbulence closure equations are employed. (work supported by DoE and NASA)

Vahala, George; Vahala, Linda; Morrison, Joseph

1996-11-01

218

NASA Technical Reports Server (NTRS)

Analysis of the effective thermal conductivity of ceramic coatings and its relation to the microstructure continued. Results (obtained in Task 1) for the three-dimensional problem of heat conduction in a solid containing an inclusion (or, in particular, cavity - thermal insulator) of the ellipsoidal shape, were further advanced in the following two directions: (1) closed form expressions of H tensor have been derived for special cases of ellipsoidal cavity geometry: spheroid, crack-like spheroidal cavity and needle shaped spheroidal cavity; (2) these results for one cavity have been incorporated to construct heat energy potential for a solid with many spheroidal cavities (in the approximation of non-interacting defects). This problem constitutes a basic building block for further analyses.

Kachanov, Mark

1998-01-01

219

Thermal modeling of a 3-D IC stack consists of three IC layers bonded back-to-face (or face up) is performed. Significant temperature rise in the top layers is projected with the presence of dielectric isolation films between the IC layers. It is found that by inserting electrically isolated thermal through silicon via (TTSV) having Cu core and oxide liner that extends

Santhosh Onkaraiah; Chuan Seng Tan

2010-01-01

220

MHD Simulations of a Moving Subclump with Heat Conduction

High resolution observations of cluster of galaxies by Chandra have revealed the existence of an X-ray emitting comet-like galaxy C153 in the core of cluster of galaxies A2125. The galaxy C153 moving fast in the cluster core has a distinct X-ray tail on one side, obviously due to ram pressure stripping, since the galaxy C153 crossed the central region of A2125. The X-ray emitting plasma in the tail is substantially cooler than the ambient plasma. We present results of two-dimensional magnetohydrodynamic simulations of the time evolution of a subclump like C153 moving in magnetized intergalactic matter. Anisotropic heat conduction is included. We found that the magnetic fields are essential for the existence of the cool X-ray tail, because in non-magnetized plasma the cooler subclump tail is heated up by isotropic heat conduction from the hot ambient plasma and does not form such a comet-like tail.

Naoki Asai; Naoya Fukuda; Ryoji Matsumoto

2004-12-15

221

A Monte Carlo solution of heat conduction and Poisson equations

A Monte Carlo method is developed for solving the heat conduction, Poisson, and Laplace equations. The method is based on properties of Brownian motion and Ito processes, the Ito formula for differentiable functions of these processes, and the similarities between the generator of Ito processes and the differential operators of these equations. The proposed method is similar to current Monte Carlo solutions, such as the fixed random walk, exodus, and floating walk methods, in the sense that it is local, that is, it determines the solution at a single point or a small set of points of the domain of definition of the heat conduction equation directly. However, the proposed and the current Monte Carlo solutions are based on different theoretical considerations. The proposed Monte Carlo method has some attractive features. The method does not require to discretize the domain of definition of the differential equation, can be applied to domains of any dimension and geometry, works for both Dirichlet and Neumann boundary conditions, and provides simple solutions for the steady-state and transient heat equations. Several examples are presented to illustrate the application of the proposed method and demonstrate its accuracy.

Grigoriu, M.

2000-02-01

222

Fabrication and test of a variable conductance heat pipe

NASA Technical Reports Server (NTRS)

A variable conductance heat pipe (VCHP) with feedback control was fabricated with a reservoir-condenser volume ratio of 10 and an axially grooved action section. Tests of the heat transport capability were greater than or equal to the analytical predictions for the no gas case. When gas was added, the pipe performance degraded by 18% at zero tilt as was expected. The placement of the reservoir heater and the test fixture cooling fins are believed to have caused a superheated vapor condition in the reservoir. Erroneously high reservoir temperature indications resulted from this condition. The observed temperature gradients in the reservoir lend support to this theory. The net result was higher than predicted reservoir temperatures. Also, significant increases in minimum heat load resulted for controller set point temperatures higher than 0 C. At 30 C, control within the tolerance band was maintained, but high reservoir heater power was required. Analyses showed that control is not possible for reasonably low reservoir heater power. This is supported by the observation of a significant reservoir heat leak through the condenser.

Lehtinen, A. M.

1978-01-01

223

Numerical Model for Conduction-Cooled Current Lead Heat Loads

Current leads are utilized to deliver electrical power from a room temperature junction mounted on the vacuum vessel to a superconducting magnet located within the vacuum space of a cryostat. There are many types of current leads used at laboratories throughout the world; however, conduction-cooled current leads are often chosen for their simplicity and reliability. Conduction-cooled leads have the advantage of using common materials, have no superconducting/normal state transition, and have no boil-off vapor to collect. This paper presents a numerical model for conduction-cooled current lead heat loads. This model takes into account varying material and fluid thermal properties, varying thicknesses along the length of the lead, heat transfer in the circumferential and longitudinal directions, electrical power dissipation, and the effect of thermal intercepts. The model is validated by comparing the numerical model results to ideal cases where analytical equations are valid. In addition, the XFEL (X-Ray Free Electron Laser) prototype current leads are modeled and compared to the experimental results from testing at DESY's XFEL Magnet Test Stand (XMTS) and Cryomodule Test Bench (CMTB).

White, M.J.; Wang, X.L.; /Fermilab; Brueck, H.D.; /DESY

2011-06-10

224

Thermal conductivity and heat capacity of synthetic fuel components

As part of a group contribution study on the liquid thermal conductivity of synthetic fuel components, experiments were performed to study the effects of dimethyl- and ethyl-group additions to cyclohexane. A transient hot-wire apparatus was used to measure the thermal conductivity of these three fluids between ambient pressure and 10.4 MPa over a temperature range of 300 to 460 K. Thermal conductivities measured with this instrument have been assigned an accuracy of {plus minus} 2% based upon a standard deviation comparison with a toluene standard established by Nieto de Castro et al. (1986). The thermal conductivities and excess thermal conductivities of the naphthenes investigated have been successfully linearized by plotting the data versus reduced density exponentiated to the power of five. By using data previously reported by Perkins (1983) and Li et al. (1984), this linear reduced density method is demonstrated for methyl, dimethyl, and ethyl additions to cyclohexane, as well as methyl and dimethyl additions to benzene. The naphthenes have been shown to have similar intercepts, with slope changes dependent upon the functional group attached to cyclohexane. The aromatics have a less pronounced slope change with additional functional groups attached to the benzene base. This instrument was also used to determine heat capacities, via the thermal diffusivity, to within {plus minus} 10%.

Voss, S.F. (Union Carbide Corp., Hahnville, LA (USA)); Sloan, E.D. (Colorado School of Mines, Golden (USA))

1989-09-01

225

Numerical modeling of thermal conductive heating in fractured bedrock.

Numerical modeling was employed to study the performance of thermal conductive heating (TCH) in fractured shale under a variety of hydrogeological conditions. Model results show that groundwater flow in fractures does not significantly affect the minimum treatment zone temperature, except near the beginning of heating or when groundwater influx is high. However, fracture and rock matrix properties can significantly influence the time necessary to remove all liquid water (i.e., reach superheated steam conditions) in the treatment area. Low matrix permeability, high matrix porosity, and wide fracture spacing can contribute to boiling point elevation in the rock matrix. Consequently, knowledge of these properties is important for the estimation of treatment times. Because of the variability in boiling point throughout a fractured rock treatment zone and the absence of a well-defined constant temperature boiling plateau in the rock matrix, it may be difficult to monitor the progress of thermal treatment using temperature measurements alone. PMID:20550586

Baston, Daniel P; Falta, Ronald W; Kueper, Bernard H

2010-01-01

226

Transient conductive and radiative heat transfer in a rectangular region

Transient conductive and radiative heat transfer in a rectangular region has been studied. The medium is emitting, absorbing, and anisotropically scattering with a refractive index ranging from 1 to 2. It is initially at a uniform temperature and then suddenly exposed to a much colder environment. The solution for temperature distribution involves simultaneously solving the transient energy equation using an implicit finite volume scheme and solving the radiative heat transfer equation using the discrete ordinate method. An 11 x 11 grid and the S{sub 8} method are found to be sufficient for the range of parameters used in this study. Effects of scattering, refractive index and phase function upon the temperature distribution and cooling rates of the medium are investigated.

Yao, C.; Chung, B.T.F.

1999-07-01

227

A note on stability in three-phase-lag heat conduction Ramon Quintanilla1

A note on stability in three-phase-lag heat conduction Ram´on Quintanilla1 Department of Applied.racke@uni-konstanz.de Abstract: In this note we consider two cases in the theory of the heat conduction models with three the heat conduction, the latter also being called theories of second sound, where the propagation of heat

Racke, Reinhard

228

Thermal Conductivity of One-Dimensional Lattices with Self-Consistent Heat Baths

Thermal Conductivity of One-Dimensional Lattices with Self-Consistent Heat Baths: A Heuristic and breathers. KEYWORDS: heat conduction, classical transport, Langevin dynamics DOI: 10.1143/JPSJ.78.044001 1. Introduction Heat conduction exhibits diversified behaviors for one- dimensional lattices in terms of heat

Li, Baowen

229

What is the optimal shape of a fin for one dimensional heat conduction?

What is the optimal shape of a fin for one dimensional heat conduction? Gilles Marck Gr of heat conduction, as well as several numerical illustrations. Keywords: heat conduction, calculus the heat flowing between a solid and a fluid phase, usually called fin. The temperature along a fin

Paris-Sud XI, Université de

230

Non-Fourier heat conduction in a single-walled carbon nanotube: Classical molecular dynamics of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan Non-stationary heat conduction in a single of the simulations exhibit non-Fourier heat conduction where the distinct amount of heat is transported in a wavelike

Maruyama, Shigeo

231

Heat conduction in one-dimensional chains Bambi Hu,1,2

Heat conduction in one-dimensional chains Bambi Hu,1,2 Baowen Li,1 and Hong Zhao1,3 1 Department is whether or not the heat conduction in a one- dimensional 1D chain obeys the Fourier heat law normal thermal conductivity and if so under what condition. The first convincing result of the Fourier heat law

232

NASA Technical Reports Server (NTRS)

A research and development program in variable conductance heat pipe technology is reported. The project involved: (1) theoretical and/or experimental studies in hydrostatics, (2) hydrodynamics, (3) heat transfer into and out of the pipe, (4) fluid selection, and (5) materials compatibility. The development, fabrication, and test of the space hardware resulted in a successful flight of the heat pipe experiment on the OAO-3 satellite. A summary of the program is provided and a guide to the location of publications on the project is included.

Anderson, W. T.; Edwards, D. K.; Eninger, J. E.; Marcus, B. D.

1974-01-01

233

The stationary state and the heat equation for a variant of Davies' model of heat conduction

NASA Astrophysics Data System (ADS)

We study a variant of Davies' model of heat conduction, consisting of a chain of (classical or quantum) harmonic oscillators, whose ends are coupled to thermal reservoirs at different temperatures, and where neighboring oscillators interact via intermediate reservoirs. In the weak coupling limit, we show that a unique stationary state exists, and that a discretized heat equation holds. We give an explicit expression of the stationary state in the case of two classical oscillators. The heat equation is obtained in the hydrodynamic limit, and it is proved that it completely describes the macroscopic behavior of the model.

Artuso, R.; Benza, V.; Frigerio, A.; Gorini, V.; Montaldi, E.

1985-03-01

234

Tunable single-photon heat conduction in electrical circuits

We build on the study of single-photon heat conduction in electronic circuits taking into account the back-action of the superconductor--insulator--normal-metal thermometers. In addition, we show that placing capacitors, resistors, and superconducting quantum interference devices (SQUIDs) into a microwave cavity can severely distort the spatial current profile which, in general, should be accounted for in circuit design. The introduction of SQUIDs also allows for in situ tuning of the photonic power transfer which could be utilized in experiments on superconducting quantum bits.

P. J. Jones; J. A. M. Huhtamki; M. Partanen; K. Y. Tan; M. Mttnen

2012-05-21

235

Pseudo-updated constrained solution algorithm for nonlinear heat conduction

NASA Technical Reports Server (NTRS)

This paper develops efficiency and stability improvements in the incremental successive substitution (ISS) procedure commonly used to generate the solution to nonlinear heat conduction problems. This is achieved by employing the pseudo-update scheme of Broyden, Fletcher, Goldfarb and Shanno in conjunction with the constrained version of the ISS. The resulting algorithm retains the formulational simplicity associated with ISS schemes while incorporating the enhanced convergence properties of slope driven procedures as well as the stability of constrained approaches. To illustrate the enhanced operating characteristics of the new scheme, the results of several benchmark comparisons are presented.

Tovichakchaikul, S.; Padovan, J.

1983-01-01

236

Combined conduction and radiation heat transfer in concentric cylindrical media

NASA Technical Reports Server (NTRS)

The exact radiative transfer expressions for gray and nongray gases which are absorbing, emitting and nonscattering, contained between infinitely long concentric cylinders with black surfaces, are given in local thermodynamic equilibrium. Resulting energy equations due to the combination of conduction and radiation modes of heat transfer, under steady state conditions for gray and nongray media, are solved numerically using the undetermined parameters method. A single 4.3-micron band of CO2 is considered for the nongray problems. The present solutions for gray and nongray gases obtained in the plane-parallel limit (radius ratio approaches to one) are compared with the plane-parallel results reported in the literature.

Pandey, D. K.

1987-01-01

237

Hierarchical Parallelism in Finite Difference Analysis of Heat Conduction

NASA Technical Reports Server (NTRS)

Based on the concept of hierarchical parallelism, this research effort resulted in highly efficient parallel solution strategies for very large scale heat conduction problems. Overall, the method of hierarchical parallelism involves the partitioning of thermal models into several substructured levels wherein an optimal balance into various associated bandwidths is achieved. The details are described in this report. Overall, the report is organized into two parts. Part 1 describes the parallel modelling methodology and associated multilevel direct, iterative and mixed solution schemes. Part 2 establishes both the formal and computational properties of the scheme.

Padovan, Joseph; Krishna, Lala; Gute, Douglas

1997-01-01

238

AdS/CFT Correspondence with Heat Conduction

We study an extension of the gravity dual to a perfect fluid model found by Janik and Peschanski. By relaxing one of the constraints, namely invariance under reflection in the longitudinal direction, we introduce a metric ansatz which includes off-diagonal terms. We also include an $R$-charge following Bak and Janik. We solve the Maxwell-Einstein equations and through holographic renormalization, we show that the off-diagonal components of the bulk metric give rise to heat conduction in the corresponding CFT on the boundary.

James Alsup; Chad Middleton; George Siopsis

2007-06-28

239

In order to assess appropriate cooling solutions for three-dimensional (3D) chip stacks in various uses, it is important to have better understanding of the total thermal resistance of a 3D chip stack. For this purpose, precise thermal resistance measurements and modeling of each component of a 3D chip stack are important. A 3D chip stack is composed of interconnections, silicon

Keiji Matsumoto; Yoichi Taira

2009-01-01

240

Homogeneous Thermal Cloak with Constant Conductivity and Tunable Heat Localization

Invisible cloak has long captivated the popular conjecture and attracted intensive research in various communities of wave dynamics, e.g., optics, electromagnetics, acoustics, etc. However, their inhomogeneous and extreme parameters imposed by transformation-optic method will usually require challenging realization with metamaterials, resulting in narrow bandwidth, loss, polarization-dependence, etc. In this paper, we demonstrate that thermodynamic cloak can be achieved with homogeneous and finite conductivity only employing naturally available materials. It is demonstrated that the thermal localization inside the coating layer can be tuned and controlled robustly by anisotropy, which enables an incomplete cloak to function perfectly. Practical realization of such homogeneous thermal cloak has been suggested by using two naturally occurring conductive materials, which provides an unprecedentedly plausible way to flexibly realize thermal cloak and manipulate heat flow with phonons. PMID:23549139

Han, Tiancheng; Yuan, Tao; Li, Baowen; Qiu, Cheng-Wei

2013-01-01

241

The form of Abstract Molecular dynamics simulations of diffusive-ballistic heat conduction

The form of Abstract Molecular dynamics simulations of diffusive-ballistic heat conduction amount of electrical current in the system. In this study, we have calculated SWNT heat conduction conduction characteristics and to gain fundamental understanding of heat conduction in quasi

Maruyama, Shigeo

242

1 Version Date: October 30, 2001 A Molecular Dynamics Simulation of Heat Conduction in Finite-ku, Tokyo 113-8656, Japan Abstract The heat conduction in finite length single walled carbon nanotubes conductivity compared to the infinitely long nanotubes. The finite length effect on the heat conduction

Maruyama, Shigeo

243

Anomalous Heat Conduction and Anomalous Diffusion in One-Dimensional Systems and Jiao Wang2

Anomalous Heat Conduction and Anomalous Diffusion in One-Dimensional Systems Baowen Li1 and Jiao normal heat conduction obeying the Fourier law (#12; 0) and that superdiffusion ( > 1) implies anomalous heat conduction with a divergent thermal conductivity (#12; > 0). More interestingly, subdiffusion

244

Heat conduction problem of an evaporating liquid T. Barta, V. Janecek, D. Prazak

Heat conduction problem of an evaporating liquid wedge T. B´arta, V. Janecek, D. Praz´ak Abstract, there are only few research publications considering solid substrate heat conduction problem in the contact line. In this paper, we focus on situation with high thermal conductivity liquids ( 1) for which solid heat conduction

Bárta, Tomás

245

NASA Astrophysics Data System (ADS)

We have succeeded in constructing a 3D POM-MOF, {H[Ni(Hbpdc)(H2O)2]2[PW12O40]8H2O}n (H2bpdc=2,2'-bipyridyl-3,3'-dicarboxylic acid), by the controllable self-assembly of H2bpdc, Keggin-anions and Ni2+ ions based on the electrostatic and coordination interactions. Interestingly, Hbpdc- as polydentate organic ligands and Keggin-anion as polydentate inorganic ligands are covalently linked transition-metal nickel at the same time. The title complex represents a new example of introducing the metal N-heterocyclic multi-carboxylic acid frameworks into POMs chemistry. Based on Keggin-anions being immobilized as part of the metal N-heterocyclic multi-carboxylic acid framework, the title complex realizes four approaches in the 1D hydrophilic channel used to engender proton conductivity in MOFs. Its water adsorption isotherm at room temperature and pressure shows that the water content in it was 31 cm3 g-1 at the maximum allowable humidity, corresponding to 3.7 water molecules per unit formula. It exhibits good proton conductivities (10-4-10-3 S cm-1) at 100 C in the relative humidity range 35-98%. The corresponding activation energy (Ea) of conductivity was estimated to be 1.01 eV.

Wei, Meilin; Wang, Xiaoxiang; Sun, Jingjing; Duan, Xianying

2013-06-01

246

A Direct Method for Measuring Heat Conductivity in Intracluster Medium

The inverse Compton scattering of the cosmic microwave background (CMB) radiation with electrons in the intracluster medium which has a temperature gradient, was examined by the third-order perturbation theory of the Compton scattering. A new type of the spectrum distortion of the CMB was found and named as gradient T Sunyaev-Zel'dovich effect (gradT SZE). The spectrum has an universal shape. The spectrum crosses over zero at 326GHz. The sign of the spectrum depends on the relative direction of the line-of-sight to the direction of the temperature gradient. This unique spectrum shape can be used to detect the gradT SZE signal by broad-band or multi-frequency observations of the SZE. The amplitude of the spectrum distortion does not depend on the electron density and is proportional to the heat conductivity. Therefore, the gradT SZE provides an unique opportunity to measure thermally nonequilibrium electron momentum distribution function when the ICM has a temperature gradient and the heat conductivity in the ICM. However, the expected amplitude of the signal is very small. The modifications to the thermal SZE spectrum due to variety of known effects, such as relativistic correction etc., can become problematic when using multi-frequency separation techniques to detect the gradT SZE signal.

Makoto Hattori; Nobuhiro Okabe

2005-02-09

247

Heating, conduction and minimum temperatures in cooling flows

There is mounting observational evidence from Chandra for strong interaction between keV gas and AGN in cooling flows. It is now widely accepted that the temperatures of cluster cores are maintained at a level of 1 keV and that the mass deposition rates are lower than earlier ROSAT/Einstein values. Recent theoretical results suggest that thermal conduction can be very efficient even in magnetized plasmas. Motivated by these discoveries, we consider a ``double heating model'' which incorporates the effects of simultaneous heating by both the central AGN and thermal conduction from the hot outer layers of clusters. Using hydrodynamical simulations, we demonstrate that there exists a family of solutions that does not suffer from the cooling catastrophe. In these cases, clusters relax to a stable final state, which is characterized by minimum temperatures of order 1 keV and density and temperature profiles consistent with observations. Moreover, the accretion rates are much reduced, thereby reducing the need for excessive mass deposition rates required by the standard cooling flow models.

Mateusz Ruszkowski; Mitchell C. Begelman

2002-08-12

248

High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems

NASA Astrophysics Data System (ADS)

In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling converter provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) is under development to allow multiple stops and restarts of the Stirling engine. The status of the ongoing effort in developing this technology is presented in this paper. An earlier, preliminary design had a radiator outside the Advanced Stirling Radioisotope Generator (ASRG) casing, used NaK as the working fluid, and had the reservoir located on the cold side adapter flange. The revised design has an internal radiator inside the casing, with the reservoir embedded inside the insulation. A large set of advantages are offered by this new design. In addition to reducing the overall size and mass of the VCHP, simplicity, compactness and easiness in assembling the VCHP with the ASRG are significantly enhanced. Also, the permanently elevated temperatures of the entire VCHP allows the change of the working fluid from a binary compound (NaK) to single compound (Na). The latter, by its properties, allows higher performance and further mass reduction of the system. Preliminary design and analysis shows an acceptable peak temperature of the ASRG case of 140 C while the heat losses caused by the addition of the VCHP are 1.8 W.

Tarau, Calin; Walker, Kara L.; Anderson, William G.

2009-03-01

249

We examine the non-equilibrium radiative heat transfer between a plate and finite cylinders and cones, making the first accurate theoretical predictions for the total heat transfer and the spatial heat flux profile for three-dimensional compact objects including corners or tips. We find qualitatively different scaling laws for conical shapes at small separations, and in contrast to a flat\\/slightly-curved object, a

Alexander P. McCauley; M. T. Homer Reid; Matthias Krger; Steven G. Johnson

2011-01-01

250

NASA Astrophysics Data System (ADS)

Electromagnetic induction (EMI) systems enable the non-invasive spatial characterization of soil structural and hydrogeological variations, since the measured apparent electrical conductivity (ECa) can be related to changes in soil moisture, soil water, clay content and/or salinity. Due to the contactless operation, ECa maps of relatively large areas, i.e. field to (small) catchment scale, can be measured in reasonably short times. A multi-configuration EMI system with one electromagnetic field transmitter and various receivers with different offsets provide simultaneous ECa measurements that are representative of different sensing depths. Unfortunately, measured ECa values can only be considered as qualitative values due to external influences like the operator, cables or other metal objects. Of course, a better vertical characterization of the subsurface is possible when quantitative measurement values could be obtained. To obtain such quantitative ECa values, the measured EMI apparent conductivities are calibrated using a linear regression approach with predicted apparent conductivities obtained from a Maxwell-based full-solution forward model using inverted electrical resistivity tomography (ERT) data as input. These calibrated apparent conductivities enable a quantitative multi-layer-inversion to resolve for the electrical conductivity of certain layers. To invert for a large scale three-layer model, a one-dimensional (1D) shuffled-complex-evolution inversion scheme was parallelized and run on JUROPA - one of the supercomputers of the Forschungszentrum Jlich. This novel inversion routine was applied to calibrated electromagnetic induction data acquired at the Selhausen test site (Germany), which has a size of about 190 x 70 m. The test site is weakly inclined and a distinct gradient in soil texture is present with considerably higher gravel content at the upper part of the field. Parallel profiles with approximately three meter distance were measured using three different coil offsets in HCP and VCP measurement modes. This resulted in six high spatial resolution data sets of approximately 60000 measurements with different sensing depths. A 5 m block-kriging was applied to all six data sets to re-grid the sampling points on the same regular grid. For each grid node, the six measured apparent conductivities were used in a three-layer inversion. The three-layer inversion results of electrical conductivity thus obtained were used to derive a three-dimensional (3D) model of subsurface heterogeneity, which clearly indicated lateral and vertical conductivity changes of the subsurface that are related to changes in soil texture and soil water content.

von Hebel, Christian; Rudolph, Sebastian; Huisman, Johan A.; van der Kruk, Jan; Vereecken, Harry

2013-04-01

251

Variable Conductance Heat Pipes for Radioisotope Stirling Systems

NASA Astrophysics Data System (ADS)

In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) was designed to allow multiple stops and restarts of the Stirling engine. A VCHP was designed for the Advanced Stirling Radioisotope Generator, with a 850 C heater head temperature. The VCHP turns on with a ?T of 30 C, which is high enough to not risk standard ASRG operation but low enough to save most heater head life. This VCHP has a low mass, and low thermal losses for normal operation. In addition to the design, a proof-of-concept NaK VCHP was fabricated and tested. While NaK is normally not used in heat pipes, it has an advantage in that it is liquid at the reservoir operating temperature, while Na or K alone would freeze. The VCHP had two condensers, one simulating the heater head, and the other simulating the radiator. The experiments successfully demonstrated operation with the simulated heater head condenser off and on, while allowing the reservoir temperature to vary over 40 to 120 C, the maximum range expected. In agreement with previous NaK heat pipe tests, the evaporator ?T was roughly 70 C, due to distillation of the NaK in the evaporator.

Anderson, William G.; Tarau, Calin

2008-01-01

252

Suppressed 3D conductivity in Mn doped Cu0.5Tl0.5Ba2Ca2-yMnyCu3O10-? superconductors

NASA Astrophysics Data System (ADS)

We have synthesised Mn-doped Cu0.5Tl0.5Ba2(Ca2-yMny)Cu3O10-? superconducting samples and studied their Fluctuation Induced Conductivity (FIC) analysis. The Tc(R = 0) and magnitude of diamagnetism are suppressed with increased Mn-doping in the final compound. FIC analyses have shown a suppression of 3D Lawrence and Doniach (LD) regime and a significant enhancement of 2D LD regime of Mn-doping of y = 0.35. In the sample with Mn-doping of y = 0.5, the 3D LD regime vanishes altogether and only 2D LD regime is observed, showing the confinement of superconductivity in the two dimensional planes. The coherence length along the c-axis and the Fermi velocity of the carriers are suppressed with increased Mn doping. Using the Ginzburg-Landau (GL) number [NG] and GL equations, the thermodynamic critical magnetic field Bc(0), the lower critical field Bc1(0), the upper critical field Bc2(0), the critical current density Jc(0), and penetration depth ?p.d are determined. The values of critical fields Bc(0) and Bc1(0) increases, despite suppression in the Tc(R = 0) with increased Mn-doping. The values of Jc(0), the penetration depth ?p.d, and inter-layer coupling are suppressed with enhanced Mn-doping. These observations suggested that Mn ions act as sub-nano-scale pinning centers between the CuO2 planes and their presence at the Ca-sites promote the de-coupling of CuO2 planes.

Qurat-ul-Ain, Khan, Nawazish A.

2013-04-01

253

Heat conduction through a trapped solid: effect of structural changes on thermal conductance

We study the conduction of heat across a narrow solid strip trapped by an external potential and in contact with its own liquid. Structural changes, consisting of addition and deletion of crystal layers in the trapped solid, are produced by altering the depth of the confining potential. Nonequilibrium molecular dynamics simulations and, wherever possible, simple analytical calculations are used to obtain the thermal resistance in the liquid, solid and interfacial regions (Kapitza or contact resistance). We show that these layering transitions are accompanied by sharp jumps in the contact thermal resistance. Dislocations, if present, are shown to increase the thermal resistance of the strip drastically.

Debasish Chaudhuri; Abhishek Chaudhuri; Surajit Sengupta

2007-03-20

254

NASA Astrophysics Data System (ADS)

The European Molasse Basin is a wedge shaped Tertiary foreland basin situated at the northern front of the European Alps. The adjoining Alps consists of tectonic nappes composed of mostly limestone, sandstone and shale stacked since the Cretaceous. This nappe structures are disrupted by uplifted crystalline cores, of which the Tauern Body is a prominent example. The basin itself, filled with clastic sediments (the Molasse), is underlain by Mesozoic sedimentary successions and a crystalline crust of Paleozoic age. The Mesozoic sediments include the Upper Jurassic karstified aquifer (Malm), which is intensively used for geothermal energy production these days. Looking on the temperature distribution in the basin area, a distinct negative thermal anomaly can be found in the southeast of Munich within the Malm aquifer, which is poorly understood so far but is of big relevance for the geothermal energy production in this area. With our study we aim to explain this thermal anomaly by investigating the structure of the basin and the temperature driving processes therein. Therefore, we used a data based lithospheric-scale 3D structural model of the basin and the adjacent Alpine area and calculated the present day conductive thermal field. Our results indicate that the pronounced negative thermal anomaly in the Malm aquifer is controlled by the position and the shape of the Tauern Body within the Alpine mass and the thermal conductivity contrast between the crystalline material of the Tauern Body and the Calcareous Alps.

Przybycin, Anna M.; Scheck-Wenderoth, Magdalena; Schneider, Michael

2014-05-01

255

Federal Register 2010, 2011, 2012, 2013, 2014

...Certain Integrated Circuit Packages Provided with Multiple Heat- Conducting Paths and Products Containing Same; Commission...of certain integrated circuit packages provided with multiple heat-conducting paths and products containing same by reason...

2012-12-12

256

We examine the non-equilibrium radiative heat transfer between a plate and finite cylinders and cones, making the first accurate theoretical predictions for the total heat transfer and the spatial heat flux profile for three-dimensional compact objects including corners or tips. We find qualitatively different scaling laws for conical shapes at small separations, and in contrast to a flat/slightly-curved object, a sharp cone exhibits a local \\emph{minimum} in the spatially resolved heat flux directly below the tip. The method we develop, in which a scattering-theory formulation of thermal transfer is combined with a boundary-element method for computing scattering matrices, can be applied to three-dimensional objects of arbitrary shape.

McCauley, Alexander P; Krger, Matthias; Johnson, Steven G

2011-01-01

257

Efficient linear and nonlinear heat conduction with a quadrilateral element

NASA Technical Reports Server (NTRS)

A method is presented for performing efficient and stable finite element calculations of heat conduction with quadrilaterals using one-point quadrature. The stability in space is obtained by using a stabilization matrix which is orthogonal to all linear fields and its magnitude is determined by a stabilization parameter. It is shown that the accuracy is almost independent of the value of the stabilization parameter over a wide range of values; in fact, the values 3, 2 and 1 for the normalized stabilization parameter lead to the 5-point finite difference, 9-point finite difference and fully integrated finite element operators, respectively, for rectangular meshes; numerical experiments reported here show that the three have identical rates of convergence in the L2 norm. Eigenvalues of the element matrices, which are needed for stability limits, are also given. Numerical applications are used to show that the method yields accurate solutions with large increases in efficiency, particularly in nonlinear problems.

Liu, W. K.; Belytschko, T.

1984-01-01

258

Application of the boundary element method to transient heat conduction

NASA Technical Reports Server (NTRS)

An advanced boundary element method (BEM) is presented for the transient heat conduction analysis of engineering components. The numerical implementation necessarily includes higher-order conforming elements, self-adaptive integration and a multiregion capability. Planar, three-dimensional and axisymmetric analyses are all addressed with a consistent time-domain convolution approach, which completely eliminates the need for volume discretization for most practical analyses. The resulting general purpose algorithm establishes BEM as an attractive alternative to the more familiar finite difference and finite element methods for this class of problems. Several detailed numerical examples are included to emphasize the accuracy, stability and generality of the present BEM. Furthermore, a new efficient treatment is introduced for bodies with embedded holes. This development provides a powerful analytical tool for transient solutions of components, such as casting moulds and turbine blades, which are cumbersome to model when employing the conventional domain-based methods.

Dargush, G. F.; Banerjee, P. K.

1991-01-01

259

Efficient linear and nonlinear heat conduction with a quadrilateral element

NASA Technical Reports Server (NTRS)

A method is presented for performing efficient and stable finite element calculations of heat conduction with quadrilaterals using one-point quadrature. The stability in space is obtained by using a stabilization matrix which is orthogonal to all linear fields and its magnitude is determined by a stabilization parameter. It is shown that the accuracy is almost independent of the value of the stabilization parameter over a wide range of values; in fact, the values 3, 2, and 1 for the normalized stabilization parameter lead to the 5-point, 9-point finite difference, and fully integrated finite element operators, respectively, for rectangular meshes and have identical rates of convergence in the L2 norm. Eigenvalues of the element matrices, which are needed for stability limits, are also given. Numerical applications are used to show that the method yields accurate solutions with large increases in efficiency, particularly in nonlinear problems.

Liu, W. K.; Belytschko, T.

1983-01-01

260

ICARUS: A general one-dimensional heat conduction code

NASA Astrophysics Data System (ADS)

A computer code for calculating one dimensional planar, cylindrical or spherical conduction heat transfer is described. The model can account for material phase change (solidification or melting, multiple material regions, temperature dependent material properties and time or temperature dependent boundary conditions. Finite difference techniques are used to discretize the differential equations. The resulting system of tri-diagonal equations are solved using a standard tri-diagonal reduction method. The equations are formulated so that the solution can be fully implicit, fully explicit or a user specified degree of mix. Six sample problems that compare numerical predictions to analytical solutions are discussed. Operation of the computer code and all input variables are described. Input file listings and typical edits for the six sample problems are given.

Sutton, S. B.

1984-07-01

261

NASA Astrophysics Data System (ADS)

A multiple step fixed random walk Monte Carlo method for solving heat conduction in solids with distributed internal heat sources is developed. In this method, the probability that a walker reaches a point a few steps away is calculated analytically and is stored in the computer. Instead of moving to the immediate neighboring point the walker is allowed to jump several steps further. The present multiple step random walk technique can be applied to both conventional Monte Carlo and the Exodus methods. Numerical results indicate that the present method compares well with finite difference solutions while the computation speed is much faster than that of single step Exodus and conventional Monte Carlo methods.

Naraghi, M. H. N.; Chung, B. T. F.

1982-06-01

262

Heat conduction in nanoscale materials: a statistical-mechanics derivation of the local heat flux.

We derive a coarse-grained model for heat conduction in nanoscale mechanical systems. Starting with an all-atom description, this approach yields a reduced model, in the form of conservation laws of momentum and energy. The model closure is accomplished by introducing a quasilocal thermodynamic equilibrium, followed by a linear response approximation. Of particular interest is the constitutive relation for the heat flux, which is expressed nonlocally in terms of the spatial and temporal variation of the temperature. Nanowires made of copper and silicon are presented as examples. PMID:25314400

Li, Xiantao

2014-09-01

263

NASA Astrophysics Data System (ADS)

Design and development of a high power ultra-wideband, 3 dB tandem hybrid coupler is presented and its application in ICRF heating of the tokamak is discussed. In order to achieve the desired frequency band of 38-112 MHz and 200 kW power handling capability, the 3 dB hybrid coupler is developed using two 3-element 8.34 0.2 dB coupled lines sections in tandem. In multi-element coupled lines, junctions are employed for the joining of coupled elements that produce the undesirable reactance called junction discontinuity effect. The effect becomes prominent in the high power multi-element coupled lines for high frequency (HF) and very high frequency(VHF) applications because of larger structural dimensions. Junction discontinuity effect significantly deteriorates coupling and output performance from the theoretical predictions. For the analysis of junction discontinuity effect and its compensation, a theoretical approach has been developed and generalized for n-element coupled lines section. The theory has been applied in the development of the 3 dB hybrid coupler. The fabricated hybrid coupler has been experimentally characterized using vector network analyzer and obtained results are found in good agreement with developed theory.

Yadav, Rana Pratap; Kumar, Sunil; Kulkarni, S. V.

2014-04-01

264

Constructal trees of circular fins for conductive and convective heat transfer

This paper extends to three dimensions and to convective heat transfer the constructal method of minimizing the thermal resistance between a volume and one point. In the first part of the paper, the heat flow mechanism is conduction, and the heat generating volume is occupied by low conductivity material (k0) and high conductivity inserts (kp). At the elemental-volume level the

A. Alebrahim; A. Bejan

1999-01-01

265

A note on stability in dualphaselag heat conduction Ram on Quintanilla 1

A note on stability in dualphaselag heat conduction Ram?? on Quintanilla 1 Department of Applied Introduction There are several hyperbolic theories of heat conduction, also called theories of second sound a theory of heat conduction, # t + div q = 0 (1.1) 0 AMS subject classification: 35 L 35, 80 A 20 Keywords

Racke, Reinhard

266

Anomalous heat conduction and anomalous diffusion in nonlinear lattices, single walled nanotubes 2004; accepted 13 October 2004; published online 28 March 2005 We study anomalous heat conduction nanotubes, to billiard gas channels. We find that in all discussed systems, the anomalous heat conductivity

Li, Baowen

267

Developing Low-Conductance Window Frames: Capabilities and Limitations of Current Window Heat on the total window heat transfer rates may be much larger. This effect is even greater in low-conductance evaluating heat transfer through the low-conductance frames. We conclude that the near-term priorities

268

A MOLECULAR DYNAMICS SIMULATION OF HEAT CONDUCTION IN A CARBON NANOTUBE

A MOLECULAR DYNAMICS SIMULATION OF HEAT CONDUCTION IN A CARBON NANOTUBE Shigeo Maruyama to be order of 100nm ~ 1µm, heat conduction of nanotubes with shorter than 1µm should have the nearly's law of heat conduction may not be obeyed for these almost one-dimensional materials when rather high

Maruyama, Shigeo

269

A HEAT CONDUCTION STUDY AT NON-CONTINUUM SCALES A Dissertation

A HEAT CONDUCTION STUDY AT NON-CONTINUUM SCALES A Dissertation Submitted to the Graduate School Rights Reserved #12;A HEAT CONDUCTION STUDY AT NON-CONTINUUM SCALES Abstract by Alejandro Guajardo Cu´ellar An extensive and detailed description of heat conduction at the micro- and nano-scale is presented. During

Sen, Mihir

270

A MECHANICAL MODEL FOR FOURIER'S LAW OF HEAT CONDUCTION. by David Ruelle.

A MECHANICAL MODEL FOR FOURIER'S LAW OF HEAT CONDUCTION. by David Ruelle. Abstract. Nonequilibrium mechanical model of a heat-conducting chain with nontrivial interactions, where kinetic energy fluctuations [22]. A fundamental derivation of Fourier's law for heat conduction remains thus an open problem

Ruelle, David

271

Equilibration and Universal Heat Conduction in Fermi-Pasta-Ulam Chains Trieu Mai,1

Equilibration and Universal Heat Conduction in Fermi-Pasta-Ulam Chains Trieu Mai,1 Abhishek Dhar,2 heat conduction. The reason why earlier simulations have obtained systematically higher exponents not been fully inves- tigated, even though the discussion of heat conductivity is in terms of Fourier's law

California at Santa Cruz, University of

272

Phase-lag heat conduction: decay rates for limit problems and well-posedness

Phase-lag heat conduction: decay rates for limit problems and well-posedness Karin Borgmeyer, Ram approximations to dual-phase-lag and three-phase-lag heat conduction equations. However, for several limit cases analysis is rigorously proved exemplarily. 1 Introduction It is well known that Fourier's heat conduction

Racke, Reinhard

273

Correlations and scaling in one-dimensional heat conduction J. M. Deutsch and Onuttom Narayan

Correlations and scaling in one-dimensional heat conduction J. M. Deutsch and Onuttom Narayan of the heat current, through the Kubo formula, gives a thermal conductivity exponent of 1/3 in agreement.40.Mg I. INTRODUCTION Heat conduction in one-dimensional systems is a simple example of the general

California at Santa Cruz, University of

274

Diffusive-Ballistic Heat Conduction of Carbon Nanotubes and Nanographene Ribbons Junichiro Shiomi-3-5800-6983 Abstract Investigations of diffusive-ballistic heat conduction of finite-length single-walled carbon of the balance between ballistic and diffusive heat conduction. For both systems, the profile indicates

Maruyama, Shigeo

275

Influence of surrounding materials on heat conduction of carbon nanotubes: Molecular dynamics the characteristics of intrinsic heat conduction of SWNTs have been explored extensively for ideal thermal boundary boundary resistances but also influence the intrinsic heat conduction. In a system with significant

Maruyama, Shigeo

276

A Bayesian inference approach to the inverse heat conduction problem Jingbo Wang and Nicholas inference approach is presented for the solution of the inverse heat conduction problem. The posterior inverse heat conduction examples are presented to demonstrate the potential of the MCMC-based Bayesian

Zabaras, Nicholas J.

277

1 Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer, Shewen et al. 1996, Wright 1996, and Zhao 1998). Less research has been conducted on heat transfer because cavities are a primary area where frame heat transfer can be minimized (the thermal conductivity

278

Spatial behavior in phase-lag heat conduction Ramon Quintanilla and Reinhard Racke

Spatial behavior in phase-lag heat conduction Ram´on Quintanilla and Reinhard Racke Abstract approximations to the heat conduction dual-phase-lag and three-phase- lag theories, reflecting Saint´e inequality 1 Introduction Fourier's heat conduction theory implies that thermal perturbations at some point

Racke, Reinhard

279

A MECHANICAL MODEL FOR FOURIER'S LAW OF HEAT CONDUCTION. by David Ruelle+.

A MECHANICAL MODEL FOR FOURIER'S LAW OF HEAT CONDUCTION. by David Ruelle+. Abstract. Nonequilibrium mechanical model of a heatconducting chain with nontrivial interactions, where kinetic energy fluctuations, as remarked by van Kampen [22]. A fundamental derivation of Fourier's law for heat conduction remains thus

Ruelle, David

280

Variational formulation of hyperbolic heat conduction problems applying Laplace transform technique

Variational formulation of hyperbolic heat conduction problems applying Laplace transform technique In this paper, a non-Fourier heat conduction problem is analyzed by employing newly developed theory-transformed hyperbolic heat conduction equation is developed. The results were used for evaluation of parameters used

281

Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes

Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes-3-1 Hongo, Bunkyo-ku Tokyo 113-8656, Japan Diffusive-ballistic heat conduction of finite-length single. A gradual transition from nearly pure ballistic to diffusive-ballistic heat conduction was identified from

Maruyama, Shigeo

282

A Molecular Dynamics Simulation of Heat Conduction of Finite Length SWNTs SHIGEO MARUYAMA

A Molecular Dynamics Simulation of Heat Conduction of Finite Length SWNTs SHIGEO MARUYAMA The heat conduction of finite length single walled carbon nanotubes (SWNTs) was simulated by the molecular is estimated, as order of 100nm 1µm, heat conduction of nanotubes with about 1µm length should have the nearly

Maruyama, Shigeo

283

1 Heat conduction of single-walled carbon nanotube isotope-superlattice structures: A molecular-mail address: maruyama@photon.t.u-tokyo.ac.jp Heat conduction of single-walled carbon nanotubes (SWNTs) isotope and junctions, which alter the heat conduction. In general, these nanoscale impurities, having scales comparable

Maruyama, Shigeo

284

Diffusive-Ballistic Heat Conduction along a Single-Walled Carbon Nanotube Shigeo Maruyama

Diffusive-Ballistic Heat Conduction along a Single-Walled Carbon Nanotube Shigeo Maruyama *E-mail address: maruyama@photon.t.u-tokyo.ac.jp The diffusive-ballistic heat conduction of finite unique stationary and non-stationary heat conduction characteristics [3,4]. Furthermore, several issues

Maruyama, Shigeo

285

A note on stability in dual-phase-lag heat conduction Ramon Quintanilla1

A note on stability in dual-phase-lag heat conduction Ram´on Quintanilla1 Department of Applied Introduction There are several hyperbolic theories of heat conduction, also called theories of second sound a theory of heat conduction, t + div q = 0 (1.1) 0 AMS subject classification: 35 L 35, 80 A 20 Keywords

Racke, Reinhard

286

Influence of interfaces on diffusive-ballistic heat conduction of carbon nanotubes Shiomi temperature. Although the characteristics of intrinsic heat conduction of SWNTs have been explored extensively not only give rise to thermal boundary resistances but also influence the intrinsic heat conduction

Maruyama, Shigeo

287

Thermal conductivity and specific heat capacity and their variation with moisture content were determined for twigs of yerba mate (Ilex paraguariensis Saint Hilaire). For the simultaneous determination of these two properties, transient heating data and the finite-difference method were used to determine the specific heat capacity and steady-state data to determine the thermal conductivity. The values of thermal conductivity varied

M. E. Schmalko; R. O. Morawicki; L. A. Ramallo

1997-01-01

288

Development of an isothermal heat-conduction photocalorimeter

NASA Astrophysics Data System (ADS)

Assessing photostability (particularly of pharmaceuticals) is of growing importance, but hampered by a lack of reliable, rapid experimental testing protocols and instrumentation. In particular, most approaches require irradiation of the sample separately from the analytical measurement, which increases both experimental complexity and the number of assumptions that must be made when calculating stability. One technique that may obviate this is photocalorimetry, principally because the reporter of change (heat) is measured directly as a sample is irradiated. Although not a new idea, the design challenges of photocalorimeters are complex, primarily because light power is being introduced to the calorimeter which can thus both saturate the amplifiers and swamp the response of the sample. Careful instrument design is thus paramount. The aim of this work was to develop a robust, compact, and easy to use photocalorimeter with the immediate focus of developing photostability assays for pharmaceuticals. The final instrument design, arrived at through a series of iterative design modifications, is based on a twin differential heat-conduction principle and achieves an average base line deflection of -0.040.11?W with light irradiating the sample cell. The performance capabilities of the instrument were demonstrated using a model system; the photodegradation of 2-nitrobenzaldehyde in solution.

Dhuna, Meena; Beezer, Anthony E.; Morris, Andrew C.; Gaisford, Simon; O'Neill, Michael A. A.; Hadgraft, Jonathan; Connor, Joseph A.; Clapham, David; Frost, John

2007-02-01

289

The steady state heat transfer characteristics of a thin vertical strip with internal heat generation is studied in this work. The nondimensional temperature distribution in the strip is obtained as a function of the following parameters: (a) the intensity and distribution of the internal heat sources, (b) the aspect ratio of the strip, (c) the longitudinal heat conductance of the

F Mndez; C Trevio

2000-01-01

290

Radiation and gas conduction heat transport across a helium dewar multilayer insulation system

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.

Green, M.A.

1994-10-10

291

We have succeeded in constructing a 3D POMMOF, (H[Ni(Hbpdc)(H{sub 2}O){sub 2}]{sub 2}[PW{sub 12}O{sub 40}]8H{sub 2}O){sub n} (H{sub 2}bpdc=2,2?-bipyridyl-3,3?-dicarboxylic acid), by the controllable self-assembly of H{sub 2}bpdc, Keggin-anions and Ni{sup 2+} ions based on the electrostatic and coordination interactions. Interestingly, Hbpdc{sup ?} as polydentate organic ligands and Keggin-anion as polydentate inorganic ligands are covalently linked transition-metal nickel at the same time. The title complex represents a new example of introducing the metal N-heterocyclic multi-carboxylic acid frameworks into POMs chemistry. Based on Keggin-anions being immobilized as part of the metal N-heterocyclic multi-carboxylic acid framework, the title complex realizes four approaches in the 1D hydrophilic channel used to engender proton conductivity in MOFs. Its water adsorption isotherm at room temperature and pressure shows that the water content in it was 31 cm{sup 3} g{sup ?1} at the maximum allowable humidity, corresponding to 3.7 water molecules per unit formula. It exhibits good proton conductivities (10{sup ?4}10{sup ?3} S cm{sup ?1}) at 100 C in the relative humidity range 3598%. The corresponding activation energy (E{sub a}) of conductivity was estimated to be 1.01 eV. - Graphical abstract: A POMMOF composite constructed by Keggin-type polyanion, Ni{sup 2+} and H{sub 2}bpdc shows good proton conductivities of 10{sup ?4}10{sup ?3} S cm{sup ?1} at 100 C under 3598% RH. - Highlights: A POMMOF was constructed by combining metal N-heterocyclic multi-carboxylic acid framework and Keggin anion. It opens a pathway for design and synthesis of multifunctional hybrid materials based on two building units. Three types of potential proton-carriers have been assembled in the 1D hydrophilic channels of the POMMOF. It achieved such proton conductivities as 10{sup ?4}10{sup ?3} S cm{sup ?1} at 100 C in the RH range 3598%.

Wei, Meilin, E-mail: weimeilinhd@163.com [School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007 (China); Wang, Xiaoxiang; Sun, Jingjing [School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007 (China); Duan, Xianying, E-mail: dxynumber@163.com [Institute of Chemistry, Henan Academy of Sciences, Zhengzhou 450002 (China)

2013-06-15

292

To support the analyses related to the conversion of the BR2 core from highly-enriched (HEU) to low-enriched (LEU) fuel, the thermal-hydraulics codes PLTEMP and RELAP-3D are used to evaluate the safety margins during steady-state operation (PLTEMP), as well as after a loss-of-flow, loss-of-pressure, or a loss of coolant event (RELAP). In the 1-D PLTEMP and RELAP simulations, conduction in the azimuthal and axial directions is not accounted. The very good thermal conductivity of the cladding and the fuel meat and significant temperature gradients in the lateral directions (axial and azimuthal directions) could lead to a heat flux distribution that is significantly different than the power distribution. To evaluate the significance of the lateral heat conduction, 3-D computational fluid dynamics (CFD) simulations, using the CFD code STAR-CD, were performed. Safety margin calculations are typically performed for a hot stripe, i.e., an azimuthal region of the fuel plates/coolant channel containing the power peak. In a RELAP model, for example, a channel between two plates could be divided into a number of RELAP channels (stripes) in the azimuthal direction. In a PLTEMP model, the effect of azimuthal power peaking could be taken into account by using engineering factors. However, if the thermal mixing in the azimuthal direction of a coolant channel is significant, a stripping approach could be overly conservative by not taking into account this mixing. STAR-CD simulations were also performed to study the thermal mixing in the coolant. Section II of this document presents the results of the analyses of the lateral heat conduction and azimuthal thermal mixing in a coolant channel. Finally, PLTEMP and RELAP simulations rely on the use of correlations to determine heat transfer coefficients. Previous analyses showed that the Dittus-Boelter correlation gives significantly more conservative (lower) predictions than the correlations of Sieder-Tate and Petukhov. STAR-CD 3-D simulations were performed to compare heat transfer predictions from CFD and the correlations. Section III of this document presents the results of this analysis.

Tzanos, C. P.; Dionne, B. (Nuclear Engineering Division)

2011-05-23

293

Incompressible Perturbations in Uniformally Stratified Viscous Heat-Conducting Fluid

NASA Astrophysics Data System (ADS)

One-component model of dissipative medium with two-parametric equation of state allows us to formulate a simple model of a stratified viscous heat-conducting fluid. At local thermodynamic equilibrium description and the simplifying assumption of constancy of the kinetic coefficients the complete system of equations of a viscous fluid can be written in the form of the equations of conservation of mass, momentum balance, entropy balance and state equation. Consequence of the equation of state is a linear relationship between changes in density and changes in pressure and entropy. In the case of an incompressible fluid change in the density does not occur when the pressure changes. This corresponds to an infinite speed of sound. As a result, change in the density is proportional to the temperature change and thermal expansion coefficient. Accordingly, the velocity of fluid flow is not solenoidal. At the constant heat capacity the entropy balance equation reduces to the heat equation, which in turn takes the form of the evolution equation of the density. This equation completes the equation of conservation of mass and the equation of fluid motion. We assume that fluid flow occurs in the gravity field and is caused by small external forces, a small source of mass and small thermal source. Let the initial state of the fluid is rest with the vertical coordinate-dependent density distribution. For simplicity it is assumed also that the stratification is uniform, i.e. the buoyancy frequency is constant. Then the weak current caused by the sources will be described by the linearized equations with constant coefficients in Boussinesq approximation. In this approximation, square of buoyancy frequency, the density at a fixed level and the transport coefficients are the basic constant coefficients of the equations. Gravity selects the vertical direction, and therefore it is convenient to divide vector characteristics of the perturbation in the horizontal and vertical parts. In turn, the horizontal components of vectors is conveniently represented by pairs of scalar potentials using the Helmholtz decomposition. Taking into account these relations complete system of equations for small perturbations can be reduced to separate equations for the characteristics of the perturbations. As a result, small perturbations of density, pressure and vectors of velocity and vorticity can be expressed in the form of various derivatives of the five quasipotentials. Four of these quasipotentials obey the same equation of sixth order with the mass, force and heat sources, respectively, on the right side. The operator left-hand side of these equations reflects the behavior of internal waves, as well as viscous and thermal relaxation. In addition to the viscosity this operator includes the kinetic coefficient, which is directly proportional to the coefficient of thermal conductivity and is inversely proportional to the specific heat. In this case the vertical componen

Gorodtsov, V. A.

2012-04-01

294

The transient Dst electromagnetic induction signal at satellite altitudes for a realistic 3-D of electromagnetic induction (EM) is conventionally carried out in the frequency domain. We use a time, The transient Dst electromagnetic induction signal at satellite altitudes for a realistic 3-D electrical

Velímsky, Jakub

295

UNIFORM ESTIMATES FOR TRANSMISSION PROBLEMS WITH HIGH CONTRAST IN HEAT CONDUCTION . Here, a represents the heat conductivity and # the electrical conductivity. We assume for Maxwell transmission problem set on a domain made up of a dielectric and a highly conducting material

Recanati, Catherine

296

NASA Astrophysics Data System (ADS)

SummaryWe combine sedimentological, hydraulic and geophysical information to characterize the 3D distribution of transport properties of an heterogeneous aquifer. We focus on the joint inversion of hydraulic head and self-potential measurements collected during an extensive experimental campaign performed at the Boise Hydrogeophysical Research Site (BHRS), Boise, Idaho, and involving a series of dipole tests. While hydraulic head data obtained from piezometric readings in open wells represent a depth-averaged value, self-potential signals provide an estimate of the water table location. The aquifer is conceptualized as a multiple-continuum, where the volumetric fraction of a geo-material within a cell of the numerical flow model is calculated by Multiple Indicator Kriging. The latter is implemented on the basis of available sedimentological information. The functional format of the indicator variograms and associated parameters are estimated on the basis of formal model identification criteria. Self-potential and hydraulic head data have been embedded jointly within a three-dimensional inverse model of groundwater flow at the site. Each identified geo-material (category) is assumed to be characterized by a constant hydraulic conductivity. The latter constitute the set of model parameters. The hydraulic conductivity associated with a numerical block is then calculated as a weighted average of the conductivities of the geo-materials which are collocated in the block by means of Multiple Indicator Kriging. Model parameters are estimated by a Maximum Likelihood fit between measured and modeled state variables, resulting in a spatially heterogeneous distribution of hydraulic conductivity. The latter is effectively constrained on the sedimentological data and conditioned on both self-potential and borehole hydraulic head readings. Minimization of the Maximum Likelihood objective function allows estimating the relative weight of measurement errors associated with self-potential and borehole-based head data. The procedure adopted allowed a reconstruction of the heterogeneity of the site with a level of details, which was not obtained in previous studies and with relatively modest computational efforts. Further validation against dipole tests which were not used in the inversion procedure supports the robustness of the results.

Straface, Salvatore; Chidichimo, Francesco; Rizzo, Enzo; Riva, Monica; Barrash, Warren; Revil, Andr; Cardiff, Michael; Guadagnini, Alberto

2011-09-01

297

Molecular dynamics simulation of heat conduction through a molecular chain.

This work deals with a molecular dynamics simulation analysis of the intramolecular vibrational energy transfer in a system of two chromophores, azulene and anthracene, bridged by an aliphatic chain and is motivated by corresponding laser experiments. After selective excitation of the azulene chromophore, the subsequent intramolecular vibrational energy redistribution is monitored by analyzing the transient temperatures of the two chromophores and the chain between them. The main focus concerns the heat conduction process in the chain. Therefore, the chain length was varied from 0 to 19 CH(2) units. In addition, methoxymethyl, 1,2-dimethoxyethyl, and a thiomethoxymethyl chains were studied. The investigation of the intramolecular vibrational energy process was decomposed into a temporal analysis and a spatial analysis. For short alkyl chains, the time constant of energy relaxation increases proportionally to the chain length. However, for longer chains, the time constant characterizing the energy decay of the azulene chromophore saturates and becomes independent of the chain length. This behavior is consistent with experimental findings. The spatial analysis shows more or less exponential decay of the temperature along the chain near the excited chromophore. In additional simulations, the two chromophores were thermostatted at different temperatures to establish a constant heat flux from the azulene to the anthracene side. The steady-state temperature profiles for longer alkyl chains show strong gradients near the two chromophores and constant but weak gradients in the central part of the chain. Both simulation methods indicate that strong Kapitza effects at the boundaries between each chromophore and the molecular chain dominate the intramolecular energy flux. PMID:19928969

Schrder, Christian; Vikhrenko, Vyacheslav; Schwarzer, Dirk

2009-12-24

298

eXtremes of heat conduction: Pushing the boundaries of the thermal

eXtremes of heat conduction: Pushing the boundaries of the thermal conductivity of materials David) supported by AFOSR, DOE-BES, ONR Carnegie/DOE Alliance Center and ARO #12;Outline · Thermal conductivity and interface thermal conductance. · eXtremes of thermal conductivity: High conductivity nanotubes, graphene

Braun, Paul

299

Scrape-off layer modeling of radiative divertor and high heat flux experiments on D3-D

NASA Astrophysics Data System (ADS)

We use a new multispecies 1-D fluid code, NEWT-1D, to model DIII-D scrape-off layer (SOL) behavior during radiative divertor and high heat flux experiments. The separatrix location and the width of the SOL are uncertain, and affect the comparison of the data in important ways. The model agrees with many of the experimental measurements for a particular prescription for the separatrix location. The model cannot explain the recent data on the separatrix T(sub i) with a conventional picture of ion and electron power flows across the separatrix. Radial transport of particles and heat in some form is required to explain the peak heat flux data before and after gas puffing. For argon puffing in the private flux region, entrainment is poor in the steady state. The calculations suggest that strike point argon puffing in a slot divertor geometry results in substantially better entrainment. Self-consistent, steady-state solutions with radiated powers up to 80 percent of the SOL power input are obtained in 1-D. We discuss significant radial effects which warrant the development of a code which can treat strongly radiating impurities in 2-D geometries.

Campbell, R. B.; Petrie, T. W.; Hill, D. N.

1992-03-01

300

Background Brown adipose tissue (BAT) plays an important role in whole body metabolism and could potentially mediate weight gain and insulin sensitivity. Although some imaging techniques allow BAT detection, there are currently no viable methods for continuous acquisition of BAT energy expenditure. We present a non-invasive technique for long term monitoring of BAT metabolism using microwave radiometry. Methods A multilayer 3D computational model was created in HFSS with 1.5 mm skin, 310 mm subcutaneous fat, 200 mm muscle and a BAT region (26 cm3) located between fat and muscle. Based on this model, a log-spiral antenna was designed and optimized to maximize reception of thermal emissions from the target (BAT). The power absorption patterns calculated in HFSS were combined with simulated thermal distributions computed in COMSOL to predict radiometric signal measured from an ultra-low-noise microwave radiometer. The power received by the antenna was characterized as a function of different levels of BAT metabolism under cold and noradrenergic stimulation. Results The optimized frequency band was 1.52.2 GHz, with averaged antenna efficiency of 19%. The simulated power received by the radiometric antenna increased 29 mdBm (noradrenergic stimulus) and 415 mdBm (cold stimulus) corresponding to increased 15-fold BAT metabolism. Conclusions Results demonstrated the ability to detect thermal radiation from small volumes (26 cm3) of BAT located up to 12 mm deep and to monitor small changes (0.5 C) in BAT metabolism. As such, the developed miniature radiometric antenna sensor appears suitable for non-invasive long term monitoring of BAT metabolism. PMID:24244831

Rodrigues, Dario B.; Maccarini, Paolo F.; Salahi, Sara; Colebeck, Erin; Topsakal, Erdem; Pereira, Pedro J. S.; Limo-Vieira, Paulo; Stauffer, Paul R.

2013-01-01

301

NASA Astrophysics Data System (ADS)

Background: Brown adipose tissue (BAT) plays an important role in whole body metabolism and could potentially mediate weight gain and insulin sensitivity. Although some imaging techniques allow BAT detection, there are currently no viable methods for continuous acquisition of BAT energy expenditure. We present a non-invasive technique for long term monitoring of BAT metabolism using microwave radiometry. Methods: A multilayer 3D computational model was created in HFSSTM with 1.5 mm skin, 3-10 mm subcutaneous fat, 200 mm muscle and a BAT region (2-6 cm3) located between fat and muscle. Based on this model, a log-spiral antenna was designed and optimized to maximize reception of thermal emissions from the target (BAT). The power absorption patterns calculated in HFSSTM were combined with simulated thermal distributions computed in COMSOL to predict radiometric signal measured from an ultra-low-noise microwave radiometer. The power received by the antenna was characterized as a function of different levels of BAT metabolism under cold and noradrenergic stimulation. Results: The optimized frequency band was 1.5-2.2 GHz, with averaged antenna efficiency of 19%. The simulated power received by the radiometric antenna increased 2-9 mdBm (noradrenergic stimulus) and 4-15 mdBm (cold stimulus) corresponding to increased 15-fold BAT metabolism. Conclusions: Results demonstrated the ability to detect thermal radiation from small volumes (2-6 cm3) of BAT located up to 12 mm deep and to monitor small changes (0.5 C) in BAT metabolism. As such, the developed miniature radiometric antenna sensor appears suitable for non-invasive long term monitoring of BAT metabolism.

Rodrigues, Dario B.; Maccarini, Paolo F.; Salahi, Sara; Colebeck, Erin; Topsakal, Erdem; Pereira, Pedro J. S.; Limo-Vieira, Paulo; Stauffer, Paul R.

2013-02-01

302

SEP BIMOD variable conductance heat pipes acceptance and characterization tests

NASA Technical Reports Server (NTRS)

A series of six heat pipes, similar in design to those flown on the Comunications Technology Satellite Hermes, for use in a prototype Solar Electric Propulsion BIMOD thrust module are evaluated. The results of acceptance and characterization tests performed on the heat pipe subassemble are reported. The performance of all the heat pipes met, or exceeded, design specifications.

Hemminger, J. A.

1981-01-01

303

What is the optimal shape of a fin for stationary heat conduction?

What is the optimal shape of a fin for stationary heat conduction? Gilles Marck Gr´egoire Nadin. Finally, we provide several extensions of these results for more general models of heat conduction Yannick Privat Abstract This article is concerned with the shape of small devices used to control the heat

Recanati, Catherine

304

Influence of Conductive Heat-Losses on the Propagation of Premixed Flames in Channels

Influence of Conductive Heat-Losses on the Propagation of Premixed Flames in Channels J. DAOU of arbitrary width, accounting for heat losses by conduction to the walls. The ratio of the width-3125, USA We study the propagation of premixed flames in two-dimensional channels accounting for heat

Heil, Matthias

305

March. 1968 RisB Report No. 175 On the Viscosity and Heat Conductivity

March. 1968 RisB Report No. 175 On the Viscosity and Heat Conductivity of a Collisionless Plasma of "magnetic viscosity" and "magnetic 3-7)heat conductivity in the hydrodynamic equations '. The expression to Macmahon's result as shown in the appendix. #12;March, 196B Ris« Report No. ITS On the Viscosity and Heat

306

Optimal Operation of Finite-time Tricycles with Heat Conduction Losses Raj K. Pathria

(1) Optimal Operation of Finite-time Tricycles with Heat Conduction Losses Raj K. Pathria the heat conduction br anches for a wide variety of cost functions. One point on this boundary represents-principle limits to the finite-time operation of a cycling working fluid acting as an agent in the transfer of heat

Salamon, Peter

307

Convection under a lid of finite conductivity: Heat flux scaling and application to continents

Convection under a lid of finite conductivity: Heat flux scaling and application to continents C. J. Tackley (2007), Convection under a lid of finite conductivity: Heat flux scaling and application April 2007; published 1 August 2007. [1] A scaling law for the heat flux out of a convective fluid

Paris-Sud XI, Université de

308

Gravitational effects on the operation of a variable conductive heat pipe

A variable conductance heat pipe, measuring 2.5 centimeters in diameter and 152 centimeters in length, was built. The heat pipe was operated in both the conventional and variable conductance modes to obtain experimental data concerning performance characteristics. The input electrical power was varied from 20 to 50 watts with the heat pipe placed in both the horizontal and vertical positions.

R. S. Owendoff

1977-01-01

309

Anomalous Heat Conduction in One-Dimensional Momentum-Conserving Systems Onuttom Narayan1,2

Anomalous Heat Conduction in One-Dimensional Momentum-Conserving Systems Onuttom Narayan1 temperature difference is applied across a system, it is expected that in steady state the heat current j will obey Fourier's law of conduction j ÿrT; (1) where T is the local temperature and is the heat con

California at Santa Cruz, University of

310

Thermographic validation of a novel, laminate body, analytical heat conduction model

NASA Astrophysics Data System (ADS)

The two-region fin model captures the heat spreading behaviour in multilayered composite bodies (i.e., laminates), heated only over a small part of their domains (finite heat source), where there is an inner layer that has a substantial capacity for heat conduction parallel to the heat exchange surface (convection cooling). This resulting heat conduction behaviour improves the overall heat transfer process when compared to heat conduction in homogeneous bodies. Long-term heat storage using supercooling salt hydrate phase change materials, stovetop cookware, and electronics cooling applications could all benefit from this kind of heat-spreading in laminates. Experiments using laminate films reclaimed from post-consumer Tetra Brik cartons were conducted with thin rectangular and circular heaters to confirm the laminate body, steady-state, heat conduction behaviour predicted by the two-region fin model. Medium to high accuracy experimental validation of the two-region fin model was achieved in Cartesian and cylindrical coordinates for forced external convection and natural convection, the latter for Cartesian only. These were conducted using constant heat flux finite heat source temperature profiles that were measured by infrared thermography. This validation is also deemed valid for constant temperature heat sources.

Desgrosseilliers, Louis; Groulx, Dominic; White, Mary Anne

2014-07-01

311

Thermal Via Planning for 3-D ICs Computer Science Department, UCLA

, because of the poor thermal conductivity of the ILD layers, the heat gener- ated by the devices cannot@cs.ucla.edu ABSTRACT Heat dissipation is one of the most serious challenges in 3- D IC designs. One effective way and heat propagation. Experimental results show that the m-ADVP algorithm is more than 200? faster than

Cong, Jason "Jingsheng"

312

Aerodynamic and heat transfer analysis of the low aspect ratio turbine using a 3D Navier-Stokes code

NASA Astrophysics Data System (ADS)

The single-stage, high-pressure ratio Garrett Low Aspect Ratio Turbine (LART) test data obtained in a shock tunnel are employed as a basis for evaluating a new three-dimensional Navier Stokes code based on the O-H grid system. It uses Coakley's two-equation turbulence modeling with viscous sublayer resolution. For the nozzle guide vanes, calculations were made based on two grid zones: an O-grid zone wrapping around airfoil and an H-grid zone outside of the O-grid zone, including the regions upstream of the leadig edge and downstream of the trailing edge. For the rotor blade row, a third O-grid zone was added for the tip-gap region leakage flow. The computational results compare well with experiment. These comparisons include heat transfer distributions on the airfoils and end-walls. The leakage flow through the tip-gap clearance is well resolved.

Choi, D.; Knight, C. J.

1991-06-01

313

A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in a new novel integrated planar porous-tube supported solid oxide electrolysis cell (SOEC). The model is of several integrated planar cells attached to a ceramic support tube. This design is being evaluated with modeling at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, activation over-potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean per-cell area-specific-resistance (ASR) values decrease with increasing current density. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, cathode and anode exchange current density, and contact resistance from the base case are presented. Contour plots of local electrolyte temperature, current density, and Nernst potential indicated the effects of heat transfer, reaction cooling/heating, and change in local gas composition. Results are discussed for using this design in the electrolysis mode. Discussion of thermal neutral voltage, enthalpy of reaction, hydrogen production, cell thermal efficiency, cell electrical efficiency, and Gibbs free energy are discussed and reported herein.

Grant Hawkes; James E. O'Brien

2008-10-01

314

Thermal flywheel effects on the time varying conduction heat transfer through structural walls

Wall time varying conduction heat transfer investigations are very important for the prediction of heating and cooling loads in air conditioning practice and absolutely essential to the passive solar heating design. The walls store heat, absorb and dissipate a fraction of it and transmit the rest into the conditioned space at a later time, which depends on the wall thermal

P. T Tsilingiris

2003-01-01

315

Effects of NCG Charging Mass on the Operational Characteristics of Variable Conductance Heat Pipe

Numerical analysis and experimental study are performed to investigate the effect of heat load and operating temperature on the thermal performance of several variable conductance heat pipe heat pipe (VCHP) with screen meshed wick. The heat pipe is designed in 200 screen meshes, 500 ? length and 12.7 ? outer diameter tube of copper, water (4.8 g) is used as

JEONG SE SUH; YOUNG SIK PARK; KYUNG TAEK CHUNG; CHANG HO KANG

316

Isotope Effects on Heat Conduction of Carbon Nanotubes Shigeo Maruyama, Yuki Taniguchi and Yasushi that the inclusion of only 1 % of 13 C natural isotope dramatically reduces the thermal conductivity of diamond. However, isotope effects on heat conduction of SWNTs have not been elucidated. We estimated isotope

Maruyama, Shigeo

317

Summary Weusedthreemethodstomeasureboundarylayer conductance to heat transfer (gbH) and water vapor of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become that produces clumped shoot morphol- ogy on sun-formed branches. Boundary layer conductances estimated

Martin, Timothy

318

In this paper, two modified types of polypropylene (PP) with high thermal conductivity up to 2.3 W/m K and 16.5 W/m K are used to manufacture the finned-tube heat exchangers, which are prospected to be used in liquid desiccant air conditioning, heat recovery, water source heat pump, sea water desalination, etc. A third plastic heat exchanger is also manufactured with ordinary PP for validation and comparison. Experiments are carried out to determine the thermal performance of the plastic heat exchangers. It is found that the plastic finned-tube heat exchanger with thermal conductivity of 16.5 W/m K can achieve overall heat transfer coefficient of 34 W/m{sup 2} K. The experimental results are compared with calculation and they agree well with each other. Finally, the effect of material thermal conductivity on heat exchanger thermal performance is studied in detail. The results show that there is a threshold value of material thermal conductivity. Below this value improving thermal conductivity can considerably improve the heat exchanger performance while over this value improving thermal conductivity contributes very little to performance enhancement. For the finned-tube heat exchanger designed in this paper, when the plastic thermal conductivity can reach over 15 W/m K, it can achieve more than 95% of the titanium heat exchanger performance and 84% of the aluminum or copper heat exchanger performance with the same dimension. (author)

Chen, Lin; Li, Zhen; Guo, Zeng-Yuan [Department of Engineering Mechanics, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing 100084 (China)

2009-07-15

319

In vitro burn model illustrating heat conduction patterns using compressed thermal papers.

To date, heat conduction from heat sources to tissue has been estimated by complex mathematical modeling. In the present study, we developed an intuitive in vitro skin burn model that illustrates heat conduction patterns inside the skin. This was composed of tightly compressed thermal papers with compression frames. Heat flow through the model left a trace by changing the color of thermal papers. These were digitized and three-dimensionally reconstituted to reproduce the heat conduction patterns in the skin. For standardization, we validated K91HG-CE thermal paper using a printout test and bivariate correlation analysis. We measured the papers' physical properties and calculated the estimated depth of heat conduction using Fourier's equation. Through contact burns of 5, 10, 15, 20, and 30 seconds on porcine skin and our burn model using a heated brass comb, and comparing the burn wound and heat conduction trace, we validated our model. The heat conduction pattern correlation analysis (intraclass correlation coefficient: 0.846, p<0.001) and the heat conduction depth correlation analysis (intraclass correlation coefficient: 0.93, p<0.001) showed statistically significant high correlations between the porcine burn wound and our model. Our model showed good correlation with porcine skin burn injury and replicated its heat conduction patterns. PMID:25421614

Lee, Jun Yong; Jung, Sung-No; Kwon, Ho

2014-11-25

320

NASA Astrophysics Data System (ADS)

In the past, fuel elements with multiple axial coolant channels have been used in nuclear propulsion applications. A novel fuel element concept that reduces weight and increases efficiency uses a stack of grooved rings. Each fuel ring consists of a hole on the interior and grooves across the top face. Many grooved ring configurations have been modeled, and a single flow channel for each design has been analyzed. For increased efficiency, a fuel ring with a higher surface-area-to-volume ratio is ideal. When grooves are shallower and they have a lower surface area, the results show that the exit temperature is higher. By coupling the physics of fluid flow with those of heat transfer, the effects on the cooler gas flowing through the grooves of the hot, fissioning ring can be predicted. Models also show differences in velocities and temperatures after dense boundary nodes are applied. Parametric studies were done to show how a pressure drop across the length of the channels will affect the exit temperatures of the gas. Geometric optimization was done to show the temperature distributions and pressure drops that result from the manipulation of various parameters, and the effects of model scaling was also investigated. The inverse Graetz numbers are plotted against Nusselt numbers, and the results of these values suggest that the gas quickly becomes fully developed, laminar flow, rather than constant turbulent conditions.

Barkett, Laura Ashley

321

The complete conjugate heat conduction, convection and radiation problem for a heated block in a differentially heated square\\u000a enclosure is solved by an operator-splitting pseudo-time-stepping finite element method. The main feature of the solution\\u000a procedure is that the multi-phases are treated as a single computational domain with unknown interfacial boundary conditions.\\u000a The temperature distribution in the heated block and in

Y. Liu; N. Phan-Thien

1999-01-01

322

conductivity, and radiogenic heat production Lijuan He,1 Shengbiao Hu,1 Shaopeng Huang,2 Wencai Yang,3 Jiyang conductivities and radiogenic heat productions on more than 400 core samples from CCSD MH. The measured thermal conductivities range between 1.71 and 3.60 W m?1 K?1 , and the radiogenic heat productions vary from 0.01 mW m?3

Huang, Shaopeng

323

Effective heat conductivity of fuel element bundles and steam generator tube bundles

NASA Astrophysics Data System (ADS)

Effective heat conductivity of rod and tube bundles is one of thermophysical properties necessary for calculation of thermo hydraulic characteristics of heat producing devices, heat exchange devices and steam generators. This report introduces results of mathematical modeling of effective heat conductivity of transversally anisotropic rod bundles in solid conductive medium. The considered bundles represented cylindrical rods fitted in corners of stretched and compressed in direction of heat transfer rectangular and triangular grids. The calculated results were compared to analytical solutions and previous numerical results.

Fedotovsky, V.; Orlov, A.

2008-06-01

324

The role of heat conduction to the formation ofThe role of heat conduction to the formation-dependent Radiation Hydrodynamics models with heat conduction for such conditions. We have then calculated of our work is that heat conduction is needed to explain X-ray properties of wind-blown bubbles also in H

325

A two-parameter nondiffusive heat conduction model for data analysis in pump-probe experiments

NASA Astrophysics Data System (ADS)

Nondiffusive heat transfer has attracted intensive research interests in last 50 years because of its importance in fundamental physics and engineering applications. It has unique features that cannot be described by the Fourier law. However, current studies of nondiffusive heat transfer still focus on studying the effective thermal conductivity within the framework of the Fourier law due to a lack of a well-accepted replacement. Here, we show that nondiffusive heat conduction can be characterized by two inherent material properties: a diffusive thermal conductivity and a ballistic transport length. We also present a two-parameter heat conduction model and demonstrate its validity in different pump-probe experiments. This model not only offers new insights of nondiffusive heat conduction but also opens up new avenues for the studies of nondiffusive heat transfer outside the framework of the Fourier law.

Ma, Yanbao

2014-12-01

326

Nonstationary heat conduction in a single-walled carbon nanotube was investigated by applying a local heat pulse with duration of subpicoseconds. The investigation was based on classical molecular dynamics simulations, where the heat pulse was generated as coherent fluctuations by connecting a thermostat to the local cell for a short duration. The heat conduction through the nanotube was observed in terms of spatiotemporal temperature profiles. Results of the simulations exhibit non-Fourier heat conduction where a distinct amount of heat is transported in a wavelike form. The geometry of carbon nanotubes allows us to observe such a phenomenon in the actual scale of the material. The resulting spatiotemporal profile was compared with the available macroscopic equations, the so-called non-Fourier heat conduction equations, in order to investigate the applicability of the phenomenological models to a quasi-one-dimensional system. The conventional hyperbolic diffusion equation fails to predict the heat conduction due to the lack of local diffusion. It is shown that this can be remedied by adopting a model with dual relaxation time. Further modal analyses using wavelet transformations reveal a significant contribution of the optical phonon modes to the observed wavelike heat conduction. The result suggests that, in carbon nanotubes with finite length where the long-wavelength acoustic phonons behave ballistically, even optical phonons can play a major role in the non-Fourier heat conduction.

Shiomi, Junichiro; Maruyama, Shigeo [Department of Mechanical Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

2006-05-15

327

NASA Astrophysics Data System (ADS)

Subcooled flow boiling is generally characterized by high heat transfer capacity and low wall superheat, which is essential for cooling applications requiring high heat transfer rate, such as nuclear reactors and fossil boilers. In this study, subcooled flow boiling on copper and stainless steel heating surfaces was experimentally investigated from both macroscopic and microscopic points of view. Flow boiling heat flux and heat transfer coefficient were experimentally measured on both surfaces under different conditions, such as pressure, flow rate and inlet subcooling. Significant boiling heat transfer coefficient differences were found between the copper and the stainless steel heating surfaces. To explain the different flow boiling behaviors on these two heating surfaces, nucleation site density and bubble dynamics were visually observed and measured at different experimental conditions utilizing a high-speed digital video camera. These two parameters are believed to be keys in determining flow boiling heat flux. Wall superheat, critical cavity size and wall heat flux were used to correlate with nucleation site density data. Among them, wall heat flux shows the best correlation for eliminating both pressure and surface property effects. The observed nucleation site distribution shows a random distribution. When compared to the spatial Poisson distribution, similarity between them was found, while the measured nucleation site distribution is more uniform. From experimental observations, for the two surface materials investigated, which have similar surface wettability but sharply different thermal properties, bubble dynamics displayed fairly similar behavior. The obtained experimental results indicate that thermal conductivity of heating surface material plays an important role in boiling heat transfer. This is due to thermal conductivity having a significant impact on the lateral heat conduction at the heating surface and consequently temperature uniformity of the heating surface. A model was then developed and solved numerically for heat conduction at the heating surface when bubbles are present. Several key parameters which impact lateral heat conduction and surface temperature profile were studied. These parameters include material thermal conductivity, bubble size, heating surface thickness, etc. Numerical results show that, temperature profile on the heating surface tends to be more uniform and have a lower average value on a heating surface with higher thermal conductivity, which agrees well with the experimental observation.

Zou, Ling

328

Theory of combustion of a condensed propellant with a flat heat-conducting element

A theoretical analysis of the rate of combustion of a condensed propellant with heat-conducting elements is a complex problem associated with the solution of nonuniform equations of heat conduction. Hence, the known theoretical papers (see [2] and and references in it) contain a number of assumptions facilitating the solution of the problem but not permitting any construction of a closed

S. S. Rybanin; L. N. Stesik

1974-01-01

329

Transient radiative and conductive heat transfer in a fibrous medium with anisotropic optical properties is investigated. Two different kinds of boundary conditions are treated: when the temperatures imposed on the boundaries vary with time and when the medium is subject to a radiation source which varies with time. A one dimensional case is considered. The non-linear transient Heat Conduction Equation

Fatmir Asllanaj; Grard Jeandel; Jean Rodolphe Roche; David Lacroix

2004-01-01

330

An inverse analysis utilizing the conjugate gradient method of minimization and the adjoint equation is used for simultaneously estimating the temperature-dependent thermal conductivity and heat capacity per unit volume of a material. No prior information is used for the functional forms of the unknown thermal conductivity and heat capacity in the present study, thus, it is classified as the function

Cheng-Hung Huang; Yan Jan-Yuan

1995-01-01

331

The evolution of interstellar clouds in a streaming hot plasma including heat conduction

To examine the evolution of giant molecular clouds in the stream of a hot plasma we performed two-dimensional hydrodynamical simulations that take full account of self-gravity, heating and cooling effects and heat conduction by electrons. We use the thermal conductivity of a fully ionized hydrogen plasma proposed by Spitzer and a saturated heat flux according to Cowie & McKee in regions where the mean free path of the electrons is large compared to the temperature scaleheight. Significant structural and evolutionary differences occur between simulations with and without heat conduction. Dense clouds in pure dynamical models experience dynamical destruction by Kelvin-Helmholtz (KH) instability. In static models heat conduction leads to evaporation of such clouds. Heat conduction acting on clouds in a gas stream smooths out steep temperature and density gradients at the edge of the cloud because the conduction timescale is shorter than the cooling timescale. This diminishes the velocity gradient between the streaming plasma and the cloud, so that the timescale for the onset of KH instabilities increases, and the surface of the cloud becomes less susceptible to KH instabilities. The stabilisation effect of heat conduction against KH instability is more pronounced for smaller and less massive clouds. As in the static case more realistic cloud conditions allow heat conduction to transfer hot material onto the cloud's surface and to mix the accreted gas deeper into the cloud.

W. Vieser; G. Hensler

2007-04-26

332

Effect of sidewall conductance on heat-transport measurements for turbulent Rayleigh, California 93106 Received 31 July 2000; published 27 December 2000 For measurements of turbulent heat transport in Rayleigh-Be´nard convection the correction for the sidewall conductance is usually neglected

Fygenson, Deborah Kuchnir

333

Nonballistic heat conduction in an integrable random-exchange Ising chain studied with quantum numerically investigate the heat conduction in a random-exchange Ising spin chain by using the quantum master equation. The chain is subject to a uniform transverse field h, while the exchange couplings Qn between

Li, Baowen

334

Removal of numerical instability in the solution of an inverse heat conduction problem

In this paper, we consider an inverse heat conduction problem (IHCP). A set of temperature measurements at a single sensor location inside the heat conduction body is required. Using a transformation, the ill-posed IHCP becomes a Cauchy problem. Since the solution of Cauchy problem, exists and is unique but not always stable, the ill-posed problem is closely approximated by a

R. Pourgholi; N. Azizi; Y. S. Gasimov; F. Aliev; H. K. Khalafi

2009-01-01

335

Estimating thermal diffusivity and specific heat from needle probe thermal conductivity data

Thermal diffusivity and specific heat can be estimated from thermal conductivity measurements made using a standard needle probe and a suitably high data acquisition rate. Thermal properties are calculated from the measured temperature change in a sample subjected to heating by a needle probe. Accurate thermal conductivity measurements are obtained from a linear fit to many tens or hundreds of

William F. Waite; Lauren Y. Gilbert; William J. Winters; David H. Mason

2006-01-01

336

Evaluation of liquid behavior in a Variable Conductance Heat Pipe by neutron radiography

A Variable Conductance Heat Pipe (VCHP) is used as a cooling device for electrical equipments. The condensation area is passively controlled by the non-condensable gas volume in the VCHP depending on the heat load. The VCHP has often a bent pipe between the evaporation and condensation area. The heat pipe performance depends much on the bent pipe shape and configuration

K. Sugimoto; H. Asano; H. Murakawa; N. Takenaka; T. Nagayasu; S. Ipposhi

2011-01-01

337

A Simple Rate Law Experiment Using a Custom-Built Isothermal Heat Conduction Calorimeter

ERIC Educational Resources Information Center

Most processes (whether physical, chemical, or biological) produce or consume heat: measuring thermal power (the heat production rate) is therefore a typical method of studying processes. Here we describe the design of a simple isothermal heat conduction calorimeter built for use in teaching; we also provide an example of its use in simultaneously

Wadso, Lars; Li, Xi.

2008-01-01

338

Thermal conductivity and diffusivity of biomaterials measured with self-heated thermistors

This paper presents an experimental method to measure the thermal conductivity and thermal diffusivity of biomaterials. Self-heated thermistor probes, inserted into the tissue of interest, are used to deliver heat as well as to monitor the rate of heat removal. An empirical calibration procedure allows accurate thermal-property measurements over a wide range of tissue temperatures. Operation of the instrument in

J. W. Valvano; J. R. Cochran; K. R. Diller

1985-01-01

339

NASA Astrophysics Data System (ADS)

Faults can provide permeable pathways for fluids at a variety of scales, from great depth in the crust to flow through fractured aquifers, geothermal fields, and hydrocarbon reservoirs (Barton et al. 1995). In terms of geothermal energy exploration, it is essential to understand the role of faults and their impact on the thermal field and fluid system. 3D numerical simulations provide a useful tool for investigating the active physical processes in the subsurface. To assess the influence of major fault zones on the thermal field and fluid system, 3D coupled fluid and heat transport simulations are carried out. The study is based on a recently published structural model of the Brandenburg area, which is located in the south-eastern part of the Northeast German Basin (NEGB) (Noack et al. 2010). Two major fault zones of the Elbe Fault System (Gardelegen and Lausitz Escarpments) vertically offset the pre-Permian basement against the Permian to Cenozoic basin fill at the southern margin by several km (Scheck et al. 2002). Within the numerical models, these two major fault zones are represented as equivalent porous media and vertical discrete elements. The coupled system of equations describing fluid flow and heat transport in saturated porous media are numerically solved by the Finite Element software FEFLOW (Diersch, 2002). Different possible geological scenarios are modelled and compared to a simulation in which no faults are considered. In one scenario the fault zones are set as impermeable. In this case, the thermal field is similar to the no fault model. Fluid flow is redirected because the fault zones act as hydraulic barriers that prevent a lateral fluid advection into the fault zones. By contrast, modelled permeable fault zones induce a pronounced thermal signature with distinctly cooler temperatures than in the no fault model. Fluid motion within the fault is initially triggered by advection due to hydraulic head gradients, but may be even enhanced by buoyancy forces caused by density gradients mainly occurring due to differences in the temperature. References: Barton, C.A., Zoback, M.D., Moos, D., 1995. Fluid flow along potentially active faults in crystalline rock. Geology 23 (8), 683-686.

Yvonne, Cherubini; Mauro, Cacace; Scheck-Wenderoth, Magdalena

2013-04-01

340

Variable Conductance Heat Pipe Cooling of Stirling Convertor and General Purpose Heat Source

NASA Technical Reports Server (NTRS)

In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental results from integrating the VCHP with an operating Stirling convertor and describes the methodology used to achieve their successful combined operation.

Tarau, Calin; Schwendeman, Carl; Anderson William G.; Cornell, Peggy A.; Schifer, Nicholas A.

2013-01-01

341

Investigation of Heat Conductivity in Relativistic Systems using a Partonic Cascade

Motivated by the classical picture of heat flow we construct a stationary temperature gradient in a relativistic microscopic transport model. Employing the relativistic Navier-Stokes ansatz we extract the heat conductivity {\\kappa} for a massless Boltzmann gas using only binary collisions with isotropic cross sections. We compare the numerical results to analytical expressions from different theories and discuss the final results. The directly extracted value for the heat conductivity can be referred to as a literature reference within the numerical uncertainties.

M. Greif; F. Reining; I. Bouras; G. S. Denicol; Z. Xu; C. Greiner

2013-01-07

342

The effect of heat conduction on the interaction of disk and corona around black holes

Heat conduction plays an important role in the balance between heating and cooling in many astrophysical objects, e.g. cooling flows in clusters of galaxies. Here we investigate the effect of heat conduction on the interaction between a cool disk and a hot corona around black holes. Using the one-radial-zone approximation, we study the vertical structure of the disk corona and

E. Meyer-Hofmeister; F. Meyer

2006-01-01

343

A two-fluid model for relativistic heat conduction

Three years ago it was presented in these proceedings the relativistic dynamics of a multi-fluid system together with various applications to a set of topical problems [1]. In this talk, I will start from such dynamics and present a covariant formulation of relativistic thermodynamics which provides us with a causal constitutive equation for the propagation of heat in a relativistic setting.

Lpez-Monsalvo, Csar S. [Instituto de Ciencias Nucleares, Universidad Nacional Autnoma de Mxico (Mexico)

2014-01-14

344

NASA Technical Reports Server (NTRS)

In the present investigation of crystalline phase internal radiation and heat conduction during the vertical Bridgman growth of a YAG-like oxide crystal, where transport through the melt is dominated by convection and conduction, heat is also noted to be conducted through ampoule walls via natural convection and enclosure radiation. The results of a quasi-steady-state axisymmetric Galerkin FEM indicate that heat transfer through the system is powerfully affected by the optical absorption coefficient of the crystal. The coupling of internal radiation through the crystal with conduction through the ampoule walls promotes melt/crystal interface shapes that are highly reflected near the ampoule wall.

Brandon, S.; Derby, J. J.

1992-01-01

345

Low heat conduction in white dwarf boundary layers?

X-ray spectra of dwarf novae in quiescence observed by Chandra and XMM-Newton provide new information on the boundary layers of their accreting white dwarfs. Comparison of observations and models allows us to extract estimates for the thermal conductivity in the accretion layer and reach conclusions on the relevant physical processes. We calculate the structure of the dense thermal boundary layer that forms under gravity and cooling at the white dwarf surface on accretion of gas from a hot tenuous ADAF-type coronal inflow. The distribution of density and temperature obtained allows us to calculate the strength and spectrum of the emitted X-ray radiation. They depend strongly on the values of thermal conductivity and mass accretion rate. We apply our model to the dwarf nova system VW Hyi and compare the spectra predicted for different values of the thermal conductivity with the observed spectrum. We find a significant deviation for all values of thermal conductivity that are a sizable fraction of the Spitzer conductivity. A good fit arises however for a conductivity of about 1% of the Spitzer value. This also seems to hold for other dwarf nova systems in quiescence. We compare this result with thermal conduction in other astrophysical situations. The highly reduced thermal conductivity in the boundary layer requires magnetic fields perpendicular to the temperature gradient. Locating their origin in the accretion of magnetic fields from the hot ADAF-type coronal flow we find that dynamical effects of these fields will lead to a spatially intermittent, localized accretion geometry at the white dwarf surface.

F. K. Liu; F. Meyer; E. Meyer-Hofmeister; V. Burwitz

2008-03-13

346

Analysis of nonsteady heat conduction between the heat exchanger pipes of a heat pump and the ground

A heat pump installation for the heating and cooling of a house is considered. During the winter months heat for the operation of the evaporator of the heat pump is taken from the ground. During the summer the heat given off by the condenser is transferred to the ground. The conditions for the heat transfer between the pipes of the

J. Neiss; E. R. F. Winter

1976-01-01

347

Heat mirrors on plastic sheet using transparent oxide conducting coatings

A technique of reactive d.c. magnetron sputtering with RF substrate bias was evolved to give metal oxide films which exhibit heat reflecting properties while remaining highly transparent. Films or indium-tin, indium and cadmium-tin oxide were were deposited onto plastic sheet at room temperature at rates of greater than 0.5 microns min. Preliminary assessments of durability with accelerated weathering with exposure

R. P. Howson; M. I. Ridge

1982-01-01

348

Heat conduction in cooling flows. [in clusters of galaxies

NASA Technical Reports Server (NTRS)

It has been suggested that electron conduction may significantly reduce the accretion rate (and star foramtion rate) for cooling flows in clusters of galaxies. A numerical hydrodynamics code was used to investigate the time behavior of cooling flows with conduction. The usual conduction coefficient is modified by an efficiency factor, mu, to realize the effects of tangled magnetic field lines. Two classes of models are considered, one where mu is independent of position and time, and one where inflow stretches the field lines and changes mu. In both cases, there is only a narrow range of initial conditions for mu in which the cluster accretion rate is reduced while a significant temperature gradient occurs. In the first case, no steady solution exists in which both conditions are met. In the second case, steady state solutions occur in which both conditions are met, but only for a narrow range of initial values where mu = 0.001.

Bregman, Joel N.; David, L. P.

1988-01-01

349

Estimation of the temperature-dependent thermal conductivity in inverse heat conduction problems

An iterative approach is presented to determine the temperature-dependent thermal conductivity from the temperature measurements taken at one side of boundary. On the basis of the proposed method, the undetermined thermal conductivity is first denoted as the unknown variables in a set of nonlinear equations, which are formulated from the measured temperature and the calculated temperature. Then, a linearization method

Ching-yu Yang

1999-01-01

350

The cold cap is a layer of reacting glass batch floating on the surface of melt in an all-electric continuous glass melter. The heat needed for the conversion of the melter feed to molten glass must be transferred to and through the cold cap. Since the heat flux into the cold cap determines the rate of melting, the heat conductivity is a key property of the reacting feed. We designed an experimental setup consisting of a large cylindrical crucible with an assembly of thermocouples that monitors the evolution of the temperature field while the crucible is heated at a constant rate. Then we used two methods to calculate the heat conductivity and thermal diffusivity of the reacting feed: the approximation of the temperature field by polynomial functions and the finite-volume method coupled with least-squares analysis. Up to 680C, the heat conductivity of the reacting melter feed was represented by a linear function of temperature.

Pokorny, Richard; Rice, Jarrett A.; Schweiger, Michael J.; Hrma, Pavel R.

2013-06-01

351

NASA Technical Reports Server (NTRS)

The phenomenon of hyperbolic heat conduction in contrast to the classical (parabolic) form of Fourier heat conduction involves thermal energy transport that propagates only at finite speeds, as opposed to an infinite speed of thermal energy transport. To accommodate the finite speed of thermal wave propagation, a more precise form of heat flux law is involved, thereby modifying the heat flux originally postulated in the classical theory of heat conduction. As a consequence, for hyperbolic heat conduction problems, the thermal energy propagates with very sharp discontinuities at the wave front. Accurate solutions are found for a class of one-dimensional hyperbolic heat conduction problems involving non-Fourier effects that can be used effectively for representative benchmark tests and for validating alternate schemes. Modeling/analysis formulations via specially tailored hybrid computations are provided for accurately modeling the sharp discontinuities of the propagating thermal wave front. Comparative numerical test models are presented for various hyperbolic heat conduction models involving non-Fourier effects to demonstrate the present formulations.

Tamma, Kumar K.; Railkar, Sudhir B.

1989-01-01

352

Comparison of HAM and HPM methods in nonlinear heat conduction and convection equations

Recently, Rajabi et al. (Application of homotopy perturbation method in nonlinear heat conduction and convection equations, Phys. Lett. A 360 (2007) 570573.) discussed the solutions of temperature distribution in lumped system of combined convectionradiation. They solved a nonlinear equation of the steady conduction in a slab with variable thermal conductivity using both perturbation and homotopy perturbation methods. They claim that

M. Sajid; T. Hayat

2008-01-01

353

Heat transfer enhancement in laminar slurry pipe flows with power law thermal conductivities

Generalized theoretical results for heat transfer in laminar pipe flow with power law varying thermal conductivities are presented. The study is motivated by experimental observations that above a threshold shear rate the effective thermal conductivity for disperse two-phase mixtures increases with shear rate. Using a relatively general three parameter power law model for conductivity as a function of shear rate,

C. W. Sohn; M. M. Chen

1984-01-01

354

Thermal conductivity and heat transfer through the snow on the ice of the Beaufort Sea

Thermal conductivity and heat transfer through the snow on the ice of the Beaufort Sea Matthew] Eighty-nine point measurements of the thermal conductivity (ks) of the snow on the sea ice estimates of the thermal conductivity of the snow (ks) based regression equations relating ks to snow

Sturm, Matthew

355

Heat conductivity in the beta-FPU lattice. Solitons and breathers as energy carriers

This paper consists of two parts. The first part proposes a new methodological framework within which the heat conductivity in 1D lattices can be studied. The total process of heat conductivity is decomposed into two contributions where the first one is the equilibrium process at equal temperatures T of both lattice ends and the second -- non-equilibrium process with the temperature \\Delta T of one end and zero temperature of the other. The heat conductivity in the limit \\Delta T \\to 0 is reduced to the heat conductivity of harmonic lattice. A threshold temperature T_{thr} scales T_{thr}(N) \\sim N^{-3} with the lattice size N. Some unusual properties of heat conductivity can be exhibited on nanoscales at low temperatures. The thermodynamics of the \\beta-FPU lattice can be adequately approximated by the harmonic lattice. The second part testifies in the favor of the soliton and breather contribution to the heat conductivity in contrast to [N. Li, B. Li, S. Flach, PRL 105 (2010) 054102]. In the continuum limit the \\beta-FPU lattice is reduced to the modified Korteweg - de Vries equation with soliton and breather solutions. Numerical simulations demonstrate their high stability. New method for the visualization of moving solitons and breathers is suggested. An accurate expression for the dependence of the sound velocity on temperature is also obtained. Our results support the conjecture on the solitons and breathers contribution to the heat conductivity.

T. Yu. Astakhova; V. N. Likhachev; G. A. Vinogradov

2011-03-18

356

Problems in suppressing cooling flows in clusters of galaxies by global heat conduction

I use a simple analytical model to show that simple heat conduction models cannot significantly suppress cluster cooling flows. I build a static medium where heat conduction globally balances radiative cooling, and then perturb it. I show that a perturbation extending over a large fraction of the cooling flow region will grow to the non-linear regime within a Hubble time. Such perturbations are reasonable in clusters which frequently experience mergers and/or AGN activity. This result strengthens previous findings which show that a steady solution does not exist for a constant heat conduction coefficient.

Noam Soker

2003-02-19

357

Author's personal copy Pyroelectric waste heat energy harvesting using heat conduction

-product of power, refrigeration, or heat pump cycles according to the second law of thermodynamics [1]. In 2009 pump, cryogenic refrigeration, and air liquefaction applications [3]. Organic Rankine cycles use heat harvesting Olsen cycle a b s t r a c t Waste heat can be directly converted into electrical energy

Pilon, Laurent

358

An empirical approach to determine the effective thermal conductivity of a binary mixed material with heat generation is developed and reported. The approach is developed for a steady state problem with spherical geometry. The approach is based on two main ideas: a structural approximation and an empirical formulation. As for the structural approximation, the binary mixed material was assumed to be equivalent to a binary layered system of adjacent fuel and moderator layers oriented perpendicular to the heat flux. An empirical approach was then used to conduct a general correlation for the effective thermal conductivity of a binary layered system with heat generation. This empirical approach was conducted systematically by considering the parametric and operational condition effects of the system on the overall effective thermal conductivity. Results are then compared to some experimental data as well as with thermal conductivity values predicted by an empirical correlation that is based on experimental data. (authors)

Abu Saleem, R. A.; Rizwan-Uddin [Dept. of Nuclear, Plasma and Radiological Engineering, Univ. of Illinois at Urbana-Champaign, 216 Talbot Lab., 104 S. Wright St, Urbana, IL 61801 (United States)

2012-07-01

359

Augmentation of Performance of a Monogroove Heat Pipe with Electrohydrodynamic Conduction Pumping

NASA Astrophysics Data System (ADS)

The electrohydrodynamic (EHD) phenomena involve the interaction of electric fields and flow fields in a dielectric fluid medium. There are three types of EHD pumps; induction, ion-drag, and conduction. EHD conduction pump is a new concept which has been explored only recently. Net pumping is achieved by properly utilizing the heterocharge layers present in the vicinity of the electrodes. Several innovative electrode designs have been investigated. This paper presents an electrode design that generates pressure heads on the order of 600 Pa per one electrode pair at 20 kV with less than 0.08 W of electric power. The working fluid is the Refrigerant R-123. An EHD conduction pump consisting of six pairs of electrodes is installed in the liquid line of a mono-grove heat pipe. The heat transport capacity of the heat pipe is measured in the absence and presence of the EHD conduction pump. Significant enhancements in the heat transport capacity of the heat pipe is achieved with the EHD conduction pump operating. Furthermore, the EHD conduction pump provides immediate recovery from the dry-out condition. The EHD conduction pump has many advantages, especially in the micro-gravity environment. It is simple in design, non-mechanical, and lightweight. It provides a rapid control of heat transfer in single-phase and two-phase flows. The electric power consumption is minimal with the very low acoustic noise level.

Jeong, S. I.; Seyed-Yagoobi, J.

2002-11-01

360

Molecular dynamics analysis of spectral characteristics of phonon heat conduction in silicon

Due to the technological significance of silicon, its heat conduction mechanisms have been studied extensively. However, there have been some lingering questions surrounding the phonon mean free path and importance of ...

Henry, Asegun Sekou Famake

2006-01-01

361

Subgrid-scale modeling of compressible magnetohydrodynamic turbulence in heat-conducting plasma

A large-eddy simulation (LES) approach for compressible magnetohydrodynamic (MHD) turbulence in heat-conducting plasma is developed for the first time. Subgrid-scale models for new terms appearing due to the presence of magnetic field are suggested. Results of modeling for decaying compressible MHD turbulence are presented. Comparison and testing with results obtained by direct numerical simulation are made. The efficiency of the developed LES technique for compressible MHD turbulence in heat-conducting plasma is shown.

Chernyshov, A. A.; Karelsky, K. V.; Petrosyan, A. S. [Theoretical Section, Space Research Institute of the Russian Academy of Sciences, Profsoyuznaya 84/32, 117997 Moscow (Russian Federation)

2006-10-15

362

We report 70 measurements of conductive heat flow at the 50-m-high, 200-m-diameter TAG active hydrothermal mound, made during submersible surveys with Alvin in 1993 and 1995 and Shinkai 6500 in 1994. The stations were all measured with 5-thermistor, 0.6- or 1-m-long Alvin heat flow probes, which are capable of determining both gradient and thermal conductivity, and were transponder-navigated to an

K. Becker; R. von Herzen; J. Kirklin; R. Evans; D. Kadko; M. Kinoshita; O. Matsubayashi; R. Mills; A. Schultz; P. Rona

1996-01-01

363

The importance of electron heat conduction in the energy balance of the F-region

NASA Technical Reports Server (NTRS)

Taking into account heat conduction in the analysis of electron temperature data acquired by the AE-C satellite during the daytime at middle latitudes is shown to bring theoretical electron temperature profiles in good agreement with experimental ones. Middle latitude passes were chosen because in this region the horizontal electron temperature gradient is negligible and the height variation can be approximated by the satellite data. Inclusion of heat conduction is shown to have little effect on low-latitude data.

Hoegy, W. R.; Brace, L. H.

1978-01-01

364

NASA Technical Reports Server (NTRS)

A numerical procedure is presented for analyzing a wide variety of heat conduction problems in multilayered bodies having complex geometry. The method is based on a finite difference solution of the heat conduction equation using a body fitted coordinate system transformation. Solution techniques are described for steady and transient problems with and without internal energy generation. Results are found to compare favorably with several well known solutions.

Masiulaniec, K. C.; Keith, T. G., Jr.; Dewitt, K. J.

1984-01-01

365

Theoretical and Numerical Studies of Noncontinuum Gas-Phase Heat Conduction in Micro\\/Nano Devices

This article presents a comprehensive study of various modeling techniques for noncontinuum gas-phase heat conduction encountered in micro\\/nano devices over a broad range of Knudsen number. A new slip model is proposed for slip flows and an analytical approach is developed for collisionless steady-state heat conduction inside a fully diffuse enclosure. Excellent agreements with direct simulation Monte Carlo (DSMC) simulations

Taishan Zhu; Wenjing Ye

2010-01-01

366

NASA Technical Reports Server (NTRS)

The theory of sound propagation is examined in a viscous, heat-conducting fluid, initially at rest and in a uniform state, and contained in a rigid, impermeable duct with isothermal walls. Topics covered include: (1) theoretical formulation of the small amplitude fluctuating motions of a viscous, heat-conducting and compressible fluid; (2) sound propagation in a two dimensional duct; and (3) perturbation study of the inplane modes.

Huerre, P.; Karamcheti, K.

1976-01-01

367

Conjugate natural convection heat transfer in a two-dimensional, air-filled enclosure containing discrete internal heat sources and an internal baffle is examined. The enclosure formed of finite conductive walls is designed to simulate the behavior of an experimental window calorimeter in order to correct for losses from the calorimeter. The equations are solved using a finite-volume method for a wide range

A. F. Emery

1997-01-01

368

??The spectacular heat transfer enhancement revealed experimentally in nanofluids suspensions is being investigated theoretically at the macro-scale level aiming at explaining the possible mechanisms that (more)

Vadasz, Johnathan J.

2005-01-01

369

This article considers the problem of conjugate heat transfer in circular pipes with finite heated length to examine the effects of wall conduction on the heat transfer characteristics of solidliquid phase-change material suspension flow. A mixture continuum approach is adopted in the formulation of the energy equation, with an approximate enthalpy model describing the phase-change process in the phase-change material

C. J. Ho; J. F. Lin; S. Y. Chiu

2004-01-01

370

NASA Astrophysics Data System (ADS)

The current 3D hype creates a lot of interest in 3D. People go to 3D movies, but are we ready to use 3D in our homes, in our offices, in our communication? Are we ready to deliver real 3D to a general public and use interactive 3D in a meaningful way to enjoy, learn, communicate? The CARARE project is realising this for the moment in the domain of monuments and archaeology, so that real 3D of archaeological sites and European monuments will be available to the general public by 2012. There are several aspects to this endeavour. First of all is the technical aspect of flawlessly delivering 3D content over all platforms and operating systems, without installing software. We have currently a working solution in PDF, but HTML5 will probably be the future. Secondly, there is still little knowledge on how to create 3D learning objects, 3D tourist information or 3D scholarly communication. We are still in a prototype phase when it comes to integrate 3D objects in physical or virtual museums. Nevertheless, Europeana has a tremendous potential as a multi-facetted virtual museum. Finally, 3D has a large potential to act as a hub of information, linking to related 2D imagery, texts, video, sound. We describe how to create such rich, explorable 3D objects that can be used intuitively by the generic Europeana user and what metadata is needed to support the semantic linking.

Pletinckx, D.

2011-09-01

371

We investigate a new method of gas analysis based on the determination of thermal conductivity, specific heat capacity and thermal diffusivity. A silicon micro-wire surrounded by the gas is supplied with transient heat power (sinusoidal or square wave signal). The induced transient changes in gas temperature are detected in several well defined distances from the heater. We demonstrate the detection

K. Kliche; S. Billat; F. Hedrich; C. Ziegler; R. Zengerle

2011-01-01

372

Transient radiative and conductive heat transfer in an absorbing, emitting and anisotropically scattering gray slab is investigated. The medium is confined within parallel walls and is excited by a heat pulse stimulation on the front face. The phase function corresponds to a second-degree anisotropic scattering and includes isotropic, linearly anisotropic and Rayleigh modes of scattering. The semi-analytical approach, based on

M. Lazard; S. Andre; D. Maillet

2001-01-01

373

Conductive heat flow anomalies over a hot spot in a moving medium

In the model the hot spot is represented by a point source of heat in an infinite half space moving uniformly in the x direction with velocity U (z is positive downward; y is horizontal and normal to motion). Only steady state conductive heat transfer is considered. The upper boundary condition, zero surface temperature, is satisfied by addition of a

Francis S. Birch

1975-01-01

374

The numerical investigation method of unsteady transfer processes in evaporating droplets in radiating media is introduced, evaluating the dependence of optical spectral properties of material upon temperature. The distribution of temperature and heat fluxes regularities in heating and simultaneously evaporating water droplets has been investigated. It is shown that as a cause of interaction of radiation and conduction processes, the

G. Miliauskas

2001-01-01

375

Observations were made of the operation of a gas loaded, variable conductance heat pipe two inches in diameter and sixty inches long. The heat pipe was operated in the horizontal and vertical positions while input power was varied from twenty five to one hundred fifty watts. Liquid crystal thermographic techniques were used to observe the temperature gradients existing when non-condensible

W. H. Batts Jr.; W. H. Jr

1975-01-01

376

Free-convection energy transport in variable conductance heat pipes (VCHP)

During gravity testing of gas loaded variable conductance heat pipes (VCHP), large axial energy transport is sometimes observed in temperature gradient lengths of the gas blocked tubing. This energy transport is shown to be caused by free convection heat and vapor mass transfer circulation created by vapor\\/gas mixture density differences near the ends of the temperature gradient lengths. An analytical

R. M. Cima

1986-01-01

377

Heat conduction in anisotropic media: Nonlinear self-adjointness and conservation laws

Nonlinear self-adjointness of the anisotropic nonlinear heat equation is investigated. Mathematical models of heat conduction in anisotropic media with a source are considered and a class of self-adjoint models is identified. Conservation laws corresponding to the symmetries of the equations in question are computed.

Nail H. Ibragimov; Elena D. Avdonina

2012-02-27

378

THE RATH MESHER--A 7090 PROGRAM FOR PREPARING INPUT DATA FOR HEAT CONDUCTION CODES

A description is given of an IBM 7090 code which divides irregularly ; shaped two-dimensional figures into mesh nodes suitable for use in heat ; conduction calculations using any of several existing general geometry heat codes. ; An example of its use is included. (auth);

Thomas; R. F. Jr

1962-01-01

379

Simultaneous wall and fluid axial conduction in laminar pipe-flow heat transfer

Consideration is given to a laminar pipe flow in which the upstream portion of the wall is externally insulated while the downstream portion of the wall is uniformly heated. An analysis of the problem is performed whose special feature is the accounting of axial conduction in both the tube wall and in the fluid. This conjugate heat transfer problem is

M. Faghri; E. M. Sparrow

1980-01-01

380

NASA Astrophysics Data System (ADS)

Melting anomalies in the Earth's upper mantle have often been attributed to the presence of mantle plumes that may originate in the lower mantle, possibly from the core-mantle boundary. Globally, mantle plumes exhibit a large range in buoyancy flux that which is proportional to their temperature and volume. Plumes with higher buoyancy fluxes should have higher temperatures and experience higher degrees of partial melting. Excess heat in mantle plumes could reflect either a) an enrichment of the heat producing elements (HPE: U, Th, K) in their mantle source leading to an increase of heat production by radioactive decay or b) advective or conductive heat transport across the core-mantle boundary. The advective transport of heat may result in a physical contribution of material from the core to the lower mantle. If core material is incorporated into the lower mantle, mantle plumes with a higher buoyancy flux should have higher core tracers, e.g. increased 186Os and Fe concentrations. Geophysical and dynamic modelling indicate that at least Afar, Easter, Hawaii, Louisville and Samoa may all originate at the core-mantle boundary. These plumes encompass the whole range of known buoyancy fluxes from 1.2 Mgs -1(Afar) to 6.5 Mgs -1 (Hawaii) providing evidence that the buoyancy flux is largely independent of other geophysical parameters. In an effort to explore whether the heat producing elements are the cause of excess heat we looked for correlations between fractionation corrected concentrations of the HPE and buoyancy flux. Our results suggest that there is no correlation between HPE concentrations and buoyancy flux (with and without an additional correction for variable degrees of partial melting). As anticipated, K, Th and U are positively correlated with each other (e.g. Hawaii, Iceland and Galapagos have significantly lower concentrations than e.g. Tristan da Cunha, the Canary Islands and the Azores). We also find no correlation between currently available Fe concentration data and buoyancy flux. The apparent lack of correlation suggests that excess heat may be a result of conductive heat contribution from the core. Additional precise 186Os and Fe data are needed to further assess these conclusions.

Rushmer, T.; Beier, C.; Turner, S.

2007-12-01

381

Effects of anisotropic conduction and heat pipe interaction on minimum mass space radiators

NASA Technical Reports Server (NTRS)

Equations are formulated for the two dimensional, anisotropic conduction of heat in space radiator fins. The transverse temperature field was obtained by the integral method, and the axial field by numerical integration. A shape factor, defined for the axial boundary condition, simplifies the analysis and renders the results applicable to general heat pipe/conduction fin interface designs. The thermal results are summarized in terms of the fin efficiency, a radiation/axial conductance number, and a transverse conductance surface Biot number. These relations, together with those for mass distribution between fins and heat pipes, were used in predicting the minimum radiator mass for fixed thermal properties and fin efficiency. This mass is found to decrease monotonically with increasing fin conductivity. Sensitivities of the minimum mass designs to the problem parameters are determined.

Baker, Karl W.; Lund, Kurt O.

1991-01-01

382

Numerical simulation of a latent heat thermal energy storage system with enhanced heat conduction

A latent heat storage system has been designed to take advantage of the off-peak electrical energy for space heating. Using an enthalpy formation and a fully implicit finite difference method, the thermal performance of such a storage system with and without fins has been analysed. For the one-dimensional simulation model, calculations have been made for the melt fraction and energy

M. Costa; D. Buddhi; A. Oliva

1998-01-01

383

RASMOT-3D PRO: a 3D motif search webserver

Detection of structural motif of residues in protein structures allows identification of structural or functional similarity between proteins. In the field of protein engineering, structural motif identification is essential to select protein scaffolds on which a motif of residues can be transferred to design a new protein with a given function. We describe here the RASMOT-3D PRO webserver (http://biodev.extra.cea.fr/rasmot3d/) that performs a systematic search in 3D structures of protein for a set of residues exhibiting a particular topology. Comparison is based on C? and C? atoms in two steps: inter-atomic distances and RMSD. RASMOT-3D PRO takes in input a PDB file containing the 3D coordinates of the searched motif and provides an interactive list of identified protein structures exhibiting residues of similar topology as the motif searched. Each solution can be graphically examined on the website. The topological search can be conducted in structures described in PDB files uploaded by the user or in those deposited in the PDB. This characteristic as well as the possibility to reject scaffolds sterically incompatible with the target, makes RASMOT-3D PRO a unique webtool in the field of protein engineering. PMID:19417073

Debret, Galle; Martel, Arnaud; Cuniasse, Philippe

2009-01-01

384

RASMOT-3D PRO: a 3D motif search webserver.

Detection of structural motif of residues in protein structures allows identification of structural or functional similarity between proteins. In the field of protein engineering, structural motif identification is essential to select protein scaffolds on which a motif of residues can be transferred to design a new protein with a given function. We describe here the RASMOT-3D PRO webserver (http://biodev.extra.cea.fr/rasmot3d/) that performs a systematic search in 3D structures of protein for a set of residues exhibiting a particular topology. Comparison is based on Calpha and Cbeta atoms in two steps: inter-atomic distances and RMSD. RASMOT-3D PRO takes in input a PDB file containing the 3D coordinates of the searched motif and provides an interactive list of identified protein structures exhibiting residues of similar topology as the motif searched. Each solution can be graphically examined on the website. The topological search can be conducted in structures described in PDB files uploaded by the user or in those deposited in the PDB. This characteristic as well as the possibility to reject scaffolds sterically incompatible with the target, makes RASMOT-3D PRO a unique webtool in the field of protein engineering. PMID:19417073

Debret, Galle; Martel, Arnaud; Cuniasse, Philippe

2009-07-01

385

Microwave absorption in powders of small conducting particles for heating applications.

In microwave chemistry there is a common misconception that small, highly conducting particles heat profusely when placed in a large microwave electric field. However, this is not the case; with the simple physical explanation that the electric field (which drives the heating) within a highly conducting particle is highly screened. Instead, it is the magnetic absorption associated with induction that accounts for the large experimental heating rates observed for small metal particles. We present simple principles for the effective heating of particles in microwave fields from calculations of electric and magnetic dipole absorptions for a range of practical values of particle size and conductivity. For highly conducting particles, magnetic absorption dominates electric absorption over a wide range of particle radii, with an optimum absorption set by the ratio of mean particle radius a to the skin depth ? (specifically, by the condition a = 2.41?). This means that for particles of any conductivity, optimized magnetic absorption (and hence microwave heating by magnetic induction) can be achieved by simple selection of the mean particle size. For weakly conducting samples, electric dipole absorption dominates, and is maximized when the conductivity is approximately ? ? 3??(0) ? 0.4 S m(-1), independent of particle radius. Therefore, although electric dipole heating can be as effective as magnetic dipole heating for a powder sample of the same volume, it is harder to obtain optimized conditions at a fixed frequency of microwave field. The absorption of sub-micron particles is ineffective in both magnetic and electric fields. However, if the particles are magnetic, with a lossy part to their complex permeability, then magnetic dipole losses are dramatically enhanced compared to their values for non-magnetic particles. An interesting application of this is the use of very small magnetic particles for the selective microwave heating of biological samples. PMID:23321957

Porch, Adrian; Slocombe, Daniel; Edwards, Peter P

2013-02-28

386

About influence of gravity on heat conductivity process of the Planets

In the present study it is shown that the interaction of a quasi-static gravitational wave through density fluctuations gives rise to a heat conductivity coefficient and hence temperature. This fact is a very important characteristics to establish a heat equilibrium process of such massive body as the Earth and other Planets. To carry out this exercise general mechanism has been provided, which makes a bridge between classical physics and quantum theory, and specific dependence of heat conductivity coefficient in wide region is also calculated.

Gladkov, S O; Ray, Saibal; Rahaman, F

2015-01-01

387

About influence of gravity on heat conductivity process of the Planets

In the present study it is shown that the interaction of a quasi-static gravitational wave through density fluctuations gives rise to a heat conductivity coefficient and hence temperature. This fact is a very important characteristics to establish a heat equilibrium process of such massive body as the Earth and other Planets. To carry out this exercise general mechanism has been provided, which makes a bridge between classical physics and quantum theory, and specific dependence of heat conductivity coefficient in wide region is also calculated.

S. O. Gladkov; Anil Yadav; Saibal Ray; F. Rahaman

2014-07-30

388

Thermal Conductivity of Argillaceous Rocks: Determination Methodology Using In Situ Heating Tests

NASA Astrophysics Data System (ADS)

This study focuses on the characterisation of thermal conductivity for three potential host rocks for radioactive waste disposal. First, the heat conduction process is reviewed on the basis of an analytical solution and key aspects related to anisotropic conduction are discussed. Then the existing information on the three rocks is summarised and a broad uncertainty range of thermal conductivity is estimated based on the mineralogical composition. Procedures to backanalyse the thermal conductivity on the basis of in situ heating tests are assessed and a methodology is put forward. Finally, this methodology is used to estimate the impact of experimental uncertainties and applied to the four in situ heating tests. In the three potential host rocks, a clear influence of the bedding planes was identified and anisotropic heat conduction was shown to be necessary to interpret the observed temperature field. Experimental uncertainties were also shown to induce a larger uncertainty on the anisotropy ratio than on the equivalent thermal conductivity defined as the geometric mean of the thermal conductivity in the three principal directions.

Garitte, Benoit; Gens, Antonio; Vaunat, Jean; Armand, Gilles

2014-01-01

389

Collisionless conductivity and stochastic heating of the plasma sheet in the geomagnetic tail

The chaotic single particle orbits in the geomagnetic tail are used to calculate the collisionless conductivity. It is shown that the stochasticity from inhomogeneous magnetic fields leads to a power law decay of the single particle correlation function similar to an elastic collisional process. The height-integrated dissipative part of the collisionless conductivity governs the irreversible stochastic heating of the plasma

Wendell Horton; T. Tajima

1991-01-01

390

The need for the engineering analysis of systems in which the transport of thermal energy occurs primarily through a conduction process is a common situation. For all but the simplest geometries and boundary conditions, analytic solutions to heat conduction problems are unavailable, thus forcing the analyst to call upon some type of approximate numerical procedure. A wide variety of numerical

Micheal W. Glass; Hogan Roy E. Jr; David K. Gartling

2010-01-01

391

Combined radiation and conduction heat transfer in high temperature fiber thermal insulation

Three different approaches for describing combined radiation and conduction heat transfer in fiber thermal insulation at high temperatures are analyzed and compared. The considered approaches include the radiation transfer equation or its approximations, approximation of radiation thermal conductivity and the radiation diffusion approximation for radiation transfer. The first causes difficulties due to the need for experimental measurement of optical properties,

Vadim A. Petrov

1997-01-01

392

An analysis of the performance of a vertically oriented, gas loaded, variable conductance heat pipe

An analysis of steady state operation of a vertically oriented, variable conductance heat pipe is presented. The effects of binary mass diffusion, axial pipe wall conduction, and gravitational effects, caused by the difference in molecular weight of the non-condensible gas and the working fluid are incorporated. Analytical expressions for the conservation of mass, momentum, and energy are combined along with

G. A. Glover Sr.

1986-01-01

393

ERIC Educational Resources Information Center

This study proposes a multi-dimensional approach to investigate, represent, and categorize students' in-depth understanding of complex physics concepts. Clinical interviews were conducted with 30 undergraduate physics students to probe their understanding of heat conduction. Based on the data analysis, six aspects of the participants' responses

Chiou, Guo-Li; Anderson, O. Roger

2010-01-01

394

Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997

Grout is used to seal the annulus between the borehole and heat exchanger loops in vertical geothermal (ground coupled, ground source, GeoExchange) heat pump systems. The grout provides a heat transfer medium between the heat exchanger and surrounding formation, controls groundwater movement and prevents contamination of water supply. Enhanced heat pump coefficient of performance (COP) and reduced up-front loop installation costs can be achieved through optimization of the grout thermal conductivity. The objective of the work reported was to characterize thermal conductivity and other pertinent properties of conventional and filled cementitious grouts. Cost analysis and calculations of the reduction in heat exchanger length that could be achieved with such grouts were performed by the University of Alabama. Two strategies to enhance the thermal conductivity of cementitious grouts were used simultaneously. The first of these was to incorporate high thermal conductivity filler in the grout formulations. Based on previous tests (Allan and Kavanaugh, in preparation), silica sand was selected as a suitable filler. The second strategy was to reduce the water content of the grout mix. By lowering the water/cement ratio, the porosity of the hardened grout is decreased. This results in higher thermal conductivity. Lowering the water/cement ratio also improves such properties as permeability, strength, and durability. The addition of a liquid superplasticizer (high range water reducer) to the grout mixes enabled reduction of water/cement ratio while retaining pumpability. Superplasticizers are commonly used in the concrete and grouting industry to improve rheological properties.

Allan, M.L.

1997-11-01

395

Thermal Science & Engineering Vol.?? No.?? (2005) - 10 - Non-Fourier Heat Conduction of Single-Walled Carbon Nanotubes Junichiro SHIOMI and Shigeo MARUYAMA Key Words: Non-Fourier Heat Conduction, Carbon Nanotube, Molecular Dynamics Simulation 1. Introduction Non-equilibrium heat conduction can not be properly

Maruyama, Shigeo

396

Mode-coupling theory and molecular dynamics simulation for heat conduction in a chain 2004) We study heat conduction in a 1D chain of particles with longitudinal as well as transverse, 66.70. f I. INTRODUCTION The problem of heat conduction is a well-studied field. More than two

Li, Baowen

397

NASA Astrophysics Data System (ADS)

The superconductivity in Cu0.5Tl0.5Ba2Ca1Cu2O8-? (Cu0.5Tl0.5-1212) thin films is studied in the light of the Aslamazov-Larkin (AL) theory of fluctuation-induced conductivity (FIC). Analysis of FIC has shown that removal/addition of oxygen in the charge reservoir layer after post-annealing of Cu0.5Tl0.5-1212 thin films changes the dimensionality of the fluctuations which induce conductivity of mobile carriers. The samples post-annealed in nitrogen have shown higher Tc(0) with 3D behavior of FIC over a wide temperature range, whereas the samples post-annealed in oxygen have smaller Tc(0) and possess only 2D fluctuations. These results suggest that the value of Tc(0) also depends on the dimensionality of thermal fluctuations which induce excess conductivity.

Khurram, A. A.; Khan, Nawazish A.

2008-01-01

398

Two-phase numerical model for thermal conductivity and convective heat transfer in nanofluids

Due to the numerous applications of nanofluids, investigating and understanding of thermophysical properties of nanofluids has currently become one of the core issues. Although numerous theoretical and numerical models have been developed by previous researchers to understand the mechanism of enhanced heat transfer in nanofluids; to the best of our knowledge these models were limited to the study of either thermal conductivity or convective heat transfer of nanofluids. We have developed a numerical model which can estimate the enhancement in both the thermal conductivity and convective heat transfer in nanofluids. It also aids in understanding the mechanism of heat transfer enhancement. The study reveals that the nanoparticle dispersion in fluid medium and nanoparticle heat transport phenomenon are equally important in enhancement of thermal conductivity. However, the enhancement in convective heat transfer was caused mainly due to the nanoparticle heat transport mechanism. Ability of this model to be able to understand the mechanism of convective heat transfer enhancement distinguishes the model from rest of the available numerical models. PMID:21711746

2011-01-01

399

Variable thermal properties and thermal relaxation time in hyperbolic heat conduction

NASA Technical Reports Server (NTRS)

Numerical solutions were obtained for a finite slab with an applied surface heat flux at one boundary using both the hyperbolic (MacCormack's method) and parabolic (Crank-Nicolson method) heat conduction equations. The effects on the temperature distributions of varying density, specific heat, and thermal relaxation time were calculated. Each of these properties had an effect on the thermal front velocity (in the hyperbolic solution) as well as the temperatures in the medium. In the hyperbolic solutions, as the density or specific heat decreased with temperature, both the temperatures within the medium and the thermal front velocity increased. The value taken for the thermal relaxation time was found to determine the 'hyperbolicity' of the heat conduction model. The use of a time dependent relaxation time allowed for solutions where the thermal energy propagated as a high temperature wave initially, but approached a diffusion process more rapidly than was possible with a constant large relaxation time.

Glass, David E.; Mcrae, D. Scott

1989-01-01

400

Artificial Ionospheric Heating Experiments Conducted by a Magnetosphere-Ionosphere Coupling Model

NASA Astrophysics Data System (ADS)

This presentation discusses computational dynamics and results of artificial heating in the ionosphere. The results are then compared to experiments including a geophysical experiment conducted at the Polar Aeronomy and Radio Science Summer School (PARS) in conjunction with the High Frequency Active Auroral Research Program (HAARP) The computational model includes the following terms: ion inertia, Ohm's law (Hall term, electron pressure term, electron neutral and electron ion collisions), ionization, recombination, electron energy (heat advection, conduction, heating through ionization, ohmic heating, gravity, energy loss to neutrals and ions), as well as parameterized collisions frequencies, and a height resolved neutral atmosphere. Atmospheric conditions for the time of the experiment (plasma density, temperature, etc) are used as initial conditions. The power and frequency of the heater facility are then used to compute the heating of the ionosphere. Data processing for the experiment and model are ongoing.

Stevens, R. J.; Otto, A.; Krzykowski, M.; Solie, D.

2007-12-01

401

-in-Chief Keywords: Inverse problem Multiple Indicator Kriging Self potential s u m m a r y We combine Indicator Kriging. The latter is implemented on the basis of available sedimentological information the set of model parameters. The hydraulic conductivity associated with a numerical block

Barrash, Warren

402

Heat conduction: hyperbolic self-similar shock-waves in solids

Analytic solutions for cylindrical thermal waves in solid medium is given based on the nonlinear hyperbolic system of heat flux relaxation and energy conservation equations. The Fourier-Cattaneo phenomenological law is generalized where the relaxation time and heat propagation coefficient have a general power law temperature dependence. From such laws one cannot form a second order parabolic or telegraph-type equation. We consider the original non-linear hyperbolic system itself with the self-similar Ansatz for the temperature distribution and for the heat flux. As results continuous and shock-wave solutions are presented. For physical establishment numerous materials with various temperature dependent heat conduction coefficients are mentioned.

Imre Ferenc Barna; Robert Kersner

2012-04-19

403

NASA Astrophysics Data System (ADS)

This study aims to investigate the role of aggregation of the hybrid nanocomposite particles on thermal conductivity and heat transfer of the phase change colloidal suspensions. It is observed that the incorporation of the hybrid nanocomposite particles substantially enhances thermal conductivity of such suspensions up to 42.4% and effectively reduces their freezing time by 19.5%. The predictions and the experimental results supports the fact that the aggregation of the hybrid nanocomposite particles largely involve in the eventual thermal conductivity enhancements and heat transfer of the phase change colloidal suspensions, with a sufficiently lesser effects realized from the nanoparticles Brownian motion.

Parameshwaran, R.; Kalaiselvam, S.

2013-11-01

404

On Energy and Entropy Influxes in the Green-Naghdi Type III Theory of Heat Conduction

The energy-influx/entropy-influx relation in the Green-Naghdi Type III theory of heat conduction is examined within a thermodynamical framework \\`a la Mueller-Liu, where that relation is not specified a priori irrespectively of the constitutive class under attention. It is shown that the classical assumption, i.e., that the entropy influx and the energy influx are proportional via the absolute temperature, holds true if heat conduction is, in a sense that is made precise, isotropic. In addition, it is proven that the standard assumption does not hold in case of transversely isotropic conduction.

Swantje Bargmann; Antonino Favata; Paolo Podio-Guidugli

2012-09-13

405

NSDL National Science Digital Library

Java3D is a low level 3D scene-graph based graphics programming API for the java language. It does not form part of the core APIs required by the Java specification. The class libraries exist under the javax.media.j3d top level package as well as utility classes provided in javax.vecmath.

406

The effect of heat conduction on the interaction of disk and corona around black holes

Heat conduction plays an important role in the balance between heating and cooling in many astrophysical objects, e.g. cooling flows in clusters of galaxies. Here we investigate the effect of heat conduction on the interaction between a cool disk and a hot corona around black holes. Using the one-radial-zone approximation, we study the vertical structure of the disk corona and derive evaporation and coronal mass flow rates for various reduced thermal conductivities. We find lower evaporation rates and a shift in the evaporation maxima to smaller radii. This implies that the spectral state transition occurs at a lower mass flow rate and a disk truncation closer to the black hole. Reductions of thermal conductivity are thought to be magnetically caused and might vary from object to object by a different configuration of the magnetic fields.

E. Meyer-Hofmeister; F. Meyer

2005-12-21

407

This paper investigates convection heat and mass transfer flow in an electrically conducting power law fluid past a vertical porous plate in presence of a transverse magnetic field, thermal radiation, and thermal diffusion. The nonlinear partial differential equations governing the flow are transformed into ordinary differential equations using the usual similarity method and the resulting similarity equations are solved numerically

B. I. Olajuwon

2010-01-01

408

Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties

Future superconducting radio frequency (SRF) cavities, as part of Project X at Fermilab, will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule-Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchangers will be utilized. Due to their compact size and ease of fabrication, plate-fin heat exchangers are an effective option. However, the design of compact and high-effectiveness cryogenic heat exchangers operating at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger. The model is used to guide design decisions on heat exchanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger to analyze the effect of heat load and cryogenic supply parameters. A numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger was developed and the effect of various design parameters on overall heat exchanger size was investigated. It was found that highly conductive metals should be avoided in the design of compact JT heat exchangers. For the geometry considered, the optimal conductivity is around 3.5 W/m-K and can range from 0.3-10 W/m-K without a large loss in performance. The model was implemented with an isenthalpic expansion process. Increasing the cold side inlet temperature from 2K to 2.2 K decreased the liquid fraction from 0.856 to 0.839 which corresponds to a 0.12 g/s increase in supercritical helium supply needed to maintain liquid level in the cooling bath. Lastly, it was found that the effectiveness increased when the heat load was below the design value. Therefore, the heat exchanger should be sized on the high end of the required heat load.

Hansen, B.J.; White, M.J.; Klebaner, A.; /Fermilab

2011-06-10

409

NASA Technical Reports Server (NTRS)

A numerical analysis is presented for the overall performance of heat pipes with single or multiple heat sources. The analysis includes the heat conduction in the wall and liquid-wick regions as well as the compressibility effect of the vapor inside the heat pipe. The two-dimensional elliptic governing equations in conjunction with the thermodynamic equilibrium relation and appropriate boundary conditions are solved numerically. The solutions are in agreement with existing experimental data for the vapor and wall temperatures at both low and high operating temperatures.

Chen, Ming-Ming; Faghri, Amir

1990-01-01

410

Heat Conduction of Lennard-Jones Particle System in Supercritical Fluid Phase

NASA Astrophysics Data System (ADS)

The heat conduction of the three-dimensional Lennard-Jones particle system is studied using nonequilibrium molecular dynamics simulation. The geometry of the system is a rectangular parallelepiped box of Lx Ly Lz dimensions. Two Nos-Hoover heat baths with different temperatures are attached to the regions near both ends of the x-direction. The density of the system and temperature of heat bath are selected so that the system is in the supercritical fluid phase. It is observed that the nonequilibrium steady state with a constant temperature gradient dT/dx and a energy (heat) flux J is realized after relaxation process from its initial configuration. The ratio of J to dT/dx denoted by ? which corresponds to the heat conductivity in the macroscopic limit is estimated for various system sizes~Lx. It is confirmed that ?(Lx) shows a size dependence as expressed ?0 + a/\\sqrt{Lx} and this dependence is consistent with the so-called long-time tail behavior. This ?0 is regarded as the macroscopic conductivity. This Lx dependence implies that the heat conductivity ?(Lx) is low for a nanoscale system. The ?(Lx) of the Lx=300 system decreases by about 10% from that of the macroscopic system.The estimated ?0 turns out to be proportional to the density.

Ogushi, Fumiko; Yukawa, Satoshi; Ito, Nobuyasu

2005-03-01

411

For bulk thermoelectrics, figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In recent years, the most significant improvements in ZT were mainly due to successful reduction of thermal conductivity. However, thermal conductivity cannot be measured directly at high temperatures. The combined measurements of thermal diffusivity and specific heat and density are required. It has been shown that thermal conductivity is the property with the greatest uncertainty and has a direct influence on the accuracy of the figure of merit. 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 is Part II of the international round-robin testing of transport properties of bulk bismuth telluride. The main focuses in Part II are on thermal diffusivity, specific heat and thermal conductivity.

Wang, Hsin [ORNL; Porter, Wallace D [ORNL; Bottner, Harold [Fraunhofer-Institute, Freiburg, Germany; Konig, Jan [Fraunhofer-Institute, Freiburg, Germany; Chen, Lidong [Chinese Academy of Sciences; Bai, Shengqiang [Chinese Academy of Sciences; Tritt, Terry M. [Clemson University; Mayolett, Alex [Corning, Inc; Senawiratne, Jayantha [Corning, Inc; Smith, Charlene [Corning, Inc; Harris, Fred [ZT-Plus; Gilbert, Partricia [Marlow Industries, Inc; Sharp, J [Marlow Industries, Inc; Lo, Jason [CANMET - Materials Technology Laboratory, Natural Resources of Canada; Keinke, Holger [University of Waterloo, Canada; Kiss, Laszlo I. [University of Quebec at Chicoutimi

2013-01-01

412

According to percolation theory the investigation of charge transport in disordered systems is equivalent to the study of the possibility of the passage of the carriers through a random network of impedances which interconnect the different lattice sites. When the site energies are not the same, the energy of a site affects the incoming as well as the outgoing impedances connected to the given site and this gives rise to correlations between neighboring impedances. This new condition characterizes the transport process and imposes the evaluation of the average number of sites accessible by a bond from a given site for all possible configurations of sites that satisfy the percolation condition. The generalized molecular crystal model, appropriate for the study of small-polaron hopping transport in disordered systems, and the Kubo formula permit the evaluation of these impedances. Taking correlations into account, theoretical percolation considerations applicable to one-dimensional and three-dimensional disordered systems, lead to analytical expressions for the temperature and electric field dependence of the DC conductivity at high (multi-phonon-assisted hopping) and low (few-phonon-assisted hopping) temperatures. The theoretical analysis reveals the effect of correlations on the non-ohmic behavior of the small-polaron hopping conductivity and permits the evaluation of the maximum hopping distance. Quantitative estimates of this effect are presented comparing the theoretical results, including correlations with those ignoring them, previously reported, applying them to recent experimental data for a wide temperature range and from low up to moderate electric fields. PMID:21403284

Dimakogianni, M; Triberis, G P

2010-09-01

413

Summary Vibration-induced nystagmus, as clinical sign, was recently introduced in outpatient clinical practice for the study and evaluation of otoneurological patients. This response, which can only be evoked by bone conducted vibratory stimulation in the mastoid region or at the location on the forehead in the midline at the hairline, was essentially designed for patients with persistent unilateral vestibular deficit and was interpreted as the result of excitatory functional activity of the vestibular system on the non-affected side. Vibratory stimulation is, in fact, considered to reach both systems, which in the case of functional asymmetry, respond asymmetrically with greater excitatory activation on the more responsive side. On the other hand, little information is available concerning vibration-induced nystagmus in subjects with symmetrical vestibular function. The limited experience with this recently proposed test and incomplete knowledge regarding its mechanisms suggest that it must be investigated in clinical conditions, having a known pathophysiological basis: the responses obtained could help provide insight into the potential of this test and contribute to the diagnostic definition of the superior semicircular canal dehiscence or otosclerosis. Analysis of Vibration-induced nystagmus, recently proposed to study transmission of excitatory stimuli by bone conduction, may be appropriate for altered input caused by defects of the labyrinthine capsule. This promises to be an interesting new field of research. PMID:20140158

Manzari, L

2009-01-01

414

Vacuum Induction Melting Unit Induction heating is a process wherein induced eddy currents heat field and circulating eddy currents are induced within the metals. Flow of eddy currents leads an AC current through a water cooled copper coil and a metallic charge is placed in a ceramic (or

Subramaniam, Anandh

415

Radiative heat exchange of a meteor body in the approximation of radiant heat conduction

The problem of the thermal and dynamic destruction of large meteor bodies moving in planetary atmospheres is fundamental for the clarification of optical observations and anomalous phenomena in the atmosphere, the determination of the physicochemical properties of meteoroids, and the explanation of the fall of remnants of large meteorites. Therefore, it is important to calculate the coefficient of radiant heat exchange (which is the determining factor under these conditions) for large meteor bodies as they move with hypersonic velocities in an atmosphere. The solution of this problem enables one to find the ablation of a meteorite during its aerodynamic heating and to determine the initial conditions for the solution of problems of the breakup of large bodies and their subsequent motion and ablation. Hypersonic flow of an inviscid gas stream over an axisymmetric blunt body is analyzed with allowance for radiative transfer in a thick-thin approximation. The gas-dynamic problem of the flow of an optically thick gas over a large body is solved by the method of asymptotic joined expansions, using a hypersonic approximation and local self-similarity. An equation is obtained for the coefficient of radiant heat exchange and the peculiarities of such heat exchange for meteor bodies of large size are noted.

Pilyugin, N.N.; Chernova, T.A.

1986-07-01

416

THE CONDUCTION OF HEAT FROM SLIDING SOLIDS J. R. BARBER Department of Mechanical Engineering, University of the lubricant. A number of solutions to the relevant heat conduction problem have been published, but these haveht. J. Heat Mass Tmnsfer. Vol. 13,pp. 857469. Pergamon Press 1970. Printed in Great Britain

Barber, James R.

417

NASA Astrophysics Data System (ADS)

The coupling of the homotopy perturbation method (HPM) and the variational iteration method (VIM) is a strong technique for solving higher dimensional initial boundary value problems. In this article, after a brief explanation of the mentioned method, the coupled techniques are applied to one-dimensional heat transfer in a rectangular radial fin with a temperature-dependent thermal conductivity to show the effectiveness and accuracy of the method in comparison with other methods. The graphical results show the best agreement of the three methods; however, the amount of calculations of each iteration for the combination of HPM and VIM was reduced markedly for multiple iterations. It was found that the variation of the dimensionless temperature strongly depends on the dimensionless small parameter {\\varepsilon_1}. Moreover, as the dimensionless length increases, the thermal conductivity of the fin decreases along the fin.

Hedayati, F.; Ganji, D. D.; Hamidi, S. M.; Malvandi, A.

2012-06-01

418

NASA Technical Reports Server (NTRS)

This paper describes the evaluation of mixed implicit-explicit finite element formulations for hyperbolic heat conduction problems involving non-Fourier effects. In particular, mixed implicit-explicit formulations employing the alpha method proposed by Hughes et al. (1987, 1990) are described for the numerical simulation of hyperbolic heat conduction models, which involves time-dependent relaxation effects. Existing analytical approaches for modeling/analysis of such models involve complex mathematical formulations for obtaining closed-form solutions, while in certain numerical formulations the difficulties include severe oscillatory solution behavior (which often disguises the true response) in the vicinity of the thermal disturbances, which propagate with finite velocities. In view of these factors, the alpha method is evaluated to assess the control of the amount of numerical dissipation for predicting the transient propagating thermal disturbances. Numerical test models are presented, and pertinent conclusions are drawn for the mixed-time integration simulation of hyperbolic heat conduction models involving non-Fourier effects.

Tamma, Kumar K.; D'Costa, Joseph F.

1991-01-01

419

Effects of gravity on gas-loaded variable conductance heat pipes

The effects of gravity on the operation of gas-loaded variable conductance heat pipes have been investigated. Experimental results have been obtained for three heat pipes (1.6 cm, 2.5 cm and 5 cm diameter) operating with methanol or Freon 113 as the working fluid and krypton or helium as the control gas. Results show that gravity tends to distort the axial

M. D. Kelleher

1977-01-01

420

Temperature control using variable conductance closed two-phase heat pipe

The concept of using variable conductance heat pipes (VCHP) for controlling the temperature of solar collectors is introduced. This closed system does not need any external force, is self-controllable and therefore ensures high reliability in thermal control. A copper\\/water heat pipe equipped with a cold reservoir and buffered with air as non-condensable gas (NCG) has been tested for temperatures from

Ioan Sauciuc; Aliakbar Akbarzadeh; Peter Johnson

1996-01-01

421

A method for enhancing the stability of parabolic inverse heat conduction problems (IHCP) is presented. The investigation extends recent work on non-iterative finite element-based IHCP algorithms which, following Becks two-step approach, first derives a discretized standard form equation relating the instantaneous global temperature and surface heat flux vectors, and then formulates a least squares-based linear matrix normal equation in the

R. G. Keanini; Xianwu Ling; H. P. Cherukuri

2005-01-01

422

This paper presents an analysis for an unsteady conjugated heat transfer problem in thermally developing laminar pipe flow, involving two-dimensional wall and fluid axial conduction. The problem is solved numerically by a finite-difference method for a thick-walled, infinitely long, two-regional pipe which is initially isothermal with a step change in the constant outside temperature of the heated downstream section. A

?efik Bilir

2002-01-01

423

NASA Astrophysics Data System (ADS)

Fourier's law of heat conduction in the one-dimensional case without heat source and the corresponding state equation are modified to account for the rapid propagation of thermodynamic phenomena, applying the approach of Szekeres (1980). The explicit linear case is treated analytically, and the implications for dynamic problems in thermoelasticity (such as those occurring in reactor technology, supersonic flight, spacecraft design, MHD generators, and high-speed internal-combustion engines) are discussed.

Farkas, I.; Szekeres, A.

424

Numerical solution of one-dimensional inverse transient heat conduction by finite difference method

A simple and accurate finite-difference extrapolation method is proposed for solving one-dimensional inverse heat conduction problems for solids with temperature history specified at two interior points. The analysis assumes constant thermal properties for the solid, but can be suitably modified to include temperature-dependent thermal properties of the material. The transient temperature distribution inside the solid, the surface temperature, heat flux

N. Dsouza

1975-01-01

425

Recent Chandra observations of clusters of galaxies revealed the existence of a sharp ridge in the X-ray surface brightness where the temperature drops across the front. This front is called the cold front. We present the results of two-dimensional magnetohydrodynamic simulations of the time evolution of a dense subcluster plasma moving in a cluster of galaxies. Anisotropic heat conduction along the magnetic field lines is included. In the models without magnetic fields, the numerical results indicate that the heat conduction from the hot ambient plasma heats the cold dense plasma of the subcluster and diffuses out the cold front. When magnetic fields exist in a cluster of galaxies, however, cold fronts can be maintained because the heat conduction across the magnetic field lines is suppressed. We found that, even when the magnetic fields in a cluster of galaxies are disordered, heat conduction across the front is restricted because the magnetic field lines are stretched along the front. Numerical results reproduced the X-ray intensity distribution observed in the A3667 cluster of galaxies.

Naoki Asai; Naoya Fukuda; Ryoji Matsumoto

2004-04-07

426

NASA Technical Reports Server (NTRS)

Three-layer monotonic electrical conductivity models for the lunar interior to a depth of 600 km are used in conjunction with laboratory measurements of the electrical conductivity of olivine and pyroxene to estimate a temperature-depth profile. The temperatures calculated for depths of 400-600 km are consistent with attenuation of the seismic shear wave. The temperature calculated at a depth of 100-250 km yields a heat flow that is in good agreement with the directly measured lunar heat flow. The temperature, however, is sufficiently close to melting that mascon anisostasy would not be maintained. Thus a better conductor is required at this depth.

Sonett, C. P.; Duba, A.

1975-01-01

427

NASA Astrophysics Data System (ADS)

Based on the heat conduction equation with fractional-order derivatives and the experimental measurements of temperature distribution in the upper layers of the Earth, the depth dependence of thermal diffusivity is studied at different values of the parameters of nonlocality in time and along the coordinates. It is shown that thermal diffusivity increases with depth, and the values of thermal diffusivity observed in the experiments coincide with the theoretical predictions provided by the solution of the nonlocal heat-conduction equation that allows for the memory effects in fractional-order time derivatives.

Shabanova, M. R.; Meilanov, R. P.; Meilanov, R. R.; Akhmedov, E. N.

2015-01-01

428

NASA Astrophysics Data System (ADS)

The temperature dependence of the heat conductivity has been obtained for a liquid crystal model based on the Gay-Berne fluid, from the isotropic phase at high temperatures through the nematic phase to the smectic A phase at low temperatures. The ratio of the parallel and the perpendicular components of the heat conductivity is about 2.5:1 in the nematic phase, which is similar to that of real systems. Both Green-Kubo methods and nonequilibrium molecular dynamics methods have been applied and the results agree within in a relative error of a couple of percent, but the latter method is much more efficient.

Sarman, Sten; Laaksonen, Aatto

2010-01-01

429

A three-dimensional selenium solar cell with the structure of Au/Se/porous TiO2/compact TiO2/fluorine-doped tin oxide-coated glass plates was fabricated by an electrochemical deposition method of selenium, which can work for the extremely thin light absorber and the hole-conducting layer. The effect of experimental conditions, such as HCl and H2SeO3 in an electrochemical solution and TiO2 particle size of porous layers, was optimized. This kind of solar cell did not use any buffer layer between an n-type electrode (porous TiO2) and a p-type absorber layer (selenium). The crystallinity of the selenium after annealing at 200C for 3 min in the air was significantly improved. The cells with a selenium layer deposited at concentrations of HCl?=?11.5 mM and H2SeO3?=?20 mM showed the best performance, resulting in 1- to 2-nm thickness of the Se layer, short-circuit photocurrent density of 8.7 mA/cm2, open-circuit voltage of 0.65 V, fill factor of 0.53, and conversion efficiency of 3.0%. PMID:23286700

2013-01-01

430

NASA Astrophysics Data System (ADS)

A three-dimensional selenium solar cell with the structure of Au/Se/porous TiO2/compact TiO2/fluorine-doped tin oxide-coated glass plates was fabricated by an electrochemical deposition method of selenium, which can work for the extremely thin light absorber and the hole-conducting layer. The effect of experimental conditions, such as HCl and H2SeO3 in an electrochemical solution and TiO2 particle size of porous layers, was optimized. This kind of solar cell did not use any buffer layer between an n-type electrode (porous TiO2) and a p-type absorber layer (selenium). The crystallinity of the selenium after annealing at 200C for 3 min in the air was significantly improved. The cells with a selenium layer deposited at concentrations of HCl = 11.5 mM and H2SeO3 = 20 mM showed the best performance, resulting in 1- to 2-nm thickness of the Se layer, short-circuit photocurrent density of 8.7 mA/cm2, open-circuit voltage of 0.65 V, fill factor of 0.53, and conversion efficiency of 3.0%.

Nguyen, Duy-Cuong; Tanaka, Souichirou; Nishino, Hitoshi; Manabe, Kyohei; Ito, Seigo

2013-01-01

431

Heat conductivity in small quantum systems: Kubo formula in Liouville space

We consider chains consisting of several identical subsystems weakly coupled by various types of next neighbor interactions. At both ends the chain is coupled to a respective heat bath with different temperature modeled by a Lindblad formalism. The temperature gradient introduced by this environment is then treated as an external perturbation. We propose a method to evaluate the heat current and the local temperature profile of the resulting stationary state as well as the heat conductivity in such systems. This method is similar to Kubo techniques used e.g. for electrical transport but extended here to the Liouville space.

Mathias Michel; Jochen Gemmer; Guenter Mahler

2005-03-22

432

Simplified technique for measuring specific heat and thermal conductivity of a liquid under pressure

A technique for simultaneously measuring the specific heat and the thermal conductivity of a liquid over a broad range of pressure is described. The technique uses a system in which the liquid circulates in a pulsating manner through a counter-current heat exchanger, or regenerator, made of parallel plates and thereby achieves the advantage of a continuous flow method where parasitic heat losses may be readily identified and eliminated. Typical results for water at 28 bar and propylene at 34.5 bar are presented.

Allen, P.C.; Paulson, D.N.; Wheatley, J.C.

1981-02-01

433

NASA Technical Reports Server (NTRS)

Continuing efforts in large gains in heat-pipe performance are reported. It was found that gas-controlled variable-conductance heat pipes can perform reliably for long periods in space and effectively provide temperature stabilization for spacecraft electronics. A solution was formulated that allows the control gas to vent through arterial heat-pipe walls, thus eliminating the problem of arterial failure under load, due to trace impurities of noncondensable gas trapped in an arterial bubble during priming. This solution functions well in zero gravity. Another solution was found that allows priming at a much lower fluid charge. A heat pipe with high capacity, with close temperature control of the heat source and independent of large variations in sink temperature was fabricated.

Enginer, J. E.; Luedke, E. E.; Wanous, D. J.

1976-01-01

434

Estimating thermal diffusivity and specific heat from needle probe thermal conductivity data

Thermal diffusivity and specific heat can be estimated from thermal conductivity measurements made using a standard needle probe and a suitably high data acquisition rate. Thermal properties are calculated from the measured temperature change in a sample subjected to heating by a needle probe. Accurate thermal conductivity measurements are obtained from a linear fit to many tens or hundreds of temperature change data points. In contrast, thermal diffusivity calculations require a nonlinear fit to the measured temperature change occurring in the first few tenths of a second of the measurement, resulting in a lower accuracy than that obtained for thermal conductivity. Specific heat is calculated from the ratio of thermal conductivity to diffusivity, and thus can have an uncertainty no better than that of the diffusivity estimate. Our thermal conductivity measurements of ice Ih and of tetrahydrofuran (THF) hydrate, made using a 1.6 mm outer diameter needle probe and a data acquisition rate of 18.2 pointss, agree with published results. Our thermal diffusivity and specific heat results reproduce published results within 25% for ice Ih and 3% for THF hydrate. ?? 2006 American Institute of Physics.

Waite, W.F.; Gilbert, L.Y.; Winters, W.J.; Mason, D.H.

2006-01-01

435

The program FANS-3D (finite analytic numerical simulation 3-dimensional) and its applications

NASA Technical Reports Server (NTRS)

In this study, the program named FANS-3D (Finite Analytic Numerical Simulation-3 Dimensional) is presented. FANS-3D was designed to solve problems of incompressible fluid flow and combined modes of heat transfer. It solves problems with conduction and convection modes of heat transfer in laminar flow, with provisions for radiation and turbulent flows. It can solve singular or conjugate modes of heat transfer. It also solves problems in natural convection, using the Boussinesq approximation. FANS-3D was designed to solve heat transfer problems inside one, two and three dimensional geometries that can be represented by orthogonal planes in a Cartesian coordinate system. It can solve internal and external flows using appropriate boundary conditions such as symmetric, periodic and user specified.

Bravo, Ramiro H.; Chen, Ching-Jen

1992-01-01

436

The Thermal Conductivity Profile of the Lower Mantle and the Present Day Net Core Heat Flux

An updated model of the lower mantle thermal conductivity profile (k(T, P)) is presented and used to calculate the present day Net Core Heat Flux (QCMB) for 4 types of boundary layers in the D'' layer. I re-evaluate the temperature and pressured dependent thermal conductivity (k(T, P)) profile of the lower mantle using the method of Brown (1986), but with

A. R. Calderwood

2001-01-01

437

Normal Heat Conductivity in a strongly pinned chain of anharmonic oscillators

We consider a chain of coupled and strongly pinned anharmonic oscillators subject to a non-equilibrium random forcing. Assuming that the stationary state is approximately Gaussian, we first derive a stationary Boltzmann equation. By localizing the involved resonances, we next invert the linearized collision operator and compute the heat conductivity. In particular, we show that the Gaussian approximation yields a finite conductivity $\\kappa\\sim\\frac{1}{\\lambda^2T^2}$, for $\\lambda$ the anharmonic coupling strength.

R. Lefevere; A. Schenkel

2005-11-03

438

Analytical treatment of gravity effects on gas loaded variable conductance heat pipes

The formulation of a one-dimensional analytical model representing steady state operation of a vertically oriented gas loaded variable conductance heat pipe is presented. The model includes not only the effects of binary mass diffusion and axial pipe-wall conduction, but also gravitational effects which exist at the vapor-gas interface region when the molecular weights of the working fluid and the noncondensible

D. C. Kane

1980-01-01

439

We study an initial-boundary-value problem for time-dependent flows of heat-conducting viscous incompressible fluids in channel-like domains on a time interval $(0,T)$. For the parabolic system with strong nonlinearities and including the artificial (the so called "do nothing") boundary conditions, we prove the local in time existence, global uniqueness and smoothness of the solution on a time interval $(0,T^*)$, where $0< T^* \\leq T$.

Michal Bene

2011-08-08

440

NASA Astrophysics Data System (ADS)

The interfacial heat transfer coefficient (IHTC) is required for the accurate simulation of heat transfer in castings especially for near net-shape processes. The large number of factors influencing heat transfer renders quantification by theoretical means a challenge. Likewise experimental methods applied directly to temperature data collected from castings are also a challenge to interpret because of the transient nature of many casting processes. Inverse methods offer a solution and have been applied successfully to predict the IHTC in many cases. However, most inverse approaches thus far focus on use of in-mold temperature data, which may be a challenge to obtain in cases where the molds are water-cooled. Methods based on temperature data from the casting have the potential to be used however; the latent heat released during the solidification of the molten metal complicates the associated IHTC calculations. Furthermore, there are limits on the maximum distance the thermocouples can be placed from the interface under analysis. An inverse conduction based method have been developed, verified and applied successfully to temperature data collected from within an aluminum casting in proximity to the mold. A modified specific heat method was used to account for latent heat evolution in which the rate of change of fraction solid with temperature was held constant. An analysis conducted with the inverse model suggests that the thermocouples must be placed no more than 2 mm from the interface. The IHTC values calculated for an aluminum alloy casting were shown to vary from 1,200 to 6,200 Wm-2 K-1. Additionally, the characteristics of the time-varying IHTC have also been discussed.

Zhang, Liqiang; Reilly, Carl; Li, Luoxing; Cockcroft, Steve; Yao, Lu

2014-07-01

441

BEAMS3D Neutral Beam Injection Model

With the advent of applied 3D fi elds in Tokamaks and modern high performance stellarators, a need has arisen to address non-axisymmetric effects on neutral beam heating and fueling. We report on the development of a fully 3D neutral beam injection (NBI) model, BEAMS3D, which addresses this need by coupling 3D equilibria to a guiding center code capable of modeling neutral and charged particle trajectories across the separatrix and into the plasma core. Ionization, neutralization, charge-exchange, viscous velocity reduction, and pitch angle scattering are modeled with the ADAS atomic physics database [1]. Benchmark calculations are presented to validate the collisionless particle orbits, neutral beam injection model, frictional drag, and pitch angle scattering effects. A calculation of neutral beam heating in the NCSX device is performed, highlighting the capability of the code to handle 3D magnetic fields.

Lazerson, Samuel

2014-04-14

442

Cooling by Heat Conduction Inside Magnetic Flux Loops and the Moderate Cluster Cooling Flow Model

I study non-radiative cooling of X-ray emitting gas via heat conduction along magnetic field lines inside magnetic flux loops in cooling flow clusters of galaxies. I find that such heat conduction can reduce the fraction of energy radiated in the X-ray band by a factor of 1.5-2. This non-radiative cooling joins two other proposed non-radiative cooling processes, which can be more efficient. These are mixing of cold and hot gas, and heat conduction initiated by magnetic fields reconnection between hot and cold gas. These processes when incorporated into the moderate cooling flow model lead to a general cooling flow model with the following ingredients. (1) Cooling flow does occur, but with a mass cooling rate about 10 times lower than in old versions of the cooling flow model. Namely, heating occurs such that the effective age of the cooling flow is much below the cluster age, but the heating can't prevent cooling altogether. (2) The cooling flow region is in a non-steady state evolution. (3) Non-radiative cooling of X-ray emitting gas can bring the model to a much better agreement with observations. (4) The general behavior of the cooling flow gas, and in particular the role played by magnetic fields, make the intracluster medium in cooling flow clusters similar in some aspects to the active solar corona.

Noam Soker

2003-11-02

443

The heat conductivity ({lambda}) and the thermal diffusivity (a) of reacting glass batch, or melter feed, control the heat flux into and within the cold cap, a layer of reacting material floating on the pool of molten glass in an all-electric continuous waste glass melter. After previously estimating {lambda} of melter feed at temperatures up to 680 deg C, we focus in this work on the {lambda}(T) function at T > 680 deg C, at which the feed material becomes foamy. We used a customized experimental setup consisting of a large cylindrical crucible with an assembly of thermocouples, which monitored the evolution of the temperature field while the crucible with feed was heated at a constant rate from room temperature up to 1100C. Approximating measured temperature profiles by polynomial functions, we used the heat transfer equation to estimate the {lambda}(T) approximation function, which we subsequently optimized using the finite-volume method combined with least-squares analysis. The heat conductivity increased as the temperature increased until the feed began to expand into foam, at which point the conductivity dropped. It began to increase again as the foam turned into a bubble-free glass melt. We discuss the implications of this behavior for the mathematical modeling of the cold cap.

Rice, Jarrett A.; Pokorny, Richard; Schweiger, Michael J.; Hrma, Pavel R.

2014-05-12

444

In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem in estimating the unknown time-dependent surface heat flux in a skin tissue, which is stratified into epidermis, dermis, and subcutaneous layers, from the temperature measurements taken within the medium. Subsequently, the temperature distributions in the tissue can be calculated as well. The concept of finite heat propagation velocity is applied to the modeling of the bioheat transfer problem. The inverse solutions will be justified based on the numerical experiments in which two different heat flux distributions are to be determined. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors on the precision of the estimated results is also investigated. Results show that an excellent estimation on the time-dependent surface heat flux can be obtained for the test cases considered in this study. PMID:24946013

Lee, Haw-Long; Chen, Wen-Lih; Chang, Win-Jin; Yang, Yu-Ching

2015-11-01

445

Spatial statistics models for stochastic inverse problems in heat conduction Jingbo Wanga

Spatial statistics models for stochastic inverse problems in heat conduction Jingbo Wanga due to the ill-posed nature of such problems. However, there is a rich statistical information) are computed in probabilistic spaces. A Bayesian statistical inference approach is presented here

Zabaras, Nicholas J.

446

TOPAZ - a finite element heat conduction code for analyzing 2-D solids

TOPAZ is a two-dimensional implicit finite element computer code for heat conduction analysis. This report provides a user's manual for TOPAZ and a description of the numerical algorithms used. Sample problems with analytical solutions are presented. TOPAZ has been implemented on the CRAY and VAX computers.

Shapiro, A.B.

1984-03-01

447

INSTABILITIES ASSOCIATED WITH HEAT CONDUCTION IN THE SOLAR WIND AND THEIR CONSEQUENCES

Associated with the large heat conduction in the solar wind is a skewing of the ion and electron distribution functions. It is shown that this collisional skewing of the electron distribution function can linearly excite collisionless ion-acoustic, electrostatic ion cyclotron, magnetoacoustic, and ion cyclotron waves in the steady-state solar wind even though the net equilibrium current parallel to B is

D. W. Forslund

1970-01-01

448

An analytical solution to the one-dimensional heat conduction-convection equation in soil

Technology Transfer Automated Retrieval System (TEKTRAN)

Heat transfer in soil occurs by conduction and convection. Infiltrating water affects soil temperature distributions, and measuring soil temperature distributions below infiltrating water can provide a signal for the flux of water. In earlier work a sine wave function (hereinafter referred to as the...

449

The simultaneous radiation and conduction heat transfer in a semitransparent slab of absorbingemitting gray medium is solved in this paper. The refractive index of the medium spatially varies in a linear relationship, and the two boundary walls are diffuse and gray. A curved ray tracing technique in combination with a pseudo-source adding method is employed to deduce the radiative intensities

Xin-Lin Xia; Yong Huang; He-Ping Tan; Xiao-Bin Zhang

2002-01-01

450

For measurements of turbulent heat transport in Rayleigh-Bnard convection the correction for the sidewall conductance is usually neglected or based on measurements or estimates for the empty cell. It is argued that the lateral thermal coupling between the fluid and the wall can invalidate these approaches, and that corrections based on calculations of the two-dimensional temperature fields are required in

Guenter Ahlers

2001-01-01

451

Review and Comparison of Nanofluid Thermal Conductivity and Heat Transfer Enhancements

This study provides a detailed literature review and an assessment of results of the research and development work forming the current status of nanofluid technology for heat transfer applications. Nanofluid technology is a relatively new field, and as such, the supporting studies are not extensive. Specifically, experimental results were reviewed in this study regarding the enhancement of the thermal conductivity

Wenhua Yu; David M. France; Jules L. Routbort

2008-01-01

452

Conduction-dominated heat transport of the annual temperature signal in soil

(1) Conductive heat transport of temperature signals into the subsurface is a central assumption of ground surface temperature (GST) reconstructions derived from present- day temperatures in deep boreholes. Here we test this assumption and its implications for annual relationships between GST and surface air temperature (SAT) by analyzing two decades of shallow soil temperature (0.01-11.7 m) and SAT time series

Jason E. Smerdon; Henry N. Pollack; John W. Enz; Matthew J. Lewis

2003-01-01

453

SUMMARY The identification and quantification of conductive and convective components in the heat transfer of a sedimentary basin is demonstrated for the Rheingraben. Three different methods of varying complexity as well as three independent data sets are employed: (1) energy budget considerations based on hydraulically perturbed thermal data from shallow boreholes (<500m), (2) 1-D vertical Peclet number analysis of thermal

C. Clauser; H. Villinger

1990-01-01

454

Effect of carbon-fiber brushes on conductive heat transfer in phase change materials

Brushes made of carbon fibers are used to improve the thermal conductivities of phase change materials packed around heat transfer tubes. The transient thermal responses measured in brush\\/n-octadecane composites essentially improve as the volume fraction of the fibers and the brush diameter increase. However, there is a critical diameter above which further improvement is not expected due to thermal resistance

Jun Fukai; Yuichi Hamada; Yoshio Morozumi; Osamu Miyatake

2002-01-01

455

Heat transfer in a gray tube with forced convection, internal radiation and axial wall conduction

NASA Technical Reports Server (NTRS)

A method of successive approximations is employed to solve the problem of heat transfer to a transparent gas flowing through a radiating-conducting tube with turbulent forced convection between the tube wall and the gas, and with energy generation in the wall. Emphasis is given to the effect of emissivity of the wall to the tube and gas temperature profiles.

Chung, B. T. F.; Thompson, J. E.

1983-01-01

456

One of the difficulties in the solution of inverse heat conduction problems is that of making sufficiently accurate initial guesses for the unknowns in order to start the iterations. In this work a direct integration method is developed for determining good initial guesses for the unknown property coefficients within about 10% error. The Levenberg-Marquardt method is then applied to refine

C. H. Huang; M. N. zi?ik

1991-01-01

457

Heat transfer and effective thermal conductivity analyses in carbon-based foams for use in thermal

.1243/146442005X34485 Abstract: The applicability of carbon-based foams as an insulation material in the thermal are very effective thermal insulators, but they suffer from a number of shortcomings, primarily (aHeat transfer and effective thermal conductivity analyses in carbon-based foams for use in thermal

Grujicic, Mica

458

Existence of Nonequilibrium Steady State for a Simple Model of Heat Conduction

NASA Astrophysics Data System (ADS)

This paper contains rigorous results for a simple stochastic model of heat conduction similar to the KMP (Knipnis-Marchiori-Presutti) model but with possibly energy-dependent interaction rates. We prove the existence and uniqueness of nonequilibrium steady states, their relation to Lebesgue measure, and exponential convergence to steady states from suitable initial conditions.

Li, Yao; Young, Lai-Sang

2013-09-01

459

ERIC Educational Resources Information Center

To help students make the connection between the concepts of heat conduction and convection to real-world phenomenon, we developed a combined experimental and computational module that can be incorporated into lecture or lab courses. The experimental system we present requires materials and apparatus that are readily accessible, and the procedure

Mendez, Sergio; AungYong, Lisa

2014-01-01

460

A BOUNDARY-DISPATCH MONTE CARLO (EXODUS) METHOD FOR ANALYSIS OF CONDUCTIVE HEAT TRANSFER PROBLEMS

A boundary-dispatch Monte Carlo (Exodus) method, in which the particles are dispatched from the boundaries of a conductive medium or source of heat, is developed. A fixed number of particles are dispatched from a boundary node to the nearest internal node. These particles make random walks within the medium similar to that of the conventional Monte Carlo method. Once a

Mohammad H. N. Naraghi; Shun-Chang Tsai

1993-01-01

461

NASA Astrophysics Data System (ADS)

Some aspects of the calculation of nonstationary heat conduction in multilayer objects with boundary conditions of the third kind are considered. The homogeneous problem with inhomogeneous boundary conditions is solved for the one-dimensional case. The proposed solution has an explicit form and may be useful in numerical calculations due to the recurrence representation of the basic relations.

Vendin, S. V.

1993-08-01

462

Heat Flow, Thermal Conductivity, and the Plausibility of the White Mars Hypothesis

NASA Technical Reports Server (NTRS)

Due to the low thermal conductivity of CO2 ice and clathrate vs. water ice, we find that liquid water reservoirs would not be confined to the deep subsurface as predicted by the controversial White Mars model, even assuming low global heat flow. Additional information is contained in the original extended abstract.

Urquhart, M. L.; Gulick, V. C.

2002-01-01

463

Lattice thermal conductivity of lower mantle minerals and heat flux from Earths core

The amount of heat flowing from Earths core critically determines the thermo-chemical evolution of both the core and the lower mantle. Consisting primarily of a polycrystalline aggregate of silicate perovskite and ferropericlase, the thermal boundary layer at the very base of Earths lower mantle regulates the heat flow from the core, so that the thermal conductivity (k) of these mineral phases controls the amount of heat entering the lowermost mantle. Here we report measurements of the lattice thermal conductivity of pure, Al-, and Fe-bearing MgSiO3 perovskite at 26GPa up to 1,073K, and of ferropericlase containing 0, 5, and 20% Fe, at 8 and 14GPa up to 1,273K. We find the incorporation of these elements in silicate perovskite and ferropericlase to result in a ?50% decrease of lattice thermal conductivity relative to the end member compositions. A model of thermal conductivity constrained from our results indicates that a peridotitic mantle would have k=9.11.2W/mK at the top of the thermal boundary layer and k=8.41.2W/mK at its base. These values translate into a heat flux of 11.01.4 terawatts (TW) from Earths core, a range of values consistent with a variety of geophysical estimates. PMID:22021444

Manthilake, Geeth M.; de Koker, Nico; Frost, Dan J.; McCammon, Catherine A.

2011-01-01

464

Discrete thermal element modelling of heat conduction in particle systems: Basic formulations

This paper proposes a novel numerical methodology, termed the discrete thermal element method (DTEM), for the effective modelling of heat