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1

Assessing the RELAPS-3D Heat Conduction Enclosure Model  

SciTech Connect

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  

SciTech Connect

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  

Microsoft Academic Search

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

THERM3D -- A boundary element computer program for transient heat conduction problems  

SciTech Connect

The computer code THERM3D implements the direct boundary element method (BEM) to solve transient heat conduction problems in arbitrary three-dimensional domains. This particular implementation of the BEM avoids performing time-consuming domain integrations by approximating a ``generalized forcing function`` in the interior of the domain with the use of radial basis functions. An approximate particular solution is then constructed, and the original problem is transformed into a sequence of Laplace problems. The code is capable of handling a large variety of boundary conditions including isothermal, specified flux, convection, radiation, and combined convection and radiation conditions. The computer code is benchmarked by comparisons with analytic and finite element results.

Ingber, M.S. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Mechanical Engineering

1994-02-01

5

Heat Conduction Analysis of 3-D Axisymmetric and Anisotropic FGM Bodies by Meshless Local Petrov–Galerkin Method  

Microsoft Academic Search

The meshless local Petrov–Galerkin method is used to analyze transient heat conduction in 3-D axisymmetric solids with continuously inhomogeneous and anisotropic material properties. A 3-D axisymmetric body is created by rotation of a cross section around an axis of symmetry. Axial symmetry of geometry and boundary conditions reduces the original 3-D boundary value problem into a 2-D problem. The cross

J. Sladek; V. Sladek; Ch. Hellmich; J. Eberhardsteiner

2007-01-01

6

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

E-print Network

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

7

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

E-print Network

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

8

TACO3D. 3-D Finite Element Heat Transfer Code  

SciTech Connect

TACO3D is a three-dimensional, finite-element program for heat transfer analysis. An extension of the two-dimensional TACO program, it can perform linear and nonlinear analyses and can be used to solve either transient or steady-state problems. The program accepts time-dependent or temperature-dependent material properties, and materials may be isotropic or orthotropic. A variety of time-dependent and temperature-dependent boundary conditions and loadings are available including temperature, flux, convection, and radiation boundary conditions and internal heat generation. Additional specialized features treat enclosure radiation, bulk nodes, and master/slave internal surface conditions (e.g., contact resistance). Data input via a free-field format is provided. A user subprogram feature allows for any type of functional representation of any independent variable. A profile (bandwidth) minimization option is available. The code is limited to implicit time integration for transient solutions. TACO3D has no general mesh generation capability. Rows of evenly-spaced nodes and rows of sequential elements may be generated, but the program relies on separate mesh generators for complex zoning. TACO3D does not have the ability to calculate view factors internally. Graphical representation of data in the form of time history and spatial plots is provided through links to the POSTACO and GRAPE postprocessor codes.

Mason, W.E. [Sandia National Labs., Albuquerque, NM (United States)

1992-03-04

9

Reduction of Thermal Conductivity by Nanoscale 3D Phononic Crystal  

PubMed Central

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

10

Heat Transfer Boundary Conditions in the RELAP5-3D Code  

Microsoft Academic Search

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

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

2008-01-01

11

3D conductive nanocomposite scaffold for bone tissue engineering  

PubMed Central

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

12

Visualisation of heat transfer in 3D unsteady flows  

Microsoft Academic Search

Heat transfer in fluid flows traditionally is examined in terms of temperature field and heat-transfer coefficients at non-adiabatic walls. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective–conductive heat flux in a way analogous to the transport of fluid by the flow field. The paths followed by the total heat flux are

M. F. M. Speetjens; A. A. van Steenhoven

2010-01-01

13

Conduction heat transfer solutions  

SciTech Connect

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

14

Conduction heat transfer solutions  

SciTech Connect

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

15

Hydraulic conductivity imaging from 3-D transient hydraulic tomography at several pumping/observation densities  

E-print Network

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

16

3D Digitization of Metallic Specular Surfaces using Scanning from Heating Approach  

E-print Network

by a camera. Due to specularity of the surface, the classical 3D scanning approach, using laser triangulation3D Digitization of Metallic Specular Surfaces using Scanning from Heating Approach Alban Bajarda Digitization, 3D Scanning of specular surfaces, Scanning From Heating 1. INTRODUCTION The 3D reconstruction

Paris-Sud XI, Université de

17

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

18

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

SciTech Connect

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

19

Conductivity of 1D electrons in anisotropic 3D medium  

Microsoft Academic Search

Discusses the phonon limited high-temperature conductivity of 1D electrons within the quasistatic limit for lattice vibrations ( omega tau <<1 where omega is the phonon frequency and tau is the electron scattering time) using both first and second Born approximations and electron-one-phonon interaction. The second-order contribution of acoustic phonons to tau -1 is shown to be divergent when the phonons

S. Marianer; V. Zevin; M. Weger; D. Moses

1982-01-01

20

A 3D reconstruction solution to ultrasound Joule heat density tomography based on acousto-electric effect: a simulation study  

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

21

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

PubMed

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 ±0.1°C of a target temperature. Hyperthermia protocols included various combinations of temperature, ranging from 37°C to 57°C, 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

22

Highly conductive, capacitive, flexible and soft electrodes based on a 3D graphene-nanotube-palladium hybrid and conducting polymer.  

PubMed

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

23

Scanning from heating: 3D shape estimation of transparent objects from local surface heating.  

PubMed

Today, with quality becoming increasingly important, each product requires three-dimensional in-line quality control. On the other hand, the 3D reconstruction of transparent objects is a very difficult problem in computer vision due to transparency and specularity of the surface. This paper proposes a new method, called Scanning From Heating (SFH), to determine the surface shape of transparent objects using laser surface heating and thermal imaging. Furthermore, the application to transparent glass is discussed and results on different surface shapes are presented. PMID:19582061

Eren, Gonen; Aubreton, Olivier; Meriaudeau, Fabrice; Sanchez Secades, L A; Fofi, David; Naskali, A Teoman; Truchetet, Frederic; Ercil, Aytul

2009-07-01

24

Residual resistance of 2D and 3D structures and Joule heat release.  

PubMed

We consider a residual resistance and Joule heat release in 2D nanostructures as well as in ordinary 3D conductors. We assume that elastic scattering of conduction electrons by lattice defects is predominant. Within a rather intricate situation in such systems we discuss in detail two cases. (1) The elastic scattering alone (i.e. without regard of inelastic mechanisms of scattering) leads to a transition of the mechanical energy (stored by the electrons under the action of an electric field) into heat in a traditional way. This process can be described by the Boltzmann equation where it is possible to do the configuration averaging over defect positions in the electron-impurity collision term. The corresponding conditions are usually met in metals. (2) The elastic scattering can be considered with the help of the standard electron-impurity collision integral only in combination with some additional averaging procedure (possibly including inelastic scattering or some mechanisms of electron wavefunction phase destruction). This situation is typical for degenerate semiconductors with a high concentration of dopants and conduction electrons. Quite often, heat release can be observed via transfer of heat to the lattice, i.e. via inelastic processes of electron-phonon collisions and can take place at distances much larger than the size of the device. However, a direct heating of the electron system can be registered too by, for instance, local measurements of the current noise or direct measurement of an electron distribution function. PMID:21628783

Gurevich, V L; Kozub, V I

2011-06-22

25

Residual resistance of 2D and 3D structures and Joule heat release  

NASA Astrophysics Data System (ADS)

We consider a residual resistance and Joule heat release in 2D nanostructures as well as in ordinary 3D conductors. We assume that elastic scattering of conduction electrons by lattice defects is predominant. Within a rather intricate situation in such systems we discuss in detail two cases. (1) The elastic scattering alone (i.e. without regard of inelastic mechanisms of scattering) leads to a transition of the mechanical energy (stored by the electrons under the action of an electric field) into heat in a traditional way. This process can be described by the Boltzmann equation where it is possible to do the configuration averaging over defect positions in the electron-impurity collision term. The corresponding conditions are usually met in metals. (2) The elastic scattering can be considered with the help of the standard electron-impurity collision integral only in combination with some additional averaging procedure (possibly including inelastic scattering or some mechanisms of electron wavefunction phase destruction). This situation is typical for degenerate semiconductors with a high concentration of dopants and conduction electrons. Quite often, heat release can be observed via transfer of heat to the lattice, i.e. via inelastic processes of electron-phonon collisions and can take place at distances much larger than the size of the device. However, a direct heating of the electron system can be registered too by, for instance, local measurements of the current noise or direct measurement of an electron distribution function.

Gurevich, V. L.; Kozub, V. I.

2011-06-01

26

Superlow thermal conductivity 3D carbon nanotube network for thermoelectric applications.  

PubMed

Electrical and thermal transportation properties of a novel structured 3D CNT network have been systematically investigated. The 3D CNT net work maintains extremely low thermal conductivity of only 0.035 W/(m K) in standard atmosphere at room temperature, which is among the lowest compared with other reported CNT macrostructures. Its electrical transportation could be adjusted through a convenient gas-fuming doping process. By potassium (K) doping, the original p-type CNT network converted to n-type, whereas iodine (I(2)) doping enhanced its electrical conductivity. The self-sustainable homogeneous network structure of as-fabricated 3D CNT network made it a promising candidate as the template for polymer composition. By in situ nanoscaled composition of 3D CNT network with polyaniline (PANI), the thermoelectric performance of PANI was significantly improved, while the self-sustainable and flexible structure of the 3D CNT network has been retained. It is hoped that as-fabricated 3D CNT network will contribute to the development of low-cost organic thermoelectric area. PMID:22132803

Chen, Jikun; Gui, Xuchun; Wang, Zewei; Li, Zhen; Xiang, Rong; Wang, Kunlin; Wu, Dehai; Xia, Xugui; Zhou, Yanfei; Wang, Qun; Tang, Zikang; Chen, Lidong

2012-01-01

27

Performance of a variable conductance heat pipe heat exchanger  

Microsoft Academic Search

The performance of an air to air heat exchanger in which heat is transferred to a finned evaporator and from a finned condenser via a heat pipe was evaluated. The variable conductance heat pipe is to the condenser fins a heat source and to the evaporator fins a heat sink. The principal advantage of the variable conductance heat pipe heat

P. D. Chancelor

1983-01-01

28

A Simple, Low-Cost Conductive Composite Material for 3D Printing of Electronic Sensors  

PubMed Central

3D printing technology can produce complex objects directly from computer aided digital designs. The technology has traditionally been used by large companies to produce fit and form concept prototypes (‘rapid prototyping’) before production. In recent years however there has been a move to adopt the technology as full-scale manufacturing solution. The advent of low-cost, desktop 3D printers such as the RepRap and Fab@Home has meant a wider user base are now able to have access to desktop manufacturing platforms enabling them to produce highly customised products for personal use and sale. This uptake in usage has been coupled with a demand for printing technology and materials able to print functional elements such as electronic sensors. Here we present formulation of a simple conductive thermoplastic composite we term ‘carbomorph’ and demonstrate how it can be used in an unmodified low-cost 3D printer to print electronic sensors able to sense mechanical flexing and capacitance changes. We show how this capability can be used to produce custom sensing devices and user interface devices along with printed objects with embedded sensing capability. This advance in low-cost 3D printing with offer a new paradigm in the 3D printing field with printed sensors and electronics embedded inside 3D printed objects in a single build process without requiring complex or expensive materials incorporating additives such as carbon nanotubes. PMID:23185319

Leigh, Simon J.; Bradley, Robert J.; Purssell, Christopher P.; Billson, Duncan R.; Hutchins, David A.

2012-01-01

29

A simple, low-cost conductive composite material for 3D printing of electronic sensors.  

PubMed

3D printing technology can produce complex objects directly from computer aided digital designs. The technology has traditionally been used by large companies to produce fit and form concept prototypes ('rapid prototyping') before production. In recent years however there has been a move to adopt the technology as full-scale manufacturing solution. The advent of low-cost, desktop 3D printers such as the RepRap and Fab@Home has meant a wider user base are now able to have access to desktop manufacturing platforms enabling them to produce highly customised products for personal use and sale. This uptake in usage has been coupled with a demand for printing technology and materials able to print functional elements such as electronic sensors. Here we present formulation of a simple conductive thermoplastic composite we term 'carbomorph' and demonstrate how it can be used in an unmodified low-cost 3D printer to print electronic sensors able to sense mechanical flexing and capacitance changes. We show how this capability can be used to produce custom sensing devices and user interface devices along with printed objects with embedded sensing capability. This advance in low-cost 3D printing with offer a new paradigm in the 3D printing field with printed sensors and electronics embedded inside 3D printed objects in a single build process without requiring complex or expensive materials incorporating additives such as carbon nanotubes. PMID:23185319

Leigh, Simon J; Bradley, Robert J; Purssell, Christopher P; Billson, Duncan R; Hutchins, David A

2012-01-01

30

Numerical computation of 3D heat transfer in complex parallel convective exchangers using generalized Graetz modes  

E-print Network

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

31

Modelling flow and heat transfer in fractured rocks: Conceptual model of a 3-D deterministic fracture network  

Microsoft Academic Search

This work examines 3-D advective-conductive heat transfer during forced water circulation through fractured crystalline rocks. The subject of the modelling investigation is the Hot-Dry-Rock (HDR) site at Soultz-sous-For?ts, Alsace, France. Fracture data from borehole logging provides an insight to the complex structure of crystalline rocks. The proposed model is based on the general idea, that flow and advective transport in

O. Kolditz

1995-01-01

32

Validation of Heat Transfer and Film Cooling Capabilities of the 3-D RANS Code TURBO  

NASA Technical Reports Server (NTRS)

The capabilities of the 3-D unsteady RANS code TURBO have been extended to include heat transfer and film cooling applications. The results of simulations performed with the modified code are compared to experiment and to theory, where applicable. Wilcox s k-turbulence model has been implemented to close the RANS equations. Two simulations are conducted: (1) flow over a flat plate and (2) flow over an adiabatic flat plate cooled by one hole inclined at 35 to the free stream. For (1) agreement with theory is found to be excellent for heat transfer, represented by local Nusselt number, and quite good for momentum, as represented by the local skin friction coefficient. This report compares the local skin friction coefficients and Nusselt numbers on a flat plate obtained using Wilcox's k-model with the theory of Blasius. The study looks at laminar and turbulent flows over an adiabatic flat plate and over an isothermal flat plate for two different wall temperatures. It is shown that TURBO is able to accurately predict heat transfer on a flat plate. For (2) TURBO shows good qualitative agreement with film cooling experiments performed on a flat plate with one cooling hole. Quantitatively, film effectiveness is under predicted downstream of the hole.

Shyam, Vikram; Ameri, Ali; Chen, Jen-Ping

2010-01-01

33

Rapid prototyping of electrically conductive components using 3D printing technology  

Microsoft Academic Search

A method of rapid prototyping of electrically conductive components is described. The method is based on 3D printing technology. The prototyped model is made of plaster-based powder bound layer-by-layer by an inkjet printing of a liquid binder. The resulting model is highly porous and can be impregnated by various liquids. In a standard prototyping process, the model is impregnated by

J. Czy?ewski; P. Burzy?ski; K. Gawe?; J. Meisner

2009-01-01

34

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

35

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

SciTech Connect

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

36

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

SciTech Connect

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

37

A 3-D conductivity model of the Australian continent using observatory and magnetometer array data  

NASA Astrophysics Data System (ADS)

An exploratory 3-D model of the electrical conductivity structure of the Australian continent is presented. The model is derived from the inversion of vertical magnetic-field transfer functions from the Australia-wide Array of Geomagnetic Stations. Crustal conductivity anomalies evident in the model are consistent with those previously mapped by independent magnetometer array studies and new electrical structures are suggested in the upper mantle. The model represents a seamless continent-scale basis for further models likely to be derived from subsequent studies. The model reveals three upper-mantle enhanced-conductivity anomalies beneath Archaean cratonic regions and two upper-mantle anomalies beneath Phanerozoic terranes in eastern Australia. Two of these anomalies have been investigated by recent magnetotelluric (MT) surveys, one in the Yilgarn Craton-Officer Basin-Musgrave Block the other in the Gawler Craton region, and are consistent with the MT results. Across much of central Australia enhanced conductivity at depths of 50-100 km is observed in the model. This region corresponds well with a recognized seismic velocity gradient at 75-100 km. Conductivity differences are also observed beneath Archaean cratons in Western Australia. The Pilbara Craton is represented as an enhanced conductivity anomaly at about 100 km, corresponding well with the lower-velocity anomaly evident in surface wave tomography models. The Yilgarn Craton is imaged as a low-conductivity body, with conductivity two orders of magnitude lower than the Pilbara Craton, continuing to greater depths.

Wang, Liejun; Hitchman, Adrian P.; Ogawa, Yasuo; Siripunvaraporn, Weerachai; Ichiki, Masahiro; Fuji-ta, Kiyoshi

2014-08-01

38

Exceptional electrical conductivity and fracture resistance of 3D interconnected graphene foam/epoxy composites.  

PubMed

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 MPa·m(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

39

3D noninvasive ultrasound Joule heat tomography based on acousto-electric effect using unipolar pulses: a simulation study  

PubMed Central

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

40

Turbomachinery Heat Transfer and Loss Modeling for 3D Navier-Stokes Codes  

NASA Technical Reports Server (NTRS)

This report's contents focus on making use of NASA Glenn on-site computational facilities,to develop, validate, and apply models for use in advanced 3D Navier-Stokes Computational Fluid Dynamics (CFD) codes to enhance the capability to compute heat transfer and losses in turbomachiney.

DeWitt, Kenneth; Ameri, Ali

2005-01-01

41

Pattern Transformation of Heat-Shrinkable Polymer by Three-Dimensional (3D) Printing Technique  

NASA Astrophysics Data System (ADS)

A significant challenge in conventional heat-shrinkable polymers is to produce controllable microstructures. Here we report that the polymer material fabricated by three-dimensional (3D) printing technique has a heat-shrinkable property, whose initial microstructure can undergo a spontaneous pattern transformation under heating. The underlying mechanism is revealed by evaluating internal strain of the printed polymer from its fabricating process. It is shown that a uniform internal strain is stored in the polymer during the printing process and can be released when heated above its glass transition temperature. Furthermore, the internal strain can be used to trigger the pattern transformation of the heat-shrinkable polymer in a controllable way. Our work provides insightful ideas to understand a novel mechanism on the heat-shrinkable effect of printed material, but also to present a simple approach to fabricate heat-shrinkable polymer with a controllable thermo-structural response.

Zhang, Quan; Yan, Dong; Zhang, Kai; Hu, Gengkai

2015-03-01

42

Pattern Transformation of Heat-Shrinkable Polymer by Three-Dimensional (3D) Printing Technique  

PubMed Central

A significant challenge in conventional heat-shrinkable polymers is to produce controllable microstructures. Here we report that the polymer material fabricated by three-dimensional (3D) printing technique has a heat-shrinkable property, whose initial microstructure can undergo a spontaneous pattern transformation under heating. The underlying mechanism is revealed by evaluating internal strain of the printed polymer from its fabricating process. It is shown that a uniform internal strain is stored in the polymer during the printing process and can be released when heated above its glass transition temperature. Furthermore, the internal strain can be used to trigger the pattern transformation of the heat-shrinkable polymer in a controllable way. Our work provides insightful ideas to understand a novel mechanism on the heat-shrinkable effect of printed material, but also to present a simple approach to fabricate heat-shrinkable polymer with a controllable thermo-structural response. PMID:25757881

Zhang, Quan; Yan, Dong; Zhang, Kai; Hu, Gengkai

2015-01-01

43

Pattern Transformation of Heat-Shrinkable Polymer by Three-Dimensional (3D) Printing Technique.  

PubMed

A significant challenge in conventional heat-shrinkable polymers is to produce controllable microstructures. Here we report that the polymer material fabricated by three-dimensional (3D) printing technique has a heat-shrinkable property, whose initial microstructure can undergo a spontaneous pattern transformation under heating. The underlying mechanism is revealed by evaluating internal strain of the printed polymer from its fabricating process. It is shown that a uniform internal strain is stored in the polymer during the printing process and can be released when heated above its glass transition temperature. Furthermore, the internal strain can be used to trigger the pattern transformation of the heat-shrinkable polymer in a controllable way. Our work provides insightful ideas to understand a novel mechanism on the heat-shrinkable effect of printed material, but also to present a simple approach to fabricate heat-shrinkable polymer with a controllable thermo-structural response. PMID:25757881

Zhang, Quan; Yan, Dong; Zhang, Kai; Hu, Gengkai

2015-01-01

44

Modelling of transient heat conduction with diffuse interface methods  

NASA Astrophysics Data System (ADS)

We present a survey on different numerical interpolation schemes used for two-phase transient heat conduction problems in the context of interface capturing phase-field methods. Examples are general transport problems in the context of diffuse interface methods with a non-equal heat conductivity in normal and tangential directions to the interface. We extend the tonsorial approach recently published by Nicoli M et al (2011 Phys. Rev. E 84 1–6) to the general three-dimensional (3D) transient evolution equations. Validations for one-dimensional, two-dimensional and 3D transient test cases are provided, and the results are in good agreement with analytical and numerical reference solutions.

Ettrich, J.; Choudhury, A.; Tschukin, O.; Schoof, E.; August, A.; Nestler, B.

2014-12-01

45

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

46

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.

Püthe, Christoph; Kuvshinov, Alexey; Olsen, Nils

2014-05-01

47

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

48

A hybrid, infrared thermography: heat diffusion equation, method for the 3D air-temperature measurement  

NASA Astrophysics Data System (ADS)

The question of how to map the 3D indoor temperature by infrared thermography is solved by a hybrid method which is a combination of infrared thermography and the well known heat diffusion equation. The idea is to use infrared thermography to get the surface temperature of each frontier of the 3D domain of interest. A suitable procedure is devoted to this, allowing an automatic scanning of the whole frontier, the registration of data and computation. These surface temperatures constitute the boundary conditions of the heat equation solved in the domain of interest. The solution of the heat equation allows analyzing and controlling the temperature of every point belonging to the considered domain. This temperature distribution is controlled over the time with a period of the same order than the necessary time to obtain the frontier temperatures and at the end to contribute to the analysis of the thermal comfort. The study is done for the steady-state conditions under various weather situations. In this case the temperature depends only on space coordinates. With such procedure, we can have an idea about the time necessary to reach thermal equilibrium; time which has a great impact on the thermal comfort sensation. The results yielded by this method are compared with those given by others techniques used for temperature measurement. Finally, the method is used to access 3D temperature distribution for various geometric shapes.

Djupkep Dizeu, F. B.; Maldague, X.; Bendada, A.; Grinzato, E.; Bison, P.

2011-05-01

49

Parallel computing simulation of electrical excitation and conduction in the 3D human heart.  

PubMed

A correctly beating heart is important to ensure adequate circulation of blood throughout the body. Normal heart rhythm is produced by the orchestrated conduction of electrical signals throughout the heart. Cardiac electrical activity is the resulted function of a series of complex biochemical-mechanical reactions, which involves transportation and bio-distribution of ionic flows through a variety of biological ion channels. Cardiac arrhythmias are caused by the direct alteration of ion channel activity that results in changes in the AP waveform. In this work, we developed a whole-heart simulation model with the use of massive parallel computing with GPGPU and OpenGL. The simulation algorithm was implemented under several different versions for the purpose of comparisons, including one conventional CPU version and two GPU versions based on Nvidia CUDA platform. OpenGL was utilized for the visualization / interaction platform because it is open source, light weight and universally supported by various operating systems. The experimental results show that the GPU-based simulation outperforms the conventional CPU-based approach and significantly improves the speed of simulation. By adopting modern computer architecture, this present investigation enables real-time simulation and visualization of electrical excitation and conduction in the large and complicated 3D geometry of a real-world human heart. PMID:25570947

Di Yu; Dongping Du; Hui Yang; Yicheng Tu

2014-01-01

50

Ballistic-Diffusive Heat-Conduction Equations  

Microsoft Academic Search

We present new heat-conduction equations, named ballistic-diffusive equations, which are derived from the Boltzmann equation. We show that the new equations are a better approximation than the Fourier law and the Cattaneo equation for heat conduction at the scales when the device characteristic length, such as film thickness, is comparable to the heat-carrier mean free path and\\/or the characteristic time,

Gang Chen; Gang

2001-01-01

51

Reconstruction of the 3D flow field in a differentially heated rotating annulus laboratory experiment  

NASA Astrophysics Data System (ADS)

In the earth's atmosphere baroclinic instability is responsible for the heat and momentum transport from low to high latitudes. In the fifties, Raymond Hide used a rather simple laboratory experiment to study such vortices in the lab. The experiment is comprised by a cooled inner and heated outer cylinder mounted on a rotating platform, which mimics the heated tropical and cooled polar regions of the earth's atmosphere. The experiment shows rich dynamics that have been studied by varying the radial temperature difference and the rate of annulus revolution. At the Brandenburg University of Technology (BTU) Cottbus the differentially heated rotating annulus is a reference experiment of the DFG priority program 'MetStröm'. The 3D structure of the annulus flow field has been numerically simulated but, to our knowledge, has not been measured in the laboratory. In the present paper we use novel interpolation techniques to reconstruct the 3D annulus flow field from synchronous Particle Image Velocimetry (PIV) and Infrared Thermography (IRT) measurements. The PIV system is used to measure the horizontal velocity components at 40, 60, 80, 100, and 120 mm above the bottom. The uppermost level is thus 15 mm below the fluid's surface. The surface temperature is simultaneously measured by an infrared (IR) camera. The PIV and infrared cameras have been mounted above the annulus and they co-rotate with the annulus. From the PIV observations alone a coherent 3D picture of the flow cannot be constructed since the PIV measurements have been taken at different instants of time. Therefore a corresponding IR image has been recorded for each PIV measurement. These IR images can be used to reconstruct the correct phase of the measured velocity fields. Each IR and PIV image for which t>0 is rotated back to the position at t=0. Then all surface waves have the same phase. In contrast, the PIV velocity fields generally have different phases since they have been taken at different vertical levels. From these rotated fields, a 3D flow field can be reconstructed that is an approximation to the true 3D flow. The PIV measurements of the horizontal velocity fields do not line up on a nice grid. We therefore use a mesh-free reconstruction method based on radial basis functions (RBFs). Additionally, we employ a filtering strategy for dealing with the noise in the measured velocity fields.

Harlander, U.; Wright, G. B.; Egbers, C.

2012-04-01

52

Estimating Hydraulic Conductivities in a Fractured Shale Formation from Pressure Pulse Testing and 3d Modeling  

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

53

Global 3-D EM inversion of Sq variations based on simultaneous source and conductivity determination: concept validation and resolution studies  

NASA Astrophysics Data System (ADS)

We present a novel global 3-D electromagnetic (EM) inverse solution that allows to work in a unified and consistent manner with frequency-domain data that originate from ionospheric and magnetospheric sources irrespective of their spatial complexity. The main idea behind the approach is simultaneous determination of the source and conductivity distribution in the Earth. Such a determination is implemented in our solution as a looped sequential procedure that involves two steps: (1) determination of the source using a fixed 3-D conductivity model and (2) recovery of a 3-D conductivity model using a fixed source. We focus in this paper on analysis of Sq data and numerically verify each step separately and combined using data synthesized from 3-D models of the Earth induced by a realistic Sq source. To determine the source we implement an approach that makes use of a known conductivity structure of the Earth with non-uniform oceans. Based on model studies we show that this approach outperforms the conventional potential method. As for recovery of 3-D conductivity in the mantle, our inverse scheme relies on a regularized least-square formulation, exploits a limited-memory quasi-Newton optimization method and makes use of the adjoint source approach to calculate efficiently the misfit gradient. We perform resolution studies with checkerboard conductivity structures at depths between 10 and 1600 km for different inverse setups and conclude from these studies that: (1) inverting Z component gives much better results than inverting all (X, Y and Z) components; (2) data from the Sq source allows for resolving 3-D structures in depth range between 100 and 520 km; (3) the best resolution is achieved in the depth range of 100-250 km.

Koch, Stephan; Kuvshinov, Alexey

2013-10-01

54

A phase-field method for 3D simulation of two-phase heat transfer , H. Babaee a  

E-print Network

A phase-field method for 3D simulation of two-phase heat transfer X. Zheng a , H. Babaee a , S s t r a c t We formulate new multi-phase convective heat transfer equations by combining the three for convergence in time/space including a conjugate heat transfer problem and also for a realistic tran- sient

Dong, Suchuan "Steven"

55

Simulation of heat transport in LHD plasmas using the integrated code: TASK3D  

NASA Astrophysics Data System (ADS)

An integrated transport simulation code for helical plasmas, TASK3D, has been developed and applied to the LHD plasmas. The neoclassical transport in LHD plasma is evaluated by the neoclassical transport database module, DGN/LHD, using a neural network technique. The radial electric field module, ER, which solves the differential equation of the radial electric field has been also developed. In this study, the behavior of the LHD plasmas is simulated with several anomalous transport models and the temperature profiles are compared with experimental observations. Reasonable agreements of the radial electric field profile between simulation results and the experimental ones are obtained by use of the ER module. It is found that the anomalous transport dominates in the electron heat transport, while the neoclassical transport plays a crucial role in the ion heat transport.

Wakasa, A.; Fukuyama, A.; Murakami, S.; Yokoyama, M.; Sato, M.; Toda, S.; Funaba, H.; Seki, R.; Tanaka, K.; Ida, K.; Yamada, H.; Nakajima, N.

2011-11-01

56

3d Numerical Analysis of Heat Exchange in Building Structures with Cavities  

NASA Astrophysics Data System (ADS)

In the paper, the heat transfer inside a building block with cavities is analyzed and a brief overview of the relevant physical problem is given. The equations governing the heat exchange processes are presented and a numerical model is derived with the help of ANSYS software. The role of radiation and convection inside the cavities is emphasized throughout the work. The results show that in such cavities the radiation mechanism of heat transfer is dominant. The authors also examine the dependence of the effective heat conductivity on the properties of clay material. Using the numerical model, attempts have been made to improve the heat resistance of a building block. Possibilities of practical application of numerical modelling in the heat insulation material engineering are discussed.

Grechenkovs, J.; Jakovich, A.; Gendelis, S.

2011-01-01

57

Numerical computation of 3D heat transfer in complex parallel heat exchangers using generalized Graetz modes  

NASA Astrophysics Data System (ADS)

We propose and develop a variational formulation dedicated to the simulation of parallel convective heat exchangers that handles possibly complex input/output conditions as well as connection between pipes. It is based on a spectral method that allows to re-cast three-dimensional heat exchangers into a two-dimensional eigenvalue problem, named the generalized Graetz problem. Our formulation handles either convective, adiabatic, or prescribed temperature at the entrance or at the exit of the exchanger. This formulation is robust to mode truncation, offering a huge reduction in computational cost, and providing insights into the most contributing structure to exchanges and transfer. Several examples of heat exchangers are analyzed, their numerical convergence is tested and the numerical efficiency of the approach is illustrated in the case of Poiseuille flow in tubes.

Pierre, Charles; Bouyssier, Julien; de Gournay, Frédéric; Plouraboué, Franck

2014-07-01

58

Transient Heat Conduction Simulation around Microprocessor Die  

NASA Astrophysics Data System (ADS)

This paper explains about fundamental formula of calculating power consumption of CMOS (Complementary Metal-Oxide-Semiconductor) devices and its voltage and temperature dependency, then introduces equation for estimating power consumption of the microprocessor for notebook PC (Personal Computer). The equation is applied to heat conduction simulation with simplified thermal model and evaluates in sub-millisecond time step calculation. In addition, the microprocessor has two major heat conduction paths; one is from the top of the silicon die via thermal solution and the other is from package substrate and pins via PGA (Pin Grid Array) socket. Even though the dominant factor of heat conduction is the former path, the latter path - from package substrate and pins - plays an important role in transient heat conduction behavior. Therefore, this paper tries to focus the path from package substrate and pins, and to investigate more accurate method of estimating heat conduction paths of the microprocessor. Also, cooling performance expression of heatsink fan is one of key points to assure result with practical accuracy, while finer expression requires more computation resources which results in longer computation time. Then, this paper discusses the expression to minimize computation workload with a practical accuracy of the result.

Nishi, Koji

59

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

NASA Astrophysics Data System (ADS)

The 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

60

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

61

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

Microsoft Academic Search

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

62

3D modeling of the heating of a metal sheet by a moving arc: application to aircraft lightning protection  

Microsoft Academic Search

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. Testé; T. Leblanc; F. Uhlig; J.-P. Chabrerie

2000-01-01

63

Finite Heat conduction in 2D Lattices  

E-print Network

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

64

Investigation of broadband electromagnetic induction scattering by highly conductive, permeable, arbitrarily shaped 3-D objects  

Microsoft Academic Search

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

65

Large variable conductance heat pipe. Transverse header  

NASA Technical Reports Server (NTRS)

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

Edelstein, F.

1975-01-01

66

Heat conductivity of a pion gas  

E-print Network

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

67

Development methods of steam turbines 3D geometry optical control for effective heat power equipment quality improvement  

NASA Astrophysics Data System (ADS)

A method for steam turbines 3D geometry optical control for effective heat power equipment quality improvement is proposed. It is shown that technical characteristics of the developed optical phase triangulation method for precision contactless geometry diagnostics of steam turbines meet modern requirements to 3D geometry measuring instruments and are perspective for further development. It is shown that used phase step method provides measurement error less than 0.024% of measurement range.

Dvoynishnikov, Sergey

2014-08-01

68

3D numerical simulation of heat transfer during horizontal direct crystallization of corundum single crystals  

NASA Astrophysics Data System (ADS)

This paper describes the numerical simulation of heat transfer in a system for growing corundum single-crystal plates (leucosapphire and ruby) of size 200×200 mm. A mathematical model accounting for the radiative and conductive heat transfer has been developed. Three-dimensional computations have been made with minor simplifications of the furnace geometry. The thermal fields at various positions of the crystal container and the effect of various setup units and their design on the temperature distribution are analyzed. The computed crystallization front shape is compared with the available experimental data. Numerical analysis was used to optimize the hot zone design.

Lukanina, M. A.; Hodosevitch, K. V.; Kalaev, V. V.; Semenov, V. B.; Sytin, V. N.; Raevsky, V. L.

2006-01-01

69

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

70

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

PubMed

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

71

Diagnostic of structures in heat and power generating industries with utilization of 3D digital image correlation  

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

72

Design of isotropic 3-D multilayered CRLH metamaterial structures using conductive mesh plates and dielectric resonators  

Microsoft Academic Search

Almost isotropic three-dimensional multilayered composite right\\/left handed metamaterial structure is proposed and designed. It is composed of conductive mesh plates and dielectric layers including dielectric resonators with high dielectric constant. Basically, the structure has uniaxial anisotropy. The polarization of incident waves is restricted to directions parallel to the stacked layers. The numerical results show that not only the wavenumber vector

Yoshiaki Sato; Tetsuya Ueda; Yuichi Kado; Tatsuo Itoh

2011-01-01

73

Inversion of multi-frequency electromagnetic induction data for 3D characterization of hydraulic conductivity  

USGS Publications Warehouse

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

74

Hierarchical self-assembly of hexagonal single-crystal nanosheets into 3D layered superlattices with high conductivity.  

PubMed

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

75

A fast technique applied to the analysis of Resistive Wall Modes with 3D conducting structures  

SciTech Connect

This paper illustrates the development of a 'fast' technique for the analysis of Resistive Wall Modes (RWMs) in fusion devices with three-dimensional conducting structures, by means of the recently developed CarMa code. Thanks to its peculiar features, the computational cost scales almost linearly with the number of discrete unknowns. Some large scale problems are solved in configurations of interest for the International Thermonuclear Experimental Reactor (ITER)

Rubinacci, Guglielmo [Ass. EURATOM/ENEA/CREATE, DIEL, Universita degli Studi di Napoli, Federico II (Italy); Ventre, Salvatore [Ass. EURATOM/ENEA/CREATE, DAEIMI, Universita degli Studi di Cassino, Via Di Biasio 43, 03043 Cassino (Italy); Villone, Fabio [Ass. EURATOM/ENEA/CREATE, DAEIMI, Universita degli Studi di Cassino, Via Di Biasio 43, 03043 Cassino (Italy)], E-mail: villone@unicas.it; Liu, Yueqiang [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)

2009-03-20

76

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

77

Albedo and heat transport in 3-D model simulations of the early Archean climate  

NASA Astrophysics Data System (ADS)

At the beginning of the Archean eon (ca. 3.8 billion years ago), the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun paradox" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-D model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. In order to do so, we have appropriately modified an intermediate complexity climate model that couples a statistical-dynamical atmosphere model (involving parameterizations of the dynamics) to an ocean general circulation model and a thermodynamic-dynamic sea-ice model. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth"). We find a reduction in meridional heat transport compared to today, which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterization of the ice-albedo feedback for 1-D model simulations of the early Archean and thus the faint young Sun problem.

Kienert, H.; Feulner, G.; Petoukhov, V.

2013-08-01

78

Phonon heat conduction in layered anisotropic crystals  

NASA Astrophysics Data System (ADS)

The thermal properties of anisotropic crystals are of both fundamental and practical interest, but transport phenomena in anisotropic materials such as graphite remain poorly understood because solutions of the Boltzmann equation often assume isotropy. Here, we extend an analytic solution of the transient, frequency-dependent Boltzmann equation to highly anisotropic solids and examine its predictions for graphite. We show that this simple model predicts key results, such as long c -axis phonon mean free paths and a negative correlation of cross-plane thermal conductivity with in-plane group velocity, that were previously observed with computationally expensive molecular-dynamics simulations. Further, using our analytic solution, we demonstrate a method to reconstruct the anisotropic mean free path spectrum of crystals with arbitrary dispersion relations without any prior knowledge of their harmonic or anharmonic properties using observations of quasiballistic heat conduction. These results provide a useful analytic framework to understand thermal transport in anisotropic crystals.

Minnich, A. J.

2015-02-01

79

3D Polyaniline Porous Layer Anchored Pillared Graphene Sheets: Enhanced Interface Joined with High Conductivity for Better Charge Storage Applications.  

PubMed

Here, we report synthesis of a 3-dimensional (3D) porous polyaniline (PANI) anchored on pillared graphene (G-PANI-PA) as an efficient charge storage material for supercapacitor applications. Benzoic acid (BA) anchored graphene, having spatially separated graphene layers (G-Bz-COOH), was used as a structure controlling support whereas 3D PANI growth has been achieved by a simple chemical oxidation of aniline in the presence of phytic acid (PA). The BA groups on G-Bz-COOH play a critical role in preventing the restacking of graphene to achieve a high surface area of 472 m(2)/g compared to reduced graphene oxide (RGO, 290 m(2)/g). The carboxylic acid (-COOH) group controls the rate of polymerization to achieve a compact polymer structure with micropores whereas the chelating nature of PA plays a crucial role to achieve the 3D growth pattern of PANI. This type of controlled interplay helps G-PANI-PA to achieve a high conductivity of 3.74 S/cm all the while maintaining a high surface area of 330 m(2)/g compared to PANI-PA (0.4 S/cm and 60 m(2)/g). G-PANI-PA thus conceives the characteristics required for facile charge mobility during fast charge-discharge cycles, which results in a high specific capacitance of 652 F/g for the composite. Owing to the high surface area along with high conductivity, G-PANI-PA displays a stable specific capacitance of 547 F/g even with a high mass loading of 3 mg/cm(2), an enhanced areal capacitance of 1.52 F/cm(2), and a volumetric capacitance of 122 F/cm(3). The reduced charge-transfer resistance (RCT) of 0.67 ? displayed by G-PANI-PA compared to pure PANI (0.79 ?) stands out as valid evidence of the improved charge mobility achieved by the system by growing the 3D PANI layer along the spatially separated layers of the graphene sheets. The low RCT helps the system to display capacitance retention as high as 65% even under a high current dragging condition of 10 A/g. High charge/discharge rates and good cycling stability are the other highlights of the supercapacitor system derived from this composite material. PMID:25783045

Sekar, Pandiaraj; Anothumakkool, Bihag; Kurungot, Sreekumar

2015-04-15

80

3D slicing of radiogenic heat production in Bahariya Formation, Tut oil field, North-Western Desert, Egypt.  

PubMed

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

81

Hierarchical self-assembly of hexagonal single-crystal nanosheets into 3D layered superlattices with high conductivity  

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

82

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

83

ARE 3D HEAT TRANSFER FORMULATIONS WITH SHORT TIME STEP AND SUN PATCH EVOLUTION NECESSARY FOR BUILDING SIMULATION?  

E-print Network

and the radiation distribution ­ Three-dimensional heat conduction ­ Enthalpy of a single air node ­ Convection be equations are developed based on a consideration of radiation, convection, air enthalpy and three-dimensional heat conduction. As buildings are exposed to rapid climatic variations (particularly incident solar

Boyer, Edmond

84

CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011  

E-print Network

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

Dyer, Bill

85

Developing Low-Conductance Window Frames: Capabilities and Limitations of Current Window Heat Transfer Design Tools  

SciTech Connect

While window frames typically represent 20-30% of the overall window area, their impact on the total window heat transfer rates may be much larger. This effect is even greater in low-conductance (highly insulating) windows that incorporate very low-conductance glazing. Developing low-conductance window frames requires accurate simulation tools for product research and development. Based on a literature review and an evaluation of current methods of modeling heat transfer through window frames, we conclude that current procedures specified in ISO standards are not sufficiently adequate for accurately evaluating heat transfer through the low-conductance frames. We conclude that the near-term priorities for improving the modeling of heat transfer through low-conductance frames are: (1) Add 2D view-factor radiation to standard modeling and examine the current practice of averaging surface emissivity based on area weighting and the process of making an equivalent rectangular frame cavity. (2) Asses 3D radiation effects in frame cavities and develop recommendation for inclusion into the design fenestration tools. (3) Assess existing correlations for convection in vertical cavities using CFD. (4) Study 2D and 3D natural convection heat transfer in frame cavities for cavities that are proven to be deficient from item 3 above. Recommend improved correlations or full CFD modeling into ISO standards and design fenestration tools, if appropriate. (5) Study 3D hardware short-circuits and propose methods to ensure that these effects are incorporated into ratings. (6) Study the heat transfer effects of ventilated frame cavities and propose updated correlations.

Gustavsen, Arild; Arasteh, Dariush; Jelle, Bjorn Petter; Curcija, Charlie; Kohler, Christian

2008-09-11

86

RELAP5-3D Modeling of Heat Transfer Components (Intermediate Heat Exchanger and Helical-Coil Steam Generator) for NGNP Application  

SciTech Connect

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

87

Radiative Heat Conduction and the Magnetorotational Instability  

E-print Network

A photon or neutrino gas--semi-contained by a baryonic species through scattering--comprises a rather peculiar MHD fluid where the magnetic field is truly frozen only to the co-moving volume associated with the mass density. Although radiative diffusion precludes an adiabatic treatment of compressive perturbations, we show that the energy equation may be cast in "quasi-adiabatic" form for exponentially growing non-propagating wave modes. Defining a generalized quasi-adiabatic index leads to a relatively straightforward dispersion relation for non-axisymmetric magnetorotational modes in the horizontal regime when an accretion disk has comparable stress contributions from diffusive and non-diffusive particle species. This analysis is generally applicable to optically thick, neutrino-cooled disks since the pressure contributions from photons, pairs and neutrinos, all have the same temperature dependence whereas only the neutrino component has radiative heat conduction properties on the time and length scales of the instability. We discuss the energy deposition process and the temporal and spatial properties of the ensuing turbulent disk structure on the basis of the derived dispersion relation.

Rafael A. Araya-Gochez; Ethan Vishniac

2003-11-21

88

Modeling a Printed Circuit Heat Exchanger with RELAP5-3D for the Next Generation Nuclear Plant  

SciTech Connect

The main purpose of this report is to design a printed circuit heat exchanger (PCHE) for the Next Generation Nuclear Plant and carry out Loss of Coolant Accident (LOCA) simulation using RELAP5-3D. Helium was chosen as the coolant in the primary and secondary sides of the heat exchanger. The design of PCHE is critical for the LOCA simulations. For purposes of simplicity, a straight channel configuration was assumed. A parallel intermediate heat exchanger configuration was assumed for the RELAP5 model design. The RELAP5 modeling also required the semicircular channels in the heat exchanger to be mapped to rectangular channels. The initial RELAP5 run outputs steady state conditions which were then compared to the heat exchanger performance theory to ensure accurate design is being simulated. An exponential loss of pressure transient was simulated. This LOCA describes a loss of coolant pressure in the primary side over a 20 second time period. The results for the simulation indicate that heat is initially transferred from the primary loop to the secondary loop, but after the loss of pressure occurs, heat transfers from the secondary loop to the primary loop.

Not Available

2010-12-01

89

Finite element procedure for heat conduction problems with internal heating  

SciTech Connect

Heat transfer problems involving temperature-dependent heat generation are formally equivalent to those involving variable specific heat such as occur in phase change situations. The use of distributed and lumped capacitance finite element methods for solving these problems is investigated. The technique is successfully applied to very severe internal heating problems such as the self-ignition of biological materials.

Pham, Q.T. [Univ. of New South Wales, Sydney (Australia). School of Chemical Engineering and Industrial Chemistry

1995-05-01

90

Two exact solutions of the DPL non-Fourier heat conduction equation with special conditions  

Microsoft Academic Search

This paper presents two exact explicit solutions for the three dimensional dual-phase lag (DLP) heat conduction equation,\\u000a during the derivation of which the method of trial and error and the authors’ previous experiences are utilized. To the authors’\\u000a knowledge, most solutions of 2D or 3D DPL models available in the literature are obtained by numerical methods, and there\\u000a are few

Youtong Zhang; Changsong Zheng; Yongfeng Liu; Liang Shao; Chenhua Gou

2009-01-01

91

Numerical solution of 3D unsteady nonlinear inverse problem of estimating surface heat flux for cylindrical geometry  

Microsoft Academic Search

A numerical algorithm is proposed for solving a three-dimensional unsteady nonlinear inverse heat conduction problem of estimating the boundary conditions at the heated surface of a solid. In this study, the geometrical form of the solid is a finite hollow half-cylinder. As additional information, needed to solve the inverse problem under study, we use both temperature measurements at the internal

Tahar Loulou; Eugene Artioukhine

2006-01-01

92

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

SciTech Connect

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

93

Heat transfer in 3-D serpentine channels with right-angle turns  

SciTech Connect

Laminar flow and heat transfer in square serpentine channels with right-angle turns, which have applications in heat exchangers, were numerically studied. A finite volume code in FORTRAN was developed to solve this problem. For solving the flow field, a colocated-grid formulation was used, as opposed to the staggered-grid formulation, and the SIMPLE algorithm was used to link the velocity and pressure. The line-by-line method was used to solve the algebraic equations. The temperature field was solved for the uniform-wall-heat-flux boundary condition. The developed numerical code was validated by solving for fully developed flow and heat transfer in a square straight channel. The grid-independent solution was established for a reference case of serpentine channel with the highest Reynolds number. Periodically fully developed flow and heat transfer fields in serpentine channels were solved for different geometry parameters, for different Reynolds numbers, and for two different Prandtl numbers (for air and water, respectively). The enhancement of the heat transfer mechanism was explained by studying the plotted flow-field velocity vectors in different planes. The heat transfer performance of serpentine channels is better than that for straight channels for Pr = 7.0 and is worse than that for straight channels for Pr = 0.7.

Chintada, S.; Ko, K.H.; Anand, N.K.

1999-12-01

94

BEM for 3D unsteady-state flow problems in porous media with a finite-conductivity horizontal wellbore  

Microsoft Academic Search

This paper presents a Boundary Element Method (BEM) for the solution of unsteady-state fluid flow problems in a 3D domain. A general 3D reservoir model was developed in a bounded porous media with Neumann's, Dirichlet's or mixed boundary conditions. To consider the influence of frictional pressure loss in a horizontal wellbore on the reservoir performance behavior, a wellbore hydraulics model

Yueming Cheng; Duane A. McVay; W. John Lee

2005-01-01

95

Numerical study of flow and heat transfer in 3D serpentine channels using colocated grids  

E-print Network

and average Nusselt number. The numerical code developed was validated by solving for fully developed flow and heat transfer in a square straight channel. Grid-independent solution was established for a reference case of serpentine channel with the highest...

Chintada, Sailesh Raju

1998-01-01

96

Superfluid heat conduction and the cooling of magnetized neutron stars  

SciTech Connect

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

97

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

98

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

99

NUMERICAL INVESTIGATION OF THERMAL TRANSPORT MECHANISMS DURING ULTRA-FAST LASER HEATING OF NANO-FILMS USING 3-D DUAL PHASE LAG (DPL) MODEL  

Microsoft Academic Search

Ultra-fast laser heating of nano-films is investigated using 3-D Dual Phase Lag heat transport equation with laser heating at different locations on the metal film. The energy absorption rate, which is used to model femtosecond laser heating, is modified to accommodate for three-dimensional laser heating. A numerical solution based on an explicit finite-difference method is employed to solve the DPL

Illayathambi Kunadian

2004-01-01

100

Scalable 3D Bicontinuous Fluid Networks: Polymer Heat Exchangers Toward Artificial Organs.  

PubMed

A scalable method for fabricating architected materials well-suited for heat and mass exchange is presented. These materials exhibit unprecedented combinations of small hydraulic diameters (13.0-0.09 mm) and large hydraulic-diameter-to-thickness ratios (5.0-30,100). This process expands the range of material architectures achievable starting from photopolymer waveguide lattices or additive manufacturing. PMID:25753365

Roper, Christopher S; Schubert, Randall C; Maloney, Kevin J; Page, David; Ro, Christopher J; Yang, Sophia S; Jacobsen, Alan J

2015-04-01

101

3-D heat and mass transfer modeling and manipulation using microwaves  

Microsoft Academic Search

An investigation is made for three-dimensional heat and mass transfer using microwave power and hot air in a cubic specimen of the processed material. Analytical and numerical approach of the microwave drying process is presented. The nonlinear system is solved numerically by finite difference techniques. Simulation is performed for a material of isothermal moisture contents and mass transfer analogue of

M. A. Saber

2003-01-01

102

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...

103

Exploring Geothermal Energy Potential in Ireland through 3-D Geophysical-Petrological Modelling of Surface Heat-Flow and Crustal and Upper-Mantle Structure  

NASA Astrophysics Data System (ADS)

Little is known of Ireland's deep, low-enthalpy geothermal resources and the potential for space heating and/or electricity generation based on geothermal energy to displace Ireland's significant reliance on carbon-based fuels. IRETHERM (www.iretherm.ie) is a four-and-a-half year, all-island, academic-government-industry collaborative project, initiated in 2011, with the overarching objective of developing a strategic and holistic understanding of Ireland's geothermal energy potential through integrated modelling of new and existing geophysical and geological data. One of the challenges in searching for deep geothermal resources in the relatively unexplored setting of Ireland lies in identifying those areas most likely to support significantly elevated temperatures at depth. Available borehole data, although sparse and clustered around areas of mineral and hydrocarbon interest, suggest a marked regional increase in surface heat-flow across Ireland, from ~40 mW/m2 in the south to >80 mW/m2 in the north. The origins of both the observed regional heat-flow trend and local temperature anomalies have not been investigated and are not currently understood. Although variations in the structure of the crust and lithosphere have been revealed by a number of active-source seismic and teleseismic experiments, their effects on surface heat-flow have not been modelled. Bulk 3-D variation in crustal heat-production across Ireland, which may contribute significantly to the observed regional and local temperature variations, has also not been determined. We investigate the origins of Ireland's regional heat-flow trend and regional and local temperature variations using the software package LitMod. This software combines petrological and geophysical modelling of the lithosphere and sub-lithospheric upper mantle within an internally consistent thermodynamic-geophysical framework, where all relevant properties are functions of temperature, pressure and chemical composition. The major regional controls on surface heat-flow and crustal temperatures are (a) crustal thickness, (b) crustal heat-production and (c) lithospheric thickness. These unknown geological variables are modelled in LitMod3D against geophysical observations at surface - heat-flow, topography, gravity and geoid data - to identify a crustal and lithospheric-mantle model that satisfies and accounts for all the observations at surface (most importantly in our context, heat-flow). We present a range of 3-D crustal and lithospheric-mantle models that satisfy all observable constraints and account for the regional sources of heat in Ireland. These models provide the basis for isolating local temperature anomalies and for assessing the extent to which local lithological variation in heat-production and thermal conductivity affects the distribution of temperatures in our target depth range of 2000 - 6000 m. Significant, well defined temperature anomalies that emerge from this work will be targeted for further assessment during IRETHERM's planned field program of magnetotelluric and controlled source electromagnetic surveys.

Fullea, J.; Muller, M. R.; Jones, A. G.

2012-04-01

104

Conduction, convection, and radiation in heat transport by BEM  

Microsoft Academic Search

Simultaneous conduction and convection of heat is analyzed using the boundary element method. Combined calculations of heat transfer involving transient conduction in solids, natural and forced convection in fluid under various boundary conditions for a complex two-dimensional geometry are presented. The flow equations for the thermal fluid are based on the Boussinesq approximation. The stream function, vorticity, and temperature are

K. Onishi; N. Tosaka; M. Tanaka

1985-01-01

105

Qualitative aspects in dualphaselag heat conduction Ram on Quintanilla 1  

E-print Network

at low temperature has been observed to propagate by means of waves. These aspects have caused intenseQualitative aspects in dual­phase­lag heat conduction Ramâ?? 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

Racke, Reinhard

106

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

107

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

108

Thermal Conductivity of Composites Under Di erent Heating Scenarios  

E-print Network

composite sample, and (iii) a continuous heat source. 1 Introduction Adhesives such as epoxies, gels thermal conductivities, such as diamond dust, carbon #12;bers, or aluminum particles, are added to create material with a pulsed heat source (laser) at one end, a heat sink at the other end (ambient air

109

3D CFD ELECTROCHEMICAL AND HEAT TRANSFER MODEL OF AN INTERNALLY MANIFOLDED SOLID OXIDE ELECTROLYSIS CELL  

SciTech Connect

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

110

3-D Numerical study on the correlation between variable inclined fin angles and thermal behavior in plate fin-tube heat exchanger  

Microsoft Academic Search

In this study, the heat transfer enhancement and pressure drop values of seven different fin angles with plain fin-tube heat exchangers were investigated. The numerical simulation of the fin-tube heat exchanger was performed by using a three dimensional (3-D) numerical computation technique. Therefore, a CFD computer code, the FLUENT was used to solve the equation for the heat transfer and

Hac? Mehmet ?ahin; Ali R?za Dal; E?ref Baysal

2007-01-01

111

Heat losses and 3D diffusion phenomena for defect sizing procedures in video pulse thermography  

NASA Astrophysics Data System (ADS)

Dynamical thermographic techniques like video pulse thermography are very useful for the non-destructive testing of structural components. In literature different models were proposed, which allow to describe the time evolution of the thermal contrast for materials with sub-superficial defects. In the case of circular defect the time evolution of the full width half maximum (FWHM) of the thermal contrast was studied both theoretically and experimentally. Nevertheless a mismatch in defect sizing between experimental results and theoretical simulations was found. Possible explanations of this disagreement was analysed. A factor widely neglected is the heat loss (radiation and convection). In this paper a theoretical analysis of the influence of these contributions is reported. Furthermore in order to explain the experimental evidence of FWHM time evolution we introduced a correction due to lateral heat diffusion around the defect. In this way a possible explanation for the experimental results was obtained. Brick samples with a circular flat bottom hole as defect was tested both for the interest in defect sizing in building material through NDT and for the low thermal diffusivity of this material which allows the study of the phenomenon in a slow motion.

Ludwig, N.; Teruzzi, P.

2002-06-01

112

3D near-to-surface conductivity reconstruction by inversion of VETEM data using the distorted Born iterative method  

USGS Publications Warehouse

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

113

Heat conduction in relativistic neutral gases revisited  

E-print Network

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

114

Coupling heat conduction, radiation and convection in complex geometries  

Microsoft Academic Search

In many industrial applications, convection radiation and conduction participate simultaneously to the heat transfers. A numerical approach able to cope with such problems has been developed. The code SYRTHES is tackling conduction and radiation (limited to non participating medium). Radiation is solved by a radiosity approach, and conduction by a finite element method. Accurate and efficient algorithms based on a

I. Rupp; C. Péniguel

1999-01-01

115

Heat conduction through the Trombe wall  

NASA Astrophysics Data System (ADS)

This paper aims to add to the theoretical understanding of Trombe walls, and to consider the most appropriate calculation methods for simulation purposes. Various control strategies can be used to improve the wall performance, but only movable insulation outside the wall produces any substantial improvement. In this case, total heat flow over a periodic cycle increases with thermal capacity to an easily calculable upper limit which can be approached quite closely with practically realizable walls. An exact solution for a two-state Trombe wall is compared with approximate solutions obtained using finite difference methods and the author's modal expansion method. The Crank-Nicholson method has oscillatory errors in some problems, but adequate overall accuracy can be obtained using time steps up to four hours. The modal expansion method is generally very accurate and efficient.

Carter, C.

1980-07-01

116

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

117

Natural Convection Heat Transfer around Heated Cylinders Inside a Cavity with Conducting Walls  

Microsoft Academic Search

A numerical study has been conducted for natural convection heat transfer for air around two vertically separated horizontal heated cylinders placed inside a rectangular enclosure having finite wall conductances. The interaction between convection in the fluid-filled cavity and conduction in the walls surrounding the cavity is investigated. Results have been obtained for Rayleigh numbers Ra between 10 and 10, dimensionless

Marcel Lacroix; Antoine Joyeux

1995-01-01

118

Kohlrausch Heat Conductivity Apparatus for Intermediate or Advanced Laboratory  

ERIC Educational Resources Information Center

Describes student experiment in measuring heat conductivity according to Kohlrausch's method. Theory, apparatus design, and experimental procedure is outlined. Results for copper are consistent to within 2 percent. (LC)

Jensen, H. G.

1970-01-01

119

Ballistic heat conduction and mass disorder in one dimension  

NASA Astrophysics Data System (ADS)

It is well-known that in the disordered harmonic chain, heat conduction is subballistic and the thermal conductivity (?) scales asymptotically as \\lim_{L\\rightarrow\\infty}\\kappa\\propto 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 (\\kappa\\propto 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.

Ong, Zhun-Yong; Zhang, Gang

2014-08-01

120

Ballistic heat conduction and mass disorder in one dimension.  

PubMed

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

121

Finite element solution of transient heat conduction using iterative solvers  

Microsoft Academic Search

Purpose – To provide an analysis of transient heat conduction, which is solved using different iterative solvers for graduate and postgraduate students (researchers) which can help them develop their own research. Design\\/methodology\\/approach – Three-dimensional transient heat conduction in homogeneous materials using different time-stepping methods such as finite difference (? explicit, implicit and Crank-Nicolson) and finite element (weighted residual and least

Mile R. Vuji?i?

2006-01-01

122

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

123

Analogous studies of simultaneous conductive and radiative heat transfer  

Microsoft Academic Search

The process of radiative heat transfer is electrically simulated by using voltage-dependent resistors in conjunction with current transference circuits, and so an analogue is devised which shows how the overall uni-directional heat transfer by simultaneous conduction and radiation across a transparent gas space is a function of the positions of radiation shields which may be interposed between the bounding surfaces.

D W Stops; R E Pearson

1966-01-01

124

Entropy and temperature gradients thermomechanics: dissipation, heat conduction  

E-print Network

Entropy and temperature gradients thermomechanics: dissipation, heat conduction inequality and heat Rendus Mécanique 340, 6 (2012) 434-443" DOI : 10.1016/j.crme.2012.04.001 #12;temperature and its gradient and the first n spatial gradients of the temperature, they showed that the internal energy and the en- tropy

Boyer, Edmond

125

Electron Heat Conduction in the Phaedrus Tandem Mirror  

Microsoft Academic Search

Experiments to investigate electron heat conduction have been performed on the University of Wisconsin tandem mirror Phaedrus. Electron temperature differences along the magnetic field were generated using a mircowave heat pulse. Probe techniques were developed for the continuous measurement of local electron temperatures with a time resolution of less than one microsecond. Parameter studies indicated that the temperature differences were

Donna Lynn Smatlak

1982-01-01

126

Radiative heat conduction and the magnetorotational instability  

NASA Astrophysics Data System (ADS)

A photon or a neutrino gas, semicontained by a non-diffusive particle species through scattering, comprises a rather peculiar magnetohydrodynamic fluid where the magnetic field is truly frozen only to the comoving volume associated with the mass density. Although radiative diffusion precludes a formal adiabatic treatment of compressive perturbations, we cast the energy equation in quasi-adiabatic form by assuming a negligible rate of energy exchange among species on the time-scale of the perturbation. This leads to a simplified dispersion relation for toroidal, non-axisymmetric magnetorotational modes when the accretion disc has comparable stress contributions from diffusive and non-diffusive components. The properties of the modes of fastest growth are shown to depend strongly on the compressibility of the mode, with a reduction in growth rate consistent with the results of Blaes & Socrates for axisymmetric modes. A clumpy disc structure is anticipated on the basis of the polarization properties of the fastest-growing modes. This analysis is accurate in the near-hole region of locally cooled, hyper-accreting flows if the electron gas becomes moderately degenerate such that non-conductive, thermalizing processes with associated electron-positron release (i.e. neutrino annihilation and neutrino absorption on to nuclei) are effectively blocked by high occupation of the Fermi levels.

Araya-Góchez, Rafael A.; Vishniac, Ethan T.

2004-12-01

127

A 3D sunspot model derived from an inversion of spectropolarimetric observations and its implications for the penumbral heating  

NASA Astrophysics Data System (ADS)

Aims:I deduced a 3D sunspot model that is in full agreement with spectropolarimetric observations, in order to address the question of a possible penumbral heating process by the repetitive rise of hot flow channels. Methods: I performed inversions of spectropolarimetric data taken simultaneously in infrared (1.5 ?m) and visible (630 nm) spectral lines. I used two independent magnetic components inside each pixel to reproduce the irregular Stokes profiles in the penumbra and studied the averaged and individual properties of the two components. By integrating the field inclination to the surface, I developed a 3D model of the spot from inversion results without intrinsic height information. Results: I find that the Evershed flow is harbored by the weaker of the two field components. This component forms flow channels that show upstreams in the inner and mid penumbra, continue almost horizontally as slightly elevated loops throughout the penumbra, and finally bend down in the outer penumbra. I find several examples where two or more flow channels are found along a radial cut from the umbra to the outer boundary of the spot. Conclusions: I find that a model of horizontal flow channels in a static background field is in good agreement with the observed spectra. The properties of the flow channels correspond very well to the moving tube simulations of Schlichenmaier et al. (1998, A&A, 337, 897). From the temporal evolution in intensity images and the properties of the flow channels in the inversion, I conclude that interchange convection of rising hot flux tubes in a thick penumbra still seems a possible mechanism for maintaining the penumbral energy balance.

Beck, C.

2008-03-01

128

DSMC Convergence for Microscale Gas-Phase Heat Conduction  

Microsoft Academic Search

The convergence of Bird's Direct Simulation Monte Carlo (DSMC) method is investigated for gas-phase heat conduction at typical microscale conditions. A hard-sphere gas is confined between two fully accommodating walls of unequal temperature. Simulations are performed for small system and local Knudsen numbers, so continuum flow exists outside the Knudsen layers. The ratio of the DSMC thermal conductivity to the

D. J. Rader; M. A. Gallis; J. R. Torczynski

2004-01-01

129

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

130

Fourier analysis of conductive heat transfer for glazed roofing materials  

SciTech Connect

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 [Faculty of Computer and Mathematical Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia); Zakaria, Nor Zaini [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia)

2014-07-10

131

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

132

Gas heat conduction in an evacuated tube solar collector  

SciTech Connect

We investigated experimentally the pressure dependency of the gas heat conduction in an evacuated plate-in-tube solar collector. A stationary heat loss experiment was built up with an electrically heated real-size collector model. The gas pressure was varied from 10{sup -3} to 10{sup 4} Pa, the temperatures of the absorber and the casing were held at 150{degree}C (electrical heaters) and 30{degree}C (water cooling), respectively. Losses by radiation and solid conduction were determined experimentally at pressures below 0.1 Pa. At higher pressures these background losses were subtracted from the total heat losses, to receive the heat losses by gas heat conduction. The experimental results were compared with approximate theoretical models. The onset of convection is in agreement with the usual theories for parallel plates taking the largest distance between the absorber and the gas tube as the plate distance. As a first approximation the pressure dependency of the gas heat conduction is described by the usual theory for parallel plates, taking the smallest distance between the absorber and the glass tube as the plate distance. 11 refs., 3 figs.

Beikircher, T.; Goldemund, G. [Ludwig-Maximilians-Universitaet Muenchen (Germany)] [Ludwig-Maximilians-Universitaet Muenchen (Germany); Benz, N. [ZAE Bayern, Muenchen (Germany)] [ZAE Bayern, Muenchen (Germany)

1996-10-01

133

Quantal Heating of Conducting Electrons with Discrete Spectrum  

SciTech Connect

Usually heating of conducting electrons by dc electric field results in an increase of electron temperature. In this paper we show that the dc heating of 2D electrons, placed in quantized magnetic fields, results in a peculiar electron distribution, which has the same broadening or an effective 'temperature' as the unbiased electron system. The quantal heating, however, violates strongly the Ohm's Law. In the conducting system with discrete electron spectrum the quantal heating results in spectacular decrease of electron resistance and transition of the electrons into a state with zero differential resistance (ZDR). Finally the heating leads to apparent dc driven metal-insulator transition, which correlates with the transition into the ZDR state. The correlation is very unexpected and is not understood.

Vitkalov, S. A. [Department of Physics, The City College of New York, New York, NY 10031 (United States); Bykov, A. A. [Institute of Semiconductor Physics, 630090 Novosibirsk (Russian Federation)

2011-12-23

134

M. Bahrami ENSC 388 (F09) Steady Conduction Heat Transfer 1 Steady Heat Conduction  

E-print Network

requirement for heat transfer is the presence of a temperature difference. The temperature difference gradient, which is the slope of the temperature curve (the rate of change of temperature T with length x and surface area A. The temperature difference across the wall is T = T2 ­ T1. Note that heat transfer

Bahrami, Majid

135

Heat conductance in nonlinear lattices at small temperature gradients  

E-print Network

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 temperature 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

136

Thermally conductive cementitious grout for geothermal heat pump systems  

DOEpatents

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

137

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

138

Global 3-D imaging of mantle electrical conductivity based on inversion of observatory C-responses - I. An approach and its verification  

NASA Astrophysics Data System (ADS)

We present a novel frequency-domain inverse solution to recover the 3-D electrical conductivity distribution in the mantle. The solution is based on analysis of local C-responses. It exploits an iterative gradient-type method - limited-memory quasi-Newton method - for minimizing the penalty function consisting of data misfit and regularization terms. The integral equation code is used as a forward engine to calculate responses and data misfit gradients during inversion. An adjoint approach is implemented to compute misfit gradients efficiently. Further improvements in computational load come from parallelizing the scheme with respect to frequencies, and from setting the most time-consuming part of the forward calculations - calculation of Green's tensors - apart from the inversion loop. Convergence, performance, and accuracy of our 3-D inverse solution are demonstrated with a synthetic numerical example. A companion paper applies the strategy set forth here to real data.

Kuvshinov, Alexey; Semenov, Alexey

2012-06-01

139

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

140

77 FR 33486 - Certain Integrated Circuit Packages Provided With Multiple Heat-Conducting Paths and Products...  

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

141

77 FR 39735 - Certain Integrated Circuit Packages Provided With Multiple Heat-Conducting Paths and Products...  

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

142

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

143

Minimizing RF heating of conducting wires in MRI.  

PubMed

Performing interventions using long conducting wires in MRI introduces the risk of focal RF heating at the wire tip. Comprehensive EM simulations are combined with carefully measured experimental data to show that method-of-moments EM field modeling coupled with heat transfer modeling can adequately predict RF heating with wires partially inserted into the patient-mimicking phantom. The effects of total wire length, inserted length, wire position in the phantom, phantom position in the scanner, and phantom size are examined. Increasing phantom size can shift a wire's length of maximum tip heating from about a half wave toward a quarter wave. In any event, with wires parallel to the scanner bore, wire tip heating is minimized by keeping the patient and wires as close as possible to the central axis of the scanner bore. At 1.5T, heating is minimized if bare wires are shorter than 0.6 m or between approximately 2.4 m and approximately 3.0 m. Heating is further minimized if wire insertion into phantoms equivalent to most aqueous soft tissues is less than 13 cm or greater than 40 cm (longer for fatty tissues, bone, and lung). The methods demonstrated can be used to estimate the absolute amount of heating in order to set RF power safety thresholds. PMID:17969097

Yeung, Christopher J; Karmarkar, Parag; McVeigh, Elliot R

2007-11-01

144

Combined Heat Transfer by Natural Convection - Conduction and Surface Radiation in an Open Cavity Under Constant Heat Flux Heating  

Microsoft Academic Search

Combined heat transfer by natural convection-conduction and surface radiation in an open cavity heated by constant flux is studied here. The laminar flow is solved numerically by employing the SIMPLE algorithm with QUICK scheme. The numerical results show that both radiation and solid conduction increase the average total Nusselt number. The average total Nusselt number is a linear increasing function

Zhiyun Wang; Mo Yang; Ling Li; Yuwen Zhang

2011-01-01

145

Generalized thermoelastic diffusive waves in heat conducting materials  

Microsoft Academic Search

Keeping in view the applications of diffusion processes in geophysics and electronics industry, the aim of the present paper is to give a detail account of the plane harmonic generalized thermoelastic diffusive waves in heat conducting solids. According to the characteristic equation, three longitudinal waves namely, elastodiffusive (ED), mass diffusion (MD-mode) and thermodiffusive (TD-mode), can propagate in such solids in

J. N. Sharma

2007-01-01

146

Human body thermal images generated by conduction or radiation heat  

Microsoft Academic Search

Humans and animals in general, are usually in a thermal steady state with respect to their surroundings. The tissues heat, generated at normal or diseases states, is lost to environment though several mechanisms: radiation, conduction, convection, evaporation, etc. Skin temperature is not the same on the entire body and a thermal body signature can be got. The temperature at skin

Gheorghe Gavriloaia; Emil Sofron; Radu Fumarel

2009-01-01

147

Numeric modeling method usage for heat conductivity equations solution  

NASA Astrophysics Data System (ADS)

The sweep method applicability for non-stationary one-dimensional differential heat conductivity equations solving is proved in this work. The sweep method applicability check is made by using exact analytical method and approximate analytical method. The confrontation carried out has shown that the obtained numeric results error isn't more 2%.

Loginov, Vladimir; Stolyarova, Alla; Parpiev, Azad

2015-01-01

148

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

149

A spectral stochastic approach to the inverse heat conduction problem  

E-print Network

by employing orthogonal poly- nomials as the trial basis in the random space. Solution to the ill-posed SIHCPA spectral stochastic approach to the inverse heat conduction problem Velamur Asokan Badri Narayanan, Nicholas Zabaras 1 Materials Process Design and Control Laboratory, Sibley School of Mechanical

Zabaras, Nicholas J.

150

Vacuum Induction Melting Unit Induction heating is a process wherein induced eddy currents heat conductive materials. This heating  

E-print Network

Vacuum Induction Melting Unit Induction heating is a process wherein induced eddy currents heat conductive materials. This heating can be used to melt metals and make alloys. Vacuum Induction melting on the melting process. The induction melting facility (Figure 1) was established in the Symmetry Lab (WL-207

Subramaniam, Anandh

151

Hierarchical Bayesian models for inverse problems in heat conduction  

NASA Astrophysics Data System (ADS)

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 models are adopted to relax the prior assumptions on the unknowns. The use of a hierarchical Bayesian method for automatic selection of the regularization parameter in the function estimation inverse problem is discussed. In addition, the method explores the length scales in the estimation of thermal variables varying in space and time. Markov chain Monte Carlo (MCMC) simulation is conducted to explore the high dimensional posterior state space. The methodologies presented are general and applicable to a number of data-driven engineering inverse problems.

Wang, Jingbo; Zabaras, Nicholas

2005-02-01

152

Variable conductance heat pipes from the laboratory to space  

NASA Technical Reports Server (NTRS)

Heat pipes were developed which can be used as (1) a variable conductance link between a heat source and sink which provides temperature stability; (2) a feedback control mechanism that acts to directly maintain the source at a constant temperature; (3) or as a thermal diode that allows heat to be transferred in one direction only. To establish flight level confidence in these basic control techniques, the Ames Heat Pipe Experiment (AHPE) was launched in August 1972 and the Advanced Thermal Control Flight Experiment (ATFE) is scheduled for launch in May 1973. The major efforts of the technology development, initial flight results of the AHPE, and ground test data of the ATFE are discussed.

Kirkpatrick, J. P.

1973-01-01

153

3D Temperature distribution and numerical modeling of heat transfers in an active fault zone: Eugene Island 330, Offshore Louisiana.  

E-print Network

: Bottom Hole Temperatures (BHT) and 3D seismic interpretation. More than 600 BHT from 200 wells allowed us the fault during the recent history of the field and are still flowing: 1) the presence of hydrocarbon seeps

Guerin, Gilles

154

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

155

Specific heat and thermal conductivity of amorphous boron  

NASA Astrophysics Data System (ADS)

From inelastic neutron scattering the phonon density of states of amorphous boron has been determined, and from this the specific heat between 30 and 500 K has been calculated. The results have been compared with the specific heat measured for amorphous boron, crystalline ?-B and Y B66. The thermal conductivity of single crystals of Y B58 and Y B67, has been measured, and has been found to be indistinguishable from that of Y B66 crystals grown in a different laboratory, in spite of very different physical and chemical perfection. This result provides further evidence that the low thermal conductivity of these crystals is intrinsic. At higher temperatures, it approaches the theoretical minimum thermal conductivity of this boron-rich compound, which in turn is equal to that of amorphous boron.

Medwick, P. A.; Cahill, David G.; Raychaudhuri, A. K.; Pohl, R. O.; Gompf, F.; Nücker, N.; Tanaka, T.

1991-07-01

156

Specific heat and thermal conductivity of amorphous boron  

SciTech Connect

From inelastic neutron scattering the phonon density of states of amorphous boron has been determined, and from this the specific heat between 30 and 500 K has been calculated. The results have been compared with the specific heat measured for amorphous boron, crystalline {beta}--{ital B} and {ital Y} {ital B}{sub 66}. The thermal conductivity of single crystals of {ital Y} {ital B}{sub 58} and {ital Y} {ital B}{sub 67}, has been measured, and has been found to be indistinguishable from that of {ital Y} {ital B}{sub 66} crystals grown in a different laboratory, in spite of very different physical and chemical perfection. This result provides further evidence that the low thermal conductivity of these crystals is intrinsic. At higher temperatures, it approaches the theoretical minimum thermal conductivity of this boron-rich compound, which in turn is equal to that of amorphous boron.

Medwick, P.A.; Cahill, D.G.; Raychaudhuri, A.K.; Pohl, R.O. (Laboratory for Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853-2501 (United States)); Gompf, F.; Nuecker, N. (Kernforschungszentrum Karlsruhe, Institute for Nuclear and Solid State Physics, P.O. Box 3640, D-7500 (Germany)); Tanaka, T. (National Institute for Research in Inorganic Materials, Namiki 1-1, Tsukuba, Ibaraki 305 (Japan))

1991-07-01

157

Thermal conductivity, electrical conductivity and specific heat of copper-carbon fiber composite  

NASA Technical Reports Server (NTRS)

A new material of copper/carbon fiber composite is developed which retains the properties of copper, i.e., its excellent electrical and thermal conductivity, and the property of carbon, i.e., a small thermal expansion coefficient. These properties of the composite are adjustable within a certain range by changing the volume and/or the orientation of the carbon fibers. The effects of carbon fiber volume and arrangement changes on the thermal and electrical conductivity, and specific heat of the composite are studied. Results obtained are as follows: the thermal and electrical conductivity of the composite decrease as the volume of the carbon fiber increases, and were influenced by the fiber orientation. The results are predictable from a careful application of the rule of mixtures for composites. The specific heat of the composite was dependent, not on fiber orientation, but on fiber volume. In the thermal fatigue tests, no degradation in the electrical conductivity of this composite was observed.

Kuniya, Keiichi; Arakawa, Hideo; Kanai, Tsuneyuki; Chiba, Akio

1988-01-01

158

Porous 3D graphene-based bulk materials with exceptional high surface area and excellent conductivity for supercapacitors  

PubMed Central

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

159

Correlations and scaling in one-dimensional heat conduction.  

PubMed

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

160

Heating rate controller for thermally stimulated conductivity and thermoluminescence measurements.  

NASA Technical Reports Server (NTRS)

A temperature controller is described which enables the temperature of a sample mounted on a cold finger to be varied linearly with time. Heating rates between 0.5 and 10 K/min can be achieved for temperatures between 90 and 300 K. Provision for terminating the sample heating at any temperature between these extremes is available. The temperature can be held at the terminating temperature or be reduced to the starting temperature in a matter of minutes. The controller has been used for thermally stimulated conductivity measurements and should be useful for thermoluminescence measurements as well.

Manning, E. G.; Littlejohn, M. A.; Oakley, E. M.; Hutchby , J. A.

1972-01-01

161

Optical conductivity renormalization of graphene on SrTiO 3 due to resonant excitonic effects mediated by Ti 3 d orbitals  

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

162

Large deviations in stochastic heat-conduction processes provide a gradient-flow structure for heat conduction  

SciTech Connect

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 (BEP(m)), a Generalized Brownian Energy Process, and the Kipnis-Marchioro-Presutti (KMP) 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 Generalized Brownian Energy Process with parameter a (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??; they involve dissipation or mobility terms of order ?{sup 2} for the linear heat equation, and a nonlinear function of ? for the nonlinear heat equation.

Peletier, Mark A., E-mail: m.a.peletier@tue.nl [Department of Mathematics and Computer Science and Institute for Complex Molecular Systems, Technische Universiteit Eindhoven, Postbus 513, 5600 MB Eindhoven (Netherlands); Redig, Frank, E-mail: f.h.j.redig@tudelft.nl [Delft Institute of Applied Mathematics, Technische Universiteit Delft, Mekelweg 4, 2628 CD Delft (Netherlands); Vafayi, Kiamars, E-mail: k.vafayi@tue.nl [Department of Mathematics and Computer Science, Technische Universiteit Eindhoven, Postbus 513, 5600 MB Eindhoven (Netherlands)

2014-09-15

163

Heat conduction nanocalorimeter for pl-scale single cell measurements  

NASA Astrophysics Data System (ADS)

An ultrasensitive nanocalorimeter for use with pl-scale biological samples using silicon microfabrication technology has been developed in which a 720 pl reaction vessel, a calibration heater, and a thermoelectric transducer of 125 ?K sensitivity were integrated into a single multilayer thin-film configuration. The resolution of the system ranged from 10 to 25 nW depending on the heat capacity, conductance and power density of the samples studied. The device has been used in heat conduction measurements of the energy released from the enzyme catalyzed hydrolysis of hydrogen peroxide using purified catalase, and for the determination of the catalase activity within a single mouse hepatocyte. The nanocalorimeter has the potential for integration in a high-density array format, where the change in temperature from ultralow volume cellular assays could be used as a generic analytical tool for high throughput screening of bioactive compounds.

Johannessen, E. A.; Weaver, J. M. R.; Cobbold, P. H.; Cooper, J. M.

2002-03-01

164

3D unsteady numerical analysis of conjugate heat transport and turbulent\\/laminar flows in LEC growth of GaAs crystals  

Microsoft Academic Search

We present the conjugated 3D unsteady numerical analysis of industrial-scale LEC GaAs crystal growth, including the calculation of heat transfer in the crystal and crucibles, melt convection, and the encapsulant flow. The analysis of unsteady turbulent melt convection is performed in terms of the large eddy simulation approach. A special procedure was introduced into the calculations to predict the geometry

O. V. Smirnova; V. V. Kalaev

2004-01-01

165

New Critical Divergences in the Heat Conductivity in the Presence of a Temperature Gradient  

Microsoft Academic Search

New effects in heat-conducting nonequilibrium fluids near critical points are predicted theoretically: The heat conductivity gains a new divergent contribution and the heat diffusivity becomes strongly nonisotropic.

Ehud Meron; Itamar Procaccia

1983-01-01

166

Fuzzy and interval finite element method for heat conduction problem  

E-print Network

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

167

Superdiffusive heat conduction in semiconductor alloys. I. Theoretical foundations  

NASA Astrophysics Data System (ADS)

Semiconductor alloys exhibit a strong dependence of effective thermal conductivity on measurement frequency. So far this quasiballistic behavior has only been interpreted phenomenologically, providing limited insight into the underlying thermal transport dynamics. Here, we show that quasiballistic heat conduction in semiconductor alloys is governed by Lévy superdiffusion. By solving the Boltzmann transport equation (BTE) with ab initio phonon dispersions and scattering rates, we reveal a transport regime with fractal space dimension 1 3 ) and cumulative conductivity spectra ??(? ;? ) ˜(?;? ) ? resolved for relaxation times or mean free paths through the simple relations ? =3 -? =1 +3 /n =2 -? . The quasiballistic transport inside alloys is no longer governed by Brownian motion, but instead is dominated by Lévy dynamics. This has important implications for the interpretation of thermoreflectance (TR) measurements with modified Fourier theory. Experimental ? values for InGaAs and SiGe, determined through TR analysis with a novel Lévy heat formalism, match ab initio BTE predictions within a few percent. Our findings lead to a deeper and more accurate quantitative understanding of the physics of nanoscale heat-flow experiments.

Vermeersch, Bjorn; Carrete, Jesús; Mingo, Natalio; Shakouri, Ali

2015-02-01

168

Two exact solutions of the DPL non-Fourier heat conduction equation with special conditions  

NASA Astrophysics Data System (ADS)

This paper presents two exact explicit solutions for the three dimensional dual-phase lag (DLP) heat conduction equation, during the derivation of which the method of trial and error and the authors’ previous experiences are utilized. To the authors’ knowledge, most solutions of 2D or 3D DPL models available in the literature are obtained by numerical methods, and there are few exact solutions up to now. The exact solutions in this paper can be used as benchmarks to validate numerical solutions and to develop numerical schemes, grid generation methods and so forth. In addition, they are of theoretical significance since they correspond to physically possible situations. The main goal of this paper is to obtain some possible exact explicit solutions of the dual-phase lag heat conduction equation as the benchmark solutions for computational heat transfer, rather than specific solutions for some given initial and boundary conditions. Therefore, the initial and boundary conditions are indeterminate before derivation and can be deduced from the solutions afterwards. Actually, all solutions given in this paper can be easily proven by substituting them into the governing equation.

Zhang, Youtong; Zheng, Changsong; Liu, Yongfeng; Shao, Liang; Gou, Chenhua

2009-04-01

169

A Correction Scheme for Thermal Conductivity Measurement Using the Comparative Cut-bar Technique Based on a 3D Numerical Simulation  

SciTech Connect

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

170

Sodium Variable Conductance Heat Pipe for Radioisotope Stirling Systems  

NASA Technical Reports Server (NTRS)

In a Stirling radioisotope system, heat must continually be removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the converter stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, and also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) has been designed to allow multiple stops and restarts of the Stirling convertor in an Advanced Stirling Radioisotope Generator (ASRG). When the Stirling convertor is turned off, the VCHP will activate when the temperatures rises 30 C above the setpoint temperature. A prototype VCHP with sodium as the working fluid was fabricated and tested in both gravity aided and against gravity conditions for a nominal heater head temperature of 790 C. The results show very good agreement with the predictions and validate the model. The gas front was located at the exit of the reservoir when heater head temperature was 790 C while cooling was ON, simulating an operating Advanced Stirling Converter (ASC). When cooling stopped, the temperature increased by 30 C, allowing the gas front to move past the radiator, which transferred the heat to the case. After resuming the cooling flow, the front returned at the initial location turning OFF the VCHP. The against gravity working conditions showed a colder reservoir and faster transients.

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

2009-01-01

171

Variable Conductance Heat Pipes for Radioisotope Stirling Systems  

NASA Technical Reports Server (NTRS)

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 turns on with a delta 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 delta T was roughly 70 C, due to distillation of the NaK in the evaporator.

Anderson, William G.; Tarau, Calin

2008-01-01

172

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

173

Manipulating Steady Heat Conduction by Sensu-shaped Thermal Metamaterials  

E-print Network

The ability to design the control of heat flow has innumerable benefits in the design of electronic systems such as thermoelectric energy harvesters, solid-state lighting, and thermal imagers, where the thermal design plays a key role in performance and device reliability. However, to realize one advanced control function of thermal flux, one needs to design one sophisticated, multilayered and inhomogeneous thermal structure with different composition/shape at different regions of one device. In this work, we employ one identical sensu-unit with facile natural composition to experimentally realize a new class of thermal metamaterials for controlling thermal conduction (e.g., thermal concentrator, focusing/resolving, uniform heating), only resorting to positioning and locating the same unit element of sensu-shape structure. The thermal metamaterial unit and the proper arrangement of multiple identical units are capable of transferring, redistributing and managing thermal energy in a versatile fashion. It is al...

Han, Tiancheng; Liu, Dan; Gao, Dongliang; Li, Baowen; Thong, John T L; Qiu, Cheng-Wei

2014-01-01

174

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

175

Variable conductance heat pipe technology. [research project resulting in heat pipe experiment on OAO-3 satellite  

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

176

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

177

Numerical time-dependent 3D simulation of flow pattern and heat distribution in an ammonothermal system with various baffle shapes  

NASA Astrophysics Data System (ADS)

A numerical analysis of an ammonothermal synthesis process for the bulk growth of nitride crystals was performed. The analysis includes the development of a thermal model for a lab-scale ammonothermal autoclave, which was validated by in situ temperature measurements and applied to tailor the temperature field inside the autoclave. Based on the results of the global thermal 2D simulations, a local 3D model was used to include convective phenomena in the analysis. Moreover, the influence of the baffle and different baffle shapes on the flow velocity was investigated. Fluctuations of the temperature as well as the flow velocities occur, indicating that 3D considerations are essential to accurately investigate the heat and mass transport in ammonothermal systems.

Erlekampf, J.; Seebeck, J.; Savva, P.; Meissner, E.; Friedrich, J.; Alt, N. S. A.; Schlücker, E.; Frey, L.

2014-10-01

178

Modeling near-field radiative heat transfer from sharp objects using a general 3d numerical scattering technique  

Microsoft Academic Search

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 Krüger; Steven G. Johnson

2011-01-01

179

Homogeneous Thermal Cloak with Constant Conductivity and Tunable Heat Localization  

PubMed Central

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

180

Time fractional dual-phase-lag heat conduction equation  

NASA Astrophysics Data System (ADS)

We build a fractional dual-phase-lag model and the corresponding bioheat transfer equation, which we use to interpret the experiment results for processed meat that have been explained by applying the hyperbolic conduction. Analytical solutions expressed by H-functions are obtained by using the Laplace and Fourier transforms method. The inverse fractional dual-phase-lag heat conduction problem for the simultaneous estimation of two relaxation times and orders of fractionality is solved by applying the nonlinear least-square method. The estimated model parameters are given. Finally, the measured and the calculated temperatures versus time are compared and discussed. Some numerical examples are also given and discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11102102, 11472161, and 91130017), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2014AQ015), and the Independent Innovation Foundation of Shandong University, China (Grant No. 2013ZRYQ002).

Xu, Huan-Ying; Jiang, Xiao-Yun

2015-03-01

181

MIXED THERMOCAPILLARY AND FORCED CONVECTION HEAT TRANSFER AROUND A HEMISPHERICAL BUBBLE IN A MINIATURE CHANNE - A 3D NUMERICAL STUDY  

Microsoft Academic Search

It has been established that for certain conditions, such as microgravity boiling, thermocapillary Marangoni flow has associated with it a significant enhancement of heat transfer. Typically, this phenomenon was investigated for the idealized case of an isolated and stationary bubble resting atop a heated solid which is immersed in a semi-infinite quiescent fluid or within a two-dimensional cavity. This paper

Cristina Radulescu

2012-01-01

182

The 3D conductive thermal field of the North Alpine Foreland Basin - Influence of the deep structure of the adjacent European Alps  

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

183

High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems  

NASA Technical Reports Server (NTRS)

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 convertor 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 convertor. 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.

2009-01-01

184

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

185

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

186

3D discrete angiogenesis dynamic model and stochastic simulation for the assessment of blood perfusion coefficient and impact on heat transfer between nanoparticles and malignant tumors.  

PubMed

Early detection of malignant tumors plays a crucial role in the survivability chances of the patient. Therefore, new and innovative tumor detection methods are constantly searched for. Tumor-specific magnetic-core nano-particles can be used with an alternating magnetic field to detect and treat tumors by hyperthermia. For the analysis of the method effectiveness, the bio-heat transfer between the nanoparticles and the tissue must be carefully studied. Heat diffusion in biological tissue is usually analyzed using the Pennes Bio-Heat Equation, where blood perfusion plays an important role. Malignant tumors are known to initiate an angiogenesis process, where endothelial cell migration from neighboring vasculature eventually leads to the formation of a thick blood capillary network around them. This process allows the tumor to receive its extensive nutrition demands and evolve into a more progressive and potentially fatal tumor. In order to assess the effect of angiogenesis on the bio-heat transfer problem, we have developed a discrete stochastic 3D model & simulation of tumor-induced angiogenesis. The model elaborates other angiogenesis models by providing high resolution 3D stochastic simulation, capturing of fine angiogenesis morphological features, effects of dynamic sprout thickness functions, and stochastic parent vessel generator. We show that the angiogenesis realizations produced are well suited for numerical bio-heat transfer analysis. Statistical study on the angiogenesis characteristics was derived using Monte Carlo simulations. According to the statistical analysis, we provide analytical expression for the blood perfusion coefficient in the Pennes equation, as a function of several parameters. This updated form of the Pennes equation could be used for numerical and analytical analyses of the proposed detection and treatment method. PMID:24462603

Yifat, Jonathan; Gannot, Israel

2014-01-22

187

Implementation of 3D homogenization techniques for the thermo-elastic FEM analysis of brazed plate-fin heat exchangers  

Microsoft Academic Search

The present study results from a research collaboration between Laboratory ERMeP (GIP-InSIC) and the company Nordon-Cryogenie\\u000a (Vosges, France), one of the major world manufacturers of heat exchangers for cryogenic processes. A general description of\\u000a a multi-stream brazed aluminium plate-fin heat exchanger is presented in Fig 1. The problem for Nordon Cryogénie is to guarantee\\u000a a thermal performance as well as

J. Dib; F. Bilteryst; J. L. Batoz; I. Lewon

188

Design and development of ultra-wideband 3 dB hybrid coupler for Ion cyclotron resonance frequency heating in tokamak.  

PubMed

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. PMID:24784637

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

2014-04-01

189

77 FR 74027 - Certain Integrated Circuit Packages Provided with Multiple Heat-Conducting Paths and Products...  

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

190

A Packer Test Design Utilizing a Discrete Fracture Network and Flow Model for the Determination of 3-D Hydraulic Conductivity Tensor in Fractured Rocks  

NASA Astrophysics Data System (ADS)

The hydraulic behavior of a fractured rock mass depends on the orientation, size, intensity, aperture, and connectivity of the fractures. The common assumption of fluid flow through a geologic continuum could be invalid for a fractured rock mass in a specified scale. Even though the Representative Elementary Volume (REV) is small for porous media, it is most likely much larger for fractured rock masses. The hydraulic behavior in a fractured rock mass may vary significantly even in a small scale. Therefore, it becomes very important to consider how to increase the efficiency and representative capability of packer tests in estimation of 3-D hydraulic conductivity tensor for a fractured rock mass. A structured approach is proposed to reach this goal. This approach is more applicable for a fractured rock mass where the flow field is dominated by fluid flow in a fracture network. First, the borehole for the packer test should allow for the acquisition of fracture information at different depths in order to perform fracture geometry modeling. This will entail the identification of statistically homogeneous depth ranges, delineation of fracture sets, and model validation. Software packages are available to analyze fracture data obtained from boreholes, which could be incorporated with the fracture data from scanlines and two-dimensional exposures. The aperture dimension and transmissivity of fractures should be accounted for during this identification. Hydraulic behaviors for each statistically homogeneous depth range can be evaluated by conducting packer tests in a typical interval. A stochastic fracture network is generated based on a built fracture geometry model in a cube of a specific size. The REV can be estimated using the directional hydraulic conductivity computed from a discrete fracture numerical flow model set up based on the stochastic fracture network and relative transmissivities for different fracture sets. Then, a Representative Elementary Length for the Test Interval along Borehole (RELTIB) needs to be estimated by conducting a number of computer stochastic simulations for intersections between different lengths of screen intervals along the borehole and fractures in the cube. RELTIB is achieved by selecting the minimum of the test interval lengths in which representative fracture features for each fracture set can be obtained. The packer tests should be performed along an interval with length dimension of RELTIB or longer to obtain representative hydraulic connection and other hydraulic attributes around the packer test borehole. For observation boreholes, an insufficient observation length could result in a lessened representative capability for hydraulic response due to the disconnection of fractures and detour of flow paths. Therefore, a Representative Elementary Length for the Observation Interval along Borehole (RELOIB) should be used to approximately obtain a point hydraulic response induced from the packer test. RELOIB can be investigated by performing a number of computer stochastic simulations for intersections between different lengths of observation intervals and fractures in the cube. Furthermore, REV should be referred in order to specify the locations of observation boreholes. Based on the packer test results through implementing the above structured approach for packer test design, the 3-D hydraulic conductivity tensor could be determined for a fractured rock mass using either a porous continuum method or discrete fracture flow approach.

Wang, M.

2001-05-01

191

A 3D POM–MOF composite based on Ni(??) ion and 2,2?-bipyridyl-3,3?-dicarboxylic acid: Crystal structure and proton conductivity  

SciTech Connect

We have succeeded in constructing a 3D POM–MOF, (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 35–98%. The corresponding activation energy (E{sub a}) of conductivity was estimated to be 1.01 eV. - Graphical abstract: A POM–MOF 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 35–98% RH. - Highlights: • A POM–MOF 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 POM–MOF. • It achieved such proton conductivities as 10{sup ?4}–10{sup ?3} S cm{sup ?1} at 100 °C in the RH range 35–98%.

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

192

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

193

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

PubMed

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

194

Analytical Methods of Parametric Optimization in Inverse Heat-Conduction Problems with Internal Heat Release  

NASA Astrophysics Data System (ADS)

Consideration is given to inverse heat-conduction problems on identification of the strength of internal heat sources or the law of their spatial distribution. The problems have been formulated in an extremum statement as problems of optimum control over an object with distributed parameters when the set of control actions is limited to the class of continuous and continuously differentiable functions. On the basis of parametrization of control actions, the problem is reduced to an unsmooth problem of mathematical programming for the solution of which we use a special method taking account of the alternance properties of the sought optimum solutions.

Diligenskaya, A. N.; Rapoport, É. Ya.

2014-09-01

195

Research on 3D simulation of coupling model among flow field, optical field and heating effects of mirrors  

NASA Astrophysics Data System (ADS)

When chemical oxygen-iodine laser (COIL) runs longtime, the influence on heating effects of mirrors has attracted attention abroad. For obtaining accurate estimate on it, relying on past experience, we carry on coupling simulation among flow field, optical field and heating effects of mirrors. At present computational condition, three-dimensional model about nozzle flow is constructed; by analyzing simulation data, coupling simulation result is obtained between flow field and optical field. Finally, the influence on heating effects of mirrors is investigated. The focus is solving the convergence of iteration between flow field and optical field. By particular analysis on the physical mechanism, coupling style is adjusted; finally, stable result is obtained, coupling iteration times is reduced greatly. The simulation result indicate if considering actual flow field disturbance, facular fragmentation is distinct; the disturbance exist from the beginning, so it influences on beam quality in the whole course.

Li, Y.; Du, Y. Y.; Li, S. X.

2015-02-01

196

High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems  

SciTech Connect

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 deg. C while the heat losses caused by the addition of the VCHP are 1.8 W.

Tarau, Calin; Walker, Kara L.; Anderson, William G. [Advanced Cooling Technologies, Inc. 1046 New Holland Ave. Lancaster, PA 17601 (United States)

2009-03-16

197

Diffusive-Ballistic Heat Conduction of Carbon Nanotubes and Nanographene Junichiro Shiomi and Shigeo Maruyama*  

E-print Network

-ballistic feature. This gives rise to some unique stationary and non-stationary heat conduction [7, 8]. OneDiffusive-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

Maruyama, Shigeo

198

Coupling of wall conduction with natural convection from heated cylinders in a rectangular enclosure  

Microsoft Academic Search

A numerical study has been conducted for natural convection heat transfer for air from two vertically separated horizontal heated cylinders confined to a rectangular enclosure having vertical walls of finite conductances and horizontal walls at the heat sink temperature. The interaction between convection in the fluid filled cavity and conduction in the vertical walls is investigated. Results have been obtained

Marcel Lacroix; Antoine Joyeux

1996-01-01

199

The transient Dst electromagnetic induction signal at satellite altitudes for a realistic 3-D electrical conductivity in the crust and mantle  

E-print Network

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

200

3-D Numerical Analysis for Heat Transfer from a Flat Plate in a Duct with Contractions Filled with Pressurized he II  

NASA Astrophysics Data System (ADS)

A computer code of three-dimensional heat transfer in superfluid helium named SUPER-3D was developed based on the two-fluid model. Critical heat fluxes (CHFs) on a flat plate located at one end of rectangular ducts having contractions with different rectangular open area were calculated by using the SUPER-3D for the liquid temperatures from 1.8 K to 2.1 K in pressurized He II. The analyses were made for the ducts with one contraction (Case A) and with two contractions (Case B). In case A, effects of the open mouth area and distance of the contraction from the flat plate were clarified. The solutions of CHF for the various open mouth areas agreed well with the experimental data. In Case B, the solutions of CHF for the two contractions with the same open areas were affected by the combination of open mouth figures. It was found from the analysis that several vortices are generated around the contractions and play an important role in determining the CHF. Three dimensional analyses are necessary to evaluate the CHF accurately.

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

2008-03-01

201

The 3D thermal analysis is performed for the radiation heat load at all stages of the HRS op-  

E-print Network

. The coil layers were separated from each other by two layers of insulation with a layer of Al in between and cost. The beam dump was designed to both accu- mulate the spent beam and keep its temperature and air dynamic heat loads to the cryogenic system, a reason- able lifetime of the coil components, acceptable -on

McDonald, Kirk

202

Computational fluid dynamics analyses of lateral heat conduction, coolant azimuthal mixing and heat transfer predictions in a BR2 fuel assembly geometry.  

SciTech Connect

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

203

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

204

Numerical 3D modeling of heat transfer in human tissues for microwave radiometry monitoring of brown fat metabolism  

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.; Limão-Vieira, Paulo; Stauffer, Paul R.

2013-02-01

205

Numerical 3D modeling of heat transfer in human tissues for microwave radiometry monitoring of brown fat metabolism  

PubMed Central

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, 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 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 1.5–2.2 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. PMID:24244831

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

2013-01-01

206

Theory and design of variable conductance heat pipes: Steady state and transient performance  

NASA Technical Reports Server (NTRS)

Heat pipe technology pertinent to the design and application of self-controlled, variable conductance heat pipes for spacecraft thermal control is discussed. Investigations were conducted to: (1) provide additional confidence in existing design tools, (2) to generate new design tools, and (3) to develop superior variable conductance heat pipe designs. A computer program for designing and predicting the performance of the heat pipe systems was developed.

Edwards, D. K.; Fleischman, G. L.; Marcus, B. D.

1972-01-01

207

DPL model analysis of non-Fourier heat conduction restricted by continuous boundary interface  

NASA Astrophysics Data System (ADS)

Dual-phase lag (DPL) model is used to describe the non-Fourier heat conduction in a finite medium where the boundary at x=0 is heated by a rectangular pulsed energy source and the other boundary is tightly contacted with another medium and satisfies the continuous boundary condition. Numerical solution of this kind of non-Fourier heat conduction is presented in this paper. The results are compared with those predicted by the hyperbolic heat conduction (HHC) equation.

Jiang, Fangming; Liu, Dengying

2001-03-01

208

3D CFD Electrochemical and Heat Transfer Model of an Integrated-Planar Solid Oxide Electrolysis Cells  

SciTech Connect

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

209

Analysis of heat conduction in a disk brake system  

Microsoft Academic Search

In this paper, the governing heat equations for the disk and the pad are extracted in the form of transient heat equations\\u000a with heat generation that is dependant to time and space. In the derivation of the heat equations, parameters such as the\\u000a duration of braking, vehicle velocity, geometries and the dimensions of the brake components, materials of the disk

Faramarz Talati; Salman Jalalifar

2009-01-01

210

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

211

Conductive and convective heat transfer in fluid flows between differentially heated and rotating cylinders  

E-print Network

The flow of fluid confined between a heated rotating cylinder and a cooled stationary cylinder is a canonical experiment for the study of heat transfer in engineering. The theoretical treatment of this system is greatly simplified if the cylinders are assumed to be of infinite length or periodic in the axial direction, in which cases heat transfer occurs only through conduction as in a solid. We here investigate numerically heat transfer and the onset of turbulence in such flows by using both periodic and no-slip boundary conditions in the axial direction. We obtain a simple linear criterion that determines whether the infinite-cylinder assumption can be employed. The curvature of the cylinders enters this linear relationship through the slope and additive constant. For a given length-to-gap aspect ratio there is a critical Rayleigh number beyond which the laminar flow in the finite system is convective and so the behaviour is entirely different from the periodic case. The criterion does not depend on the Pra...

Lopez, Jose M; Avila, Marc

2015-01-01

212

Summary Weusedthreemethodstomeasureboundarylayer conductance to heat transfer (gbH) and water vapor transfer  

E-print Network

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 diffusion, the boundary layer around a leaf also provides resistance to the transfer of heat between a leaf

Martin, Timothy

213

Influence of interfaces on diffusive-ballistic heat conduction of carbon Shiomi, Junichiro, Maruyama, Shigeo  

E-print Network

is expected to be a good heat conductor with the extraordinary long phonon mean free paths. This gives rise not only give rise to thermal boundary resistances but also influence the intrinsic heat conductionInfluence of interfaces on diffusive-ballistic heat conduction of carbon nanotubes Shiomi

Maruyama, Shigeo

214

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

E-print Network

effect gives rise to the long-time heat flux correlation.11) More recently, the length dependenceMolecular 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

Maruyama, Shigeo

215

Wave transmission, phonon localization, and heat conduction of a one-dimensional Frenkel-Kontorova chain  

E-print Network

Wave transmission, phonon localization, and heat conduction of a one-dimensional Frenkel the fundamental properties, such as the wave transmission, heat conduction, and other low these related properties, namely, the wave transmission, the heat conduc- tion, and the phonon localization in 1

Li, Baowen

216

Non-Fourier heat conduction in a single-walled carbon nanotube: Classical molecular dynamics simulations  

E-print Network

to predict the heat conduction due to the lack of local diffusion. It is shown that this can be remedied. In a typical macroscopic description, a well-known model of heat wave propagation was formulated by Cattaneo = + , (1) where heat is conducted as a wave whose amplitude decays with an effective relaxation time . Here

Maruyama, Shigeo

217

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

218

3D modeling of heat transfer and gas flow in a grooved ring fuel element for nuclear thermal propulsion  

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

219

An analytical treatment for combined heat transfer by radiation, convection and conduction within a heat insulating wall structure  

Microsoft Academic Search

An analytical procedure has been proposed to attack a highly conjugate thermal problem associated with radiation, convection and conduction within a heat insulating wall structure. Firstly, an analytical solution is derived for fully-developed mixed convective flow through parallel plates. Secondly, the resulting expressions for convection are coupled with radiation and conduction equations to form a set of heat balance equations

A. Nakayama; F. Kuwahara; G. Xu; F. Kato

2004-01-01

220

Performance of a variable conductance heat pipe heat exchanger. Final scientific report, 15 May 1982-14 February 1983  

Microsoft Academic Search

The primary objective of the work is to evaluate the performance of an air to air variable conductance heat pipe heat exchanger (VCHPHX). This type of heat exchanger is of particular interest to the commercial aircraft industry because of its unique control system. The results from this research will help to provide the engineer with experimental data necessary to design

Chancelor

1983-01-01

221

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

E-print Network

in industrial applications, e.g. boiling heat exchangers or heat pipes. Special case of such problem as heat exchange fluid. A common interest is avoiding boiling of this cooling medium, i.e. nucleationHeat conduction problem of an evaporating liquid wedge T. B´arta, V. Janecek, D. Praz´ak Abstract

Bárta, Tomás

222

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

Microsoft Academic Search

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

M. A. Green

1994-01-01

223

Constructal-theory network of conducting paths for cooling a heat generating volume  

Microsoft Academic Search

This paper develops a solution to the fundamental problem of how to collect and ‘channel’ to one point the heat generated volumetrically in a low conductivity volume of given size. The amount of high conductivity material that is available for building channels (high conductivity paths) through the volume is fixed. The total heat generation rate is also fixed. The solution

Adrian Bejan

1997-01-01

224

Experimental investigation of plastic finned-tube heat exchangers, with emphasis on material thermal conductivity  

SciTech Connect

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

225

A complete conjugate conduction convection and radiation problem for a heated block in a vertical differentially heated square enclosure  

Microsoft Academic Search

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

226

Performance tests of a conductive magnetic refrigerator using a 4.5 K heat sink  

NASA Astrophysics Data System (ADS)

Initial performance test results of a prototype, conductive magnetic refrigerator rejecting heat to a 4.5 K heat sink are presented. The prototype uses Gadolinium Gallium Garnet as the working material, operates in a Carnot cycle, uses NbTi magnets and employs conduction heat transfer internally. The data presented are used to validate an analytical model of the device. Performance limitations from circumferential conduction and internal friction are identified and discussed.

Prenger, F. C.; Hill, D. D.; Trueblood, J.; Servais, T.; Laatsch, J.; Barclay, J. A.

227

Steady heat conduction-based thermal conductivity measurement of single walled carbon nanotubes thin film using a micropipette thermal sensor  

PubMed Central

In this paper, we describe the thermal conductivity measurement of single-walled carbon nanotubes thin film using a laser point source-based steady state heat conduction method. A high precision micropipette thermal sensor fabricated with a sensing tip size varying from 2 ?m to 5 ?m and capable of measuring thermal fluctuation with resolution of ±0.01 K was used to measure the temperature gradient across the suspended carbon nanotubes (CNT) film with a thickness of 100 nm. We used a steady heat conduction model to correlate the temperature gradient to the thermal conductivity of the film. We measured the average thermal conductivity of CNT film as 74.3 ± 7.9 W m?1 K?1 at room temperature. PMID:23556837

Shrestha, R.; Lee, K. M.; Chang, W. S.; Kim, D. S.; Rhee, G. H.; Choi, T. Y.

2013-01-01

228

October 2011 SDI FEP Issues Heat Conduction Issues (HC)  

E-print Network

the heaters. Background: Halite thermal conductivity (k) is inversely related to porosity. The higher porosity additional information on the higher temperature-lower thermally conductive nature of halite and its affect on distal temperatures. Background: Halite thermal k is inversely related to temperature. A higher

229

Solving Heat Conduction Problems by the Direct Meshless Local Petrov-Galerkin (DMLPG) method  

E-print Network

Solving Heat Conduction Problems by the Direct Meshless Local Petrov-Galerkin (DMLPG) method Davoud¨ottingen, Germany. SUMMARY As an improvement of the Meshless Local Petrov­Galerkin (MLPG), the Direct Meshless Local; Meshless methods; MLPG methods; DMLPG methods; Heat conduction problem. 1. INTRODUCTION Meshless methods

Schaback, Robert

230

Quantitative analyses of damp-heat-induced degradation in transparent conducting oxides  

E-print Network

Quantitative analyses of damp-heat-induced degradation in transparent conducting oxides Jae Ik Kim online 9 January 2014 Keywords: Transparent conducting oxides Al-doped ZnO Damp-heat test Photovoltaics atmosphere) for sputter-deposited aluminum-doped zinc oxide (ZnO:Al) thin films were quantitatively studied

Park, Byungwoo

231

A numerical method for natural convection and heat conduction around and in a horizontal circular pipe  

Microsoft Academic Search

Natural convection around a horizontal circular pipe coupled with heat conduction in the solid structure is numerically investigated using a preconditioning method for solving incompressible and compressible Navier–Stokes equations. In this method, fundamental equations are completely reduced to an equation of heat conduction when the flow field is static (zero velocity). Therefore, not only compressible flows but also very slow

Satoru Yamamoto; Daisuke Niiyama; Byeong Rog Shin

2004-01-01

232

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

Microsoft Academic Search

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

233

Nonballistic heat conduction in an integrable random-exchange Ising chain studied with quantum master equations  

E-print Network

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

234

Thermal conductivity and specific heat of sorghum grain  

E-print Network

to three volt range, the voltmeter resistance was 300 ohms. Leads for this meter were soldered to the element to provide good electrical connections. Prior to any testing this meter was calibrated by the Electrical Engineering Department of the A &. M... is the length of the heating element in the voltmeter circuit. Length b could only be measured accurately after the voltmeter leads were soldered to the heating element. Two working equations were then developed by substituting the value of Q in Equation 2...

Miller, Clinton Frank

1963-01-01

235

Developing Low-Conductance Window Frames: Capabilities and Limitations of Current Window Heat Transfer Design Tools  

E-print Network

on the total window heat transfer rates may be much larger. This effect is even greater in low on a literature review and an evaluation of current methods of modeling heat transfer through window frames, we evaluating heat transfer through the low-conductance frames. We conclude that the near-term priorities

236

Influence of surrounding materials on heat conduction of carbon nanotubes: Molecular dynamics simulations  

E-print Network

-length in many applications even at room temperature. This gives rise to unique steady and unsteady heat/sources is expected to determine the overall heat transfer performance. Such interfaces not only give rise to thermalInfluence of surrounding materials on heat conduction of carbon nanotubes: Molecular dynamics

Maruyama, Shigeo

237

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

Microsoft Academic Search

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

238

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

239

Optimal expansion of a heated working fluid for maximum work output with time-dependent heat conductance and generalized radiative heat transfer law  

NASA Astrophysics Data System (ADS)

The optimal configuration of the expansion process of a heated working fluid inside a cylinder for maximum work output with a movable piston and time-dependent heat conductance is determined in this paper using finite-time thermodynamics. The heat transfer between the working fluid and the external heat bath is assumed to obey the generalized radiative heat transfer law (q ? ?(Tn )). The heat conductance (product of heat transfer coefficient and heat transfer surface area) of cylinder walls is assumed to depend on the time-dependent heat transfer surface area of the walls in contact with gas. Euler-Lagrange formalism is applied to obtain the optimal process that maximizes the work output of the working fluid with fixed initial energy, initial volume, final volume, and total time allowed for the expansion. The optimal initial value of internal energy of the Euler-Lagrange arc is determined by numerical techniques. Numerical examples for the optimal configurations with time-dependent heat conductance for the cases of five special heat transfer laws (n = -1, 1, 2, 3, and 4) are provided, and the obtained results are compared with those obtained for the cases of constant heat conductance. The optimal configurations with time-dependent heat conductance for the cases of five special heat transfer laws are also compared with each other. The optimization problems with the generalized radiative heat transfer law are helpful for the further understanding of the effect of heat transfer law on the general performance and the inherent character of thermodynamic processes and cycles. The results presented herein can provide the basis for both determining optimal operating conditions and designing real systems operating with the generalized radiative heat transfer law.

Chen, Lingen; Ma, Kang; Sun, Fengrui

2011-06-01

240

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

241

A high reliability variable conductance heat pipe space radiator  

Microsoft Academic Search

The heat pipes in this radiator for space applications incorporate a central-core wrapped screen wick, which primes and reprimes under adverse conditions in the presence of noncondensable gas. A step change in mesh size provides low resistance to liquid flow in the condenser while at the same time retaining high pumping capability in the evaporator region. The envelope and wick

G. L. Fleischman; G. F. Pasley; R. J. McGrath; L. D. Loudenback

1978-01-01

242

DPL model analysis of non-Fourier heat conduction restricted by continuous boundary interface  

Microsoft Academic Search

Dual-phase lag (DPL) model is used to describe the non-Fourier heat conduction in a finite medium where the boundary at x=0 is heated by a rectangular pulsed energy source and the other boundary is tightly contacted with another medium and satisfies\\u000a the continuous boundary condition. Numerical solution of this kind of non-Fourier heat conduction is presented in this paper.\\u000a The

Fangming Jiang; Dengying Liu

2001-01-01

243

Heat transfer in vertical Bridgman growth of oxides - Effects of conduction, convection, and internal radiation  

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

244

Study of hydromagnetic heat and mass transfer flow over an inclined heated surface with variable viscosity and electric conductivity  

Microsoft Academic Search

The effects of variable electric conductivity and temperature dependent viscosity on hydromagnetic heat and mass transfer flow along a radiate isothermal inclined permeable surface in a stationary fluid in the presence of internal heat generation (or absorption) are analyzed numerically presenting local similarity solutions for various values of the physical parameters. The research shows that the difference in the results

Mohammad M. Rahman; K. M. Salahuddin

2010-01-01

245

Propagation of a cylindrical shock wave in a rotating dusty gas with heat conduction and radiation heat flux  

Microsoft Academic Search

A self-similar solution for the propagation of a cylindrical shock wave in a dusty gas with heat conduction and radiation heat flux, which is rotating about the axis of symmetry, is investigated. The shock is assumed to be driven out by a piston (an inner expanding surface) and the dusty gas is assumed to be a mixture of non-ideal gas

J. P. Vishwakarma; G. Nath

2010-01-01

246

Similarity solution for a cylindrical shock wave in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux  

Microsoft Academic Search

The propagation of shock waves in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux, which has a variable azimuthally fluid velocity together with a variable axial fluid velocity, is investigated. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It

J. P. Vishwakarma; G. Nath

2012-01-01

247

Fast-ion conduction and flexibility and rigidity of solid electrolyte glasses M. Micoulaut,1 M. Malki,2,3 D. I. Novita,4 and P. Boolchand4  

E-print Network

Fast-ion conduction and flexibility and rigidity of solid electrolyte glasses M. Micoulaut,1 MRevB.80.184205 PACS number s : 61.43.Fs I. INTRODUCTION Fast-ion conduction in solid electrolyte glasses of these materials in solid-state batteries, sensors, and nonvola- tile memories. Electrical conductivity can

Boolchand, Punit

248

Experimental investigation of plastic finned-tube heat exchangers, with emphasis on material thermal conductivity  

Microsoft Academic Search

In this paper, two modified types of polypropylene (PP) with high thermal conductivity up to 2.3W\\/m K and 16.5W\\/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

Lin Chen; Zhen Li; Zeng-Yuan Guo

2009-01-01

249

Experimental investigation of plastic finned-tube heat exchangers, with emphasis on material thermal conductivity  

Microsoft Academic Search

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

Lin Chen; Zhen Li; Zeng-Yuan Guo

2009-01-01

250

A Taylor discontinuous Galerkin method for the thermal solution in 3D mold filling  

Microsoft Academic Search

In continuity with the work of the authors, a Taylor discontinuous Galerkin method is introduced to solve the thermal problem in the context of the 3D mold filling by viscous incompressible fluid. This numerical scheme is designed to deal with the physical phenomena of shear and temperature dependent viscosity, viscous heat generation and heat transfer by conduction and convection. A

E. Pichelin; T. Coupez

1998-01-01

251

Determination of temperature-dependent heat conductivity and thermal diffusivity of waste glass melter feed  

SciTech Connect

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 680°C, 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

252

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

Microsoft Academic Search

Recently, Rajabi et al. (Application of homotopy perturbation method in nonlinear heat conduction and convection equations, Phys. Lett. A 360 (2007) 570–573.) discussed the solutions of temperature distribution in lumped system of combined convection–radiation. 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

253

Thermal conductivity in nanostructured materials and analysis of local angle between heat fluxes  

NASA Astrophysics Data System (ADS)

The phonon Boltzmann transport equation with the frequency-dependent model is solved numerically to study the thermal conductivity in nanoporous thin film and nanocomposite. Local angle between heat fluxes, defined as the angle between the directions of heat flux component qx and the local heat flux q, is introduced. At a fixed porosity or interface area, the thermal conductivity, local angle distribution, and the average angle of the two-dimensional nanoporous thin films with circular, hexagonal, square, and triangular pores are reported, and the thermal conductivity decreases with the increase in the interface area or porosity. Furthermore, the relationship between the thermal conductivity and average angle is also discussed for the three-dimensional nanoporous thin films with aligned or staggered pores, and silicon-germanium embedded and compacted nanocomposites. All the results show that the nanostructured material with a larger average angle between heat fluxes has a lower thermal conductivity.

Fu, B.; Tang, G. H.; Bi, C.

2014-09-01

254

Tables for solution of the heat-conduction equation with a time-dependent heating rate  

E-print Network

Tables are presented for the solution of the transient onedimensional heat flow in a solid body of constant material properties with the heating rate at one boundary dependent on time. These tables allow convenient and ...

Bergles A. E.

1962-01-01

255

Phonon Transport in Graphene: Umklapp Quenching and Heat Conduction  

NASA Astrophysics Data System (ADS)

Since its exfoliation, graphene attracted tremendous attention of the research community. Graphene, which consists of a single atomic plane of carbon atoms, revealed many unique properties including extremely high electron mobility. In this talk I will show that unusual properties of graphene are not limited to electrons alone. Phonons also behave differently in two-dimensional (2D) system such as graphene. We have recently discovered experimentally that thermal conductivity of suspended graphene layers is extremely high and exceeds that of diamond or graphite [2-3]. We explained our results theoretically by considering the Umklapp and edge scattering of phonons in graphene [3]. Unlike in bulk graphite, the phonon transport in graphene is pure 2D for all phonon energies. As a result, the thermal conductivity of graphene can become extremely high. The extraordinary high thermal conductivity of graphene can be used for thermal management of nanoscale electronic devices. This work was supported by SRC-DARPA Functional Engineered Nano Architectonics (FENA) center and Interconnect Focus Center (IFC). [1] A.A. Balandin, et al. Nano Letters, 8, 902 (2008); S. Ghosh, et al., Appl. Phys. Lett., 92, 151911 (2008). [2] D.L. Nika, et al., Phys. Rev. B, 79, 155413 (2009); D.L. Nika et al., Appl. Phys. Lett., 94, 203103 (2009)

Balandin, Alexander

2009-11-01

256

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

E-print Network

-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

257

Europeana and 3D  

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

258

Heat conduction in a chain of dissociating particles: Effect of dimensionality  

NASA Astrophysics Data System (ADS)

The paper considers heat conduction in a model chain of composite particles with hard core and elastic external shell. Such model mimics three main features of realistic interatomic potentials—hard repulsive core, quasilinear behavior in a ground state, and possibility of dissociation. It has become clear recently that this latter feature has crucial effect on convergence of the heat conduction coefficient in thermodynamic limit. We demonstrate that in one-dimensional chain of elastic particles with hard core the heat conduction coefficient also converges, as one could expect. Then we explore effect of dimensionality on the heat transport in this model. For this sake, longitudinal and transversal motions of the particles are allowed in a long narrow channel. With varying width of the channel, we observe sharp transition from "one-dimensional" to "two-dimensional" behavior. Namely, the heat conduction coefficient drops by about order of magnitude for relatively small widening of the channel. This transition is not unique for the considered system. Similar phenomenon of transition to quasi-1D behavior with growth of aspect ratio of the channel is observed also in a gas of densely packed hard (billiard) particles, both for two- and three-dimensional cases. It is the case despite the fact that the character of transition in these two systems is not similar, due to different convergence properties of the heat conductivity. In the billiard model, the divergence pattern of the heat conduction coefficient smoothly changes from logarithmic to power-like law with increase of the length.

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

2015-03-01

259

Nanoflare statistics in an active region 3D MHD coronal model  

E-print Network

Context. We investigate the statistics of the spatial and temporal distribution of the coronal heating in a three-dimensional magneto- hydrodynamical (3D MHD) model. The model describes the temporal evolution of the corona above an observed active region. The model is driven by photospheric granular motions which braid the magnetic field lines. This induces currents and their dissipation heats the plasma. We evaluate the transient heating as subsequent heating events and analyze their statistics. The results are then interpreted in the context of observed flare statistics and coronal heating mechanisms. Methods. To conduct the numerical experiment we use a high order finite difference code which solves the partial differential equations for the conservation of mass, the momentum and energy balance, and the induction equation. The energy balance includes the Spitzer heat conduction and the optical thin radiative loss in the corona. Results. The temporal and spatial distribution of the Ohmic heating in the 3D M...

Bingert, Sven

2012-01-01

260

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

E-print Network

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

261

Effect of viscosity and wall heat conduction on shock attenuation in narrow channels  

NASA Astrophysics Data System (ADS)

In the present work, the effects due to viscosity and wall heat conduction on shock propagation and attenuation in narrow channels are numerically investigated. A two-dimensional viscous shock tube configuration is simulated, and heat conduction in the channel walls is explicitly included. The simulation results indicate that the shock attenuation is significantly less in case of an adiabatic wall, and the use of an isothermal wall model is adequate to take into account the wall heat conduction. A parametric study is performed to characterize the effects of viscous forces and wall heat conduction on shock attenuation, and the behaviour is explained on the basis of boundary layer formation in the post-shock region. A dimensionless parameter that describes the shock attenuation is correlated with the diaphragm pressure ratio and a dimensionless parameter which is expressed using the characteristic Reynolds number and the dimensionless shock travel.

Deshpande, A.; Puranik, B.

2015-02-01

262

Transition from near-field thermal radiation to phonon heat conduction at sub-nanometre gaps.  

PubMed

When the separation of two surfaces approaches sub-nanometre scale, the boundary between the two most fundamental heat transfer modes, heat conduction by phonons and radiation by photons, is blurred. Here we develop an atomistic framework based on microscopic Maxwell's equations and lattice dynamics to describe the convergence of these heat transfer modes and the transition from one to the other. For gaps >1?nm, the predicted conductance values are in excellent agreement with the continuum theory of fluctuating electrodynamics. However, for sub-nanometre gaps we find the conductance is enhanced up to four times compared with the continuum approach, while avoiding its prediction of divergent conductance at contact. Furthermore, low-frequency acoustic phonons tunnel through the vacuum gap by coupling to evanescent electric fields, providing additional channels for energy transfer and leading to the observed enhancement. When the two surfaces are in or near contact, acoustic phonons become dominant heat carriers. PMID:25849305

Chiloyan, Vazrik; Garg, Jivtesh; Esfarjani, Keivan; Chen, Gang

2015-01-01

263

Conjugate conduction-convection heat transfer with a high-speed boundary layer  

Microsoft Academic Search

A space-marching boundary-layer program has been extensively modified to model conjugate conduction-convection heat transfer for the case of co-flowing high-speed gas and liquid coolant. Solid body conduction is modeled as one-dimensional, constant property heat transfer. The coolant is modeled empirically as a bulk fluid with combined forced convection and subcooled nucleate boiling. The flow solver was modified to solve the

Frederick L. Shope

1994-01-01

264

Effect of heat treatment on the thermal conductivity of plasma-sprayed thermal barrier coatings  

Microsoft Academic Search

The effect of heat treatment on the thermal conductivity of plasma-sprayed Y2O3 stabilized ZrO2 (YSZ) and Al2O3 coatings was investigated. A heat treatment of 1300 °C in flowing argon for 50 h was found to significantly increase the\\u000a thermal conductivity of the coatings when compared to measurements in the assprayed condition. Transmission electron microscopy\\u000a (TEM) examination of the microstructures of

Rollie Dutton; Robert Wheeler; K. S. Ravichandran; K. An

2000-01-01

265

The Boundary Element Method for the Solution of the Backward Heat Conduction Equation  

Microsoft Academic Search

In this paper we consider the numerical solution of the one-dimensional, unsteady heat conduction equation in which Dirichlet boundary conditions are specified at two space locations and the temperature distribution at a particular time, say T0, is given. The temperature distribution for all times, t < T0, is now required and this backward heat conduction problem is a well-known improperly

H. Han; D. B. Ingham; Y. Yuan

1995-01-01

266

Effects of friction and heat conduction on sound propagation in ducts. [analyzing complex aerodynamic noise problems  

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

267

Simulation of convective-conductive-radiative heat transfer in a cooling basin  

Microsoft Academic Search

The three-dimensional mathematical model of complex research of heat and mass transfer in water media was used. This allows examining the interaction of some transfer processes in the natural cooling basin (lake Dr?kšiai): heat convection and conduction, direct and diffusive solar radiation, variable density of the water and heat transfer coefficient of the water-air interface. The combined effect of these

P. Vaitiek?nas; D. Paliulis

268

Effective thermal conductivity for combined radiation and free convection in an optically thick heated fluid layer  

Microsoft Academic Search

The effective thermal conductivity for radiative heat transfer within an optically thick fluid layer undergoing high Rayleigh number convection is derived. This result is combined with available ''pure'' free-convection heat-transfer correlations to obtain closed-form analytical descriptions of the gross properties of a radiating fluid layer heated internally or form below. These simple solutions compare favorably with recent work in which

M. Epstein; F. B. Cheung; T. C. Chawla; G. M. Hauser

1981-01-01

269

Three-dimensional simulation of the coupled convective, conductive, and radiative heat transfer during decay heat removal in an HTR  

Microsoft Academic Search

A three-dimensional model has been constructed to simulate the passive heat removal in a modular prismatic-block high temperature reactor during a loss of active cooling accident. This model, developed using the STAR-CD general computational fluid dynamics code, solves the combined conductive, convective, and radiative heat transfer within a 30° section of the core and reactor vessel. To accommodate the different

Jan-Patrice Simoneau; Julien Champigny; Brian Mays; Lewis Lommers

2007-01-01

270

The Heat Conductivity of Tungsten and the Cooling Effects of Leads upon Filaments at Low Temperatures  

Microsoft Academic Search

The theory and the equations governing the temperature distribution, resistance, and heat flow in a tungsten filament as affected by its leads are given for the low temperature range (<600°K), both for the general case and for several special cases. A low temperature vs. current scale for tungsten is calculated from these equations using measurements of heat conductivity given in

Irving Langmuir; John Bradshaw Taylor

1936-01-01

271

Transient heat conduction analysis in functionally graded materials by the meshless local boundary integral equation method  

Microsoft Academic Search

Advanced computational method for transient heat conduction analysis in continuously nonhomogeneous functionally graded materials (FGM) is proposed. The method is based on the local boundary integral equations with moving least square approximation of the temperature and heat flux. The initial-boundary value problem is solved by the Laplace transform technique. Both Papoulis and Stehfest algorithms are applied for the numerical Laplace

J. Sladek; V. Sladek; Ch. Zhang

2003-01-01

272

Influence of convection, conduction, and radiation on the frequency response of heat fluxmeters  

Microsoft Academic Search

A simple model for a heat fluxmeter, exchanging heat by radiation, convection, and conduction with the surrounding air is introduced. The final analytical solution is interpreted by means of electronic analog circuits and an explanation of the properties of the radiometer of Gier and Dunkle (AIEE Trans. 70, 107–114, 1953) is given.

H. Malcorps

1982-01-01

273

Simultaneous radiative, convective and conductive heat transfer from a developed surface  

Microsoft Academic Search

The paper considers the simultaneous radiative, conductive and convective heat transfer from three types of developed systems: (1) a longitudinally ribbed flat surface, (2) a longitudinally ribbed cylinder, and (3) a peripherally ribbed cylinder. The Monte Carlo method is used to analyze the radiation characteristics of the surfaces. Attention is given to the effects of heat transfer parameters and geometrical

T. Kunitomo; S. Tanaka

1976-01-01

274

Conjugate heat transfer by natural convection, conduction and radiation in open cavities  

Microsoft Academic Search

In this paper, we investigate conjugate heat transfer by natural convection, conduction and radiation in open cavities in which a uniform heat flux is applied to the inside surface of the solid wall facing the opening. Conservation equations are solved by finite difference–control volume numerical method. The relevant governing parameters are: the Rayleigh numbers from 109 to 1012, the Prandtl

H. Nouanegue; A. Muftuoglu; E. Bilgen

2008-01-01

275

Effect of sidewall conductance on heat-transport measurements for turbulent Rayleigh-Benard convection  

E-print Network

-Be´nard convection Guenter Ahlers Department of Physics and iQUEST, University of California, Santa Barbara transport in Rayleigh-Be´nard convection the correction for the sidewall conductance is usually neglected convection of a fluid heated from below is the global heat transport of the system 1 , as expressed

Fygenson, Deborah Kuchnir

276

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

E-print Network

at low temperature has been observed to propagate by means of waves. These aspects have caused intense+ corresponds to the heat flux vector at the same point at time t+q. The delay time is causedQualitative aspects in dual-phase-lag heat conduction Ram´on Quintanilla1 Department of Applied

Racke, Reinhard

277

Analysis of dielectric heating and conductive cooling of pyrite in coal  

Microsoft Academic Search

Electrical and thermal properties of pyrite and coal were used to obtain a theoretical analysis of dielectric heating and conductive cooling of pyrite in coal. The results were used to establish radiation levels required to produce pyrite-coal temperature differentials in solid coals. The objective of dielectric heating of pyrite in coal is to raise its temperature to a point where

D. D. Bluhm; G. E. Fanslow; S. O. Nelson

1981-01-01

278

A Bayesian inference approach to the inverse heat conduction problem Jingbo Wang and Nicholas Zabaras1  

E-print Network

probability density function (PPDF) of the boundary heat flux is computed given temperature measurements state space is exploited using Markov Chain Monte Carlo (MCMC) algorithms in order to obtain estimates inverse heat conduction examples are presented to demonstrate the potential of the MCMC-based Bayesian

Zabaras, Nicholas J.

279

3D Freehand Canvas  

Microsoft Academic Search

This paper presents a 3D freehand sketching system. Replacing the traditional 3D cartoon process, which contains modeling,\\u000a texture mapping, it uses 2D input for generating projective strokes on a user-definable 3D canvas, which makes it possible\\u000a that artist can sketch freehand in 3D space with no limitation. The freehand style animation could be created, which is nearly\\u000a impossible for modern

Miao Wang; Guangzheng Fei; Zijun Xin; Yi Zheng; Xin Li

2008-01-01

280

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

281

Java 3D  

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.

282

Effects of axial plate heat conduction on the thermal performance of a laminar counterflow flat plate heat exchanger  

E-print Network

(December 19SO) Jonathan Alexander Demko, B. S. M. E. , Texas A&M University Chairman of Advisory Committee: Dr. Louis C. Chow A flat plate heat exchanger (PHE) was examined analytically with focus on assessing the effects of axial conduction along... AND DISCUSSION 15 Bulk Temperature Heat Exchanger Performance Fully Developed Flows Unbalanced Flows 17 25 30 CHAPTER IV SUMMARY AND CONCLUSIONS REFERENCES APPENDIX 3B 40 VITA 56 LIST OF FIGURES ~Fi ure ~Pa e Model of a flat plate heat exchanger...

Demko, Jonathan Alexander

1980-01-01

283

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

Microsoft Academic Search

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

284

3D stability analysis of Rayleigh-Bénard convection of a liquid metal layer in the presence of a magnetic field—effect of wall electrical conductivity  

NASA Astrophysics Data System (ADS)

Rayleigh-Bénard stability of a liquid metal layer of rectangular cross section is examined in the presence of a strong magnetic field that is aligned with the horizontal direction of the cross section. The latter is much longer than the vertical direction and the cross section assumes a large aspect ratio. The side walls are treated as highly conducting. Linear stability analysis is performed allowing for three-dimensional instabilities that develop along the longitudinal direction. The finite element methodology is employed for the discretization of the stability analysis formulation while accounting for the electrical conductivity of the cavity walls. The Arnoldi method provides the dominant eigenvalues and eigenvectors of the problem. In order to facilitate parallel implementation of the numerical solution at large Hartmann numbers, Ha, domain decomposition is employed along the horizontal direction of the cross section. As the Hartmann number increases a real eigenvalue emerges as the dominant unstable eigenmode, signifying the onset of thermal convection, whose major vorticity component in the core of the layer is aligned with the direction of the magnetic field. Its wavelength along the longitudinal direction of the layer is on the order of twice its height and increases as Ha increases. The critical Grashof was obtained for large Ha and it was seen to scale like Ha 2 signifying the balance between buoyancy and Lorentz forces. For well conducting side walls, the nature of the emerging flow pattern is determined by the combined conductivity of Hartmann walls and Hartmann layers, cH + Ha -1. When poor conducting Hartmann walls are considered, cH ? 1, the critical eigensolution is characterized by well defined Hartmann and side layers. The side layers are characterized by fast fluid motion in the magnetic field direction as a result of the electromagnetic pumping in the vicinity of the Hartmann walls. Increasing the electrical conductivity of the Hartmann walls was seen to delay the onset of thermal convection, while retaining the above scaling at criticality. Furthermore, for both conducting and insulating Hartmann walls and the entire range of Ha numbers that was examined, there was no tendency for a well defined quasi two-dimensional structure to develop owing to the convective motion in the core. A connection is made between the above findings and previous experimental investigations indicating the onset of standing waves followed by travelling waves as Gr is further increased beyond its critical value.

Dimopoulos, Dimitrios; Pelekasis, Nikos A.

2014-10-01

285

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

PubMed

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

286

The World of 3-D.  

ERIC Educational Resources Information Center

Students explore three-dimensional properties by creating red and green wall decorations related to Christmas. Students examine why images seem to vibrate when red and green pieces are small and close together. Instructions to conduct the activity and construct 3-D glasses are given. (MDH)

Mayshark, Robin K.

1991-01-01

287

Thermophoretic hydromagnetic dissipative heat and mass transfer with lateral mass flux, heat source, Ohmic heating and thermal conductivity effects: Network simulation numerical study  

Microsoft Academic Search

A two-dimensional mathematical model is presented for the laminar heat and mass transfer of an electrically-conducting, heat generating\\/absorbing fluid past a perforated horizontal surface in the presence of viscous and Joule (Ohmic) heating. The Talbot–Cheng–Scheffer–Willis formulation (1980) is used to introduce a thermophoretic coefficient into the concentration boundary layer equation. The governing partial differential equations are non-dimensionalized and transformed into

Joaquín Zueco; O. Anwar Bég; H. S. Takhar; V. R. Prasad

2009-01-01

288

Thermoelasticity of thin shells based on the time-fractional heat conduction equation  

NASA Astrophysics Data System (ADS)

The time-nonlocal generalizations of Fourier's law are analyzed and the equations of the generalized thermoelasticity based on the time-fractional heat conduction equation with the Caputo fractional derivative of order 0 < ? ? 2 are presented. The equations of thermoelasticity of thin shells are obtained under the assumption of linear dependence of temperature on the coordinate normal to the median surface of a shell. The conditions of Newton's convective heat exchange between a shell and the environment have been assumed. In the particular case of classical heat conduction ( ? = 1) the obtained equations coincide with those known in the literature.

Povstenko, Yuriy

2013-06-01

289

Thermoelasticity of thin shells based on the time-fractional heat conduction equation  

NASA Astrophysics Data System (ADS)

The time-nonlocal generalizations of Fourier's law are analyzed and the equations of the generalized thermoelasticity based on the time-fractional heat conduction equation with the Caputo fractional derivative of order 0 < ? ? 2 are presented. The equations of thermoelasticity of thin shells are obtained under the assumption of linear dependence of temperature on the coordinate normal to the median surface of a shell. The conditions of Newton's convective heat exchange between a shell and the environment have been assumed. In the particular case of classical heat conduction (? = 1) the obtained equations coincide with those known in the literature.

Povstenko, Yuriy

2013-06-01

290

About influence of gravity on heat conductivity process of the Planets  

E-print Network

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

291

About influence of gravity on heat conductivity process of the Planets  

E-print Network

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

292

Molecular dynamics simulation of heat conduction in near-critical fluids Toshiyuki Hamanaka, Ryoichi Yamamoto, and Akira Onuki  

E-print Network

average of the convective heat flux nT sv thus gives rise to the critical heat conduction. WithinMolecular dynamics simulation of heat conduction in near-critical fluids Toshiyuki Hamanaka fluids near the gas-liquid critical point under heat flow in two dimensions. We calculate the steady

293

Fully automated system for simultaneous measurement of thermal conductivity and heat capacity from 4 to 300 K  

Microsoft Academic Search

A fully automated system which is capable of measuring specific heat and thermal conductivity simultaneously from liquid helium to room temperature is presented. Thermal conductivity is measured by a steady-state longitudinal heat flow technique, and specific heat by a thermal relaxation method. A numerical simulation of the one-dimensional heat flow equation is used to examine the basic operational principle. The

R. S. Kwok; S. E. Brown

1990-01-01

294

A Multi-Dimensional Cognitive Analysis of Undergraduate Physics Students' Understanding of Heat Conduction  

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

295

Thermal conduction and heating by nonthermal electrons in the X-ray halo of M87  

NASA Technical Reports Server (NTRS)

A hydrostatic model for the X-ray halo around the giant elliptical galaxy M87 is presented. It is shown that by taking into account the processes of thermal conduction, and nonthermal heating by relativistic electrons in the radio lobes, a self-consistent hydrostatic model can be constructed. There is no need to invoke radiative accretion or the suppression of thermal conductivity.

Tucker, W. H.; Rosner, R.

1983-01-01

296

Two-Dimensional Computational Fluid Dynamics and Conduction Simulations of Heat Transfer in Window Frames  

E-print Network

-transfer process involves a combination of conduction, convection, and radiation. To fully describe heat transfer Dynamics (CFD) modeling to assess the accuracy of the simplified frame cavity conduction/convection models the convection effects and to use either view-factors or ray- tracing techniques to determine the radiation

297

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

E-print Network

Convection under a lid of finite conductivity: Heat flux scaling and application to continents C of the dichotomy between oceans and continents, which imposes heterogeneous thermal boundary conditions and continents represented by nondeformable lids of finite thermal conductivity set above the surface

Paris-Sud XI, Université de

298

Thermal conductivity and specific heat of pure and iodine doped polyacetylene (CH)x  

E-print Network

1453 Thermal conductivity and specific heat of pure and iodine doped polyacetylene (CH)x N and iodine doped samples of polyacetylene (CH)x are presented here. The thermal conductivity of pure (CH)x is about 75 mW/cm . K at room temperature and decreases monotonically to 1.6 mW/cm . K at 25 K

Paris-Sud XI, Université de

299

Heat Conduction through Surface Structures and Mixtures using Electric Circuits as Analogs  

Microsoft Academic Search

We present a mathematical model using electric analogs to simulate vertical and lateral conductive heat flow in surface layers of planetary bodies with topography. The model can also be used to determine average electric and thermal conductivities of small-scale granular mixtures (as opposed to molecular mixtures). The algorithm is general and applicable to complex compositions. Analogies between thermal and electric

W. F. Huebner; D. C. Boice; J. R. Green

1998-01-01

300

Local temperature redistribution and structural transition during joule-heating-driven conductance switching in VO2.  

PubMed

Joule-heating induced conductance-switching is studied in VO2 , a Mott insulator. Complementary in situ techniques including optical characterization, blackbody microscopy, scanning transmission X-ray microscopy (STXM) and numerical simulations are used. Abrupt redistribution in local temperature is shown to occur upon conductance-switching along with a structural phase transition, at the same current. PMID:23868142

Kumar, Suhas; Pickett, Matthew D; Strachan, John Paul; Gibson, Gary; Nishi, Yoshio; Williams, R Stanley

2013-11-13

301

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

SciTech Connect

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

302

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

303

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

304

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

E-print Network

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

305

Coupled conductive radiative heat transfer problem for two-layer slab  

NASA Astrophysics Data System (ADS)

The coupled conductive radiative transfer problem in two homogeneous layers slab of anisotropic scattering with specularly reflecting boundaries has been considered. A Galerkin-iterative technique is used to solve the coupled conductive radiative heat equations in integral forms for the two layers. Numerical results are obtained for the temperature, the conductive, radiative and the total heat fluxes for the two homogeneous layers with isotropic and anisotropic scattering. The calculations are also carried out for homogeneous plane parallel medium with anisotropic scattering which show good agreement with the published calculations.

Elghazaly, A.

2006-12-01

306

Convection Heat and Mass Transfer in an Electrical Conducting Power Law Flow over a Heated Vertical Porous Plate  

Microsoft Academic Search

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 non–linear 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

307

Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties  

SciTech Connect

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

308

Conductivity heating a subterranean oil shale to create permeability and subsequently produce oil  

SciTech Connect

This patent describes an improvement in a process in which oil is produced from a subterranean oil shale deposit by extending at least one each of heat-injecting and fluid-producing wells into the deposit, establishing a heat-conductive fluid-impermeable barrier between the interior of each heat-injecting well and the adjacent deposit, and then heating the interior of each heat-injecting well at a temperature sufficient to conductively heat oil shale kerogen and cause pyrolysis products to form fractures within the oil shale deposit through which the pyrolysis products are displaced into at least one production well. The improvement is for enhancing the uniformity of the heat fronts moving through the oil shale deposit. Also described is a process for exploiting a target oil shale interval, by progressively expanding a heated treatment zone band from about a geometric center of the target oil shale interval outward, such that the formation or extension of vertical fractures from the heated treatment zone band to the periphery of the target oil shale interval is minimized.

Van Meurs, P.; DeRouffignac, E.P.; Vinegar, H.J.; Lucid, M.F.

1989-12-12

309

The effect of correlations on the non-ohmic behavior of the small-polaron hopping conductivity in 1D and 3D disordered systems  

NASA Astrophysics Data System (ADS)

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.

Dimakogianni, M.; Triberis, G. P.

2010-09-01

310

The effect of correlations on the non-ohmic behavior of the small-polaron hopping conductivity in 1D and 3D disordered systems.  

PubMed

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

311

Prolonged bone-conducted vibration in superior semicircular canal dehiscence and in otosclerosis: comparison of the 3D eye movement evaluation  

PubMed Central

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

312

3D and Education  

NASA Astrophysics Data System (ADS)

Today the industry offers a chain of 3D products. Learning to "read" and to "create in 3D" becomes an issue of education of primary importance. 25 years professional experience in France, the United States and Germany, Odile Meulien set up a personal method of initiation to 3D creation that entails the spatial/temporal experience of the holographic visual. She will present some different tools and techniques used for this learning, their advantages and disadvantages, programs and issues of educational policies, constraints and expectations related to the development of new techniques for 3D imaging. Although the creation of display holograms is very much reduced compared to the creation of the 90ies, the holographic concept is spreading in all scientific, social, and artistic activities of our present time. She will also raise many questions: What means 3D? Is it communication? Is it perception? How the seeing and none seeing is interferes? What else has to be taken in consideration to communicate in 3D? How to handle the non visible relations of moving objects with subjects? Does this transform our model of exchange with others? What kind of interaction this has with our everyday life? Then come more practical questions: How to learn creating 3D visualization, to learn 3D grammar, 3D language, 3D thinking? What for? At what level? In which matter? for whom?

Meulien Ohlmann, Odile

2013-02-01

313

A-site deficient lanthanum-calcium chromite-titanates doped with 3d transition metals: synthesis, oxygen nonstoichiometry, electrical conductivity, and catalytic activity  

Microsoft Academic Search

Six $$ {\\\\text{La}}_{{0.4}} {\\\\text{Ca}}_{{0.5}} {\\\\text{Ti}}_{{0.5}} {\\\\text{Cr}}_{{0.4}} {\\\\text{M}}_{{0.1}} {\\\\text{O}}_{{3 - \\\\delta }} $$ (M?=?Cr, Mn, Fe, Co, Ni, Cu) and two $$ {\\\\text{La}}_{{0.4}} {\\\\text{Ca}}_{{0.4}} {\\\\text{Ti}}_{{0.4}} {\\\\text{Cr}}_{{0.4}} {\\\\text{M}}_{{0.2}} {\\\\text{O}}_{{3 - \\\\delta }} $$ (M?=?Ni, Cu) single-phase compositions were prepared by conventional solid-state reactions. Oxygen nonstoichiometry, electrical\\u000a conductivity, phase transformations under reduction-reoxidation at high temperatures and catalytic activity for hydrocarbons\\u000a oxidation of these

V. Vashook; R. Müller; J. Zosel; K. Ahlborn; F. Gerlach; P. Tietz; G. Stöver; U. Guth

2007-01-01

314

An International Round-Robin Study, Part II: Thermal Diffusivity, Specific Heat and Thermal Conductivity  

SciTech Connect

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

315

3-D solar cells by electrochemical-deposited Se layer as extremely-thin absorber and hole conducting layer on nanocrystalline TiO2 electrode  

PubMed Central

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 200°C 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

316

The role of heat-conducting walls in the measurement of heat and mass transport in transient grating experiments  

NASA Astrophysics Data System (ADS)

We present a two-dimensional model to account for the role of heat-conducting walls in the measurement of heat transport and Soret-effect-driven mass transport in transient holographic grating experiments. Heat diffusion into the walls leads to non-exponential decay of the temperature grating. Under certain experimental conditions it can be approximated by an exponential function and assigned an apparent thermal diffusivity Dth, app < Dth, s, where Dth,s is the true thermal diffusivity of the sample. The ratio Dth, app/Dth, s depends on only three dimensionless parameters, d /ls, ?s/?w, and Dth, s/Dth, w. d is the grating period, ls the sample thickness, ?s and ?w the thermal conductivities of sample and wall, respectively, and Dth,w the thermal diffusivity of the wall. If at least two measurements are performed at different d /ls, both Dth,s and ?s can be determined. Instead of costly solving PDEs, Dth,s can be obtained by finding the zero of an analytic function. For thin samples and large grating periods, heat conduction into the walls plays a predominant role and the concentration grating in binary mixtures is no longer one-dimensional. Nevertheless, the normalized heterodyne diffraction efficiency of the concentration grating remains unaffected and the true thermal and collective diffusion coefficient and the correct Soret coefficient are still obtained from a simple one-dimensional model.

Hartung, M.; Köhler, W.

2005-06-01

317

Similarity solution for a cylindrical shock wave in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux  

NASA Astrophysics Data System (ADS)

The propagation of shock waves in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux, which has a variable azimuthally fluid velocity together with a variable axial fluid velocity, is investigated. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-condition is maintained and variable energy input is continuously supplied by the piston (or inner expanding surface). The fluid velocities in the ambient medium are assume to be vary and obey power laws. The density of the ambient medium is assumed to be constant, the heat conduction is express in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient ?R are assumed to vary with temperature and density. In order to obtain the similarity solutions the angular velocity of the ambient medium is assume to be decreasing as the distance from the axis increases. The effects of the variation of the heat transfer parameter and non-idealness of the gas in the mixture are investigated. The effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are also investigated.

Vishwakarma, J. P.; Nath, G.

2012-01-01

318

An integral equation approach to radiative heat transfer between heat conducting solids of arbitrary shape  

Microsoft Academic Search

The main purpose of this paper is to present a nonlinear integral equation formulation to numerically solve composite boundary value problems encountered in the physical problem of radiative heat transfer between solids of arbitrary shape. The main difficulty in solving these types of boundary value problems is due to the nonlinear boundary conditions, which impose additional difficulties on the use

S. Colle; R. C. de Abreu; M. B. Halal

1981-01-01

319

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

SciTech Connect

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

320

An Analytical Study on a Model Describing Heat Conduction in Rectangular Radial Fin with Temperature-Dependent Thermal Conductivity  

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

321

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

322

Note on heat conduction in liquid metals. A comparison of laminar and turbulent flow effects  

NASA Astrophysics Data System (ADS)

The difference between heat transfer in liquid metals with electric currents and magnetic fields on the one hand and heat transfer in electrically insulating fluids and in conducting solids on the other is pointed out. Laminar and turbulent flow effects in liquid metal sliding electric contacts for homopolar machines are considered. Large temperature gradients can develop within a small region of liquid metal. A model of a liquid-metal sliding electrical contact is developed and analyzed.

Talmage, G.

1994-05-01

323

Thermodynamically compatible conservation laws in the model of heat conducting radiating gas  

NASA Astrophysics Data System (ADS)

Thermodynamic compatibility of the mass, momentum, and energy conservation laws that describe the motion of heat conducting gas in the presence of radiation heat exchange is considered. The study is based on the one-velocity two-component mathematical model of continuous compressible medium with the gas and radiation components. The work uses experimental data for radiation and other experimental data of modern physics.

Ivanov, M. Ya.

2011-01-01

324

BEAMS3D Neutral Beam Injection Model  

SciTech Connect

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

325

Basic Inquiry: Radiation and Heat Transfer by Conduction (title provided or enhanced by cataloger)  

NSDL National Science Digital Library

This activity consists of two parts in which students investigate heat transfer by radiation and by conduction. In the first part, students design and conduct an experiment to test the effect of color on an object's ability to radiate energy (heat). In the second part, they investigate the transfer of energy from a hotter object to a cooler one, in this case, containers of hot and cold water. In both experiments, they are required to state a hypothesis, make a list of materials and procedures needed for the experiment, collect and graph data, and state a conclusion. Each experiment is accompanied by a set of analysis and conclusion questions.

David Robison

326

Ultrahigh resolution characterizing nanoscale Seebeck coefficient via the heated, conductive AFM probe  

NASA Astrophysics Data System (ADS)

An ultrahigh resolution probe technique for charactering nanoscale Seebeck coefficient was developed based on a modified conductive AFM probe with local heating function. The heated AFM conductive tip realizes nanoscale thermal contact between the AFM tip and the thermoelectric samples and successfully excites nanoscale thermoelectric signal. Excellent agreement was found between nanoscale Seebeck coefficient values and their corresponding macroscopy measurements in thermoelectric bulk and thin films. Such AFM-based thermoelectric probe technique provides a very convenient and promising tool for measuring nanoscale thermoelectric parameters with ultrahigh resolution up to 15 nm.

Xu, K. Q.; Zeng, H. R.; Yu, H. Z.; Zhao, K. Y.; Li, G. R.; Song, J. Q.; Shi, X.; Chen, L. D.

2015-01-01

327

Determining the thermal diffusivity of sediments using the fractional nonlocal heat conduction equation  

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

328

The temperature dependence of the heat conductivity of a liquid crystal studied by molecular dynamics simulation  

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

329

Flight data analysis and further development of variable-conductance heat pipes. [for aircraft control  

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

330

LDEF (Prelaunch), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09  

NASA Technical Reports Server (NTRS)

LDEF (Prelaunch), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 EL-1994-00302 LDEF (Prelaunch), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 The prelaunch photograph was taken in SAEF II at KSC prior to installation of the Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) on the LDEF. The Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) occupies a 6 inch deep LDEF peripheral experiment tray and consist of two series connected variable conductance heatpipes, a black chrome solar collector panel and a silvered TEFLON® radiator panel, a power source to support six thermistor-type temperature monitoring sensors and actuations of two valves. Fiberglass standoffs and internal insulation blankets thermally isolated the experiment from the experiment tray and the LDEF interior. The outside of the CVCHPE, except the collector and radiator panels, was covered with an aluminumized Kapton multilayer insulation (MLI) blanket with an outer layer of 0.076 mm thick Kapton. The two patches of thin film materials, part of Experiment S1001 by NASA GSFC, were attached to the cover of the external thermal blanket with Kapton tape. The experiment was assembled and mounted in the experiment tray with non-magnetic stainless steel fasteners.

1983-01-01

331

a Direct( Pseudo-Spectral Solver of the 2D\\/3D Stokes Problem: Transition to Unsteadiness of Natural-Convection Flow in a Differentially Heated Cubical Cavity  

Microsoft Academic Search

A direct solver( named projection-diffusion) of the 2D\\/3D unsteady Stokes problem is presented. The pressure operator on which it rests is very close to the Poisson operator, out no pressure boundary condition is needed to invert it. It is applied, with a Chebyshev collocation scheme, to compute the transition to unsteadiness of the natural-convection flow of air in a differentially

G. Labrosse; E. Tric; H. Khallouf; M. Betrouni

1997-01-01

332

Cyberchase 3D Builder  

NSDL National Science Digital Library

This Cyberchase iOS geometry app ($) enables students to use 2D nets to create 3D shapes. The app includes eight levels which increase in difficulty; increasing the complexity of the nets and combining different 3D shapes together.

PBS Kids

2014-01-21

333

3D Shapes Video  

NSDL National Science Digital Library

This upbeat music video reviews 3D shapes including the sphere, cylinder, cube, and cone. As each 3D shape is presented, examples of things we see every day that have the same shape are also shown for reinforcement. (Length: 3:18)

Harry Kindergarten

2011-06-17

334

One-dimensional heat conductivity exponent from a random collision model J. M. Deutsch and Onuttom Narayan  

E-print Network

to conductivity would predict that if the temperature gradient "T in a material is small, the heat current flowing in the system conserve momentum, the con- ductivity is singular, due to advection of heat in long wave- lengthOne-dimensional heat conductivity exponent from a random collision model J. M. Deutsch and Onuttom

California at Santa Cruz, University of

335

Development of an inverse heat conduction model and its application to determination of heat transfer coefficient during casting solidification  

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

336

Estimation of surface heat flux and temperature distributions in a multilayer tissue based on the hyperbolic model of heat conduction.  

PubMed

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

2015-01-01

337

Lattice thermal conductivity of lower mantle minerals and heat flux from Earth’s core  

PubMed Central

The amount of heat flowing from Earth’s 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 Earth’s 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 26 GPa up to 1,073 K, and of ferropericlase containing 0, 5, and 20% Fe, at 8 and 14 GPa up to 1,273 K. 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 = 9.1 ± 1.2 W/m K at the top of the thermal boundary layer and k = 8.4 ± 1.2 W/m K at its base. These values translate into a heat flux of 11.0 ± 1.4 terawatts (TW) from Earth’s 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

338

Nonlinear thermal bending response of FGM plates due to heat conduction  

Microsoft Academic Search

Nonlinear thermal bending analysis is presented for a simply supported, shear deformable functionally graded plate without or with piezoelectric actuators subjected to the combined action of thermal and electrical loads. Heat conduction and temperature-dependent material properties are both taken into account. The temperature field considered is assumed to be a uniform distribution over the plate surface and varied in the

Hui-Shen Shen

2007-01-01

339

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

340

Heat conduction in simple networks: The effect of interchain coupling Zonghua Liu1,2  

E-print Network

, and are attracting increasing attention in recent years from different fields such as biology, social sci- ence with the number of added bonds 3,4 . The whole electric resistance of a network can be figured out found that both the normal and anomalous heat conduction can be described by an effective phonon theory

Li, Baowen

341

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

SciTech Connect

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

342

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

Microsoft Academic Search

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

343

Reinforcing Concepts of Transient Heat Conduction and Convection with Simple Experiments and COMSOL Simulations  

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

344

Enhancement and reduction of one-dimensional heat conduction with correlated mass disorder  

NASA Astrophysics Data System (ADS)

Short-range order in strongly disordered structures plays an important role in their heat conduction property. Using numerical and analytical methods, we show that short-range spatial correlation (with a correlation length of ?m) in the mass distribution of the one-dimensional (1D) alloylike random binary lattice leads to a dramatic enhancement of the high-frequency phonon transmittance but also increases the low-frequency phonon opacity. High-frequency semiextended states are formed while low-frequency modes become more localized. This results in ballistic heat conduction at finite lengths but also paradoxically higher thermal resistance that scales as ?{?m} in the L ?? limit. We identify an emergent crossover length (Lc) below which the onset of thermal transparency appears. The crossover length is linearly dependent on but is two orders of magnitude larger than ?m. Our results suggest that the phonon transmittance spectrum and heat conduction in a disordered 1D lattice can be controlled via statistical clustering of the constituent component atoms into domains. They also imply that the detection of ballistic heat conduction in disordered 1D structures may be a signature of the intrinsic mass correlation at a much smaller length scale.

Ong, Zhun-Yong; Zhang, Gang

2014-10-01

345

Coupled Conduction, Convection, Radiation Heat Transfer with Simultaneous Mass Transfer in Ice Rinks  

Microsoft Academic Search

This article presents numerical predictions of velocity, temperature, and absolute humidity distributions in an indoor ice rink with ventilation and heating. The computational fluid dynamics (CFD) simulation includes the effects of radiation between all inside surfaces of the building envelope, turbulent mixed convection, and vapor diffusion, as well as conduction through the walls and condensation on the ice. The net

O. Bellache; M. Ouzzane; N. Galanis

2005-01-01

346

A new hybrid transfinite element computational methodology for applicability to conduction\\/convection\\/radiation heat transfer  

Microsoft Academic Search

This paper describes new and recent advances in the development of a hybrid transfinite element computational methodology for applicability to conduction\\/convection\\/radiation heat transfer problems. The transfinite element methodology, while retaining the modeling versatility of contemporary finite element formulations, is based on application of transform techniques in conjunction with classical Galerkin schemes and is a hybrid approach. The purpose of this

Kumar K. Tamma; Sudhir B. Railkar

1988-01-01

347

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...

348

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

Microsoft Academic Search

In this note we compare two different mathematical hyperbolic models in dual-phase-lag heat conduction proposed by Tzou, and we ask for the parameter regions where stability can be expected. It is demonstrated that the parameter regions for the two lag-parameters ?q and ?? are different for the two models. That is, for certain parameters, in one model stability is expected

Ramón Quintanilla; Reinhard Racke

2006-01-01

349

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

E-print Network

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.

350

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

351

Optimal modified method for a fractional-diffusion inverse heat conduction problem  

Microsoft Academic Search

We consider the determination of the boundary temperature from one measured transient data temperature at some interior point of a one-dimensional semi-infinite conductor. Mathematically, it can be formulated as a fractional-diffusion inverse heat conduction problem where data are given at x = l and we want to determine a solution for 0 < x < l. This problem arises in

Zhi Qian

2010-01-01

352

Conductive heat flow variations from bottom-simulating reflectors on the Hikurangi margin, New Zealand  

Microsoft Academic Search

Bottom simulating reflectors (BSRs) represent the base of a gas hydrate zone underlain by widespread free gas. The extent of BSRs (>40,000 km2) has been mapped on the continental slope of the Hikurangi margin using industry and research seismic data. A conductive model was used to calculate heat flow from the depth of the BSR to the surface. A regional

Stuart A. Henrys; Susan Ellis; Christopher Uruski

2003-01-01

353

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

Microsoft Academic Search

(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

354

Performance evaluation of a distributed algorithm for an inverse heat conduction problem  

E-print Network

, subject to cutting, is vital in order to optimise the life time of the cutting tool and to guaranteePerformance evaluation of a distributed algorithm for an inverse heat conduction problem C for such problems becomes very important [10, 8]. One industrial problem, amongst many others, is the cutting

Lai, Choi-Hong

355

Application of the boundary element method to inverse heat conduction problems  

Microsoft Academic Search

The solution of the one-dimensional, linear, inverse, unsteady heat conduction problem (IHCP) in a slab geometry is analysed. The initial temperature is known, together with a condition on an accessible part of the boundary of the body under investigation. Additional temperature measurements in time are taken with a sensor positioned at an arbitrary location within the solid material, and it

D. Lesnic; L. Elliott; D. B. Ingham

1996-01-01

356

Electrical Conductivity Beneath the Payún Matrú Volcanic Field in the Andean Back-arc of Argentina near 36.5S: Insights into the Magma Source and Results of 3D Modeling  

NASA Astrophysics Data System (ADS)

Southern Mendoza and northern Neuquen Provinces, south of the Nazca flat slab in western Argentina, have widespread, geologically young basaltic volcanism, but no historic activity. The youngest basalts, erupted in the vicinity of the large Payún Matrú volcanic center have essentially no arc signature. Kay, et al. (2006) and Folguera, et al. (2006) argue that this back-arc igneous province is the result of extension due to trench roll-back following steepening of a flat slab that existed in the middle to late Miocene. Magnetotelluric data collected in 2005 at 18 sites along an east-west profile from 70W to 67W have been used to probe the source of the Payún Matrú basalts. These data imply significantly 3D structure. However, preliminary analysis of an arguably 2D region at the center of the profile allows tentative identification of a conductive mantle plume surfacing at Payún Matrú that rises from below 200 km depth. This suggests that Payún Matrú Volcanic Field is sampling mantle deeper than 200 km, perhaps just above the subducted Nazca slab or perhaps from the mantle transition near where the Nazca slab penetrates into it at 400 km. The 2008 fieldwork extends the earlier profile to a spatial array extending from Laguna Llancanelo north of Payún Matrú to beyond the Cortaderas Lineament that bounds the basaltic province to the south. These 19 new sites consist of 5 to 10 days of 4 Hz horizontal electric and 3-component magnetic field time- series. Data processing in the field suggests that the deep crust or upper mantle has northwest-southeast striking structure increases in conductivity to the southwest of Payún Matrú. This underlies shallow structure with north-south strike between Payún Matrú and the Colorado River. This complexity explains our initial difficulty with 2D interpretation. We will display a preliminary 3D interpretation of these new data.

Burd, A.; Booker, J.; Larsen, J.; Pomposiello, C.; Favetto, A.

2008-12-01

357

Soliton mechanism of the uranium nitride microdynamics and heat conductivity at high temperatures  

SciTech Connect

The microdynamics of soliton waves and localized modes of nonlinear acoustic and optical oscillations in uranium nitride has been investigated. It is shown that, upon heating, the energies of solitons in the gap between the optical and acoustic phonon bands increase, while the energies of local modes decrease. The experimentally observed quasi-resonance features, which are shifted in the gap with a change in temperature, can be manifestations of the revealed soliton waves and local modes. The microdynamics of uranium nitride heat conductivity with the stochastic generation of the observed solitons and local modes at remote energy absorption have been investigated. The temperature dependence of the heat conductivity coefficient has been determined from the temperature gradient and energy flux within the standard approach (which is to be generalized).

Semenov, V. A.; Dubovsky, O. A., E-mail: dubov@ippe.ru; Orlov, A. V. [State Scientific Center of the Russian Federation Leipunsky Institute for Physics and Power Engineering (Russian Federation)

2011-12-15

358

Remediation of NAPL below the water table by steam-induced heat conduction  

NASA Astrophysics Data System (ADS)

Previous experimental studies have shown that NAPL will be removed when it is contacted by steam. However, in full-scale operations, steam may not contact the NAPL directly and this is the situation addressed in this study. A two-dimensional intermediate scale sand box experiment was performed where an organic contaminant was emplaced below the water table at the interface between a coarse and a fine sand layer. Steam was injected above the water table and after an initial heating period the contaminant was recovered at the outlet. The experiment was successfully modeled using the numerical code T2VOC and the dominant removal mechanism was identified to be heat conduction induced boiling of the separate phase contaminant. Subsequent numerical modeling showed that this mechanism was insensitive to the porous medium properties and that it could be evaluated by considering only one-dimensional heat conduction.

Gudbjerg, J.; Sonnenborg, T. O.; Jensen, K. H.

2004-08-01

359

Effect of heat treatment time on microstructure and electrical conductivity in LATP glass ceramics  

SciTech Connect

Glass-ceramic is prepared by heat treatment of melt quenched 14Li{sub 2}O?9Al{sub 2}O{sub 3}?38TiO{sub 2}?39P{sub 2}O{sub 5} glass in the vicinity of crystallization temperature. Growth of ceramic phase is controlled by tuning heat treatment time at fixed temperature. Ceramic phase was identified to be LiTi{sub 2}(PO{sub 4}){sub 3} from X Ray Diffraction analysis. Microstructural evolution of this phase with hold time was observed under high resolution Scanning Electron Microscope. DC conductivity is observed to increase by 4-5 orders of magnitude in this glass-ceramic compared to parent glass. However, formation of pores and cracks with very large heat treatment time seem to hinder further increase of conductivity.

Sonigra, Dhiren, E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in; Soman, Swati, E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in; Kulkarni, Ajit R., E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in [Dept. of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai-400076 (India)

2014-04-24

360

Evaluation of heat current formulations for equilibrium molecular dynamics calculations of thermal conductivity.  

PubMed

Equilibrium molecular dynamics combined with the Green-Kubo formula can be used to calculate the thermal conductivity of materials such as germanium and carbon. The foundation of this calculation is extracting the heat current from the results and implementing it into the Green-Kubo formula. This work considers all formulations from the literature that calculate the heat current for the Tersoff potential, the interatomic potential most applicable to semiconductor materials. The formulations for the heat current are described, and results for germanium and carbon are presented. The formulations are compared with respect to how well they capture the physics of the Tersoff potential and how well the calculated value of the thermal conductivity reflects the experimentally measured value. PMID:20232951

Guajardo-Cuéllar, Alejandro; Go, David B; Sen, Mihir

2010-03-14

361

Ultrafine particle emissions from desktop 3D printers  

NASA Astrophysics Data System (ADS)

The development of low-cost desktop versions of three-dimensional (3D) printers has made these devices widely accessible for rapid prototyping and small-scale manufacturing in home and office settings. Many desktop 3D printers rely on heated thermoplastic extrusion and deposition, which is a process that has been shown to have significant aerosol emissions in industrial environments. However, we are not aware of any data on particle emissions from commercially available desktop 3D printers. Therefore, we report on measurements of size-resolved and total ultrafine particle (UFP) concentrations resulting from the operation of two types of commercially available desktop 3D printers inside a commercial office space. We also estimate size-resolved (11.5 nm-116 nm) and total UFP (<100 nm) emission rates and compare them to emission rates from other desktop devices and indoor activities known to emit fine and ultrafine particles. Estimates of emission rates of total UFPs were large, ranging from ˜2.0 × 1010 # min-1 for a 3D printer utilizing a polylactic acid (PLA) feedstock to ˜1.9 × 1011 # min-1 for the same type of 3D printer utilizing a higher temperature acrylonitrile butadiene styrene (ABS) thermoplastic feedstock. Because most of these devices are currently sold as standalone devices without any exhaust ventilation or filtration accessories, results herein suggest caution should be used when operating in inadequately ventilated or unfiltered indoor environments. Additionally, these results suggest that more controlled experiments should be conducted to more fundamentally evaluate particle emissions from a wider arrange of desktop 3D printers.

Stephens, Brent; Azimi, Parham; El Orch, Zeineb; Ramos, Tiffanie

2013-11-01

362

Mixed Thermocapillary and Forced Convection Heat Transfer Around a Hemispherical Bubble in a Miniature Channel—A 3D Numerical Study  

Microsoft Academic Search

It has been established that for certain conditions, such as microgravity boiling, thermocapillary Marangoni flow has associated with it a significant enhancement of heat transfer. Typically, this phenomenon was investigated for the idealized case of an isolated and stationary bubble resting atop a heated solid that is immersed in a semi-infinite quiescent fluid or within a two-dimensional cavity. This article

Cristina Radulescu

2012-01-01

363

A molecular dynamics study on heat conduction characteristics in DPPC lipid bilayer  

NASA Astrophysics Data System (ADS)

In this paper, nonequilibrium molecular dynamics simulations were performed on a single component 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine lipid bilayer in order to investigate the thermal conductivity and its anisotropy. To evaluate the thermal conductivity, we applied a constant heat flux to the lipid bilayer along and across the membrane with ambient water. The contribution of molecular interaction to the heat conduction was also evaluated. Along the bilayer plane, there is little transfer of thermal energy by the interaction between lipid molecules as compared with the interaction between water molecules. Across the bilayer plane, the local thermal conductivity depends on the constituents (i.e., water, head group, and tail group of lipid molecule) that occupy the domain. Although the intramolecular transfer of thermal energy in the tail groups of lipid molecules works efficiently to promote high local thermal conductivity in this region, the highest thermal resistance appears at the center of lipid bilayer where acyl chains of lipid molecules face each other due to a loss of covalent-bond and low number density. The overall thermal conductivities of the lipid bilayer in the directions parallel and perpendicular to the lipid membrane have been compared, and it was found that the thermal conductivity normal to the membrane is higher than that along the membrane, but it is still smaller than that of bulk water.

Nakano, Takeo; Kikugawa, Gota; Ohara, Taku

2010-10-01

364

Thermal conductance and basal metabolic rate are part of a coordinated system for heat transfer regulation  

PubMed Central

Thermal conductance measures the ease with which heat leaves or enters  an organism's body. Although the analysis of this physiological variable in relation to climatic and ecological factors can be traced to studies by Scholander and colleagues, only small advances have occurred ever since. Here, we analyse the relationship between minimal thermal conductance estimated during summer (Cmin) and several ecological, climatic and geographical factors for 127 rodent species, in order to identify the exogenous factors that have potentially affected the evolution of thermal conductance. In addition, we evaluate whether there is compensation between Cmin and basal metabolic rate (BMR)—in such a way that a scale-invariant ratio between both variables is equal to one—as could be expected from the Scholander–Irving model of heat transfer. Our major findings are (i) annual mean temperature is the best single predictor of mass-independent Cmin. (ii) After controlling for the effect of body mass, there is a strong positive correlation between log10 (Cmin) and log10 (BMR). Further, the slope of this correlation is close to one, indicating an almost perfect compensation between both physiological variables. (iii) Structural equation modelling indicated that Cmin values are adjusted to BMR values and not the other way around. Thus, our results strongly suggest that BMR and thermal conductance integrate a coordinated system for heat regulation in endothermic animals and that summer conductance values are adjusted (in an evolutionary sense) to track changes in BMRs. PMID:23902915

Naya, Daniel E.; Spangenberg, Lucía; Naya, Hugo; Bozinovic, Francisco

2013-01-01

365

Thermal conductivity of highly asymmetric binary mixtures: how important are heat/mass coupling effects?  

PubMed

The coupling of mass and heat fluxes is responsible for the Soret effect in fluid mixtures containing particles of dissimilar mass and/or size. We investigate using equilibrium and non-equilibrium molecular dynamics simulations the relevance of these coupling effects in determining the thermal transport in fluids consisting of binary mixtures where the individual components feature significant mass, 1?:?8, or size, 1?:?3, asymmetries. We quantify the thermal transport by using both boundary driven molecular dynamics simulations (NEMD) and the equilibrium Green-Kubo (GK) approach and investigate the impact of different heat flux definitions, relevant in kinetic theory and experiments, in the quantification of the thermal conductivity. We find that the thermal conductivities obtained from the different definitions agree within numerical accuracy, suggesting that the Soret coefficient does not lead to significant changes in the thermal conduction, even for the large asymmetries considered here, which lead to significant Soret coefficients (?10(-2) K(-1)). The asymmetry in size and mass introduces large differences in the specific enthalpy of the individual components that must be carefully considered to compute accurate thermal conductivities using the GK approach. Neglecting the enthalpic contributions, results in large overestimations of the thermal conductivity, typically between 20% and 50%. Further, we quantify the time dependent behavior of the internal energy and mass flux correlation functions and propose a microscopic mechanism for the heat transport in these asymmetric mixtures. PMID:24818599

Armstrong, Jeff; Bresme, Fernando

2014-06-28

366

Thermal conductance and basal metabolic rate are part of a coordinated system for heat transfer regulation.  

PubMed

Thermal conductance measures the ease with which heat leaves or enters an organism's body. Although the analysis of this physiological variable in relation to climatic and ecological factors can be traced to studies by Scholander and colleagues, only small advances have occurred ever since. Here, we analyse the relationship between minimal thermal conductance estimated during summer (Cmin) and several ecological, climatic and geographical factors for 127 rodent species, in order to identify the exogenous factors that have potentially affected the evolution of thermal conductance. In addition, we evaluate whether there is compensation between Cmin and basal metabolic rate (BMR)-in such a way that a scale-invariant ratio between both variables is equal to one-as could be expected from the Scholander-Irving model of heat transfer. Our major findings are (i) annual mean temperature is the best single predictor of mass-independent Cmin. (ii) After controlling for the effect of body mass, there is a strong positive correlation between log10 (Cmin) and log10 (BMR). Further, the slope of this correlation is close to one, indicating an almost perfect compensation between both physiological variables. (iii) Structural equation modelling indicated that Cmin values are adjusted to BMR values and not the other way around. Thus, our results strongly suggest that BMR and thermal conductance integrate a coordinated system for heat regulation in endothermic animals and that summer conductance values are adjusted (in an evolutionary sense) to track changes in BMRs. PMID:23902915

Naya, Daniel E; Spangenberg, Lucía; Naya, Hugo; Bozinovic, Francisco

2013-09-22

367

Determination of temperature and thermal stresses distribution in power boiler elements with use inverse heat conduction method  

NASA Astrophysics Data System (ADS)

The following paper presents the method for solving one-dimensional inverse boundary heat conduction problems. The method is used to estimate the unknown thermal boundary condition on inner surface of a thick-walled Y-branch. Solution is based on measured temperature transients at two points inside the element's wall thickness. Y-branch is installed in a fresh steam pipeline in a power plant in Poland. Determination of an unknown boundary condition allows for the calculation of transient temperature distribution in the whole element. Next, stresses caused by non-uniform transient temperature distribution and by steam pressure inside a Y-branch are calculated using the finite element method. The proposed algorithm can be used for thermal-strength state monitoring in similar elements, when it is not possible to determine a 3-D thermal boundary condition. The calculated temperature and stress transients can be used for the calculation of element durability. More accurate temperature and stress monitoring will contribute to a substantial decrease of maximal stresses that occur during transient start-up and shut-down processes.

Gr?dziel, s?awomir

2011-12-01

368

Review of the influence of nanoparticles on thermal conductivity, nucleate pool boiling and critical heat flux  

NASA Astrophysics Data System (ADS)

Nanofluids, the fluid suspensions of nonmaterials, have shown many interesting properties and the unique features offer unprecedented potential for many applications. Research on nanofluids has progressed rapidly since its enhanced thermal conductivity was first noted, about a decade ago, though much debate and inconsistency have been reported. Insufficient understanding of the formulation, mechanism of nanofluids further limits their applications [1-34]. Inconsistent data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers [35-43] have noted an enhancement in the critical heat flux during nanofluid boiling. Some researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux augmentation. In the review, the future developments of these technologies are discussed. In order to be able to put the nanofluid heat transfer technologies into practice, fundamental of these studies are greatly needed to comprehend the physical mechanisms.

Kshirsagar, Jagdeep M.; Shrivastava, Ramakant

2015-03-01

369

A Review on the Finite Element Methods for Heat Conduction in Functionally Graded Materials  

NASA Astrophysics Data System (ADS)

The review presented in this paper focuses mainly on the application of finite element methods for investigating the effect of heat transfer, variation of temperature and other parameters in the functionally graded materials. Different methods have been investigated for thermal conduction in functionally graded materials. The use of FEM for steady state heat transfer has been addressed in this work. The authors have also discussed the utilization of FEM based shear deformation theories and FEM in combination with other methods for the problems involving complexity of the shape and geometry of functionally graded materials. Finite element methods proved to be effective for the solution of heat transfer problem in functionally graded materials. These methods can be used for steady state heat transfer and as well as for transient state.

Sharma, R.; Jadon, V. K.; Singh, B.

2015-01-01

370

Experimental and Theoretical Study of Heat Conduction for Air up to 5000 K  

NASA Technical Reports Server (NTRS)

The theoretical value of the integral of thermal conductivity is compared with the experimental values from shock-tube measurements. The particular case considered is the one-dimensional nonsteady flow of heat through air at constant pressure. This approach has been previously described in NASA TR R-27. experiment was uncertain because of the large scatter in the experimental data. In this paper, an attempt is made to improve the correlation by use of a more refined calculation of the integral of thermal conductivity, and by use of improved experimental techniques and instrumentation. As a result of these changes, a much closer correlation is shown between the experimental and theoretical heat-flux potentials. This indicates that the predicted values of the coefficient of thermal conductivity for high-temperature air may be suitably accurate for many engineering needs, up to the limits of the test (4600 K).

Peng, Tzy-Cheng; Ahtye, Warren F.

1961-01-01

371

Fourier heat conduction as a phenomenon described within the scope of the second law  

NASA Astrophysics Data System (ADS)

The historical development of the Carnot cycle necessitated the construction of isothermal and adiabatic pathways within the cycle that were also mechanically "reversible" which lead eventually to the Kelvin-Clausius development of the entropy function S where for any reversible closed path C, ?C dS = 0 based on an infinite number of concatenated Carnot engines that approximated the said path and where for each engine ?Q1/T1+?Q2/T2 = 0 where the Q's and T's are the heat absorption increments and temperature respectively with the subscripts indicating the isothermal paths (1;2) where for the Carnot engine, the heat absorption is for the diathermal (isothermal) paths of the cycle only. Since 'heat' has been defined as that form of energy that is transferred as a result of a temperature difference and a corollary of the Clausius statement of the Second law is that it is impossible for heat to be transferred from a cold to a hot reservoir with no other effect on the environment, these statements suggested that the local mode of transfer of 'heat' in the isothermal segments of the pathway does imply a Fourier heat conduction mechanism (to conform to the definition of 'heat') albeit of a "reversible" kind, but on the other hand, the Fourier mechanism is apparently irreversible, leading to an increase in entropy of the combined reservoirs at either end of the material involved in the conveyance of the heat energy. These and several other considerations lead Benofy and Quay (BQ) to postulate the Fourier heat conduction phenomenon to be an ancillary principle in thermodynamics, with this principle being strictly local in nature, where the global Second law statements could not be applied to this local process. Here we present equations that model heat conduction as a thermodynamically reversible but mechanically irreversible process where due to the belief in mechanical time reversible symmetry, thermodynamical reversibility has been unfortunately linked to mechanical reversibility, that has discouraged such an association. The modeling is based on an application of a "recoverable transition", defined and developed earlier on ideas derived from thermal desorption of particles from a surface where the Fourier heat conduction process is approximated as a series of such desorption processes. We recall that the original Carnot engine required both adiabatic and isothermal steps to complete the zero entropy cycle, and this construct lead to the consequent deduction that any Second law statement that refers to heat-work conversion processes are only globally relevant. Here, on the other hand, we examine Fourier heat conduction from MD simulation and model this process as a zero-entropy forward scattering process relative to each of the atoms in the lattice chain being treated as a system where the Carnot cycle can be applied individually. The equations developed predicts the "work" done to be equal to the energy transfer rate. The MD simulations conducted shows excellent agreement with the theory. Such views and results as these, if developed to a successful conclusion could imply that the Carnot cycle be viewed as describing a local process of energy-work conversion and that irreversible local processes might be brought within the scope of this cycle, implying a unified treatment of thermodynamically (i) irreversible, (ii) reversible, (iii) isothermal and (iv) adiabatic processes.

Jesudason, Christopher G.

2014-12-01

372

3D Plasmon Ruler  

SciTech Connect

In this animation of a 3D plasmon ruler, the plasmonic assembly acts as a transducer to deliver optical information about the structural dynamics of an attached protein. (courtesy of Paul Alivisatos group)

None

2011-01-01

373

Google Maps 3D  

NSDL National Science Digital Library

Several major companies, including Google, are working on getting elaborate 3D maps online. This latest iteration of Google maps for Android-powered devices allows users to browse select cities in a 3D fashion. Utilizing aerial imagery, the buildings appear in a three-dimensional format, which can aid people navigating their way around an unfamiliar urban environment. Visitors can customize their own views with the "tilt" and "compass" mode features, which makes things a bit more fun.

2012-07-20

374

3-D Simulations  

NSDL National Science Digital Library

Three-dimensional (3-D) rendering and animation technology is not only used for entertainment, but also for research and educational purposes. The technology can be used for purposes of scientific simulation in fields such as physics, biology, or chemistry. For example, Stanford University's Folding@home project (1) uses 3-D simulations and distributed computing to study protein folding, misfolding, aggregation, and related diseases. Three-D simulations can also be used to observe phenomena that would normally be impossible to scrutinize in detail, as is demonstrated on this website on Nanorobotics (2). This next website describes work by the Robotics Research Group (3) in using 3-D simulations to enhance undergraduate and graduate engineering education. The EdCenter (4) makes available several compressed files of 3-D simulations that model earthquake data, Mars, a San Diego Fly Through, and more. On this website (5 ), Martin Baker provides "all you need to know about 3D theory" and this website (6) provides access to a free open-source software package which "makes it easy to build 3-D simulations of decentralized systems and artificial life." This last article from Cyberbotics, Ltd. (7) discusses how mobile robotics simulation programs can be used to design robots.

375

Heat Conduction Analysis in a Tissue Phantom Calculated by FDTD and HCE Method  

SciTech Connect

In order to study hyperthermia in tissue, it is important to predict accurately the heat distribution. This paper describes a preliminary study of the comparison between simulation and experiment for heat conduction in a simple tissue phantom. Since it is well known that the heat increase in tissue depends on the sound intensity and the absorption coefficient, the sound pressure distribution is calculated using a Finite Difference Time Domain (FDTD) method. The thermal diffusion profile in tissue generated by the energy of the sound pulse is also simulated using the Heat Conduction Equation (HCE) method. The calculation area is 100 x 40 [mm]. The simple tissue phantom is made of agar, water and graphite. The phantom whose attenuation coefficient is 1.1 dB/cm/MHz is placed in a temperature controlled water bath. This is kept at 37 deg. [C] while sound pulses of 1 MHz are emitted over 10 minutes. Temperatures at six points on the acoustic axis are measured in the phantom. The calculation and experiment results are compared to confirm the accuracy of the proposed method. As a result, the calculation results show the validity of the combined FDTD-HCE method for thermal conduction analysis.

Endoh, Nobuyuki; Tsuchiya, Takenobu; Saito, Yoshikazu; Ishizeki, Takahiro [Department of Electronics, Electronics and Information Engineering, Kanagawa University, High-Tech Research Center, Kanagawa University, Yokohama (Japan)

2005-03-28

376

Heat-conduction error of temperature sensors in a fluid flow with nonuniform and unsteady temperature distribution.  

PubMed

In temperature measurement of non-isothermal fluid flows by a contact-type temperature sensor, heat conduction along the sensor body can cause significant measurement error which is called "heat-conduction error." The conventional formula for estimating the heat-conduction error was derived under the condition that the fluid temperature to be measured is uniform. Thus, if we apply the conventional formula to a thermal field with temperature gradient, the heat-conduction error will be underestimated. In the present study, we have newly introduced a universal physical model of a temperature-measurement system to estimate accurately the heat-conduction error even if a temperature gradient exists in non-isothermal fluid flows. Accordingly, we have been able to successfully derive a widely applicable estimation and/or evaluation formula of the heat-conduction error. Then, we have verified experimentally the effectiveness of the proposed formula using the two non-isothermal fields-a wake flow formed behind a heated cylinder and a candle flame-whose fluid-dynamical characteristics should be quite different. As a result, it is confirmed that the proposed formula can represent accurately the experimental behaviors of the heat-conduction error which cannot be explained appropriately by the existing formula. In addition, we have analyzed theoretically the effects of the heat-conduction error on the fluctuating temperature measurement of a non-isothermal unsteady fluid flow to derive the frequency response of the temperature sensor to be used. The analysis result shows that the heat-conduction error in temperature-fluctuation measurement appears only in a low-frequency range. Therefore, if the power-spectrum distribution of temperature fluctuations to be measured is sufficiently away from the low-frequency range, the heat-conduction error has virtually no effect on the temperature-fluctuation measurements even by the temperature sensor accompanying the heat-conduction error in the mean-temperature measurements. PMID:23635222

Khine, Soe Minn; Houra, Tomoya; Tagawa, Masato

2013-04-01

377

Asymptotic expansions of solutions of the heat conduction equation in internally bounded cylindrical geometry  

USGS Publications Warehouse

The formal solutions of problems involving transient heat conduction in infinite internally bounded cylindrical solids may be obtained by the Laplace transform method. Asymptotic series representing the solutions for large values of time are given in terms of functions related to the derivatives of the reciprocal gamma function. The results are applied to the case of the internally bounded infinite cylindrical medium with, (a) the boundary held at constant temperature; (b) with constant heat flow over the boundary; and (c) with the "radiation" boundary condition. A problem in the flow of gas through a porous medium is considered in detail.

Ritchie, R.H.; Sakakura, A.Y.

1956-01-01

378

Conductivity  

NSDL National Science Digital Library

Students make a simple conductivity tester using a battery and light bulb. They learn the difference between conductors and insulators of electrical energy as they test a variety of materials for their ability to conduct electricity.

Integrated Teaching and Learning Program,

379

A 3D model for simulating the spatial and temporal distribution of temperature within ellipsoidal fruit  

Microsoft Academic Search

A physical model simulating the spatio-temporal distribution of temperature in an ellipsoidal fruit has been developed. It is based on the numerical resolution of the three-dimensional (3D) unsteady heat conduction equation with unsteady and non-homogeneous heat fluxes as boundary conditions. The numerical scheme and the physical models have been tested by comparing with an analytical solution for simple configurations. The

Marc Saudreau; Hervé Sinoquet; Olivier Santin; André Marquier; Boris Adam; Jean-Jacques Longuenesse; Lydie Guilioni; Michaël Chelle

2007-01-01

380

Coupled Ablation, Heat Conduction, Pyrolysis, Shape Change and Spallation of the Galileo Probe  

NASA Technical Reports Server (NTRS)

The Galileo probe enters the atmosphere of Jupiter in December 1995. This paper presents numerical methodology and detailed results of our final pre-impact calculations for the heat shield response. The calculations are performed using a highly modified version of a viscous shock layer code with massive radiation coupled with a surface thermochemical ablation and spallation model and with the transient in-depth thermal response of the charring and ablating heat shield. The flowfield is quasi-steady along the trajectory, but the heat shield thermal response is dynamic. Each surface node of the VSL grid is coupled with a one-dimensional thermal response calculation. The thermal solver includes heat conduction, pyrolysis, and grid movement owing to surface recession. Initial conditions for the heat shield temperature and density were obtained from the high altitude rarefied-flow calculations of Haas and Milos. Galileo probe surface temperature, shape, mass flux, and element flux are all determined as functions of time along the trajectory with spallation varied parametrically. The calculations also estimate the in-depth density and temperature profiles for the heat shield. All this information is required to determine the time-dependent vehicle mass and drag coefficient which are necessary inputs for the atmospheric reconstruction experiment on board the probe.

Milos, Frank S.; Chen, Y.-K.; Rasky, Daniel J. (Technical Monitor)

1995-01-01

381

The effect of the overall heat transfer coefficient variation on the optimal distribution of the heat transfer surface conductance or area in a Stirling engine  

Microsoft Academic Search

This study aims to assess for a Stirling engine the influence of the overall heat transfer coefficient variation on the optimum state and on the optimum distribution of the heat transfer surface conductance or area among the machine heat exchangers. The analysis is based on a Stirling machine optimization method, previously elaborated, which is now applied to a cycle with

M. Costea; M. Feidt

1998-01-01

382

Lateral conduction effects on heat-transfer data obtained with the phase-change paint technique  

NASA Technical Reports Server (NTRS)

A computerized tool, CAPE, (Conduction Analysis Program using Eigenvalues) has been developed to account for lateral heat conduction in wind tunnel models in the data reduction of the phase-change paint technique. The tool also accounts for the effects of finite thickness (thin wings) and surface curvature. A special reduction procedure using just one time of melt is also possible on leading edges. A novel iterative numerical scheme was used, with discretized spatial coordinates but analytic integration in time, to solve the inverse conduction problem involved in the data reduction. A yes-no chart is provided which tells the test engineer when various corrections are large enough so that CAPE should be used. The accuracy of the phase-change paint technique in the presence of finite thickness and lateral conduction is also investigated.

Maise, G.; Rossi, M. J.

1974-01-01

383

Oceanic heat flow and thermal conductivity of sediments with lithology and depth  

NASA Astrophysics Data System (ADS)

The present study is three fold. The first part analyzes oceanic heat flow data for "pogo" (closely-spaced) measurements, to test if for regions where convection is the dominant mode of heat transfer, the measured heat flow values are more scattered and skewed to lower values, and for areas where conduction prevails, the values are normally (Gaussian) distributed and show less scatter, like previous studies suggest. Various descriptive statistics, test of the normality of the distribution, and the evolution of the scatter are used to this end and interpreted, for sites grouped according to geographic proximity. The second part uses many more data compared to previous studies from the Ocean Drilling Program (ODP), Legs 101-128, to determine how porosity decreases with depth, to about 1 km below the seafloor, in different sedimentary environments. The goal is to determine which trend, either linear or exponential, best fits these data over this depth range. Some spatial trends of rate of porosity decrease are examined, and an attempt to predict porosity at depth is made for various tectonic settings. Finally, the third part uses data from the Ocean Drilling Program, Legs 101-129, to determine how thermal conductivity increases with depth, to about 1 km below the seafloor, in different sedimentary environments. Again, the goal is to determine which trend, either linear or exponential, best fits these data over this depth range, and how it compares to the results of the geometric mean model of thermal conductivity as a function of porosity. The depth at which thermal conductivity starts to steadily increase is examined, and an attempt is made to predict thermal conductivity at depth for various tectonic settings. Finally, some spatial trends of rate of thermal conductivity increase in terms of lithologies and tectonic settings are observed as well.

Engberts, Cynthia J.

384

MICROACTUATED SELF-ASSEMBLING OF 3D POLYSILICON STRUCTURES  

E-print Network

(b) Elastic deformationby actuator The batch fabrication of integrated three-dimensional (3D a permanent 3D shape, plastic deformation of the beam is produced. A current resulting in Joule heatingMICROACTUATED SELF-ASSEMBLING OF 3D POLYSILICON STRUCTURES WITH RESHAPING TECHNOLOGY Y. Fukuta, D

Yang, Eui-Hyeok

385

Numerical solution of transient heat conduction in a cylindrical section during quenching  

SciTech Connect

A two-dimensional numerical solution is developed for transient heat conduction in a copper test section (20 mm thick and 50.8 mm in diameter) during quenching of its downward facing curved surface (surface radius 148 mm) in saturated water. The solution used the measured temperatures in the test section near the surface ({approximately}0.5 mm) to derive the transient pool boiling curves at different locations on the surface. The study investigated the effects of lateral conduction near the surface on local heat flux and local surface temperature in the different pool boiling regimes. The solution employed a fully implicit, alternating direction, control volume method to ensure numerical stability and reduce the storage and computation time. A parametric analysis is performed to assess the effect of the computation grid size and the value of the convergence coefficient on the accuracy of calculations as well as the computation time on a 50-MHz, 486 PC.

El-Genk, M.S.; Glebov, A. [Univ. of New Mexico, Albuquerque, NM (United States)

1995-11-01

386

CTS-type variable conductance heat pipes for SEP FM/PPU  

NASA Technical Reports Server (NTRS)

The development effort for, and the fabrication and testing of, six CTS-type variable conductance heat pipes is described. The heat pipes are constructed of stainless steel, use methanol as a working fluid, and a nitrogen/helium mixture as the control gas. The wicking structure consists of interior wall grooves, a metal-felt diametral slab wick, and two wire-mesh arteries. The heat pipes are used to cool two Functional Model/Power Processing Units in a Solar Electric Propulsion prototype BIMOD thruster subsystem assembly. The Power Processing Units convert the electric power from a spacecraft solar array system to the voltages required to operate the electric thrusters which are part of the BIMOD assembly.

Antoniuk, D.; Luedke, E. E.

1978-01-01

387

Radiochromic 3D Detectors  

NASA Astrophysics Data System (ADS)

Radiochromic materials exhibit a colour change when exposed to ionising radiation. Radiochromic film has been used for clinical dosimetry for many years and increasingly so recently, as films of higher sensitivities have become available. The two principle advantages of radiochromic dosimetry include greater tissue equivalence (radiologically) and the lack of requirement for development of the colour change. In a radiochromic material, the colour change arises direct from ionising interactions affecting dye molecules, without requiring any latent chemical, optical or thermal development, with important implications for increased accuracy and convenience. It is only relatively recently however, that 3D radiochromic dosimetry has become possible. In this article we review recent developments and the current state-of-the-art of 3D radiochromic dosimetry, and the potential for a more comprehensive solution for the verification of complex radiation therapy treatments, and 3D dose measurement in general.

Oldham, Mark

2015-01-01

388

The accuracy of approximating radiative heat transfer using a temperature dependent thermal conductivity  

Microsoft Academic Search

Radiative heat transfer across the gap between two coaxial cylinders can be approximated using an equivalent thermal conductivity that is a cubic polynomial in the temperatures T(sub 1) and T(sub 2) of the two surfaces (T(sub 1) greater than T(sub 2)). It is convenient to write the polynomial in terms of the average temperature, yielding T(sub avg(exp 3)) multiplied by

J. R. Creighton

1993-01-01

389

Transient heat conduction during quenching of downward facing copper and stainless steel convex surfaces  

SciTech Connect

Quenching experiments were performed to determine the effect of wall material properties on pool boiling heat transfer for downward facing convex surfaces (radius of curvature 218.5 mm) in saturated water. Experiments employed 303e-type stainless steel and copper test sections having identical dimensions (75 mm in diameter and 20 mm thick). Pool boiling curves were constructed on the basis of two-dimensional numerical solution of transient heat conduction in spherical coordinates, (r, {theta}) in test sections during quenching. The measured temperature histories at nine interior locations near the boiling surface ({approximately}0.5 mm) provided a time-dependent boundary condition for the numerical solution. To ensure stability and reduce both computer storage and execution time, the numerical solution used the alternating direction implicit (ADI) method with control volume representations. A sensitivity analysis was conducted to assess the effect of grid size on computation time as well as the accuracy of calculated temperatures and pool boiling heat flux values. Best results were obtained using a 20 x 20 network of control volumes and a noniterative approach, whereas the computation time on a Pentium 90-MHz PC for the entire pool boiling curve was about 7% of real time. Calculated temperatures near the top surface ({approximately}5 mm) agreed with measured values to within 0.5 and 2.5 K for copper and stainless steel, respectively. The error in the overall energy balance in the test section, performed after each time interval, was less than 0.001%. The thermal diffusivity of test section material strongly affected both radial conduction within the section and lateral conduction near the boiling surface and, hence, the local pool boiling curves as well as the maximum and minimum pool boiling heat flux values.

El-Genk, M.S.; Gao, C. [Univ. of New Mexico, Albuquerque, NM (United States)

1996-05-10

390

Comparison of four different versions of the variable metric method for solving inverse heat conduction problems  

NASA Astrophysics Data System (ADS)

In this study, four different versions of the variable metric method (VMM) are investigated in solving standard one-dimensional inverse heat conduction problems in order to evaluate their efficiency and accuracy. These versions include Davidon Fletcher Powell (DFP), Broydon Fletcher Goldfarb Shanno (BFGS), Symmetric Rank-one (SR1), and Biggs formula of the VMM. These investigations are carried out using temperature data obtained from numerical simulations.

Pourshaghaghy, A.; Kowsary, F.; Behbahaninia, A.

2007-01-01

391

Three-Dimensional Conduction Heat Transfer Model for Laser Cladding Process  

Microsoft Academic Search

Cladding is the process of depositing a superior built-up layer on a substrate by fusion. In the present study a three-dimensional conduction heat transfer model is developed and solved using the finite-volume method in a nonorthogonal grid system for a blown-powder laser cladding process. Comparisons with experimental data for deposition of copper powder on SS316 stainless steel show that the

S. Kumar; S. Roy; C. P. Paul; A. K. Nath

2008-01-01

392

Shock tube determination of the heat conductivity of non-ionized and partially ionized argon  

Microsoft Academic Search

A procedure to determine the heat conductivity of a monatomic gas, from measurements of the structure of the unsteady thermal boundary layer at the end-wall of a shock tube, is proposed. In the non-ionized case the structure of the boundary layer determined by means of laser schlieren measurements appears to be self-similar. Improved analysis of the schlieren data and accurate

A. Hirschberg

1981-01-01

393

An iterative boundary element method for solving the one-dimensional backward heat conduction problem  

Microsoft Academic Search

In this paper, the iterative algorithm proposed by V.A. Kozlov and V.G. Maz'ya [Leningrad Math. J. 5 (1990) 1207–1228] is numerically implemented using the boundary element method (BEM) in order to solve the backward heat conduction problem (BHCP). The convergence and the stability of the numerical method are investigated and a stopping criterion is proposed. The numerical results obtained confirm

N. S. Mera; L. Elliott; D. B. Ingham; D. Lesnic

2001-01-01

394

A new angular discretization scheme of the finite volume method for 3-D radiative heat transfer in absorbing, emitting and anisotropically scattering media  

Microsoft Academic Search

This paper presents a new angular discretization scheme, FTn, of the finite volume method (FVM) in three-dimensional radiative heat transfer. The FTn FVM is applied to absorbing, emitting and anisotropically scattering media with variable optical thickness in a rectangular enclosure. Results show that the FTn FVM performs better than the discrete ordinate method (DOM) and the FVM with N?×N? uniform

Seung Hyun Kim; Kang Y. Huh

2000-01-01

395

3D modelling of a multi pass dissimilar tube welding and post weld heat treatment of nickel based alloy and chromium steel  

Microsoft Academic Search

A dissimilar tube welding is performed between the nickel based Alloy617 and creep resistant steel VM12 using the former as the weld material. SYSWELD welding software is used to model the thermal and mechanical analysis. A readily available thermal history is used to calibrate the heat source input for the thermal analysis to generate the adequate thermal cycle by fitting

Ram Kumar-Krishnasamy; Dieter Siegele

2010-01-01

396

Mixed Convection with Conduction and Surface Radiation from a Vertical Channel with Discrete Heating  

NASA Astrophysics Data System (ADS)

A numerical investigation into fluid flow and heat transfer for the geometry of a vertical parallel plate channel subjected to conjugate mixed convection with radiation is attempted here. The channel considered has three identical flush-mounted discrete heat sources in its left wall, while the right wall that does not contain any heat source acts as a sink. Air, assumed to be a radiatively non-participating and having constant thermophysical properties subject to the Boussinesq approximation, is the cooling agent. The heat generated in the left wall gets conducted along it and is later dissipated by mixed convection and radiation. The governing equations, considered in their full strength sans the boundary layer approximations, are converted into vorticity-stream function form and are then normalized. These equations along with pertinent boundary conditions are solved through finite volume method coupled with Gauss-Seidel iterative technique. The effects of modified Richardson number, surface emissivity, thermal conductivity and aspect ratio on local temperature distribution along the channel, maximum channel temperature and relative contributions of mixed convection and radiation have been thoroughly studied. The prominence of radiation in the present problem has been highlighted.

Londhe, S. D.; Rao, C. G.

2013-10-01

397

Tree-shaped fluid flow and heat storage in a conducting solid  

NASA Astrophysics Data System (ADS)

This paper documents the time-dependent thermal interaction between a fluid stream configured as a plane tree of varying complexity embedded in a conducting solid with finite volume and insulated boundaries. The time scales of the convection-conduction phenomenon are identified. Two-dimensional and three-dimensional configurations are simulated numerically. The number of length scales of the tree architecture varies from one to four. The results show that the heat transfer density increases, and the time of approach to equilibrium decreases as the complexity of the tree designs increases. These results are then formulated in the classical notation of energy storage by sensible heating, which shows that the effective number of heat transfer units increases as the complexity of the tree design increases. The complexity of heat transfer designs in many applications is constrained by first cost and operating cost considerations. This work provides a fundamental basis for objective evaluation of cost and performance tradeoffs in thermal design of energy systems with complexity as an unconstrained parameter that can be actively varied over a broad range to determine the optimum system design.

Combelles, L.; Lorente, S.; Anderson, R.; Bejan, A.

2012-01-01

398

Tree-Shaped Fluid Flow and Heat Storage in a Conducting Solid  

SciTech Connect

This paper documents the time-dependent thermal interaction between a fluid stream configured as a plane tree of varying complexity embedded in a conducting solid with finite volume and insulated boundaries. The time scales of the convection-conduction phenomenon are identified. Two-dimensional and three-dimensional configurations are simulated numerically. The number of length scales of the tree architecture varies from one to four. The results show that the heat transfer density increases, and the time of approach to equilibrium decreases as the complexity of the tree designs increases. These results are then formulated in the classical notation of energy storage by sensible heating, which shows that the effective number of heat transfer units increases as the complexity of the tree design increases. The complexity of heat transfer designs in many applications is constrained by first cost and operating cost considerations. This work provides a fundamental basis for objective evaluation of cost and performance tradeoffs in thermal design of energy systems with complexity as an unconstrained parameter that can be actively varied over a broad range to determine the optimum system design.

Combelles, L.; Lorente, S.; Anderson, R.; Bejan, A.

2012-01-01

399

The effect of heat conduction on the realization of the primary standard for sound pressure  

NASA Astrophysics Data System (ADS)

Pressure reciprocity calibration of microphones provides the basis for primary measurement standards for sound pressure in air. At low frequencies, reciprocity calibration requires that a heat conduction correction be employed to account for energy transfer to and from the bounding surfaces of the close-coupled microphone arrangement. The standard governing reciprocity calibration, IEC 61094-2?:?2009, provides two models for the heat conduction correction: the Low Frequency Solution, and the Broadband Solution. Analysis has revealed significant and unexplained differences in behaviour between the models at very low frequencies, leading to inconsistency in calibration results, which has been quantified. Additionally, both heat conduction solutions given in IEC 61094-2 are simplifications that strictly apply only above their respective lower limiting frequencies. An international comparison on microphone calibration is currently underway that includes measurements below the lower limiting frequencies of the models. In this paper, the origin and nature of the Broadband simplifications have been identified, and estimates of the error given. A flaw in the Broadband theory is identified and its effect quantified. Simplification error for the Low Frequency solution is evaluated, and the full spectrum solution is given. This paper urges caution in the application of the models at low frequency and provides data useful for assessing the contribution to the measurement uncertainty.

Jackett, Richard J.

2014-10-01

400

A direct approach to finding unknown boundary conditions in steady heat conduction  

NASA Technical Reports Server (NTRS)

The capability of the boundary element method (BEM) in determining thermal boundary conditions on surfaces of a conducting solid where such quantities are unknown was demonstrated. The method uses a non-iterative direct approach in solving what is usually called the inverse heat conduction problem (IHCP). Given any over-specified thermal boundary conditions such as a combination of temperature and heat flux on a surface where such data is readily available, the algorithm computes the temperature field within the object and any unknown thermal boundary conditions on surfaces where thermal boundary values are unavailable. A two-dimensional, steady-state BEM program was developed and was tested on several simple geometries where the analytic solution was known. Results obtained with the BEM were in excellent agreement with the analytic values. The algorithm is highly flexible in treating complex geometries, mixed thermal boundary conditions, and temperature-dependent material properties and is presently being extended to three-dimensional and unsteady heat conduction problems. The accuracy and reliability of this technique was very good but tended to deteriorate when the known surface conditions were only slightly over-specified and far from the inaccessible surface.

Martin, Thomas J.; Dulikravich, George S.

1993-01-01

401

Conditions for Aeronomic Applicability of the Classical Electron Heat Conduction Formula  

NASA Technical Reports Server (NTRS)

Conditions for the applicability of the classical formula for heat conduction in the electrons in ionized gas are investigated. In a fully ionised gas ( V(sub en) much greater than V(sub ei)), when the mean free path for electron-electron (or electron-ion) collisions is much larger than the characteristic thermal scale length of the observed system, the conditions for applicability break down. In the case of the Venus ionosphere this breakdown is indicated for a large fraction of the electron temperature data from altitudes greater than 180 km, for electron densities less than 10(exp 4)/cc cm. In a partially ionised gas such that V(sub en) much greater than V(sub ei) there is breakdown of the formula not only when the mean free path of electrons greatly exceeds the thermal scale length, but also when the gradient of neutral particle density exceeds the electron thermal gradient. It is shown that electron heat conduction may be neglected in estimating the temperature of joule heated electrons by observed strong 100 Hz electric fields when the conduction flux is limited by the saturation flux. The results of this paper support our earlier aeronomical arguments against the hypothesis of planetary scale whistlers for the 100 Hz electric field signal. In turn this means that data from the 100 Hz signal may not be used to support the case for lightning on Venus.

Cole, K. D.; Hoegy, W. R.

1998-01-01

402

First 3D Printout  

Microsoft Academic Search

\\u000a I didn’t want to keep you waiting for too long, so in this chapter you’ll print your first 3D model using the Shapeways Creator\\u000a and Co-Creator. “What? I thought this book was about using SketchUp to develop models for 3D printing!” Well, you aren’t done\\u000a with SketchUp yet. You’ll be learning how to develop custom models using SketchUp starting in

Sandeep Singh

403

A Reduced-Boundary-Function Method for Convective Heat Transfer With Axial Heat Conduction and Viscous Dissipation  

SciTech Connect

We introduce a new method of solution for the convective heat transfer under forced laminar flow that is confined by two parallel plates with a distance of 2a or by a circular tube with a radius of a. The advection-conduction equation is first mapped onto the boundary. The original problem of solving the unknown field T(x,r,t) is reduced to seek the solutions of T at the boundary (r = a or r = 0, r is the distance from the centerline shown in Fig. 1), i.e., the boundary functions T{sub a}(x,t) {triple_bond} T(x,r=a,t) and/or T{sub 0}(x,t) {triple_bond} T(x,r=0,t). In this manner, the original problem is significantly simplified by reducing the problem dimensionality from 3 to 2. The unknown field T(x,r,t) can be eventually solved in terms of these boundary functions. The method is applied to the convective heat transfer with uniform wall temperature boundary condition and with heat exchange between flowing fluids and its surroundings that is relevant to the geothermal applications. Analytical solutions are presented and validated for the steady-state problem using the proposed method.

Zhijie Xu

2012-07-01

404

A Reduced-Boundary-Function Method for Convective Heat Transfer with Axial Heat Conduction and Viscous Dissipation  

SciTech Connect

We introduce a method of solution for the convective heat transfer under forced laminar flow that is confined by two parallel plates with a distance of 2a or by a circular tube with a radius of a. The advection-conduction equation is first mapped onto the boundary. The original problem of solving the unknown field is reduced to seek the solutions of T at the boundary (r=a or r=0, r is the distance from the centerline shown in Fig. 1), i.e. the boundary functions and/or . In this manner, the original problem is significantly simplified by reducing the problem dimensionality from 3 to 2. The unknown field can be eventually solved in terms of these boundary functions. The method is applied to the convective heat transfer with uniform wall temperature boundary condition and with heat exchange between flowing fluids and its surroundings that is relevant to the geothermal applications. Analytical solutions are presented and validated for the steady state problem using the proposed method.

Xu, Zhijie

2012-07-01

405

Measurement of thermal conductivity, thermal diffusivity and heat capacity of highly porous building materials using transient plane source technique  

Microsoft Academic Search

This paper presents both experimental and theoretical works concerning evaluation of the thermal conductivity, thermal diffusivity and heat capacity of wood composites. Moreover, the aim of this study is to show that the transient plane source technique originally used for measuring thermal properties of isotropic materials can be spread worthy of heat capacity, thermal conductivity and thermal diffusivity measurements of

M. B. Diop

2001-01-01

406

Transient heat conduction in homogeneous and non-homogeneous materials by the Laplace transform Galerkin boundary element method  

Microsoft Academic Search

The Green's function for three-dimensional transient heat conduction (diffusion equation) for functionally graded materials (FGMs) is derived. The thermal conductivity and heat capacitance both vary exponentially in one coordinate. In the process of solving this diffusion problem numerically, a Laplace transform (LT) approach is used to eliminate the dependence on time. The fundamental solution in Laplace space is derived and

Alok Sutradhar; Glaucio H. Paulino; L. J. Gray

2002-01-01

407

Heat, chloride, and specific conductance as ground water tracers near streams  

USGS Publications Warehouse

Commonly measured water quality parameters were compared to heat as tracers of stream water exchange with ground water. Temperature, specific conductance, and chloride were sampled at various frequencies in the stream and adjacent wells over a 2-year period. Strong seasonal variations in stream water were observed for temperature and specific conductance. In observation wells where the temperature response correlated to stream water, chloride and specific conductance values were similar to stream water values as well, indicating significant stream water exchange with ground water. At sites where ground water temperature fluctuations were negligible, chloride and/or specific conductance values did not correlate to stream water values, indicating that ground water was not significantly influenced by exchange with stream water. Best-fit simulation modeling was performed at two sites to derive temperature-based estimates of hydraulic conductivities of the alluvial sediments between the stream and wells. These estimates were used in solute transport simulations for a comparison of measured and simulated values for chloride and specific conductance. Simulation results showed that hydraulic conductivities vary seasonally and annually. This variability was a result of seasonal changes in temperature-dependent hydraulic conductivity and scouring or clogging of the streambed. Specific conductance fits were good, while chloride data were difficult to fit due to the infrequent (quarterly) stream water chloride measurements during the study period. Combined analyses of temperature, chloride, and specific conductance led to improved quantification of the spatial and temporal variability of stream water exchange with shallow ground water in an alluvial system. ?? 2007 National Ground Water Association.

Cox, M.H.; Su, G.W.; Constantz, J.

2007-01-01

408

Steady-state and unsteady heat transfer between a fluid and a flat plate with coupled convection, conduction and radiation  

Microsoft Academic Search

The problem of heat exchange between a flat plate and a fluid is considered. An analysis applicable to laminar and turbulent flow is presented in order to determine the distribution of surface temperature along a plate undergoing simultaneous convective heat transfer, radiative transfer with the environment, conduction in a plate and internal heat sources. Both steady and unsteady cases are

R. Karvinen

1976-01-01

409

Radiative effect on the conjugated forced convection-conduction analysis of heat transfer in a plate fin  

Microsoft Academic Search

In the present consideration of the transfer of heat by fins to a surrounding fluid by forced convection and radiation, the heat transfer coefficient along the fin is not prescribed, but solved in advance on the basis of the boundary layer convection flow. The modified local heat transfer coefficient is accordingly determined by a highly coupled interaction among fin conduction,

C.-K. Chen; J. W. Cleaver; F.-S. Lien

1985-01-01

410

The impact of bio-optical heating on the properties of the upper ocean: A sensitivity study using a 3-D circulation model for the Labrador Sea  

Microsoft Academic Search

The impact of bio-optical heating on the properties of the upper Labrador Sea water was investigated by considering changes in light attenuation in water associated with the seasonal change of chlorophyll distribution. The time- and depth-dependent attenuation coefficients were obtained from remotely sensed SeaWiFS ocean-colour data. Sea-surface temperature (SST) and mixed-layer depth (MLD) were computed from a three-dimensional ocean circulation

Yongsheng Wu; Charles C. L. Tang; Shubha Sathyendranath; Trevor Platt

2007-01-01

411

Heat conduction in disordered harmonic lattices with energy-conserving noise  

NASA Astrophysics Data System (ADS)

We study heat conduction in a harmonic crystal whose bulk dynamics is supplemented by random reversals (flips) of the velocity of each particle at a rate ?. The system is maintained in a nonequilibrium stationary state (NESS) by contacts with white-noise Langevin reservoirs at different temperatures. We show that the one-body and pair correlations in this system are the same (after an appropriate mapping of parameters) as those obtained for a model with self-consistent reservoirs. This is true both for the case of equal and random (quenched) masses. While the heat conductivity in the NESS of the ordered system is known explicitly, much less is known about the random mass case. Here we investigate the random system with velocity flips. We improve the bounds on the Green-Kubo conductivity obtained by Bernardin [J. Stat. Phys.JSTPBS0022-471510.1007/s10955-008-9620-1 133, 417 (2008)]. The conductivity of the one-dimensional system is then studied both numerically and analytically. This sheds some light on the effect of noise on the transport properties of systems with localized states caused by quenched disorder.

Dhar, Abhishek; Venkateshan, K.; Lebowitz, J. L.

2011-02-01

412

3D Shape Match  

NSDL National Science Digital Library

This interactive Flash applet provides a Concentration-type game (called pelmanism in the UK) in which students must discern the properties of three-dimensional solids and their colors in order to match them in pairs. Spheres, cones, prisms and other standard 3-D shapes are hidden face down on cards. Time and number of trials needed to solve are recorded.

Dan Bunker

2011-01-01

413

3-D Cardboard Busts.  

ERIC Educational Resources Information Center

Provides a lesson for a high school art course on three-dimensional design. Based on a portrait bust by Naum Gabo, the project involves the construction of a 3-D portrait bust using railroad board. Describes techniques that students will need to be taught before beginning. (DSK)

Payne, Debra

1998-01-01

414

NaK Variable Conductance Heat Pipe for Radioisotope Stirling Systems  

NASA Technical Reports Server (NTRS)

In a Stirling radioisotope power system, heat must continually be removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides most of this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending use of that convertor for the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) was designed to allow multiple stops and restarts of the Stirling convertor. In the design of the VCHP for the Advanced Stirling Radioisotope Generator, the VCHP reservoir temperature can vary between 40 and 120 C. While sodium, potassium, or cesium could be used as the working fluid, their melting temperatures are above the minimum reservoir temperature, allowing working fluid to freeze in the reservoir. In contrast, the melting point of NaK is -12 C, so NaK can't freeze in the reservoir. One potential problem with NaK as a working fluid is that previous tests with NaK heat pipes have shown that NaK heat pipes can develop temperature non-uniformities in the evaporator due to NaK's binary composition. A NaK heat pipe was fabricated to measure the temperature non-uniformities in a scale model of the VCHP for the Stirling Radioisotope system. The temperature profiles in the evaporator and condenser were measured as a function of operating temperature and power. The largest delta T across the condenser was 2S C. However, the condenser delta T decreased to 16 C for the 775 C vapor temperature at the highest heat flux applied, 7.21 W/ square cm. This decrease with increasing heat flux was caused by the increased mixing of the sodium and potassium in the vapor. This temperature differential is similar to the temperature variation in this ASRG heat transfer interface without a heat pipe, so NaK can be used as the VCHP working fluid.

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

2008-01-01

415

Nonlinear Electron Heat Conduction Equation and Self similar method for 1-D Thermal Waves in Laser Heating of Solid Density DT Fuel  

E-print Network

Electron heat conduction is one of the ways that energy transports in laser heating of fusible target material. The aim of Inertial Confinement Fusion (ICF) is to show that the thermal conductivity is strongly dependent on temperature and the equation of electron heat conduction is a nonlinear equation. In this article, we solve the one-dimensional (1-D) nonlinear electron heat conduction equation with a self-similar method (SSM). This solution has been used to investigate the propagation of 1-D thermal wave from a deuterium-tritium (DT) plane source which occurs when a giant laser pulse impinges onto a DT solid target. It corresponds to the physical problem of rapid heating of a boundary layer of material in which the energy of laser pulse is released in a finite initial thickness.

A. Mohammadian Pourtalari; M. A. Jafarizadeh; M. Ghoranneviss

2011-11-23

416

Acousto-thermometric recovery of the deep temperature profile using heat conduction equations  

NASA Astrophysics Data System (ADS)

In a model experiment using the acousto-thermographic method, deep temperature profiles varying in time are recovered. In the recovery algorithm, we used a priori information in the form of a requirement that the calculated temperature must satisfy the heat conduction equation. The problem is reduced to determining two parameters: the initial temperature and the temperature conductivity coefficient of the object under consideration (the plasticine band). During the experiment, there was independent inspection using electronic thermometers mounted inside the plasticine. The error in the temperature conductivity coefficient was about 17% and the error in initial temperature determination was less than one degree. Such recovery results allow application of this approach to solving a number of medical problems. It is experimentally proved that acoustic irregularities influence the acousto-thermometric results as well. It is shown that in the chosen scheme of experiment (which corresponds to measurements of human muscle tissue), this influence can be neglected.

Anosov, A. A.; Belyaev, R. V.; Vilkov, V. A.; Dvornikova, M. V.; Dvornikova, V. V.; Kazanskii, A. S.; Kuryatnikova, N. A.; Mansfel'd, A. D.

2012-09-01

417

Natural convection in inclined rectangular enclosures with perfectly conducting fins attached on the heated wall  

NASA Astrophysics Data System (ADS)

The natural convection heat transfer in inclined rectangular enclosures with perfectly conducting fins attached to the heated wall is numerically studied. The parameters governing this problem are the Rayleigh number (102<=Ra<=2×105), the aspect ratio of the enclosures (2.5<=A=H'/L'<=?), the dimensionless lengths of the partitions (0<=B=l'/L'<=1), the aspect ratio of micro-cavities (A<=C=h'/L'<=0.33), the inclination angle (0<=?<=60?) and the Prandtl number (Pr=0.72). The results indicate that the heat transfer through the cover is considerably affected by the presence of the fins. At low Rayleigh numbers, the heat transfer regime is dominated by conduction. When B 0.75 and C 0.33, the heat transfer through the cold wall decreases considerably. This trend is enhanced when the enclosure is inclined. Useful engineering correlations are derived for practical applications. Zusammenfassung In einer numerischen Studie wird der Wärmeübergang bei natürlicher Konvektion in geneigten, rechteckigen Behältern mit ideal leitenden Rippen an der beheizten Wand untersucht. Die das Problem beschreibenden Parameter sind: die Rayleigh-Zahl (102<=Ra<=2.105), das Seitenverhältnis des Behälters (2,5<=A =H'/L'<=?), die dimensionslose Rippenhöhe (0<=B =l'/L'<=1), das Seitenverhältnis der Teilkammern (A<=C=h'/L'<=0,33), der Neigungswinkel (0<=?<=60?) und die Prandtl-Zahl (Pr=0,72). Die Ergebnisse zeigen, daß der Wärmeübergang durch Anbringung von Rippen ganz wesentlich beeinflußt werden kann. Für B 0,75 und C 0,33 erniedrigt sich der Wärmestrom durch die Kaltwand erheblich, insbesondere bei geneigtem Behälter. Bei niedrigen Rayleigh-Zahlen erfolgt der Wärmetransport hauptsächlich durch Leitung. Für praktische Anwendungen werden leicht handhabbare Gebrauchsformeln angegeben.

Lakhal, E. K.; Hasnaoui, M.; Bilgen, E.; Vasseur, P.

418

Heat Transfer Simulation of Reactor Cavity Cooling System Experimental Facility using RELAP5-3D and Generation of View Factors using MCNP  

E-print Network

. These features make the location of the reactor more flexible. Among all the new concept designs, High Temperature Gas-cooled Reactor (HTGR) is one of the most attracting reactor designs (as shown in Figure 1). It is an inherently safe, graphite... both radiated and convected from the vessel as it flows through the inner riser pipes. The buoyancy acts as the driven force to move the air to the top of the cavity via the risers. The atmosphere is the ultimate heat sink for air-cooled RCCS...

Wu, Huali

2013-08-08

419

Radio-frequency-transparent, electrically conductive graphene nanoribbon thin films as deicing heating layers.  

PubMed

Deicing heating layers are frequently used in covers of large radio-frequency (RF) equipment, such as radar, to remove ice that could damage the structures or make them unstable. Typically, the deicers are made using a metal framework and inorganic insulator; commercial resistive heating materials are often nontransparent to RF waves. The preparation of a sub-skin-depth thin film, whose thickness is very small relative to the RF skin (or penetration) depth, is the key to minimizing the RF absorption. The skin depth of typical metals is on the order of a micrometer at the gigahertz frequency range. As a result, it is very difficult for conventional conductive materials (such as metals) to form large-area sub-skin-depth films. In this report, we disclose a new deicing heating layer composite made using graphene nanoribbons (GNRs). We demonstrate that the GNR film is thin enough to permit RF transmission. This metal-free, ultralight, robust, and scalable graphene-based RF-transparent conductive coating could significantly reduce the size and cost of deicing coatings for RF equipment covers. This is important in many aviation and marine applications. This is a demonstration of the efficacy and applicability of GNRs to afford performances unattainable by conventional materials. PMID:24328320

Volman, Vladimir; Zhu, Yu; Raji, Abdul-Rahman O; Genorio, Bostjan; Lu, Wei; Xiang, Changsheng; Kittrell, Carter; Tour, James M

2014-01-01

420

Transient Heat Conduction in a Functionally Graded Cylindrical Panel Based on the Dual Phase Lag Theory  

NASA Astrophysics Data System (ADS)

The transient heat conduction in a functionally graded cylindrical panel is investigated based on the dual phase lag (DPL) theory in this article. Except for the phase lags which are assumed to be constant, all the other material properties of the panel are assumed to change continuously along the radial direction according to a power-law formulation with different non-homogeneity indices. The heat conduction equations based on the DPL theory in the cylindrical coordinate system are written in a general form which are then used for the analyses of four different geometries: (1) a hollow cylinder of an infinite length; (2) a hollow cylinder of a finite length; (3) a cylindrical panel of an infinite length; and (4) a cylindrical panel of a finite length. Using the Laplace transform, the analytical solutions for temperature and heat flux are obtained in the Laplace domain. The solutions are then converted into the time domain by employing the fast Laplace inversion technique. The exact expressions for the radial thermal wave speed are obtained for the four different geometries. The numerical results are displayed to reveal the effect of different approximations of the DPL theory on the temperature distribution for various non-homogeneity indices. The results are verified with those reported in the literature.

Akbarzadeh, A. H.; Chen, Z. T.

2012-06-01

421

Simultaneous determination of thermal conductivity, thermal diffusivity and specific heat in sI methane hydrate  

USGS Publications Warehouse

Thermal conductivity, thermal diffusivity and specific heat of sI methane hydrate were measured as functions of temperature and pressure using a needle probe technique. The temperature dependence was measured between ?20°C and 17°C at 31.5 MPa. The pressure dependence was measured between 31.5 and 102 MPa at 14.4°C. Only weak temperature and pressure dependencies were observed. Methane hydrate thermal conductivity differs from that of water by less than 10 per cent, too little to provide a sensitive measure of hydrate content in water-saturated systems. Thermal diffusivity of methane hydrate is more than twice that of water, however, and its specific heat is about half that of water. Thus, when drilling into or through hydrate-rich sediment, heat from the borehole can raise the formation temperature more than 20 per cent faster than if the formation's pore space contains only water. Thermal properties of methane hydrate should be considered in safety and economic assessments of hydrate-bearing sediment.

Waite, W.F.; Stern, L.A.; Kirby, S.H.; Winters, W.J.; Mason, D.H.

2007-01-01

422

ORMDIN: a finite element program for two-dimensional nonlinear inverse heat conduction analysis  

SciTech Connect

The calculation of the surface temperature and surface heat flux from measured temperature transients at one or more interior points of a body is identified in the literature as the inverse heat conduction problem. Heretofore, analytical and computational methods of treating this problem have been limited to one-dimensional nonlinear or two-dimensional linear material models. This report presents, to the authors' knowledge, the first inverse solution technique applicable to the two-dimensional nonlinear model with temperature-dependent thermophysical properties. This technique, representing an extension of the one-dimensional formulation previously developed by one of the authors, utilizes a finite element heat conduction model and a generalization of Beck's one-dimensional nonlinear estimation procedure. A digital computer program ORMDIN (Oak Ridge Multi-Dimensional INverse) is developed from the formulation and applied to the cross section of a composite cylinder with temperature-dependent material properties. Results are presented to demonstrate that the inverse formulation is capable of successfully treating experimental data. An important feature of the method is that small time steps are permitted while avoiding severe oscillations or numerical instabilities due to experimental errors in measured data.

Bass, B.R.; Drake, J.B.; Ott, L.J.

1980-12-01

423

GRABER: The Duct Tape of Space and JIMO Heat Conducting Foam  

NASA Technical Reports Server (NTRS)

Crack formation in the space shuttle's heat shield during flight poses a major safety concern to everyone on board. Cracking weakens the structure of the shield and lessens the protection it offers against the high temperatures and forces encountered during re-entry. Astronauts need a way to mend these cracks while in space. This is GRABER s function; it can be spackled into the cracks by an astronaut. The material then hardens, or cures, due to being in a vacuum and the heat encountered when it faces the sun. A great deal of work and testing is necessary to create a material that will be workable in a vacuum over a wide range of temperatures, will cure without cracking, will adhere to the sides of the crack, and that can withstand the extreme temperatures of re-entry. A Brookfield PVS Rheometer is being used to characterize GRABER's viscosity at various temperatures and stirring rates. Various compositions of GRABER are being heat treated in a vacuum to determine probably curing times in space. The microstructures of cured samples of each composition are being examined using both optical and electron microscopy. Jupiter s Icy Moon Orbiter (JIMO) will be lifting off sometime around 2013. JIMO will have more power than its predecessor, Galileo, allowing it to change orbits to circle three of Jupiter s moons. Both of the engine types being considered require large heat dissipation systems. These systems will be comprised of heat conductive tubing and plates with a liquid flowing through them. In order to maximize the speed of heat transfer between the tubes and the panels, the in-between areas will be filled with heat conductive silicon carbide foam. Two different foam systems are being considered for this foam. Currently, experimentation is underway with adding Sic, carbon, and carbon fibers to a two part fuel retardant foam. The foam is them pyrolized and its mass and dimensional changes are measured. The structure of the foam will be examined using optical and electron microscopy as well. Work is also planned with a foam system developed by an Italian team.

Gamble, Eleanor A.

2004-01-01

424

Cooling performance of a nanofluid flow in a heat sink microchannel with axial conduction effect  

NASA Astrophysics Data System (ADS)

In this work, the forced convection of a nanofluid flow in a microscale duct has been investigated numerically. The governing equations have been solved utilizing the finite volume method. Two different conjugated domains for both flow field and substrate have been considered in order to solve the hydrodynamic and thermal fields. The results of the present study are compared to those of analytical and experimental ones, and a good agreement has been observed. The effects of Reynolds number, thermal conductivity and thickness of substrate on the thermal and hydrodynamic indexes have been studied. In general, considering the wall affected the thermal parameter while it had no impact on the hydrodynamics behavior. The results show that the effect of nanoparticle volume fraction on the increasing of normalized local heat transfer coefficient is more efficient in thick walls. For higher Reynolds number, the effect of nanoparticle inclusion on axial distribution of heat flux at solid-fluid interface declines. Also, less end losses and further uniformity of axial heat flux lead to an increase in the local normalized heat transfer coefficient.

Izadi, M.; Shahmardan, M. M.; Norouzi, M.; Rashidi, A. M.; Behzadmehr, A.

2014-09-01

425

Cooling performance of a nanofluid flow in a heat sink microchannel with axial conduction effect  

NASA Astrophysics Data System (ADS)

In this work, the forced convection of a nanofluid flow in a microscale duct has been investigated numerically. The governing equations have been solved utilizing the finite volume method. Two different conjugated domains for both flow field and substrate have been considered in order to solve the hydrodynamic and thermal fields. The results of the present study are compared to those of analytical and experimental ones, and a good agreement has been observed. The effects of Reynolds number, thermal conductivity and thickness of substrate on the thermal and hydrodynamic indexes have been studied. In general, considering the wall affected the thermal parameter while it had no impact on the hydrodynamics behavior. The results show that the effect of nanoparticle volume fraction on the increasing of normalized local heat transfer coefficient is more efficient in thick walls. For higher Reynolds number, the effect of nanoparticle inclusion on axial distribution of heat flux at solid-fluid interface declines. Also, less end losses and further uniformity of axial heat flux lead to an increase in the local normalized heat transfer coefficient.

Izadi, M.; Shahmardan, M. M.; Norouzi, M.; Rashidi, A. M.; Behzadmehr, A.

2014-12-01

426

Thermally conductive cementitious grouts for geothermal heat pumps. Progress report FY 1998  

SciTech Connect

Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98. The developed thermally conductive grout consists of cement, water, a particular grade of silica sand, superplasticizer and a small amount of bentonite. While the primary function of the grout is to facilitate heat transfer between the U-loop and surrounding formation, it is also essential that the grout act as an effective borehole sealant. Two types of permeability (hydraulic conductivity) tests was conducted to evaluate the sealing performance of the cement-sand grout. Additional properties of the proposed grout that were investigated include bleeding, shrinkage, bond strength, freeze-thaw durability, compressive, flexural and tensile strengths, elastic modulus, Poisson`s ratio and ultrasonic pulse velocity.

Allan, M.L.; Philippacopoulos, A.J.

1998-11-01

427

Interactives: 3D Shapes  

NSDL National Science Digital Library

How much liquid can that glass hold? What are the dimensions of that package that's heading off to a friend overseas? Answers to both of those questions (and many more) can be found in this lovely interactive feature on 3D shapes created by experts at the Annenberg Media group. Visitors to this site will learn about three-dimensional geometric shapes by examining a number of objects through a number of interactive exercises and games. The materials are divided into four sections, which include "3D Shapes", "Surface Area & Volume", and "Platonic Solids". The "Platonic Solids" area is quite a bit of fun, as visitors will get the opportunity to print out foldable shapes such as a tetrahedron. A short fifteen question quiz that tests the materials covered by these various activities rounds out the site.

428

Smithsonian X 3D  

NSDL National Science Digital Library

Would you like to explore a wooly mammoth skeleton in great detail? How about some ceremonial masks created by Pacific Northwest Native Americans? The Smithsonian X 3D project makes all of this possible for visitors from all over the world. This site was created by the Smithsonian's Digitization Program Office and currently visitors can examine twelve digitized models, including a fossilized dolphin skull and the gun of noted explorer, David Livingston. The Video Gallery is a great addition as it contains short films that discuss the project's conservation work, along with a great film titled "What is 3D digitization?" Moving on, the Educators area contains a wonderful set of classroom resources that can be used in conjunction with some of the objects. Finally, the Tours area contains dozens of short films demonstrating these objects, including Seeing Around the Remnant of a Supernova, and Carving and Painting the Cosmic Buddha.

429

The gravitational heat conduction and the hierarchical structure in solar interior  

NASA Astrophysics Data System (ADS)

With the assumption of local Tsallis equilibrium, the newly defined gravitational temperature is calculated in the solar interior, whose distribution curve can be divided into three parts: the solar core region, the radiation region and the convection region, in excellent agreement with the solar hierarchical structure. By generalizing Fourier's law, one new mechanism of heat conduction, based on the gradient of the gravitational temperature, is introduced into the astrophysical system. This mechanism is related to the self-gravity of such self-gravitating system whose characteristic scale is large enough. It perhaps plays an important role in the astrophysical system which, in the solar interior, leads to the heat accumulation at the bottom of the convection layer and then motivates the convection motion.

Yahui, Zheng; Jiulin, Du

2014-03-01

430

Wave transmission, phonon localization and heat conduction of 1D Frenkel-Kontorova chain  

E-print Network

We study the transmission coefficient of a plane wave through a 1D finite quasi-periodic system -- the Frenkel-Kontorova (FK) model -- embedding in an infinite uniform harmonic chain. By varying the mass of atoms in the infinite uniform chain, we obtain the transmission coefficients for {\\it all} eigenfrequencies. The phonon localization of the incommensurated FK chain is also studied in terms of the transmission coefficients and the Thouless exponents. Moreover, the heat conduction of Rubin-Greer-like model for FK chain at low temperature is calculated. It is found that the stationary heat flux $J(N)\\sim N^{\\alpha}$, and $\\alpha$ depends on the strength of the external potential.

Peiqing Tong; Baowen Li; Bambi Hu

1999-01-20

431

3D Flyover Movies  

NSDL National Science Digital Library

This collection of 3D flyover movies depicts geologically interesting localities in the Southwest United States. The selection includes well-known landmarks such as Meteor Crater, Monument Valley, Hopi Buttes, and others. They are available in a number of different formats and file sizes. The movies, the data files used to make them, and the software to view them are all available for free download. There is also a link to a tutorial on how to make Fledermaus scenes and movies.

Marvin Simkin

2005-01-01

432

Calc3D Pro  

NSDL National Science Digital Library

The calculator can do statistics, best fits, function plotting, integration. It handles vectors, matrices, complex numbers, quaternions, coordinates, regular polygons and intersections. For point, line, plane, sphere, circle Calc 3D calculates distances, intersections, and some additional information like volume and area. Cartesian, spherical and cylindrical coordinates can be transformed into each other. Carthesian plot, polar plot, parametric plot, best fit, fast fourier transformation, histogram, smooth, and others.

433

Nano-engineered Multiwall Carbon Nanotube-copper Composite Thermal Interface Material for Efficient Heat Conduction  

NASA Technical Reports Server (NTRS)

Efforts in integrated circuit (IC) packaging technologies have recently been focused on management of increasing heat density associated with high frequency and high density circuit designs. While current flip-chip package designs can accommodate relatively high amounts of heat density, new materials need to be developed to manage thermal effects of next-generation integrated circuits. Multiwall carbon nanotubes (MWNT) have been shown to significantly enhance thermal conduction in the axial direction and thus can be considered to be a candidate for future thermal interface materials by facilitating efficient thermal transport. This work focuses on fabrication and characterization of a robust MWNT-copper composite material as an element in IC package designs. We show that using vertically aligned MWNT arrays reduces interfacial thermal resistance by increasing conduction surface area, and furthermore, the embedded copper acts as a lateral heat spreader to efficiently disperse heat, a necessary function for packaging materials. In addition, we demonstrate reusability of the material, and the absence of residue on the contacting material, both novel features of the MWNT-copper composite that are not found in most state-of-the-art thermal interface materials. Electrochemical methods such as metal deposition and etch are discussed for the creation of the MWNT-Cu composite, detailing issues and observations with using such methods. We show that precise engineering of the composite surface affects the ability of this material to act as an efficient thermal interface material. A thermal contact resistance measurement has been designed to obtain a value of thermal contact resistance for a variety of different thermal contact materials.

Ngo, Quoc; Cruden, Brett A.; Cassell, Alan M.; Sims, Gerard; Li, Jun; Meyyappa, M.; Yang, Cary Y.

2005-01-01

434

The psychology of the 3D experience  

NASA Astrophysics Data System (ADS)

With 3D televisions expected to reach 50% home saturation as early as 2016, understanding the psychological mechanisms underlying the user response to 3D technology is critical for content providers, educators and academics. Unfortunately, research examining the effects of 3D technology has not kept pace with the technology's rapid adoption, resulting in large-scale use of a technology about which very little is actually known. Recognizing this need for new research, we conducted a series of studies measuring and comparing many of the variables and processes underlying both 2D and 3D media experiences. In our first study, we found narratives within primetime dramas had the power to shift viewer attitudes in both 2D and 3D settings. However, we found no difference in persuasive power between 2D and 3D content. We contend this lack of effect was the result of poor conversion quality and the unique demands of 3D production. In our second study, we found 3D technology significantly increased enjoyment when viewing sports content, yet offered no added enjoyment when viewing a movie trailer. The enhanced enjoyment of the sports content was shown to be the result of heightened emotional arousal and attention in the 3D condition. We believe the lack of effect found for the movie trailer may be genre-related. In our final study, we found 3D technology significantly enhanced enjoyment of two video games from different genres. The added enjoyment was found to be the result of an increased sense of presence.

Janicke, Sophie H.; Ellis, Andrew

2013-03-01

435

A Beale-Kato-Majda Criterion for Three Dimensional Compressible Viscous Heat-Conductive Flows  

NASA Astrophysics Data System (ADS)

We prove a blow-up criterion in terms of the upper bound of ( ?, ? -1, ?) for a strong solution to three dimensional compressible viscous heat-conductive flows. The main ingredient of the proof is an a priori estimate for a quantity independently introduced in Haspot (Regularity of weak solutions of the compressible isentropic Navier-Stokes equation, arXiv:1001.1581, 2010) and Sun et al. (J Math Pure Appl 95:36-47, 2011), whose divergence can be viewed as the effective viscous flux.

Sun, Yongzhong; Wang, Chao; Zhang, Zhifei

2011-08-01

436

Heat conductivity from molecular chaos hypothesis in locally confined billiard systems.  

PubMed

We study the transport properties of a large class of locally confined Hamiltonian systems, in which neighboring particles interact through hard-core elastic collisions. When these collisions become rare and the systems large, we derive a Boltzmann-like equation for the evolution of the probability densities. We solve this equation in the linear regime and compute the heat conductivity from a Green-Kubo formula. The validity of our approach is demonstrated by comparing our predictions with the results of numerical simulations performed on a new class of high-dimensional defocusing chaotic billiards. PMID:19113325

Gilbert, Thomas; Lefevere, Raphaël

2008-11-14

437

Subsurface Temperature, Moisture, Thermal Conductivity and Heat Flux, Barrow, Area A, B, C, D  

SciTech Connect

Subsurface temperature data are being collected along a transect from the center of the polygon through the trough (and to the center of the adjacent polygon for Area D). Each transect has five 1.5m vertical array thermistor probes with 16 thermistors each. This dataset also includes soil pits that have been instrumented for temperature, water content, thermal conductivity, and heat flux at the permafrost table. Area C has a shallow borehole of 2.5 meters depth is instrumented in the center of the polygon.

Cable, William; Romanovsky, Vladimir

2014-03-31

438

Subsurface Temperature, Moisture, Thermal Conductivity and Heat Flux, Barrow, Area A, B, C, D  

DOE Data Explorer

Subsurface temperature data are being collected along a transect from the center of the polygon through the trough (and to the center of the adjacent polygon for Area D). Each transect has five 1.5m vertical array thermistor probes with 16 thermistors each. This dataset also includes soil pits that have been instrumented for temperature, water content, thermal conductivity, and heat flux at the permafrost table. Area C has a shallow borehole of 2.5 meters depth is instrumented in the center of the polygon.

Cable, William; Romanovsky, Vladimir

439

Analytical evaluation of thermal conductance and heat capacities of one-dimensional material systems  

SciTech Connect

We theoretically predict some thermal properties versus temperature dependence of one dimensional (1D) material nanowire systems. A known method is used to provide an efficient and reliable analytical procedure for wide temperature range. Predicted formulas are expressed in terms of Bloch-Grüneisen functions and Debye functions. Computing results has proved that the expressions are in excellent agreement with the results reported in the literature even if it is in very low dimension limits of nanowire systems. Therefore the calculation method is a fully predictive approach to calculate thermal conductivity and heat capacities of nanowire material systems.

Saygi, Salih [Department of Physics, Gaziosmanpasa University, Tokat, 60200 Turkey (Turkey)] [Department of Physics, Gaziosmanpasa University, Tokat, 60200 Turkey (Turkey)

2014-02-15

440

Effects of friction and heat conduction on sound propagation in ducts  

NASA Technical Reports Server (NTRS)

A theoretical formulation of the propagation of sound in a viscous and heat conducting medium is presented. The problem is reduced to the determination of two scalar potentials related to pressure and entropy fluctuations respectively, and a vector potential related to vorticity fluctuations. The particular case of a two-dimensional duct of constant width is thoroughly investigated in the low, high, and very high frequency ranges. It is shown that three distinct families of modes may propagate along the duct axis, namely, pressure, entropy, and vorticity dominated modes. Perturbation methods are used to study the variations of attenuation rates, phase velocities, and mode shapes, as a function of frequency and duct width.

Huerre, P.; Karamcheti, K.

1975-01-01

441

Fully automated system for simultaneous measurement of thermal conductivity and heat capacity from 4 to 300 K  

NASA Astrophysics Data System (ADS)

A fully automated system which is capable of measuring specific heat and thermal conductivity simultaneously from liquid helium to room temperature is presented. Thermal conductivity is measured by a steady-state longitudinal heat flow technique, and specific heat by a thermal relaxation method. A numerical simulation of the one-dimensional heat flow equation is used to examine the basic operational principle. The method is tested using GE 214 fused quartz and AISI 304 stainless-steel rods, and the results compare favorably with values quoted in the literature.

Kwok, R. S.; Brown, S. E.

1990-02-01

442

Laser heating of an absorbing and conducting media applied to laser flash property measurements  

SciTech Connect

The laser flash technique is widely used for determining the thermal diffusivity of a sample. In this work, the temperature distribution throughout the sample is investigated, identifying localized, highly-heated regions near the front surface of the sample as a function of: (1) pulse duration, (2) incident beam uniformity, and (3) sample opacity. These high-temperature regions result in an increase in the uncertainty due to temperature-dependent properties, an increase in the heat loss from the sample, and an increased risk of sample damage. The temperature within a semi-transparent media is also investigated in order to establish a regime for which the media can reasonably be considered as opaque. This analysis illustrates that, for same total energy deposition, treatment of the incident energy as a continuous heat source, as opposed to an infinitesimal pulse of energy, results in a factor of 2 increase in the front surface temperature during heating. Also, for the same total energy deposition and approximate beam size, use of a Gaussian intensity distribution increases the front surface temperature during heating by more than a factor of 2 as compared to the use of a uniform temperature distribution. By analyzing the front surface temperature of an absorbing and conducting semi-transparent sample subjected to a Gaussian intensity distribution, it is concluded that the media can be treated as opaque, (i.e. the energy can be applied as a boundary condition) for {var_epsilon} = kd > 50, where k is the extinction coefficient and d is the beam diameter. For materials with a sufficiently small absorption coefficient and thermal diffusivity, a closed-form solution suitable for design use is presented for the front-surface temperature at a location coincident with the beam centerline.

Gritzo, L.A. [Sandia National Labs., Albuquerque, NM (United States); Anderson, E.E. [Texas Tech Univ., Lubbock, TX (United States). Dept. of Mechanical Engineering

1993-12-31

443

A new hybrid transfinite element computational methodology for applicability to conduction/convection/radiation heat transfer  

NASA Technical Reports Server (NTRS)

This paper describes new and recent advances in the development of a hybrid transfinite element computational methodology for applicability to conduction/convection/radiation heat transfer problems. The transfinite element methodology, while retaining the modeling versatility of contemporary finite element formulations, is based on application of transform techniques in conjunction with classical Galerkin schemes and is a hybrid approach. The purpose of this paper is to provide a viable hybrid computational methodology for applicability to general transient thermal analysis. Highlights and features of the methodology are described and developed via generalized formulations and applications to several test problems. The proposed transfinite element methodology successfully provides a viable computational approach and numerical test problems validate the proposed developments for conduction/convection/radiation thermal analysis.

Tamma, Kumar K.; Railkar, Sudhir B.

1988-01-01

444

Experimental thermal conductivity, thermal diffusivity, and specific heat values for mixtures of nitrogen, oxygen, and argon  

NASA Technical Reports Server (NTRS)

Experimental measurements of thermal conductivity and thermal diffusivity obtained with a transient hot-wire apparatus are reported for three mixtures of nitrogen, oxygen, and argon. Values of the specific heat, Cp, are calculated from these measured values and the density calculated with an equation of state. The measurements wer