These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

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

2

Radial heat flux transformer  

NASA Technical Reports Server (NTRS)

Unit moves heat radially from small diameter shell to larger diameter shell, or vice versa, with negligible temperature drop, making device useful wherever heating or cooling of concentrically arranged materials, substances, and structures is desired.

Basiulis, A.; Buzzard, R. J.

1971-01-01

3

Radial flow heat exchanger  

DOEpatents

A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.

Valenzuela, Javier (Hanover, NH)

2001-01-01

4

Radial base heat-transfer gradients in turbulent flow  

Microsoft Academic Search

An experimental analysis of radial base heat-transfer gradients was conducted to determine the application to base heatshield design for various hypersonic entry vehicles. A geometric relation is derived from previous results to determine the radial base heat-transfer distribution for a slender cone at zero angle of attack. Turbulent heat transfer is shown to vary nearly linearly across a flat base.

B. M. Bulmer

1974-01-01

5

New constraints on Earth's radial conductivity structure  

NASA Astrophysics Data System (ADS)

We present a new model of Earth's radial (1-D) conductivity structure at depths between 10 km and the core-mantle boundary. It is based on CM5, the latest version in the Comprehensive Model series that has been derived using 13 years (September 2000 to September 2013) of magnetic data collected by the three satellites Oersted, CHAMP and SAC-C and at the global network of geomagnetic observatories. CM5 describes contributions due to sources in core, lithosphere, ionosphere and magnetosphere (and corresponding induced parts) in form of spherical harmonic expansion (SHE) coefficients. Removing predictions of the core, lithospheric and ionospheric field contributions as given by CM5 from the observations, we determine time series of the dominating external and induced SHE coefficients of the magnetic potential due to the magnetospheric ring current. Scalar Q-responses are estimated from these coefficients. An iterative approach is used to correct the estimated responses for 3-D effects arising from lateral heterogeneities in the top 10 km. The corrected Q-responses are converted to C-responses; the latter are subsequently inverted for the layered 1-D mantle conductivity profile with the Newton method. The Hessian matrix of the misfit function, which is derived analytically, is used to estimate confidence limits for the conductivity of each layer. The resulting conductivity-depth profile is compared to 1-D conductivity models of Earth's mantle recovered in previous studies.

Püthe, Christoph; Kuvshinov, Alexey; Olsen, Nils; Sabaka, Terence

2014-05-01

6

Conducting the Heat  

NASA Technical Reports Server (NTRS)

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

2003-01-01

7

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

8

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

9

ORMDIN. 2-D Nonlinear Inverse Heat Conduction  

SciTech Connect

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

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

1990-05-01

10

Variable conductance heat pipe technology  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

11

Heat conduction models for the transient hot wire technique  

Microsoft Academic Search

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

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

2009-01-01

12

Heat conduction in three dimensions  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

13

A Model of Heat Conduction  

E-print Network

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

Pierre Collet; Jean-Pierre Eckmann

2008-04-18

14

Radial heat transfer from a moving plasma  

E-print Network

from a plasma stream of air produced by a gas vortex stabilized dc-plasma jet to the stagnation region of a plane surface using a constant-flow water calorimeter. These measurements were of the rate of heat trans? fer through a central circular area...-temperature gas caused to emerge from one of the ends. A dc-plasma jet is then a device having two elec- trodes -- cathode and anode -- between which an arc has been "struck" and constricted to provide a continuous flame. The cathode or negative electrode...

Johnson, James Randall

2012-06-07

15

HEAT CONDUCTION NETWORKS: DISPOSITION OF HEAT BATHS AND INVARIANT MEASURE  

E-print Network

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

Paris-Sud XI, Université de

16

Extremal structures of multiphase heat conducting composites  

E-print Network

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

Cherkaev, Andrej

17

Variable boundary II heat conduction  

NASA Technical Reports Server (NTRS)

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

Gramer, J.; Oneill, R. F.

1972-01-01

18

The heat transfer characteristics of the jacket-type radial heat pipe  

NASA Astrophysics Data System (ADS)

A simple, rapid mathematical model to calculate the non-steady-state startup process of the jacket-type radial heat pipe is presented in this paper. The model is based on the special structure and using conditions of the jacket-type radial heat pipe, the vapor temperature in heat pipe only changes over time. The startup performance of the heat pipe with variation input heat flux and the filling rate is analyzed. The results manifest that the filling rate increased will reduce the maximum operating temperature of the heat pipe and shorten the startup time of the heat pipe. With the increase of input heat flux, the operating temperature increases and the time to reach the steady state of the heat pipe is added. The total thermal resistance of heat pipe decreases with the increase of the input heat flux and filling rate. The variation of the local convective heat transfer coefficient and the maximum temperature of the water are investigated with different cooling water inlet conditions.

Jiao, Yonggang; Xia, Guodong; Wang, Dan

2013-07-01

19

Heat conduction fronts in planetary nebulae  

NASA Technical Reports Server (NTRS)

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

Soker, Noam

1994-01-01

20

Entropy and temperature gradients thermomechanics: dissipation, heat conduction  

E-print Network

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

Boyer, Edmond

21

Heat conductivity in linear mixing systems  

E-print Network

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

Baowen Li; Giulio Casati; Jiao Wang

2002-08-06

22

Light dynamics in materials with radially inhomogeneous thermal conductivity.  

PubMed

We study the properties of bright and vortex solitons in thermal media with nonuniform thermal conductivity and homogeneous refractive index, whereby the local modulation of the thermal conductivity strongly affects the entire refractive index distribution. While regions where the thermal conductivity is increased effectively expel light, self-trapping may occur in the regions with reduced thermal conductivity, even if such regions are located close to the material boundary. As a result, strongly asymmetric self-trapped beams may form inside a ring with reduced thermal conductivity and perform persistent rotary motion. Also, such rings are shown to support stable vortex solitons, which may feature strongly noncanonical shapes. PMID:24177108

Kartashov, Yaroslav V; Vysloukh, Victor A; Torner, Lluis

2013-11-01

23

Heat Transfer Derivation of differential equations for heat transfer conduction  

E-print Network

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

Veress, Alexander

24

Heat conduction controlled combustion for scramjet applications  

NASA Technical Reports Server (NTRS)

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

Ferri, A.; Agnone, A. M.

1974-01-01

25

Cryogenic regenerator including sarancarbon heat conduction matrix  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

26

ORINC. 1-D Implicit Heat Conduction Solution  

Microsoft Academic Search

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

Ott

1989-01-01

27

Radial phononic thermal conductance in thin membranes in the Casimir limit: Design guidelines for devices  

NASA Astrophysics Data System (ADS)

In a previous publication [I. J. Maasilta, AIP Advances 1, 041704 (2011)], we discussed the formalism and some computational results for phononic thermal conduction in the suspended membrane geometry for radial heat flow from a central source, which is a common geometry for some low-temperature detectors, for example. We studied the case where only diffusive surface scattering is present, the so called Casimir limit, which can be experimentally relevant at temperatures below ˜ 10 K in typical materials, and even higher for ultrathin samples. Here, we extend our studies to much thinner membranes, obtaining numerical results for geometries which are more typical in experiments. In addition, we interpret the results in terms of the small signal and differential thermal conductance, so that guidelines for designing devices, such as low-temperature bolometric detectors, are more easily obtained. Scaling with membrane dimensions is shown to differ significantly from the bulk scattering, and, in particular, thinning the membrane is shown to lead to a much stronger reduction in thermal conductance than what one would envision from the simplest bulk formulas.

Puurtinen, T. A.; Maasilta, I. J.

2014-12-01

28

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

Microsoft Academic Search

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

E. Meyer-Hofmeister; F. Meyer

2006-01-01

29

The Conduction of Heat through Cryogenic Regenerative Heat Exchangers  

NASA Astrophysics Data System (ADS)

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

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

2006-04-01

30

Leaf Hydraulic Conductance for a Tank Bromeliad: Axial and Radial Pathways for Moving and Conserving Water  

PubMed Central

Epiphytic plants in the Bromeliaceae known as tank bromeliads essentially lack stems and absorptive roots and instead take up water from reservoirs formed by their overlapping leaf bases. For such plants, leaf hydraulic conductance is plant hydraulic conductance. Their simple strap-shaped leaves and parallel venation make them suitable for modeling leaf hydraulic conductance based on vasculature and other anatomical and morphological traits. Plants of the tank bromeliad Guzmania lingulata were investigated in a lowland tropical forest in Costa Rica and a shaded glasshouse in Los Angeles, CA, USA. Stomatal conductance to water vapor and leaf anatomical variables related to hydraulic conductance were measured for both groups. Tracheid diameters and numbers of vascular bundles (veins) were used with the Hagen–Poiseuille equation to calculate axial hydraulic conductance. Measurements of leaf hydraulic conductance using the evaporative flux method were also made for glasshouse plants. Values for axial conductance and leaf hydraulic conductance were used in a model based on leaky cable theory to estimate the conductance of the radial pathway from the vein to the leaf surface and to assess the relative contributions of both axial and radial pathways. In keeping with low stomatal conductance, low stomatal density, low vein density, and narrow tracheid diameters, leaf hydraulic conductance for G. lingulata was quite low in comparison with most other angiosperms. Using the predicted axial conductance in the leaky cable model, the radial resistance across the leaf mesophyll was predicted to predominate; lower, more realistic values of axial conductance resulted in predicted radial resistances that were closer to axial resistance in their impact on total leaf resistance. Tracer dyes suggested that water uptake through the tank region of the leaf was not limiting. Both dye movement and the leaky cable model indicated that the leaf blade of G. lingulata was structurally and hydraulically well-suited to conserve water. PMID:23596446

North, Gretchen B.; Lynch, Frank H.; Maharaj, Franklin D. R.; Phillips, Carly A.; Woodside, Walter T.

2013-01-01

31

Compact pulsed laser having improved heat conductance  

NASA Technical Reports Server (NTRS)

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

Yang, L. C. (inventor)

1977-01-01

32

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

33

Single-mode heat conduction by photons.  

PubMed

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

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

2006-11-01

34

Single-mode heat conduction by photons  

NASA Astrophysics Data System (ADS)

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

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

2006-11-01

35

Heat conduction model for nanowire applications  

NASA Astrophysics Data System (ADS)

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

Tohmyoh, Hironori

2013-02-01

36

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

37

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

38

Effects of anisotropic heat conduction on solidification  

NASA Technical Reports Server (NTRS)

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

Weaver, J. A.; Viskanta, R.

1989-01-01

39

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

40

Finite-element technique applied to heat conduction in solids with temperature dependent thermal conductivity  

NASA Technical Reports Server (NTRS)

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

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

1969-01-01

41

Qualitative aspects in dualphaselag heat conduction Ram on Quintanilla 1  

E-print Network

Qualitative 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 of heat conduction based on Fourier's law predicts infinite heat propagation speed. Heat transmission

Racke, Reinhard

42

ME 6010 CONDUCTION HEAT TRANSFER 1998 Catalog Data: ME 6010. Conduction Heat Transfer. Lec. 3. Cr. 3.  

E-print Network

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

Panchagnula, Mahesh

43

Long and high conductance helium heat pipe  

NASA Astrophysics Data System (ADS)

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

Gully, Philippe

2014-11-01

44

Smoothed particle hydrodynamics: Applications to heat conduction  

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

45

SPATIAL STATISTICS MODELS FOR STOCHASTIC INVERSE PROBLEMS IN HEAT CONDUCTION  

E-print Network

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

Zabaras, Nicholas J.

46

NON FOURIER HEAT CONDUCTION IN MICROSCOPIC MODELS OF DIELECTRICS  

E-print Network

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

Adler, Joan

47

Parallelized solvers for heat conduction formulations  

NASA Technical Reports Server (NTRS)

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

Padovan, Joe; Kwang, Abel

1991-01-01

48

Heat conduction in X-ray clusters: Spitzer over 3  

E-print Network

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

Andrei Gruzinov

2002-03-04

49

Nonintegrability and the Fourier heat conduction law.  

PubMed

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

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

2014-09-01

50

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

E-print Network

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

Paris-Sud XI, Université de

51

NUMERICAL SIMULATION OF A VISCOELASTIC FLUID WITH ANISOTROPIC HEAT CONDUCTION  

E-print Network

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

Wapperom, Peter

52

October 2011 SDI FEP Issues Heat Conduction Issues (HC)  

E-print Network

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

53

Heat Conduction in Fine Scale Mixtures With Interfacial Contact Resistance  

E-print Network

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

54

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

E-print Network

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

Reinhardt, Hans-Jürgen

55

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: 121 Roberts Hall Phone: 994-6295 Lecture Periods: 12:45- 2:00, TR TEXT: Heat Conduction, M. N. Ozisik of conduction heat transfer. Important results which are useful for engineering application will also

Dyer, Bill

56

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

E-print Network

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

Li, Baowen

57

Experimental investigation of a direct driven radial compressor for domestic heat pumps  

Microsoft Academic Search

The presence of oil in domestic heat pumps is an obstacle toward higher efficiency, particularly for enhanced surface evaporators and for advanced concepts based on two-stage cycles. Very compact direct driven radial compressors supported on oil-free bearings represent a promising alternative. This paper presents the derivation of the specifications, the choice for an appropriate refrigerant fluid and the design of

J. Schiffmann; D. Favrat

2009-01-01

58

Interphase Momentum and Heat Exchange in Turbulent Dust-Laden Plasma Jet under Continuous Radial Powder Injection  

SciTech Connect

Potential possibilities of an advanced approach based on the usage of DC cascade torch providing an axially symmetric plasma jet outflow, and continuous radial injection of powder into a plasma flow are discussed. Comparison is made of the results, obtained using two models of interphase heat and momentum exchange between polydisperse alumina particles and air plasma jet, other factors being the same. The widely used model of gradientless particles' heating was applied for computing the two-phase plasma jets' temperature and velocity fields. The model is compared with corresponding model of gradient particle heating computed by using an efficient numerical method developed. Calculations were conducted under different scales of dense loading conditions to estimate the maximum productivity of plasma spray process.

Solonenko, Oleg P.; Smirnov, Audrey V. [Institute of Theoretical and Applied Mechanics, Siberian Branch of Russian Academy of Sciences, 4/1 Institutskaya street, Novosibirsk, 630090 (Russian Federation); Sorokin, Anatoly L. [Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences, 1 Lavrentieva Avenue, Novosibirsk, 630090 (Russian Federation)

2006-05-05

59

Heat Conduction in Fine Scale Mixtures With Interfacial Contact Resistance  

E-print Network

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

60

Non-conductive heat transfer associated with frozen soils  

Microsoft Academic Search

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

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

2001-01-01

61

Experimental evidence of hyperbolic heat conduction in processed meat  

Microsoft Academic Search

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

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

1995-01-01

62

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

E-print Network

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

E. Meyer-Hofmeister; F. Meyer

2005-12-21

63

Thermal Conductivity of Composites Under Di erent Heating Scenarios  

E-print Network

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

64

Extended Development of Variable Conductance Heat Pipes  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

65

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

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

2009-03-06

66

Superfluid Heat Conduction and the Cooling of Magnetized Neutron Stars  

E-print Network

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

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

2008-07-29

67

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

68

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

69

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

70

Communications technology satellite - A variable conductance heat pipe application  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

71

E × B shear pattern formation by radial propagation of heat flux waves  

SciTech Connect

A novel theory to describe the formation of E×B flow patterns by radially propagating heat flux waves is presented. A model for heat avalanche dynamics is extended to include a finite delay time between the instantaneous heat flux and the mean flux, based on an analogy between heat avalanche dynamics and traffic flow dynamics. The response time introduced here is an analogue of the drivers' response time in traffic dynamics. The microscopic foundation for the time delay is the time for mixing of the phase space density. The inclusion of the finite response time changes the model equation for avalanche dynamics from Burgers equation to a nonlinear telegraph equation. Based on the telegraph equation, the formation of heat flux jams is predicted. The growth rate and typical interval of jams are calculated. The connection of the jam interval to the typical step size of the E×B staircase is discussed.

Kosuga, Y., E-mail: kosuga@riam.kyushu-u.ac.jp [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of); IAS and RIAM, Kyushu University, Fukuoka (Japan); Diamond, P. H. [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of) [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of); CASS and CMTFO, University of California, San Diego, California 92093 (United States); Dif-Pradalier, G. [CEA, IRFM, Paul-lez-Durance Cedex (France)] [CEA, IRFM, Paul-lez-Durance Cedex (France); Gürcan, Ö. D. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau (France)] [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau (France)

2014-05-15

72

Heat conduction in carbon nanotube materials: Strong effect of intrinsic thermal conductivity of carbon nanotubes  

E-print Network

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

Zhigilei, Leonid V.

73

The conduction of heat from sliding solids  

Microsoft Academic Search

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

J. R. BARBER

1970-01-01

74

Challenges in microscale conductive and radiative heat transfer  

Microsoft Academic Search

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

C. L. Tien; G. Chen

1994-01-01

75

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

76

Hierarchical Bayesian models for inverse problems in heat conduction  

Microsoft Academic Search

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

Jingbo Wang; Nicholas Zabaras

2005-01-01

77

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

78

Heat conductivity of the DNA double helix  

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

79

INVERSE HEAT CONDUCTION PROBLEM OF SIMULTANEOUSLY ESTIMATING SPATIALLY VARYING THERMAL CONDUCTIVITY AND HEAT CAPACITY PER UNIT VOLUME  

Microsoft Academic Search

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

G. P. Flach; M. N. Özi?ik

1989-01-01

80

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

Microsoft Academic Search

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

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

2010-01-01

81

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

82

Cascade variable-conductance heat pipe (A0076)  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

83

White dwarf heating in response to radial and tangential accretion in close binaries.  

NASA Astrophysics Data System (ADS)

The comprehensive study of the long term evolution of accreting white dwarfs in close binaries by Iben (1982) has provided the first numerical estimates of compressional heating, and of the long term effect of accretion on the thermal evolution of the underlying degenerate core. In the the following years, a theoretical framework has emerged for understanding radial and tangential accretion and for interpreting the quiescent surface temperatures and luminosities of white dwarfs in dwarf novae, symbiotic variables, symbiotic novae, and supersoft sources. Far-UV HST studies of exposed accreting hot degenerates in dwarf novae during quiescence provide provide fundamental empirical tests of this framework by yielding rotation rates, chemical abundances of accreted atmospheres, the thermal response of the accreting white dwarf to heating by irradiation, compressional heating and shear mixing, and the first evidence for sustained accretion belts on the white dwarf accreter.

Sion, E. M.

84

Electrical conductivity of rocks in the heating and cooling cycle  

Microsoft Academic Search

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

Marcela Lastovicková; F. Janák

1978-01-01

85

Experimental evidence of hyperbolic heat conduction in processed meat  

SciTech Connect

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

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

1995-08-01

86

Hierarchical Bayesian Models for Inverse Problems in Heat Conduction  

E-print Network

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

Zabaras, Nicholas J.

87

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

88

A study of temperature distributions due to conduction reservoir heating  

E-print Network

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

Connaughton, Charles Richard

1969-01-01

89

Convective heat transfer from a pulsating radial jet reattachment (PRJR) nozzle  

SciTech Connect

Impinging jets of fluid have been used to cool, heat or dry surfaces in many industries including high temperature gas turbines, paper and glass manufacturing, textile drying, and electronic components. Jets may be broadly classified as either inline or radial. Inline jets typically have some type of circular or planer opening through which the fluid exits. The circular opening may be converging, well rounded, or of the same diameter as the nozzle or tube through which the fluid is delivered. Here, a numerical investigation for air exiting a Pulsating Radial Jet Reattachment (PRJR) nozzle was performed with various flow and geometric conditions. The transient ensemble averaged Navier-Stokes equation with the standard {kappa}-{epsilon} turbulence model and the standard transient turbulent energy equation were solved to predict the velocity, pressure, and temperature distributions as a function of the pulsation rate, nondimensionalized nozzle-to-plate spacing, amplitude ratio, exit angle and gap Reynolds number. Sinusoidal profile, square and triangular pulsation profiles were simulated to determine the effect on the convective heat transfer during pulsation of nozzle. Grid movement is coupled to the flow field in a manner by a grid convection. Calculated reattachment radii for various conditions correlated well with previously obtained experimental results. Calculated convective heat transfer coefficients and surface pressure profiles for various geometric and flow conditions were compared with experimental results. Convective heat transfer coefficient calculations matched the experimental values very well outside the reattachment regions and underpredicted the convective heat transfer data underneath the nozzle in the dead water region and on the reattachment radius.

Pak, J.Y.; James, D.L.; Parameswaran, S.

1999-07-01

90

Use of Spreadsheets in Solving Heat Conduction Problems in Fins  

NSDL National Science Digital Library

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

Karimi, Amir

2011-04-04

91

Weak coupling limits in a stochastic model of heat conduction  

E-print Network

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

Frank Redig; Kiamars Vafayi

2011-01-14

92

Stationary non-equilibrium properties for a heat conduction model  

E-print Network

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

Cedric Bernardin

2008-08-05

93

Heat conduction in relativistic systems: alternatives and perspectives  

E-print Network

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

C. S. Lopez-Monsalvo

2010-11-30

94

Initial and boundary value problems of hyperbolic heat conduction  

Microsoft Academic Search

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

Wolfgang Dreyer; Matthias Kunik

1999-01-01

95

Conductive heat transfer in salt gradient stabilized solar ponds  

Microsoft Academic Search

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

Thakus

1983-01-01

96

Magnonic domain wall heat conductance in ferromagnetic wires.  

PubMed

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

Yan, Peng; Bauer, Gerrit E W

2012-08-24

97

Single-photon heat conduction in electrical circuits  

E-print Network

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

P. J. Jones; J. A. M. Huhtamäki; K. Y. Tan; M. Möttönen

2011-07-14

98

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

99

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

100

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

SciTech Connect

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

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

2010-01-07

101

Peak scaling method to measure temperatures in the laser-heated diamond anvil cell and application to the thermal conductivity of MgO  

NASA Astrophysics Data System (ADS)

test and characterize a new method to measure 2-D radial temperature distributions in the laser-heated diamond anvil cell using comparisons against real and synthetic data. We show that this method (1) incorporates an inexpensive and robust design for laser-heated diamond cell temperature measurements, (2) yields precise measurements of radial temperature distributions of laser-heated samples, and (3) can be used in conjunction with numerical models to measure the pressure and temperature dependence of thermal conductivity of materials. We apply the method to determine the high-pressure, high-temperature thermal conductivity of MgO.

Rainey, E. S. G.; Kavner, A.

2014-11-01

102

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 $T T_{\\rm thr}$. 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

103

Combined conduction and radiation heat transfer in porous materials heated by intense solar radiation  

Microsoft Academic Search

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

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

1985-01-01

104

Variable Conductance Heat Pipe Performance after Extended Periods of Freezing  

NASA Astrophysics Data System (ADS)

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

Ellis, Michael C.; Anderson, William G.

2009-03-01

105

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

106

Heat conduction from a sphere to an infinite external region  

SciTech Connect

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

Amos, D.E.

1979-07-01

107

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

108

Mechanical control of heat conductivity in molecular chains.  

PubMed

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

Savin, A V; Gendelman, O V

2014-01-01

109

Heat conduction in one-dimensional aperiodic quantum Ising chains.  

PubMed

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

Li, Wenjuan; Tong, Peiqing

2011-03-01

110

Rotation effect on jet impingement heat transfer in smooth rectangular channels with four heated walls and radially outward crossflow  

SciTech Connect

The effect of channel rotation on jet impingement cooling by arrays of circular jets in two channels was studied. Jet flow direction was in the direction of rotation in one channel and opposite to the rotation direction in the other channel. The jets impinged normally on two smooth target walls. Heat transfer results are presented for these two target walls, for the jet walls containing the jet producing orifices, and for side walls connecting the target and jet walls. The flow exited the channels in a single direction, radially outward, creating a crossflow on jets at larger radii. The mean test model radius-to-jet diameter ratio was 397. The jet rotation number was varied from 0.0 to 0.0028 and the isolated effects of jet Reynolds number (5000 and 10,000), and wall-to-coolant temperature difference ratio (0.0855 and 0.129) were measured. The results for nonrotating conditions show that the Nusselt numbers for the target and jet walls in both channels are about the same and are greater than those for the side walls of both channels. However, as rotation number increases, the heat transfer coefficients for all walls in both channels decrease up to 20% below those results that correspond to nonrotating conditions. As the wall-to-coolant temperature difference ratio increases, heat transfer coefficient decreases up to 10% with other parameters held constant.

Parsons, J.A.; Han, J.C. [Texas A and M Univ., College Station, TX (United States); Lee, C.P. [GE Aircraft Engines, Cincinnati, OH (United States)

1998-01-01

111

Neutrino Heat Conduction and Inhomogeneities in the Early Universe  

NASA Technical Reports Server (NTRS)

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

Heckler, A.; Hogan, C. J.

1993-01-01

112

Application of Genetic Algorithms in Nonlinear Heat Conduction Problems  

PubMed Central

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

Khan, Waqar A.

2014-01-01

113

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

114

A mechanical model for Fourier's law of heat conduction  

E-print Network

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

David Ruelle

2011-02-27

115

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

116

Numerical experiments using hierarchical finite element method for nonlinear heat conduction in plates  

E-print Network

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

Kaneko, Hideaki

117

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

E-print Network

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

Maruyama, Shigeo

118

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

Federal Register 2010, 2011, 2012, 2013

...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

119

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

Federal Register 2010, 2011, 2012, 2013

...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

120

Tunable heat conduction through coupled Fermi-Pasta-Ulam chains  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

121

Using Markov Chain Monte Carlo Simulation for Heat Conduction Problems  

NASA Astrophysics Data System (ADS)

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

Gembarovic, Jozef

2011-10-01

122

On the Exact Solution for Axisymmetric Flow and Heat Transfer over a Nonlinear Radially Stretching Sheet  

NASA Astrophysics Data System (ADS)

We investigate the boundary-layer flow and heat transfer of a magnetohydrodynamic viscous fluid over a nonlinear radially porous stretching sheet within a porous medium. The flow is generated due to a nonlinear stretching sheet and influenced by a continuous suction/blowing of the fluid through the porous sheet. The governing momentum and thermal boundary layer equations are converted into ordinary differential equations by appropriate similarity transformations. The exact solution for the velocity and the temperature fields are derived in the form of an incomplete Gamma function. Also analytic solutions are found by the homotopy analysis method. The graphical results for velocity and temperature fields are presented and discussed. Further, the numerical values of the skin friction coefficient and the Nusselt number are calculated and discussed.

Azeem, Shahzad; Ramzan, Ali; Masood, Khan

2012-08-01

123

Water Transport in Onion (Allium cepa L.) Roots (Changes of Axial and Radial Hydraulic Conductivities during Root Development).  

PubMed Central

The hydraulic architecture of developing onion (Allium cepa L. cv Calypso) roots grown hydroponically was determined by measuring axial and radial hydraulic conductivities (equal to inverse of specific hydraulic resistances). In the roots, Casparian bands and suberin lamellae develop in the endodermis and exodermis (equal to hypodermis). Using the root pressure probe, changes of hydraulic conductivities along the developing roots were analyzed with high resolution. Axial hydraulic conductivity (Lx) was also calculated from stained cross-sections according to Poiseuille's law. Near the base and the tip of the roots, measured and calculated Lx values were similar. However, at distances between 200 and 300 mm from the apex, measured values of Lx were smaller by more than 1 order of magnitude than those calculated, probably because of remaining cross walls between xylem vessel members. During development of root xylem, Lx increased by 3 orders of magnitude. In the apical 30 mm (tip region), axial resistance limited water transport, whereas in basal parts radial resistances (low radial hydraulic conductivity, Lpr) controlled the uptake. Because of the high axial hydraulic resistance in the tip region, this zone appeared to be "hydraulically isolated" from the rest of the root. Changes of the Lpr of the roots were determined by measuring the hydraulic conductance of roots of different length and referring these data to unit surface area. At distances between 30 and 150 mm from the root tip, Lpr was fairly constant (1.4 x 10-7 m s-1 MPa-1). In more basal root zones, Lpr was considerably smaller and varied between roots. The low contribution of basal zones to the overall water uptake indicated an influence of the exodermal Casparian bands and/or suberin lamellae in the endodermis or exodermis, which develop at distances larger than 50 to 60 mm from the root tip. PMID:12231786

Melchior, W.; Steudle, E.

1993-01-01

124

Comet Grains and Implications for Heating and Radial Mixing in the Protoplanetary Disk  

NASA Astrophysics Data System (ADS)

Observations of comets and chondritic porous interplanetary dust particles (CP IDPs, grains likely shed from comets), as well as of protoplanetary disks, show that a large fraction of the submicrometer silicate grains in these objects are Mg-rich crystalline silicates. Here we review observations of the mineralogy and crystallinity of cometary grains and anhydrous CP IDPs, including new spectroscopy of the dust liberated by the Deep Impact experiment on 9P/Tempel. Some key results of these observations are that crystalline silicates are very Mg-rich, and in most disks (including the solar system's) a gradient in the silicate crystalline fraction exists. We discuss the mechanisms by which Mg-rich crystals can be produced in protoplanetary disks, including complete evaporation followed by slow recondensation or reduction of Fe in Mg-Fe silicates (possibly facilitated by C combustion to CO or CO2), combined with thermal annealing. Finally, we discuss how these processes might occur in protoplanetary disks. We conclude that there are three viable scenarios that may operate in protoplanetary disks to produce Mgrich crystalline silicates with a crystallinity gradient: (1) Steady-state conditions can maintain temperatures high enough in the inner disk (radial transport of the dust produced. (2) Transient heating events, probably shocks, may evaporate dust in the outer disk (heating events (shocks) may heat amorphous Mg-Fe silicates only to ?1200-1400 K, enough to anneal the dust without destroying it; excess Fe in the silicate must be simultaneously reduced to Fe metal. On the other hand, the presence and characteristics of volatile and refractory organics in cometary materials demonstrate that a significant fraction of the outer disk mass sustained low temperatures (~30-150 K), and so did not pass through the hottest, inner regions of the disk in the early collapse phase nor was shocked. All models are as yet too incomplete for us to favor any of them: Outward radial transport by turbulent diffusion suffers from a lack of knowledge of the cause of the turbulence, and shock models have not been developed sufficiently to say where in disks shocks can heat or vaporize dust, and for how long. All processes might be simultaneously occurring in disks. What is clear is that cometary grains and anhydrous CP IDPs contain a component of dust - crystalline Mg-rich silicates - that necessarily saw very high temperatures, either by large-scale radial excursions through the solar nebula disk, or by very energetic transient heating events in the comet-forming zone.

Wooden, D.; Desch, S.; Harker, D.; Gail, H.-P.; Keller, L.

125

A Monte Carlo solution of heat conduction and Poisson equations  

Microsoft Academic Search

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

M. Grigoriu

2000-01-01

126

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

127

Duality and exact correlations for a model of heat conduction  

E-print Network

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

C. Giardiná; J. Kurchan; F. Redig

2006-12-07

128

Aluminum variable-conductive heat pipes of the communication satellites  

Microsoft Academic Search

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

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

1999-01-01

129

Development of variable conductance heat pipe at ISAC  

Microsoft Academic Search

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

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

1984-01-01

130

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

131

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

E-print Network

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

Zeng, Lingping

132

Quantum Model of Phonon Transport and Heat Conductivity in Carbon Nanoclusters and Nanotubes  

NASA Astrophysics Data System (ADS)

Our theoretical study is based on a phonon quantum discrete model (PQDM) describing phonon dynamics and kinetics in discrete carbon molecular nets of closed and open geometries. The model starts with elastic constants that characterize three freedom's degrees of atomic vibrations. We analysed in PQDM the classical dynamical equations for all modes in zero-approximation assuming that radial rho-mode, tangential phi-mode and axial z-mode can be considered independently. Phonon band parameters, density of states and amplitudes distribution were calculated and compared for nanotubes and graphitic sheets. The second task is developing a PQDM of nonlinear phonon umklapp-processes. In framework of PQDM the heat propagation processes are investigated for carbon nanotubes and 2-3-4-polar transistor-like systems. Macroscopic quantum generalization of thermal conductivity equation (GTCE) is obtained for large carbon nanoclusters. It is shown that GTCE has essentially non-classical form. The mechanism of thermal conductivity temperature damping is discussed.

Glushko, E. Ya.; Evteev, V. N.; Moiseenko, M. V.; Slusarenko, N. A.; Zakhidov, A. A.

2003-03-01

133

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

ERIC Educational Resources Information Center

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

Bacon, Michael E.; And Others

1995-01-01

134

Development of a high capacity variable conductance heat pipe.  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

135

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

136

Large Deviations in Stochastic Heat-Conduction Processes Provide a Gradient-Flow Structure for Heat Conduction  

E-print Network

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

Mark A. Peletier; Frank Redig; Kiamars Vafayi

2014-03-19

137

A 3-D FINITE ELEMENT FORMULATION FOR THE DETERMINATION OF UNKNOWN BOUNDARY CONDITIONS IN HEAT CONDUCTION  

E-print Network

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

Dennis, Brian

138

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

E-print Network

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

Racke, Reinhard

139

An eigenvalue method for solving transient heat conduction problems  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

140

Kinematic Self-Similar Heat Conducting and Charge Solutions  

E-print Network

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

M. Sharif; Wajiha Javed

2010-12-01

141

Comparative evaluation of fuel element heat conduction models  

SciTech Connect

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

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

1986-01-01

142

Non-steady-state heat conduction in composite walls.  

PubMed

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

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

2014-05-01

143

Numerical simulation of hyperbolic heat conduction with convection boundary conditions and pulse heating effects  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

144

Micro to Nano Scale Heat Conduction in Thermoelectric Materials  

NASA Astrophysics Data System (ADS)

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

Maldovan, Martin

2011-03-01

145

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

146

Heat Conduction in Ceramic Coatings: Relationship Between Microstructure and Effective Thermal Conductivity  

NASA Technical Reports Server (NTRS)

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

Kachanov, Mark

1998-01-01

147

MHD Simulations of a Moving Subclump with Heat Conduction  

E-print Network

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

Naoki Asai; Naoya Fukuda; Ryoji Matsumoto

2004-12-15

148

A Monte Carlo solution of heat conduction and Poisson equations  

SciTech Connect

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

Grigoriu, M.

2000-02-01

149

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

150

Numerical Model for Conduction-Cooled Current Lead Heat Loads  

SciTech Connect

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

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

2011-06-10

151

Thermal conductivity and heat capacity of synthetic fuel components  

SciTech Connect

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

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

1989-09-01

152

Numerical modeling of thermal conductive heating in fractured bedrock.  

PubMed

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

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

2010-01-01

153

Transient conductive and radiative heat transfer in a rectangular region  

SciTech Connect

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

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

1999-07-01

154

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

E-print Network

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

Racke, Reinhard

155

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

E-print Network

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

Li, Baowen

156

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

E-print Network

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

Paris-Sud XI, Université de

157

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

E-print Network

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

Maruyama, Shigeo

158

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

E-print Network

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

159

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

160

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

161

Tunable single-photon heat conduction in electrical circuits  

E-print Network

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

P. J. Jones; J. A. M. Huhtamäki; M. Partanen; K. Y. Tan; M. Möttönen

2012-05-21

162

Pseudo-updated constrained solution algorithm for nonlinear heat conduction  

NASA Technical Reports Server (NTRS)

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

Tovichakchaikul, S.; Padovan, J.

1983-01-01

163

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

164

Hierarchical Parallelism in Finite Difference Analysis of Heat Conduction  

NASA Technical Reports Server (NTRS)

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

Padovan, Joseph; Krishna, Lala; Gute, Douglas

1997-01-01

165

AdS/CFT Correspondence with Heat Conduction  

E-print Network

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

James Alsup; Chad Middleton; George Siopsis

2007-06-28

166

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

167

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

E-print Network

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

Maruyama, Shigeo

168

Version Date: October 30, 2001 A Molecular Dynamics Simulation of Heat Conduction in Finite Length SWNTs  

E-print Network

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

Maruyama, Shigeo

169

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

E-print Network

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

170

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

E-print Network

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

Bárta, Tomás

171

A Direct Method for Measuring Heat Conductivity in Intracluster Medium  

E-print Network

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

Makoto Hattori; Nobuhiro Okabe

2005-02-09

172

Heating, conduction and minimum temperatures in cooling flows  

E-print Network

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

Mateusz Ruszkowski; Mitchell C. Begelman

2002-08-12

173

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

174

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

175

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

E-print Network

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

Debasish Chaudhuri; Abhishek Chaudhuri; Surajit Sengupta

2007-03-20

176

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

Federal Register 2010, 2011, 2012, 2013

...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

177

A Global Stability Analysis of Clusters of Galaxies with Conduction and AGN Feedback Heating  

E-print Network

We investigate a series of steady-state models of galaxy clusters, in which the hot intracluster gas is efficiently heated by active galactic nucleus (AGN) feedback and thermal conduction, and in which the mass accretion rates are highly reduced compared to those predicted by the standard cooling flow models. We perform a global Lagrangian stability analysis. We show for the first time that the global radial instability in cool core clusters can be suppressed by the AGN feedback mechanism, provided that the feedback efficiency exceeds a critical lower limit. Furthermore, our analysis naturally shows that the clusters can exist in two distinct forms. Globally stable clusters are expected to have either: 1) cool cores stabilized by both AGN feedback and conduction, or 2) non-cool cores stabilized primarily by conduction. Intermediate central temperatures typically lead to globally unstable solutions. This bimodality is consistent with the recently observed anticorrelation between the flatness of the temperature profiles and the AGN activity (Dunn & Fabian 2008) and the observation by Rafferty et al. (2008) that the shorter central cooling times tend to correspond to significantly younger AGN X-ray cavities.

Fulai Guo; S. Peng Oh; M. Ruszkowski

2008-08-07

178

Efficient linear and nonlinear heat conduction with a quadrilateral element  

NASA Technical Reports Server (NTRS)

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

Liu, W. K.; Belytschko, T.

1984-01-01

179

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

180

Efficient linear and nonlinear heat conduction with a quadrilateral element  

NASA Technical Reports Server (NTRS)

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

Liu, W. K.; Belytschko, T.

1983-01-01

181

ICARUS: A general one-dimensional heat conduction code  

NASA Astrophysics Data System (ADS)

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

Sutton, S. B.

1984-07-01

182

A multiple step random walk Monte Carlo method for heat conduction involving distributed heat sources  

NASA Astrophysics Data System (ADS)

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

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

1982-06-01

183

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

184

Constructal trees of circular fins for conductive and convective heat transfer  

Microsoft Academic Search

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

A. Alebrahim; A. Bejan

1999-01-01

185

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

E-print Network

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

Racke, Reinhard

186

Anomalous heat conduction and anomalous diffusion in nonlinear lattices, single walled nanotubes, and billiard gas channels  

E-print Network

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

Li, Baowen

187

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

E-print Network

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

188

A MOLECULAR DYNAMICS SIMULATION OF HEAT CONDUCTION IN A CARBON NANOTUBE  

E-print Network

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

Maruyama, Shigeo

189

A HEAT CONDUCTION STUDY AT NON-CONTINUUM SCALES A Dissertation  

E-print Network

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

Sen, Mihir

190

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

E-print Network

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

Li, Baowen

191

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

E-print Network

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

Ruelle, David

192

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

E-print Network

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

California at Santa Cruz, University of

193

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

E-print Network

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

Racke, Reinhard

194

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

E-print Network

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

California at Santa Cruz, University of

195

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

E-print Network

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

Maruyama, Shigeo

196

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

E-print Network

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

Maruyama, Shigeo

197

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

E-print Network

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

Zabaras, Nicholas J.

198

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

E-print Network

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

199

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

E-print Network

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

Racke, Reinhard

200

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

E-print Network

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

Ruelle, David

201

Variational formulation of hyperbolic heat conduction problems applying Laplace transform technique  

E-print Network

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

202

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

E-print Network

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

Maruyama, Shigeo

203

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

E-print Network

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

Maruyama, Shigeo

204

Heat conduction of single-walled carbon nanotube isotope-superlattice structures: A molecular dynamics study  

E-print Network

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

Maruyama, Shigeo

205

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

E-print Network

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

Maruyama, Shigeo

206

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

E-print Network

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

Racke, Reinhard

207

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

E-print Network

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

Maruyama, Shigeo

208

Simultaneous determination of specific heat capacity and thermal conductivity using the finite-difference method  

Microsoft Academic Search

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

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

1997-01-01

209

Development of an isothermal heat-conduction photocalorimeter  

NASA Astrophysics Data System (ADS)

Assessing photostability (particularly of pharmaceuticals) is of growing importance, but hampered by a lack of reliable, rapid experimental testing protocols and instrumentation. In particular, most approaches require irradiation of the sample separately from the analytical measurement, which increases both experimental complexity and the number of assumptions that must be made when calculating stability. One technique that may obviate this is photocalorimetry, principally because the reporter of change (heat) is measured directly as a sample is irradiated. Although not a new idea, the design challenges of photocalorimeters are complex, primarily because light power is being introduced to the calorimeter which can thus both saturate the amplifiers and swamp the response of the sample. Careful instrument design is thus paramount. The aim of this work was to develop a robust, compact, and easy to use photocalorimeter with the immediate focus of developing photostability assays for pharmaceuticals. The final instrument design, arrived at through a series of iterative design modifications, is based on a twin differential heat-conduction principle and achieves an average base line deflection of -0.04±0.11?W with light irradiating the sample cell. The performance capabilities of the instrument were demonstrated using a model system; the photodegradation of 2-nitrobenzaldehyde in solution.

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

2007-02-01

210

The conjugate conduction–natural convection heat transfer along a thin vertical plate with non-uniform internal heat generation  

Microsoft Academic Search

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

F Méndez; C Treviño

2000-01-01

211

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

SciTech Connect

This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulate a 4 K liquid helium cryostat. The method described here permits one to estimate the insulation potential for a multilayer insulation system from first principles. The heat transfer regimes included are: radiation, conduction by free molecule gas conduction, and conduction through continuum gas conduction. Heat transfer in the transition region between the two gas conduction regimes is also included.

Green, M.A.

1994-10-10

212

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

213

Theoretical and experimental study of aerodynamics, heat transfer and performance of a radial turbine  

NASA Technical Reports Server (NTRS)

A two-dimensional finite difference numerical technique is presented to determine the temperature distribution in a solid blade of a radial turbine guide vane. A computer program is written in FORTRAN 4 for the IBM 370/165 computer. The computer results obtained from these programs have a similar behavior and trend as those obtained by experimental results.

Tabakoff, W.

1975-01-01

214

UNIFORM ESTIMATES FOR TRANSMISSION PROBLEMS WITH HIGH CONTRAST IN HEAT CONDUCTION AND ELECTROMAGNETISM  

E-print Network

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

Recanati, Catherine

215

Molecular dynamics simulation of heat conduction through a molecular chain.  

PubMed

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

Schröder, Christian; Vikhrenko, Vyacheslav; Schwarzer, Dirk

2009-12-24

216

eXtremes of heat conduction: Pushing the boundaries of the thermal  

E-print Network

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

Braun, Paul

217

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

218

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

E-print Network

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

Recanati, Catherine

219

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

E-print Network

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

Heil, Matthias

220

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

E-print Network

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

221

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

E-print Network

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

Salamon, Peter

222

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

Paris-Sud XI, Université de

223

Gravitational effects on the operation of a variable conductive heat pipe  

Microsoft Academic Search

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

R. S. Owendoff

1977-01-01

224

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

E-print Network

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

California at Santa Cruz, University of

225

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

226

EXACT SOLUTION OF HEAT CONDUCTION IN A TWO-DOMAIN COMPOSITE CYLINDER WITH AN ORTHOTROPIC OUTER LAYER.  

SciTech Connect

The transient exact solution of heat conduction in a two-domain composite cylinder is developed using the separation of variables technique. The inner cylinder is isotropic and the outer cylindrical layer is orthotropic. Temperature solutions are obtained for boundary conditions of the first and second kinds at the outer surface of the orthotropic layer. These solutions are applied to heat flow calorimeters modeling assuming that there is heat generation due to nuclear reactions in the inner cylinder. Heat flow calorimeter simulations are carried out assuming that the inner cylinder is filled with plutonium oxide powder. The first objective in these simulations is to predict the onset of thermal equilibrium of the calorimeter with its environment. Two types of boundary conditions at the outer surface of the orthotropic layer are used to predict thermal equilibrium. The procedure developed to carry out these simulations can be used as a guideline for the design of calorimeters. Another important application of these solutions is on the estimation of thermophysical properties of orthotropic cylinders. The thermal conductivities in the vertical, radial and circumferential directions of the orthotropic outer layer can be estimated using this exact solution and experimental data. Simultaneous estimation of the volumetric heat capacity and thermal conductivities is also possible. Furthermore, this solution has potential applications to the solution of the inverse heat conduction problem in this cylindrical geometry. An interesting feature of the construction of this solution is that two different sets of eigenfunctions need to be considered in the eigenfunction expansion. These eigenfunctions sets depend on the relative values of the thermal diffusivity of the inner cylinder and the thermal diffusivity in the vertical direction of the outer cylindrical layer.

C. AVILES-RAMOS; C. RUDY

2000-11-01

227

Instability of the vertical annular flow with a radial heating and rotating inner cylinder  

NASA Astrophysics Data System (ADS)

A linear stability analysis of the flow confined in a differentially rotating cylindrical annulus with a radial temperature gradient has been performed. Depending on values of control parameters (the Taylor number, the Grashof number, and the Froude number), it has shown flow destabilization to axisymmetric or non-axisymmetric modes. Analysis of different terms involved in the evolution rate of the perturbation kinetic energy has allowed us to isolate the dominant terms (centrifugal force or buoyancy force) in the destabilization process. We have shown that the centrifugal buoyancy can induce the asymmetry of the temperature gradient on critical states.

Yoshikawa, H. N.; Nagata, M.; Mutabazi, I.

2013-11-01

228

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

Microsoft Academic Search

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

P. T Tsilingiris

2003-01-01

229

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

Microsoft Academic Search

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

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

230

Isotope Effects on Heat Conduction of Carbon Nanotubes Shigeo Maruyama, Yuki Taniguchi and Yasushi Shibuta  

E-print Network

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

Maruyama, Shigeo

231

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 that produces clumped shoot morphol- ogy on sun-formed branches. Boundary layer conductances estimated

Martin, Timothy

232

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

233

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

PubMed

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

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

2014-11-25

234

In-situ Laser Heating and Pressure Change With Radial Diffraction to Investigate Deformation of Deep Earth Relevant Minerals  

NASA Astrophysics Data System (ADS)

: Many deep Earth mineral phases have stability fields that are accessible only with diamond anvil cell (DAC), and currently this remains the only method for studying these mineral phases at pressures relevant to the deep Earth. So far radial diffraction DAC experiments have had two serious limitations, pressure and stress could only be applied incrementally ex-situ and deformation was limited to ambient temperature. These limitations bring into question the applicability of these experiments to deformation behavior in the deep earth where minerals are deforming at high-temperature and pressure. To address this issue we developed a novel combination of remotely controlled radial DAC with in-situ laser heating. This enables us to change pressure and thus stress on the sample while at high temperature. For remotely controlling the pressure we constructed a holding frame which can be used for different radial cell designs. The DAC is placed within the holding frame together with a gas-driven membrane. Inflating the membrane pushes the piston into the cylinder which is retained by the frame. While the membrane applies force from the bottom, the top of the assembly provides optical access for one- sided laser heating. The laser is directed from the top, vertically along the symmetry axis of the DAC onto the sample. The gas-pressure can be controlled remotely from outside the hutch, thus allowing for pressure change during heating and X-ray exposure. Using in-situ laser heating we induce recrystallization in a sample of Mg0.75Fe0.25O that had been deformed at room temperature. We observe grain growth and texture strengthening upon recrystallization. The remote pressure control is used to deform bcc Fe into the hcp Fe stability field and then back into the bcc phase on decompression. We observe development of strong textures in both the bcc phase and the hcp phase of Fe as well as texture change during decompression of the hcp phase. By combining the techniques, we convert in-situ a sample of natural San Carlos olivine (Fo90.7Fa9.3) into an assemblage of perovskite and periclase in the DAC. This sample was deformed at pressures from 30 to 50 GPa and at a temperature of 1100 ± 100 K. Both perovskite and periclase develop texture during deformation with periclase developing the stronger texture of the two. Texture in periclase is different from that obtained in room temperature compression experiments and this could be due to deformation in a two phase aggregate or deformation at high temperature. Elastic lattice strains are significantly lower in the perovskite and periclase assemblage when deformed at high temperature as compared to a room temperature experiment.

Miyagi, L.; Kunz, M.; Voltolini, M.; Wenk, H.

2007-12-01

235

Free convection heat transfer from the outside of radial fin tubes  

NASA Astrophysics Data System (ADS)

Heat transfer rates for a variety of finned tubes in water and asphalt-water emulsion were determined experimentally. From these data, free convection heat transfer coefficients on the outside of the tube were calculated as a function of the Rayleigh number. A correlation of the form Nusselt number = a constant times the Rayleigh number to second constant power was then determined by a least-squares fit of the data.

Wiebelt, J. A.; Parker, J. D.; Henderson, J. B.

1980-06-01

236

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

237

Heat flow study at the Chinese Continental Scientific Drilling site: Borehole temperature, thermal conductivity,  

E-print Network

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

Huang, Shaopeng

238

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

NASA Astrophysics Data System (ADS)

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

Fedotovsky, V.; Orlov, A.

2008-06-01

239

The role of heat conduction to the formation ofThe role of heat conduction to the formation of Planetary NebulPlanetary Nebul with H-deficient fast windswith H-deficient fast winds  

E-print Network

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

240

The Effect of Light Therapy on Superficial Radial Nerve Conduction Using a Clustered Array of Infrared Super luminous Diodes and Red Light Emitting Diodes  

PubMed Central

Introduction: Lasers, light emitting diodes (LEDs) and super luminous diodes (SLDs) are widely used to treat selected musculoskeletal, integumentary and neurological conditions.The mechanisms underlying the reported treatment effects of light therapy are unclear and the physiologic effect of light on a variety of tissues, particularly neurological, is mostly unknown. A few researchers have reported on the effects of lasers and to a lesser extent infrared LEDs on nerve conduction in superficial nerves, but there is little evidence of the effects of SLDs and red LEDs on conduction parameters of peripheral nerves. The purpose of this study was to examine the effects of a light therapy generated by cluste rprobe containing an array of infrared super luminous and red light emitting diodes on superficial radial nerve conduction. Methods: This was a single blind, randomized controlled trial conducted in an academic clinical laboratory. Thirty-two healthy participants (mean age = 25 years) were randomized to a treatment group or a placebo group. The treatment group received light irradiation through the application of a cluster probe containing 32 infrared (880nm) SLDs and 4 red (660nm) LEDs for 30 seconds at a dose of 6 J/cm2 to each of the two 5 cm2 segments of skin overlying the superficial radial nerve. The placebo group received identical set-up without the application of light irradiation. Negative peak latency (NPL) and conduction velocity (NCV) for the superficial radial nerve were measured before treatment and for 10-minutes following treatment at 2-minute intervals. Skin temperature was monitored throughout. Results: No significant differences between groups and over time for NPL, NCV, or temperature difference scores were identified. However, a significant increase in skin temperature was measured over time at each time point compared to baseline. Conclusion: Light irradiation using a cluster probe containing infrared super luminous and red light emitting diodes does not impact the neurophysiological properties of the superficial radial nerve.

Telemeco, Todd Allen; Schrank, Edward Carl

2013-01-01

241

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

NASA Astrophysics Data System (ADS)

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

Ma, Yanbao

2014-12-01

242

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

SciTech Connect

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

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

2006-05-15

243

Experimental study on subcooled flow boiling on heating surfaces with different thermal conductivities  

NASA Astrophysics Data System (ADS)

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

Zou, Ling

244

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

Microsoft Academic Search

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

S. S. Rybanin; L. N. Stesik

1974-01-01

245

Transient combined radiation and conduction heat transfer in fibrous media with temperature and flux boundary conditions  

Microsoft Academic Search

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

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

2004-01-01

246

An inverse problem in simultaneously measuring temperature-dependent thermal conductivity and heat capacity  

Microsoft Academic Search

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

Cheng-Hung Huang; Yan Jan-Yuan

1995-01-01

247

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

E-print Network

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

W. Vieser; G. Hensler

2007-04-26

248

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

E-print Network

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

Fygenson, Deborah Kuchnir

249

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

250

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

Microsoft Academic Search

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

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

2009-01-01

251

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

252

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

Microsoft Academic Search

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

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

2011-01-01

253

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

254

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

255

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

256

Investigation of Heat Conductivity in Relativistic Systems using a Partonic Cascade  

E-print Network

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

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

2013-01-07

257

A two-fluid model for relativistic heat conduction  

SciTech Connect

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

López-Monsalvo, César S. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México (Mexico)

2014-01-14

258

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

259

Low heat conduction in white dwarf boundary layers?  

E-print Network

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

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

2008-03-13

260

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

Microsoft Academic Search

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

J. Neiss; E. R. F. Winter

1976-01-01

261

RODCON: a finite difference heat conduction computer code in cylindrical coordinates  

SciTech Connect

RODCON, a finite difference computer code, was developed to calculate the internal temperature distribution of the fuel rod simulator (FRS) for the Core Flow Test Loop (CFTL). RODCON solves the implicit, time-dependent forward-differencing heat transfer equation in 2-dimensional (Rtheta) cylindrical coordinates at an axial plane with user specified radial material zones and surface conditions at the FRS periphery. Symmetry of the boundary conditions of coolant bulk temperatures and film coefficients at the FRS periphery is not necessary.

Conklin, J.C.

1980-09-16

262

Heat mirrors on plastic sheet using transparent oxide conducting coatings  

Microsoft Academic Search

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

R. P. Howson; M. I. Ridge

1982-01-01

263

Precise measurements of radial temperature gradients in the laser-heated diamond anvil cell.  

PubMed

A new spectroradiometry system specialized for measuring two-dimensional temperature gradients for samples at high pressure in the laser heated diamond anvil cell has been designed and constructed at UCLA. Emitted light intensity from sample hotspots is imaged by a videocamera for real time monitoring, an imaging spectroradiometer for temperature measurement, and a high-dynamic-range camera that examines a magnified image of the two-dimensional intensity distribution of the heated spot, yielding precise measurements of temperature gradients. With this new system, most systematic errors in temperature measurement due to chromatic aberration are bypassed. We use this system to compare several different geometries of temperature measurement found in the literature, including scanning a pinhole aperture, and narrow-slit and wide-slit entrance apertures placed before the imaging spectrometer. We find that the most accurate way of measuring a temperature is to use the spectrometer to measure an average hotspot temperature and to use information from the imaging charge coupled device to calculate the temperature distribution to the hotspot. We investigate the effects of possible wavelength- and temperature-dependent emissivity, and evaluate their errors. We apply this technique to measure the anisotropy in temperature distribution of highly oriented graphite at room temperature and also at high pressures. A comparison between model and experiment demonstrates that this system is capable of measuring thermal diffusivity in anisotropic single crystals and is also capable of measuring relative thermal diffusivity at high pressures and temperatures among different materials. This shows the possibility of using this system to provide information about thermal diffusivity of materials at high pressure and temperature. PMID:18315322

Kavner, A; Nugent, C

2008-02-01

264

Heat conduction in cooling flows. [in clusters of galaxies  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

265

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

Microsoft Academic Search

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

Ching-yu Yang

1999-01-01

266

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

267

Comparison between two common collocation approaches based on radial basis functions for the case of heat transfer equations arising in porous medium  

Microsoft Academic Search

In this paper two common collocation approaches based on radial basis functions have been considered; one be computed through the integration process (IRBF) and one be computed through the differentiation process (DRBF). We investigated the two approaches on natural convection heat transfer equations embedded in porous medium which are of great importance in the design of canisters for nuclear wastes

K. Parand; S. Abbasbandy; S. Kazem; A. R. Rezaei

2011-01-01

268

Reduction of Ion Thermal Diffusivity Associated with the Transition of the Radial Electric Field in Neutral-Beam-Heated Plasmas in the Large Helical Device  

Microsoft Academic Search

Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the

K. Ida; H. Funaba; S. Kado; K. Narihara; K. Tanaka; Y. Takeiri; Y. Nakamura; N. Ohyabu; K. Yamazaki; M. Yokoyama; S. Murakami; N. Ashikawa; P. C. Devries; M. Emoto; M. Goto; H. Idei; K. Ikeda; S. Inagaki; N. Inoue; M. Isobe; K. Itoh; O. Kaneko; K. Kawahata; K. Khlopenkov; A. Komori; S. Kubo; R. Kumazawa; Y. Liang; S. Masuzaki; T. Minami; J. Miyazawa; T. Morisaki; S. Morita; T. Mutoh; S. Muto; Y. Nagayama; H. Nakanishi; K. Nishimura; N. Noda; T. Notake; T. Kobuchi; S. Ohdachi; K. Ohkubo; Y. Oka; M. Osakabe; T. Ozaki; R. O. Pavlichenko; B. J. Peterson; A. Sagara; K. Saito; S. Sakakibara; R. Sakamoto; H. Sanuki; H. Sasao; M. Sasao; K. Sato; M. Sato; T. Seki; T. Shimozuma; M. Shoji; H. Suzuki; S. Sudo; N. Tamura; K. Toi; T. Tokuzawa; Y. Torii; K. Tsumori; T. Yamamoto; H. Yamada; I. Yamada; S. Yamaguchi; S. Yamamoto; Y. Yoshimura; K. Y. Watanabe; T. Watari; Y. Hamada; O. Motojima; M. Fujiwara

2001-01-01

269

Specially tailored transfinite-element formulations for hyperbolic heat conduction involving non-Fourier effects  

NASA Technical Reports Server (NTRS)

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

Tamma, Kumar K.; Railkar, Sudhir B.

1989-01-01

270

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

271

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

Microsoft Academic Search

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

C. W. Sohn; M. M. Chen

1984-01-01

272

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

E-print Network

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

Sturm, Matthew

273

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

E-print Network

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

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

2011-03-18

274

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

E-print Network

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

Noam Soker

2003-02-19

275

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

276

Effective thermal conductivity of binary mixed materials with and without heat generation - An empirical approach  

SciTech Connect

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

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

2012-07-01

277

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

NASA Astrophysics Data System (ADS)

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

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

2002-11-01

278

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

279

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

SciTech Connect

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

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

2006-10-15

280

Conductive heat flow at the TAG active hydrothermal mound: Results from 1993-1995 submersible surveys  

Microsoft Academic Search

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

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

1996-01-01

281

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

282

Finite difference solutions of heat conduction problems in multi-layered bodies with complex geometries  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

283

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

Microsoft Academic Search

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

Taishan Zhu; Wenjing Ye

2010-01-01

284

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

285

Effects of wall conduction, internal heat sources and an internal baffle on natural convection heat transfer in a rectangular enclosure  

Microsoft Academic Search

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

A. F. Emery

1997-01-01

286

Heat transfer enhancement in nano-fluids suspensions : thermal wave effects and hyperbolic heat conduction.  

E-print Network

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

Vadasz, Johnathan J.

2005-01-01

287

HEAT TRANSFER OF SOLID–LIQUID PHASECHANGE MATERIAL SUSPENSIONS IN CIRCULAR PIPES: EFFECTS OF WALL CONDUCTION  

Microsoft Academic Search

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

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

2004-01-01

288

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

289

Sensor for gas analysis based on thermal conductivity, specific heat capacity and thermal diffusivity  

Microsoft Academic Search

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

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

2011-01-01

290

Transient coupled radiative–conductive heat transfer in a gray planar medium with anisotropic scattering  

Microsoft Academic Search

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

M. Lazard; S. Andre; D. Maillet

2001-01-01

291

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

Microsoft Academic Search

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

Francis S. Birch

1975-01-01

292

Regularities of unsteady radiative–conductive heat transfer in evaporating semitransparent liquid droplets  

Microsoft Academic Search

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

G. Miliauskas

2001-01-01

293

Investigation of gravitational effects on a variable conductance heat pipe utilizing liquid crystal thermography  

Microsoft Academic Search

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

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

1975-01-01

294

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

Microsoft Academic Search

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

R. M. Cima

1986-01-01

295

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

E-print Network

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

Nail H. Ibragimov; Elena D. Avdonina

2012-02-27

296

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

Microsoft Academic Search

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

Thomas; R. F. Jr

1962-01-01

297

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

Microsoft Academic Search

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

M. Faghri; E. M. Sparrow

1980-01-01

298

New Insights Into the Heat Sources of Mantle Plumes, or: Where Does all the Heat Come From, Heat Producing Elements, Advective or Conductive Heat Flow?  

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

299

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

300

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

301

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

302

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

303

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

304

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

305

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

Microsoft Academic Search

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

Wendell Horton; T. Tajima

1991-01-01

306

COYOTE : a finite element computer program for nonlinear heat conduction problems. Part I, theoretical background  

Microsoft Academic Search

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

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

2010-01-01

307

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

Microsoft Academic Search

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

Vadim A. Petrov

1997-01-01

308

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

Microsoft Academic Search

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

G. A. Glover Sr.

1986-01-01

309

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

310

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

311

Thermal Science & Engineering Vol.?? No.?? (2005) Non-Fourier Heat Conduction of Single-Walled Carbon Nanotubes  

E-print Network

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

Maruyama, Shigeo

312

Mode-coupling theory and molecular dynamics simulation for heat conduction in a chain with transverse motions  

E-print Network

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

Li, Baowen

313

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

314

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

PubMed Central

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

2011-01-01

315

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

316

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

317

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

318

Effect of aggregation on thermal conductivity and heat transfer in hybrid nanocomposite phase change colloidal suspensions  

NASA Astrophysics Data System (ADS)

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

Parameshwaran, R.; Kalaiselvam, S.

2013-11-01

319

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

E-print Network

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

Swantje Bargmann; Antonino Favata; Paolo Podio-Guidugli

2012-09-13

320

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

321

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

322

Chemical composition of apoplastic transport barriers in relation to radial hydraulic conductivity of corn roots (Zea mays L.).  

PubMed

The hydraulic conductivity of roots (Lp(r)) of 6- to 8-d-old maize seedlings has been related to the chemical composition of apoplastic transport barriers in the endodermis and hypodermis (exodermis), and to the hydraulic conductivity of root cortical cells. Roots were cultivated in two different ways. When grown in aeroponic culture, they developed an exodermis (Casparian band in the hypodermal layer), which was missing in roots from hydroponics. The development of Casparian bands and suberin lamellae was observed by staining with berberin-aniline-blue and Sudan-III. The compositions of suberin and lignin were analyzed quantitatively and qualitatively after depolymerization (BF(3)/methanol-transesterification, thioacidolysis) using gas chromatography/mass spectrometry. Root Lp(r) was measured using the root pressure probe, and the hydraulic conductivity of cortical cells (Lp) using the cell pressure probe. Roots from the two cultivation methods differed significantly in (i) the Lp(r) evaluated from hydrostatic relaxations (factor of 1.5), and (ii) the amounts of lignin and aliphatic suberin in the hypodermal layer of the apical root zone. Aliphatic suberin is thought to be the major reason for the hydrophobic properties of apoplastic barriers and for their relatively low permeability to water. No differences were found in the amounts of suberin in the hypodermal layers of basal root zones and in the endodermal layer. In order to verify that changes in root Lp(r) were not caused by changes in hydraulic conductivity at the membrane level, cell Lp was measured as well. No differences were found in the Lp values of cells from roots cultivated by the two different methods. It was concluded that changes in the hydraulic conductivity of the apoplastic rather than of the cell-to-cell path were causing the observed changes in root Lp(r). PMID:10664137

Zimmermann, H M; Hartmann, K; Schreiber, L; Steudle, E

2000-01-01

323

An analysis of the vapor flow and the heat conduction through the liquid-wick and pipe wall in a heat pipe with single or multiple heat sources  

NASA Technical Reports Server (NTRS)

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

Chen, Ming-Ming; Faghri, Amir

1990-01-01

324

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

NASA Astrophysics Data System (ADS)

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

Ogushi, Fumiko; Yukawa, Satoshi; Ito, Nobuyasu

2005-03-01

325

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

326

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 field and circulating eddy currents are induced within the metals. Flow of eddy currents leads an AC current through a water cooled copper coil and a metallic charge is placed in a ceramic (or

Subramaniam, Anandh

327

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

328

ht. J. Heat Mass Tmnsfer. Vol. 13,pp. 857469. Pergamon Press 1970. Printed in Great Britain THE CONDUCTION OF HEAT FROM SLIDING SOLIDS  

E-print Network

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

Barber, James R.

329

Transient modeling/analysis of hyperbolic heat conduction problems employing mixed implicit-explicit alpha method  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

330

Effects of gravity on gas-loaded variable conductance heat pipes  

Microsoft Academic Search

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

M. D. Kelleher

1977-01-01

331

Temperature control using variable conductance closed two-phase heat pipe  

Microsoft Academic Search

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

Ioan Sauciuc; Aliakbar Akbarzadeh; Peter Johnson

1996-01-01

332

A modified sequential function specification finite element-based method for parabolic inverse heat conduction problems  

Microsoft Academic Search

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

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

2005-01-01

333

Transient conjugated heat transfer in pipes involving two-dimensional wall and axial fluid conduction  

Microsoft Academic Search

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

?efik Bilir

2002-01-01

334

Application of the modified law of heat conduction and state equation to dynamical problems of thermoelasticity  

NASA Astrophysics Data System (ADS)

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

Farkas, I.; Szekeres, A.

335

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

Microsoft Academic Search

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

N. Dsouza

1975-01-01

336

Magnetohydrodynamic Simulations of the Formation of Cold Fronts in Clusters of Galaxies including Heat Conduction  

E-print Network

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

Naoki Asai; Naoya Fukuda; Ryoji Matsumoto

2004-04-07

337

Lunar temperature and global heat flux from laboratory electrical conductivity and lunar magnetometer data  

NASA Technical Reports Server (NTRS)

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

Sonett, C. P.; Duba, A.

1975-01-01

338

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

339

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

340

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

E-print Network

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

Mathias Michel; Jochen Gemmer; Guenter Mahler

2005-03-22

341

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

SciTech Connect

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

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

1981-02-01

342

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

343

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

USGS Publications Warehouse

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

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

2006-01-01

344

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

Microsoft Academic Search

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

A. R. Calderwood

2001-01-01

345

Normal Heat Conductivity in a strongly pinned chain of anharmonic oscillators  

E-print Network

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

R. Lefevere; A. Schenkel

2005-11-03

346

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

Microsoft Academic Search

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

D. C. Kane

1980-01-01

347

Strong Solutions to Non-Stationary Channel Flows of Heat-Conducting Viscous Incompressible Fluids with Dissipative Heating  

E-print Network

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

Michal Beneš

2011-08-08

348

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

349

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

E-print Network

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

Noam Soker

2003-11-02

350

Determination of heat conductivity and thermal diffusivity of waste glass melter feed: Extension to high temperatures  

SciTech Connect

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

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

2014-05-12

351

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

2015-11-01

352

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.

353

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

354

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

355

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...

356

Simultaneous radiation and conduction heat transfer in a graded index semitransparent slab with gray boundaries  

Microsoft Academic Search

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

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

2002-01-01

357

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

Microsoft Academic Search

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

Guenter Ahlers

2001-01-01

358

Review and Comparison of Nanofluid Thermal Conductivity and Heat Transfer Enhancements  

Microsoft Academic Search

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

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

2008-01-01

359

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

360

Analysis of conductive and convective heat transfer in a sedimentary basin, demonstrated for the Rheingraben  

Microsoft Academic Search

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

C. Clauser; H. Villinger

1990-01-01

361

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

Microsoft Academic Search

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

Jun Fukai; Yuichi Hamada; Yoshio Morozumi; Osamu Miyatake

2002-01-01

362

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

363

DIRECT INTEGRATION APPROACH FOR SIMULTANEOUSLY ESTIMATING TEMPERATURE DEPENDENT THERMAL CONDUCTIVITY AND HEAT CAPACITY  

Microsoft Academic Search

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

C. H. Huang; M. N. Özi?ik

1991-01-01

364

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

E-print Network

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

Grujicic, Mica

365

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

NASA Astrophysics Data System (ADS)

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

Li, Yao; Young, Lai-Sang

2013-09-01

366

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

367

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

Microsoft Academic Search

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

Mohammad H. N. Naraghi; Shun-Chang Tsai

1993-01-01

368

Calculation of nonstationary heat conduction in multilayer objects with boundary conditions of the third kind  

NASA Astrophysics Data System (ADS)

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

Vendin, S. V.

1993-08-01

369

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

370

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

371

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

Microsoft Academic Search

This paper proposes a novel numerical methodology, termed the discrete thermal element method (DTEM), for the effective modelling of heat conduction in systems comprising a large number of circular particles in 2D cases. Based on an existing analytical integral solution for the temperature distribution over a circular domain subjected to the Neumann boundary condition, a linear algebraic system of thermal

Y. T. Feng; K. Han; C. F. Li; D. R. J. Owen

2008-01-01

372

Enthalpy, Heat Capacity and Thermal Conductivity of Boneless Mutton between ?40 and +40 °C  

Microsoft Academic Search

The thermal properties of boneless lamb meat were determined in a temperature range usually encountered in both freezing and refrigeration processes. The specific heat and the enthalpy were measured by differential scanning calorimetry (DSC) while thermal conductivity was measured by the transient probe method. Values thus measured were compared with predictive equations from the literature. Also, experimental data of thermal

Ana M. Tocci; Ethel S. E. Flores; Rodolfo H. Mascheroni

1997-01-01

373

Global large solutions of magnetohydrodynamics with temperature-dependent heat conductivity  

NASA Astrophysics Data System (ADS)

In this paper, we consider an initial boundary value problem for the magnetohydrodynamic compressible flows. By assuming that the heat conductivity depends on temperature with ? (?) = ? q , q > 0, we prove the existence and uniqueness of global strong solutions with large initial data and show that neither shock waves nor vacuum and concentration of mass in the solutions are developed in a finite time.

Hu, Yuxi; Ju, Qiangchang

2014-08-01

374

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

E-print Network

One-dimensional heat conductivity exponent from a random collision model J. M. Deutsch and Onuttom to conductivity would predict that if the temperature gradient "T in a material is small, the heat current flowing January 2003; published 18 July 2003 We obtain numerically the thermal conductivity of a quasi

California at Santa Cruz, University of

375

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

NASA Astrophysics Data System (ADS)

A scaling law for the heat flux out of a convective fluid covered totally or partially by a finitely conducting lid is proposed. This scaling is constructed in order to quantify the heat transfer out of the Earth's mantle, taking into account the effect of the dichotomy between oceans and continents, which imposes heterogeneous thermal boundary conditions at the surface of the mantle. The effect of these heterogeneous boundary conditions is studied here using simple two-dimensional models, with the mantle represented by an isoviscous fluid heated from below and continents represented by nondeformable lids of finite thermal conductivity set above the surface of the model. We use free-slip boundary conditions under the oceanic and continental zones in order to study in an isolated way the possible thermal effect of continents, independently of all mechanical effect. A systematic study of the heat transfer as a function of the Rayleigh number of the fluid, of the width of the lid, and of its thermal properties is carried out. We show that estimates of continental lithosphere thickness imply a strong insulating effect from continents on mantle heat loss, at least locally. The heat flux below continents was low in the past and of the order of the present one if the continental thickness has remained broadly constant over the Earth's history.

Grigné, C.; Labrosse, S.; Tackley, P. J.

2007-08-01

376

Conductive heating and microwave hydrolysis under identical heating profiles for advanced anaerobic digestion of municipal sludge.  

PubMed

Microwave (2.45 GHz, 1200 W) and conventional heating (custom pressure vessel) pretreatments were applied to dewatered municipal waste sludge (18% total solids) using identical heating profiles that span a wide range of temperatures (80-160 °C). Fourteen lab-scale semi-continuous digesters were set up to optimize the energy (methane) output and sludge retention time (SRT) requirements of untreated (control) and thermally pretreated anaerobic digesters operated under mesophilic and thermophilic temperatures. Both pretreatment methods indicated that in the pretreatment range of 80-160 °C, temperature was a statistically significant factor (p-value < 0.05) for increasing solubilization of chemical oxygen demand and biopolymers (proteins, sugars, humic acids) of the waste sludge. However, the type of pretreatment method, i.e. microwave versus conventional heating, had no statistically significant effect (p-value >0.05) on sludge solubilization. With the exception of the control digesters at a 5-d SRT, all control and pretreated digesters achieved steady state at all three SRTs, corresponding to volumetric organic loading rates of 1.74-6.96 g chemical oxygen demand/L/d. At an SRT of 5 d, both mesophilic and thermophilic controls stopped producing biogas after 20 d of operation with total volatile fatty acids concentrations exceeding 1818 mg/L at pH <5.64 for mesophilic and 2853 mg/L at pH <7.02 for thermophilic controls, while the pretreated digesters continued producing biogas. Furthermore, relative (to control) organic removal efficiencies dramatically increased as SRT was shortened from 20 to 10 and then 5 d, indicating that the control digesters were challenged as the organic loading rate was increased. Energy analysis showed that, at an elevated temperature of 160 °C, the amount of methane recovered was not enough to compensate for the energy input. Among the digesters with positive net energy productions, control and pretreated digesters at 80 °C were more favorable at an SRT of 10 d. PMID:23866153

Mehdizadeh, Seyedeh Neda; Eskicioglu, Cigdem; Bobowski, Jake; Johnson, Thomas

2013-09-15

377

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

378

Heat conduction in a turbulent magnetic field, with application to solar-wind electrons.  

NASA Technical Reports Server (NTRS)

Consideration of random, long-wavelength fluctuations in a turbulent magnetic field, showing that they can appreciably decrease the heat conductivity of a plasma along the magnetic field. In simple cases of interest, the reduction along the average field is approximately by the factor (cos delta theta) squared, where delta theta is the angle of the local magnetic field relative to the average field. Application to solar-wind electrons indicates that this reduction in heat conductivity due to observed fluctuations in the interplanetary magnetic field may be of the order of a factor of 2. This may help to explain recent measurements which indicate a rather low electron heat flux in the solar wind.

Hollweg, J. V.; Jokipii, J. R.

1972-01-01

379

Hybrid transfinite element modeling/analysis of nonlinear heat conduction problems involving phase change  

NASA Technical Reports Server (NTRS)

The present paper describes the applicability of hybrid transfinite element modeling/analysis formulations for nonlinear heat conduction problems involving phase change. The methodology is based on application of transform approaches and classical Galerkin schemes with finite element formulations to maintain the modeling versatility and numerical features for computational analysis. In addition, in conjunction with the above, the effects due to latent heat are modeled using enthalpy formulations to enable a physically realistic approximation to be dealt computationally for materials exhibiting phase change within a narrow band of temperatures. Pertinent details of the approach and computational scheme adapted are described in technical detail. Numerical test cases of comparative nature are presented to demonstrate the applicability of the proposed formulations for numerical modeling/analysis of nonlinear heat conduction problems involving phase change.

Tamma, Kumar K.; Railkar, Sudhir B.

1988-01-01

380

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

381

Heat conduction in systems with Kolmogorov-Arnold-Moser phase space structure  

E-print Network

We study heat conduction in a billiard channel formed by two sinusoidal walls and the diffusion of particles in the corresponding channel of infinite length; the latter system has an infinite horizon, i.e., a particle can travel an arbitrary distance without colliding with the rippled walls. For small ripple amplitudes, the dynamics of the heat carriers is regular and analytical results for the temperature profile and heat flux are obtained using an effective potential. The study also proposes a formula for the temperature profile that is valid for any ripple amplitude. When the dynamics is regular, ballistic conductance and ballistic diffusion are present. The Poincar\\'e plots of the associated dynamical system (the infinitely long channel) exhibit the generic transition to chaos as ripple amplitude is increased.When no Kolmogorov-Arnold-Moser (KAM) curves are present to forbid the connection of all chaotic regions, the mean square displacement grows asymptotically with time t as tln(t).

I. F. Herrera-González; H. I. Pérez-Aguilar; A. Mendoza-Suárez; E. S Tututi

2012-09-28

382

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

383

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

384

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

385

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

386

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

2014-08-01

387

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

388

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

389

Radial Erosion  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

The ejecta surrounding the crater (off image to the left) in this image has undergone significant erosion by the wind. The wind has stripped the surface features from the ejecta and has started to winnow away the ejecta blanket. Near the margin of the ejecta the wind is eroding along a radial pattern -- taking advantage of radial emplacement. Note the steep margin of the ejecta blanket. Most, if not all, of the fine ejecta material has been removed and the wind in now working on the more massive continuous ejecta blanket.

Image information: VIS instrument. Latitude 12.5, Longitude 197.4 East (162.6 West). 37 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2005-01-01

390

Comparison between two common collocation approaches based on radial basis functions for the case of heat transfer equations arising in porous medium  

E-print Network

In this paper two common collocation approaches based on radial basis functions have been considered; one be computed through the integration process (IRBF) and one be computed through the differentiation process (DRBF). We investigated the two approaches on natural convection heat transfer equations embedded in porous medium which are of great importance in the design of canisters for nuclear wastes disposal. Numerical results show that the IRBF be performed much better than the common DRBF, and show good accuracy and high rate of convergence of IRBF process.

K. Parand; S. Abbasbandy; S. Kazem; A. R. Rezaei

2010-08-16

391

Comparison between two common collocation approaches based on radial basis functions for the case of heat transfer equations arising in porous medium  

E-print Network

In this paper two common collocation approaches based on radial basis functions have been considered; one be computed through the integration process (IRBF) and one be computed through the differentiation process (DRBF). We investigated the two approaches on natural convection heat transfer equations embedded in porous medium which are of great importance in the design of canisters for nuclear wastes disposal. Numerical results show that the IRBF be performed much better than the common DRBF, and show good accuracy and high rate of convergence of IRBF process.

Parand, K; Kazem, S; Rezaei, A R; 10.1016/j.cnsns.2010.07.011

2010-01-01

392

Comparison between two common collocation approaches based on radial basis functions for the case of heat transfer equations arising in porous medium  

NASA Astrophysics Data System (ADS)

In this paper two common collocation approaches based on radial basis functions have been considered; one be computed through the integration process (IRBF) and one be computed through the differentiation process (DRBF). We investigated the two approaches on natural convection heat transfer equations embedded in porous medium which are of great importance in the design of canisters for nuclear wastes disposal. Numerical results show that the IRBF be performed much better than the common DRBF, and show good accuracy and high rate of convergence of IRBF process.

Parand, K.; Abbasbandy, S.; Kazem, S.; Rezaei, A. R.

2011-03-01

393

Radial turbine cooling  

NASA Technical Reports Server (NTRS)

The technology of high temperature cooled radial turbines is reviewed. Aerodynamic performance considerations are described. Heat transfer and structural analysis are addressed, and in doing so the following topics are covered: cooling considerations, hot side convection, coolant side convection, and rotor mechanical analysis. Cooled rotor concepts and fabrication are described, and the following are covered in this context: internally cooled rotor, hot isostatic pressure bonded rotor, laminated rotor, split blade rotor, and the NASA radial turbine program.

Roelke, Richard J.

1992-01-01

394

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

395

Nonequilibrium Temperature and Thermometry in Heat-Conducting Phi-4 Models  

E-print Network

We analyze temperature and thermometry for simple nonequilibrium heat-conducting models. We show in detail, for both two- and three-dimensional systems, that the ideal gas thermometer corresponds to the concept of a local instantaneous mechanical kinetic temperature. For the Phi-4 models investigated here the mechanical temperature closely approximates the local thermodynamic equilibrium temperature. There is a significant difference between kinetic temperature and the nonlocal configurational temperature. Neither obeys the predictions of extended irreversible thermodynamics. Overall, we find that kinetic temperature, as modeled and imposed by the Nos\\'e-Hoover thermostats developed in 1984, provides the simplest means for simulating, analyzing, and understanding nonequilibrium heat flows.

Wm. G. Hoover; Carol G. Hoover

2008-02-23

396

Algorithms for Solving Non-Stationary Heat Conduction Problem for Design of a Technical Device  

E-print Network

A model of a multilayer device with non-trivial geometrical and material structure and its working process is suggested. The thermal behavior of the device as one principle characteristic is simulated. The algorithm for solving the non-stationary heat conduction problem with a time-dependent periodical heating source is suggested. The algorithm is based on finite difference explicit--implicit method. The OpenCL realization of the algorithm is discussed. The results show that the chosen characteristics of the device configuration are suitable for the working requirements for application.

Ayriyan, Alexander; Donets, Eugeny E; Grigorian, Hovik; Pribis, Jan

2014-01-01

397

Thermal conductance of and heat generation in tire-pavement interface and effect on aircraft braking  

NASA Technical Reports Server (NTRS)

A finite-difference analysis was performed on temperature records obtained from a free rolling automotive tire and from pavement surface. A high thermal contact conductance between tire and asphalt was found on a statistical basis. Average slip due to squirming between tire and asphalt was about 1.5 mm. Consequent friction heat was estimated as 64 percent of total power absorbed by bias-ply, belted tire. Extrapolation of results to aircraft tire indicates potential braking improvement by even moderate increase of heat absorbing capacity of runway surface.

Miller, C. D.

1976-01-01

398

Adiabatic versus conductive heat transfer in off-critical SF6 in the absence of convection  

NASA Astrophysics Data System (ADS)

The process of adiabatic heating of compressible fluids [piston effect (PE)] has been investigated in SF6 at off-critical density ?~=1.27?c near the coexistence temperature in the absence of convection. The temperature response of the fluid to an internal heat pulse has been recorded at different distances from the heat source confirming a (spatially) homogeneous temperature rise outside an expanding boundary layer during heating. This process can be distinguished from the following conductive heat transfer when the energy contained in the boundary layer diffuses. This observation is confirmed by both experiment and calculations. During and after the heating process, (P,?,T) data of the fluid behaves according to a given equation of state at equilibrium because hydrodynamic velocities remain small. The isentropic character of the PE was confirmed by both calculations from the pressure and density measurements. The presented experimental results were obtained on ESA's critical point facility (CPF) during the Spacelab IML-2 mission in July 1994.

Fröhlich, T.; Guenoun, P.; Bonetti, M.; Perrot, F.; Beysens, D.; Garrabos, Y.; Le Neindre, B.; Bravais, P.

1996-08-01

399

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

400

Development and adaptation of conduction and radiation heat-transfer computer codes for the CFTL. [Core Flow Test Loop; RODCON; HOTTEL  

SciTech Connect

RODCON and HOTTEL are two computational methods used to calculate thermal and radiation heat transfer for the Core Flow Test Loop (CFTL) analysis efforts. RODCON was developed at ORNL to calculate the internal temperature distribution of the fuel rod simulator (FRS) for the CFTL. RODCON solves the time-dependent heat transfer equation in two-dimensional (R angle) cylindrical coordinates at an axial plane with user-specified radial material zones and time- and position-variant surface conditions at the FRS periphery. Symmetry of the FRS periphery boundary conditions is not necessary. The governing elliptic, partial differential heat equation is cast into a fully implicit, finite-difference form by approximating the derivatives with a forward-differencing scheme with variable mesh spacing. The heat conduction path is circumferentially complete, and the potential mathematical problem at the rod center can be effectively ignored. HOTTEL is a revision of an algorithm developed by C.B. Baxi at the General Atomic Company (GAC) to be used in calculating radiation heat transfer in a rod bundle enclosed in a hexagonal duct. HOTTEL uses geometric view factors, surface emissivities, and surface areas to calculate the gray-body or composite view factors in an enclosure having multiple reflections in a nonparticipating medium.

Conklin, J.C.

1981-08-01

401

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

402

The effect of temperature-dependent thermal conductivity in heat transfer simulations of frozen biomaterials.  

PubMed

The thermal conductivity value of pure water ice is inversely proportional to the temperature and decreases about 5-fold as the temperature increases from the liquid nitrogen boiling temperature (77 K to the freezing point of pure water. The temperature dependency of the thermal conductivity is typically overlooked in bioheat transfer simulations. A closed-form solution of the one-dimensional temperature distribution in frozen water and blood is presented in this study, based on a new thermal conductivity model. Results indicate that temperatures are overestimated up to 38K, and heat fluxes through the frozen region boundaries are underestimated by a factor of 2, when the temperature dependency of the thermal conductivity is neglected. PMID:12148047

Rabin, Y

2000-01-01

403

The role of electron heat conductivity and radiation transport in 1D simulations of wire explosions in Zebra experiments  

Microsoft Academic Search

Experiments at the Zebra facility at the University of Nevada, Reno, have been conducted to study the behavior of thick metal wires at ultrahigh magnetic fields. Currents of about 1 MA with 100 ns rise time were passed through 0.5 mm to 2 mm diameter aluminum wires. A number of diagnostic techniques used in the experiments provided data on radial

S. F. Garanin; S. D. Kuznetsov

2009-01-01

404

Solution algorithms for nonlinear transient heat conduction analysis employing element-by-element iterative strategies  

NASA Technical Reports Server (NTRS)

The particular problems investigated in the present study arise from nonlinear transient heat conduction. One of two types of nonlinearities considered is related to a material temperature dependence which is frequently needed to accurately model behavior over the range of temperature of engineering interest. The second nonlinearity is introduced by radiation boundary conditions. The finite element equations arising from the solution of nonlinear transient heat conduction problems are formulated. The finite element matrix equations are temporally discretized, and a nonlinear iterative solution algorithm is proposed. Algorithms for solving the linear problem are discussed, taking into account the form of the matrix equations, Gaussian elimination, cost, and iterative techniques. Attention is also given to approximate factorization, implementational aspects, and numerical results.

Winget, J. M.; Hughes, T. J. R.

1985-01-01

405

Two-Gradient Convection in a Vertical Slot with Maxwell-Cattaneo Heat Conduction  

SciTech Connect

We study the effect of the Maxwell-Cattaneo law of heat conduction (MCHC) on the 1D flow in a vertical slot subject to both vertical and horizontal temperature gradients. The gravitational acceleration is allowed to oscillate, which provides an opportunity to investigate the quantitative contribution of thermal inertia as epitomized by MCHC. The addition of the time derivative in MCHC increases the order of the system. We use a spectral expansion with Rayleigh's beam functions as the basis set, which is especially suited to fourth order boundary value problems (BVP). We show that the time derivative (relaxation of the thermal flux) has a dissipative nature and leads to the appearance of purely real negative eigenvalues. Yet it also increases the absolute value of the imaginary part and decreases the absolute value of the real part of the complex eigenvalues. Thus, the system has a somewhat more oscillatory behavior than the one based on Fourier's heat conduction law (FHC)

Papanicolaou, N. C. [Department of Computer Science, University of Nicosia, P.O. Box 24005, 1700 Nicosia (Cyprus); Christov, C. I. [Department of Mathematics, University of Louisiana at Lafayette, LA 70504-1010 (United States); Jordan, P. M. [Entropy Reversal Consultants (L.L.C), P. O. Box 691, Abita Springs, LA 70420 (United States); Code 7181, Naval Research Lab., Stennis Space Ctr., MS 39529 (United States)

2009-10-29

406

Self-similar ablative flow of nonstationary accelerating foil due to nonlinear heat conduction  

SciTech Connect

Ablating plasma flow of an accelerating foil driven by nonlinear heat conduction is investigated theoretically. It is shown that the hydrodynamic system admits a new self-similar solution describing the nonstationary ablation process, through which the payload mass decreases to burn out at the end. In contrast to previous analyses based on stationary flow, the present solution provides a practical physical picture with a finite peak density and a distinct vacuum boundary at the front. The system is solved as a novel eigenvalue problem such that the acceleration and the heat conductivity are restrictive with each other under the self-similar evolution. Scaling laws are obtained to describe the temporal evolution for the shell acceleration and such ablation performances as the mass ablation rate and the ablation pressure.

Murakami, M.; Sakaiya, T.; Sanz, J. [Institute of Laser Engineering, Osaka University, Osaka (Japan)

2007-02-15

407

On Approximate Solutions for Unsteady Conduction in Slabs with Uniform Heat Flux  

NASA Astrophysics Data System (ADS)

In this paper, the Transversal Method of Lines (TMOL) or Rothe's method is employed to obtain analytical expressions of simple form for the unsteady one-dimensional heat conduction in a slab. Initially, the slab is maintained at a uniform temperature, and then a uniform heat flux is applied to its surfaces. Implementation of TMOL generates a sequence of adjoint ordinary differential equations, where the spatial coordinate is the only independent variable and the time becomes a parameter. In spite of the anticipated expectations that the semi-discrete solutions produced by TMOL would yield accurate temperature responses for short times only, detailed calculations demonstrate the opposite trend. Surprisingly, the temperature results associated with two equal time steps are excellent not only for short times, but during the entire heating period.

Salazar, Abraham; Campo, Antonio; Morrone, Biagio

1998-08-01

408

Numerical identification of boundary conditions on nonlinearly radiating inverse heat conduction problems  

NASA Technical Reports Server (NTRS)

An explicit and unconditionally stable finite difference method for the solution of the transient inverse heat conduction problem in a semi-infinite or finite slab mediums subject to nonlinear radiation boundary conditions is presented. After measuring two interior temperature histories, the mollification method is used to determine the surface transient heat source if the energy radiation law is known. Alternatively, if the active surface is heated by a source at a rate proportional to a given function, the nonlinear surface radiation law is then recovered as a function of the interface temperature when the problem is feasible. Two typical examples corresponding to Newton cooling law and Stefan-Boltzmann radiation law respectively are illustrated. In all cases, the method predicts the surface conditions with an accuracy suitable for many practical purposes.

Murio, Diego A.

1991-01-01

409

Hamiltonian Dynamics of Thermostated Systems: Two-Temperature Heat-Conducting phi-4 Chains  

E-print Network

We consider and compare four Hamiltonian formulations of thermostated mechanics, three of them kinetic, and the other one configurational. Though all four approaches ``work'' at equilibrium, their application to many-body nonequilibrium simulations can fail to provide a proper flow of heat. All the Hamiltonian formulations considered here are applied to the same prototypical two-temperature "phi-4" model of a heat-conducting chain. This model incorporates nearest-neighbor Hooke's-Law interactions plus a quartic tethering potential. Physically correct results, obtained with the isokinetic Gaussian and Nose-Hoover thermostats, are compared with two other Hamiltonian results. The latter results, based on constrained Hamiltonian thermostats, fail correctly to model the flow of heat.

Wm G Hoover; Carol G Hoover

2007-01-20

410

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

Microsoft Academic Search

Eighty-nine point measurements of the thermal conductivity (ks) of the snow on the sea ice of the Beaufort Sea were made using a heated needle probe. Average values ranged from 0.078 W m-1 K-1 for new snow to 0.290 W m-1 K-1 for an ubiquitous wind slab. ks increased with increasing density, consistent with published equations, but could also be

Matthew Sturm; Donald K. Perovich; Jon Holmgren

2002-01-01

411

Importance of multi-dimensional conductive heat flows in and around buildings  

Microsoft Academic Search

The modelling of certain structures in a manner consistent with current practice can lead to significant errors as a result of the non-treatment of multi-dimensional conductive heat flows. A series of multi-dimensional simulations using a modified whole building thermal simulation model have been performed in order to highlight this problem. As a result, it is suggested that all building thermal

M. Davies; A. Tindale; J. Littler

1995-01-01

412

Existence and uniqueness of solutions of nonlinear systems of conductive-radiative heat transfer equations  

Microsoft Academic Search

We prove an existence and uniqueness results for a system of nonlinear integro-differential equations that model steady-state combined radiative-conductive heat transfer. Our approach uses two different formulations of the system as a compact fixed-point problem. One formulation, which has been used in numerical work, is used for uniqueness and a new one is used for the existence proof.

C. T. Kelley

1996-01-01

413

On heat conduction in multicomponent, non-Maxwellian spherically symmetric solar wind plasmas  

NASA Technical Reports Server (NTRS)

A generalized expression for the steady-state heat flux in multicomponent, moderately non-Maxwellian spherically symmetric plasmas is presented and discussed. The work was motivated by the inability of the simple, Fourier-type formula for the thermal conductivity to explain the observed correlations in the solar wind. The results hold for situations not far from local thermodynamic equilibrium. The generalized expression includes not only correlations that have been observed but also correlations not sought for previously.

Cuperman, S.; Dryer, M.

1985-01-01

414

A blow-up criterion for compressible viscous heat-conductive flows  

E-print Network

We study an initial boundary value problem for the Navier-Stokes equations of compressible viscous heat-conductive fluids in a 2-D periodic domain or the unit square domain. We establish a blow-up criterion for the local strong solutions in terms of the gradient of the velocity only, which coincides with the famous Beale-Kato-Majda criterion for ideal incompressible flows.

Song Jiang; Yaobin Ou

2010-06-12

415

The initial value problem for motion of micropolar fluids with heat conduction in Banach spaces  

E-print Network

We consider the abstract initial value problem for the system of evolution equations which describe motion of micropolar fluids with heat conduction in a bounded domain. This problem has uniquely a mild solution locally in time for general initial data, and globally in time for small initial data. Moreover, a mild solution of this problem can be a strong or classical solution under appropriate assumptions for initial data. We prove the above properties by the theory of analytic semigroups on Banach spaces.

Ryôhei Kakizawa

2009-10-04

416

COUPLEFLO: A computer program for coupled creeping viscous flow and conductive-convective heat transfer addendum  

Microsoft Academic Search

COUPLEFLO, a two-dimensional finite element code for plane strain or axisymmetric analyses of thermomechanically coupled systems, is described. It is capable of analyzing the creeping flow of non-Newtonian fluids or the primary and secondary creep of solids. COUPLEFLO solves equations for conductive-convective heat transfer to determine the thermal response of a system. Thermomechanical coupling between the flow field and temperature

P. F. Chavez; P. R. Dawson

1980-01-01

417

A variable conductance heat pipe/radiator for the lunar surface magnetometer.  

NASA Technical Reports Server (NTRS)

The device was developed to supplement the existing cooling system of the Apollo 16 Lunar Surface Magnetometer (LSM). Analysis and tests showed that two such devices, inserted by an astronaut into receptacles on opposite sides of the electronics package, would reduce the diurnal temperature variation by about 40% and thereby would considerably increase the reliability of 50,000 welded connections. The LSM design constraints, selection of a variable conductance technique, heat pipe/radiator design features, and thermal performance are discussed.

Kirkpatrick, J. P.; Marcus, B. D.

1972-01-01

418

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

419

Investigation of Solar Coronal Heating Using a Time Dependent MHD Model with Full Conductivity Tensor  

NASA Astrophysics Data System (ADS)

The transition region and lower corona is investigated using a newly developed time dependent MHD model that includes gravity and a self consistently computed conductivity tensor that depends on temperature, magnetic field, and density. The model is tested by its ability to preserve FAL equilibrium profiles, and to generate MHD waves with dispersion relations similar to those predicted by linear theory for the general types of MHD waves. The model is then used to examine solar atmospheric heating by Pedersen and magnetic field aligned current dissipation. Numerical experiments are conducted in which MHD waves are launched from either the transition region upward, or from the lower corona downward. Results from parametric studies of the evolution of these waves as a function of wavelength and amplitude are presented. In particular, the heating rate due to wave dissipation is compared with the FAL cooling rate, and with analytic results presented in M. Goodman [1,2]. % . The relative importance of physical dissipation due to the conductivity tensor, and numerical dissipation is estimated using Von Neumann stability analysis (VNSA) and numerical experiments with and without physical dissipation. It is then attempted to extrapolate from the simulation data the waves which could potentially lead to the correct heating rate, assumed to be the FAL net radiative loss rate. Realistic solar atmospheric data is used throughout the numerical investigations. This work was supported in part by NSF grant ATM-0242820 to the Institute for Scientific Research.

Kazeminezhad, F.; Goodman, M. L.

2005-05-01

420

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

421

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

422

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

423

Evaluation of the conduction shape factor with a CFD code for a liquid–metal heat transfer in heated triangular rod bundles  

Microsoft Academic Search

A heat transfer due to conduction through a coolant itself is not negligible in a liquid–metal cooled reactor (LMR). This portion of a heat transfer is frequently described with a conduction shape factor during the thermal-hydraulic design of an LMR. The conduction shape factor, which is highly dependent on a pitch-to-diameter (P\\/D) ratio, is defined as the ratio of the

Hae-yong Jeong; Kwi-seok Ha; Young-min Kwon; Yong-bum Lee; Dohee Hahn; James E. Cahalan; Floyd E. Dunn

2007-01-01

424

When it comes to transporting energy, nature has two vital tools at its disposal: conduction by heat and by  

E-print Network

­ a device that can conduct heat in only one direction. The directional thermal effect was first ob- servedWhen it comes to transporting energy, nature has two vital tools at its disposal: conduction by heat and by electricity. But these two phenomena have never been treated equally by scientists

Li, Baowen

425

Analysis of combined conductive and radiative heat transfer in a two-dimensional rectangular enclosure using the discrete ordinates method  

Microsoft Academic Search

An efficient tool to deal with multidimensional radiative heat transfer is in strong demand to analyze the various thermal problems combined either with other modes of heat transfer or with combustion phenomena. The current study examines the discrete ordinates method (DOM) for coupled radiative and conductive heat transfer in rectangular enclosures in which either a nonscattering or scattering medium is

Taik Young Kim; Seung Wook Baek

1991-01-01

426

Thermal analysis of microelectric packages and printed circuit boards using an analytic solution to the heat conduction equation  

Microsoft Academic Search

This paper provides an overview of the solution and application of the three-dimensional heat conduction equation for a rectangular-shaped, multilayer structure with discrete surface heat sources. A Fourier series expansion is used to represent both the heat source function and temperature solution. Trigonometric terms are used for the two planar coordinates whereas the Fourier coefficient for the temperature expansion provides

Gordon N. Ellison

1995-01-01

427

Heat conduction in disordered harmonic lattices with energy-conserving noise.  

PubMed

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. 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. PMID:21405819

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

2011-02-01

428

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

429

Analysis of combined conductive-radiative heat transfer in a two-dimensional rectangular enclosure with a gray medium  

Microsoft Academic Search

Combined conductive-radiative heat transfer in a two-dimensional enclosure is considered. The numerical procedure is based on a combination of two previous techniques that have been demonstrated to be successful for a two-dimensional pure radiation problem and a one-dimensional combined conductive-radiative heat transfer problem, respectively. Both temperature profile and heat transfer distributions are generated efficiently and accurately. Numerical data are presented

W. W. Yuen; E. E. Takara

1988-01-01

430

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

431

Thermal conductivity and thermal diffusivity of pulse-heated W-Re alloys  

SciTech Connect

Results are reported for the thermal conductivity and thermal diffusivity as a function of temperature for four W-Re alloys (4.0, 21.24, 24.07, and 31.09 mass % of Re) over a wide temperature range covering the solid and liquid states. The measurements allow the determination of specific heat and dependences among electrical resistivity, temperature, and density of the alloys into the liquid phase. The thermal conductivity is calculated using the Wiedman-Franz law. Additionally, data for thermal conductivity and thermal diffusivity of the constituent elements, tungsten and rhenium, are presented for the first time. Both metals have been previously studied with the same experimental technique.

Seifter, A.; Didoukh, V.; Pottlacher, G.

1999-07-01

432

Influence of mashed potato dielectric properties and circulating water electric conductivity on radio frequency heating at 27 MHz.  

PubMed

Experiments and computer simulations were conducted to systematically investigate the influence of mashed potato dielectric properties and circulating water electric conductivity on electromagnetic field distribution, heating rate, and heating pattern in packaged food during radio frequency (RF) heating processes in a 6 kW, 27 MHz laboratory scale RF heating system. Both experimental and simulation results indicated that for the selected food (mashed potato) in this study, the heating rate decreased with an increase of electric conductivity of circulating water and food salt content. Simplified analytical calculations were carried out to verify the simulation results, which further indicated that the electric field distribution in the mashed potato samples was also influenced by their dielectric properties and the electric conductivity of the surrounding circulating water. Knowing the influence of water electric conductivity and mashed potato dielectric properties on the heating rate and heating pattern is helpful in optimizing the radio frequency heating process by properly adjusting these factors. The results demonstrate that computer simulation has the ability to demonstrate influence on RF heat pattern caused by the variation of material physical properties and the potential to aid the improvement on construction and modification of RF heating systems. PMID:19227075

Wang, Jian; Olsen, Robert G; Tang, Juming; Tang, Zhongwei

2008-01-01

433

Coupled radiative and conductive heat transfer in a non-grey absorbing and emitting semitransparent media under collimated radiation  

Microsoft Academic Search

This paper deals with heat transfer in non-grey semitransparent two-dimensional sample. Considering an homogeneous purely absorbing medium, we calculated the temperature field and heat fluxes of a material irradiated under a specific direction. Coupled radiative and conductive heat transfer were considered. The radiative heat transfer equation (RTE) was solved using a S8 quadrature and a discrete ordinate method. Reflection and

David Lacroix; Gilles Parent; Fatmir Asllanaj; Gérard Jeandel

2002-01-01

434

Effects of silica fume, latex, methylcellulose, and carbon fibers on the thermal conductivity and specific heat of cement paste  

Microsoft Academic Search

Due to their poor conductivity, latex (20–30% by weight of cement), methylcellulose (0.4–0.8% by weight of cement), and silica fume (15% by weight of cement) decreased the thermal conductivity of cement paste by up to 46%. In addition, these admixtures increased the specific heat of cement paste by up to 10%. The thermal conductivity decreased and the specific heat increased

X. Fu; D. D. L. Chung

1997-01-01

435

Transport properties, specific heat and thermal conductivity of GaN nanocrystalline ceramic  

SciTech Connect

The structural and transport properties (resistivity, thermopower and Hall effect), specific heat and thermal conductivity have been measured for GaN nanocrystalline ceramic prepared by hot pressing. It was found that the temperature dependence of resistivity in temperature range 10-300 K shows the very low activation energy, which is ascribed to the shallow donor doping originating in amorphous phase of sample. The major charge carriers are electrons, what is indicated by negative sign of Hall constant and Seebeck coefficient. The thermopower attains large values (-58 {mu}V/K at 300 K) and was characterized by linear temperature dependence which suggests the diffusion as a major contribution to Seebeck effect. The high electron concentration of 1.3x10{sup 19} cm{sup -3} and high electronic specific heat coefficient determined to be 2.4 mJ/molK{sup 2} allow to conclude that GaN ceramic demonstrates the semimetallic-like behavior accompanied by very small mobility of electrons ({approx}0.1 cm{sup 2}/V s) which is responsible for its high resistivity. A low heat conductivity of GaN ceramics is associated with partial amorphous phase of GaN grains due to high pressure sintering. - Graphical Abstract: Thermal resistivity and thermopower measurements indicates the high phonon scattering and lack of phonon-drag contribution to thermopower in GaN nanoceramics pressed under 4 GPa at 800 {sup o}C.

Sulkowski, Czeslaw [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland); ChuchmaLa, Andrzej, E-mail: andrzej.chuchmala@pwr.wroc.p [Wroclaw University of Technology, Institute of Electrical Engineering Fundamentals (I7), Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Zaleski, Andrzej J.; Matusiak, Marcin; Mucha, Jan; GLuchowski, PaweL; Strek, WiesLaw [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland)

2010-10-15

436

The validation of the robust input estimation approach to two-dimensional inverse heat conduction problems  

SciTech Connect

A novel adaptive and robust input estimation inverse methodology of estimating the time-varying unknown heat flux, named as the input, on the two active boundaries of a 2-D inverse heat conduction problem is presented. The algorithm includes using the Kalman filter to propose a regression model between the residual innovation and the two thermal unknown boundaries flux through given 2-D heat conduction state-space models and noisy measurement sequence. Based on this regression equation, a recursive least-square estimator (RLSE) weighted by the forgetting factor is proposed to on-line estimate these unknowns. The adaptive and robust weighting technique is essential since unknowns input are time-varied and have unpredictable changing status. In this article, the authors provide the bandwidth analysis together with bias and variance tests to construct an efficient and robust forgetting factor as the ratio between the standard deviation of measurement and observable bias innovation at each time step. Herein, the unknowns are robustly and adaptively estimated under the system involving measurement noise, process error, and unpredictable change status of time-varying unknowns. The capabilities of the proposed algorithm are demonstrated through the comparison with the conventional input estimation algorithm and validated by two benchmark performance tests in 2-D cases. Results show that the proposed algorithm not only exhibits superior robust capability but also enhances the estimation performance and highly facilitates practical implementation.

Tuan, P.C.; Ju, M.C.

2000-03-01

437

Surface roughness and three-dimensional heat conduction in thermophysical models  

NASA Astrophysics Data System (ADS)

A thermophysical model is presented that considers surface roughness, cast shadows, multiple or single scattering of radiation, visual and thermal infrared self heating, as well as heat conduction in one or three dimensions. The code is suitable for calculating infrared spectral energy distributions for spatially resolved or unresolved minor Solar System bodies without significant atmospheres or sublimation, such as the Moon, Mercury, asteroids, irregular satellites or inactive regions on comet nuclei. It is here used to explore the effects of surface roughness on spatial scales small enough for heat conduction to erase lateral temperature gradients. Analytically derived corrections to one-dimensional models that reproduce the results of three-dimensional modeling are presented. We find that the temperature of terrains with such small-scale roughness is identical to that of smooth surfaces for certain types of topographies and non-scattering material. However, systematic differences between smooth and rough terrains are found for scattering materials, or topographies with prominent positive relief. Contrary to common beliefs, the roughness on small spatial scales may therefore affect the thermal emission of Solar System bodies.

Davidsson, Björn J. R.; Rickman, Hans

2014-11-01

438

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

439

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

440

Heat Conduction and Entropy Production in Anharmonic Crystals with Self-Consistent Stochastic Reservoirs  

E-print Network

We investigate a class of anharmonic crystals in $d$ dimensions, $d\\ge 1$, coupled to both external and internal heat baths of the Ornstein-Uhlenbeck type. The external heat baths, applied at the boundaries in the 1-direction, are at specified, unequal, temperatures $\\tlb$ and $\\trb$. The temperatures of the internal baths are determined in a self-consistent way by the requirement that there be no net energy exchange with the system in the non-equilibrium stationary state (NESS). We prove the existence of such a stationary self-consistent profile of temperatures for a finite system and show it minimizes the entropy production to leading order in $(\\tlb -\\trb)$. In the NESS the heat conductivity $\\kappa$ is defined as the heat flux per unit area divided by the length of the system and $(\\tlb -\\trb)$. In the limit when the temperatures of the external reservoirs goes to the same temperature $T$, $\\kappa(T)$ is given by the Green-Kubo formula, evaluated in an equilibrium system coupled to reservoirs all having the temperature $T$. This $\\kappa(T)$ remains bounded as the size of the system goes to infinity. We also show that the corresponding infinite system Green-Kubo formula yields a finite result. Stronger results are obtained under the assumption that the self-consistent profile remains bounded.

Federico Bonetto; Joel L. Lebowitz; Jani Lukkarinen; Stefano Olla

2008-11-21

441

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

442

An implicit-iterative solution of the heat conduction equation with a radiation boundary condition  

NASA Technical Reports Server (NTRS)

For the problem of predicting one-dimensional heat transfer between conducting and radiating mediums by an implicit finite difference method, four different formulations were used to approximate the surface radiation boundary condition while retaining an implicit formulation for the interior temperature nodes. These formulations are an explicit boundary condition, a linearized boundary condition, an iterative boundary condition, and a semi-iterative boundary method. The results of these methods in predicting surface temperature on the space shuttle orbiter thermal protection system model under a variety of heating rates were compared. The iterative technique caused the surface temperature to be bounded at each step. While the linearized and explicit methods were generally more efficient, the iterative and semi-iterative techniques provided a realistic surface temperature response without requiring step size control techniques.

Williams, S. D.; Curry, D. M.

1977-01-01

443

Influence of conductive heat-losses on the propagation of premixedflames in channels  

Microsoft Academic Search

We study the propagation of premixed flames in two-dimensional channels\\u000d\\u000a\\u0009accounting for heat-losses by conduction to the channel’s walls and\\u000d\\u000a\\u0009a prescribed Poiseuille flow. A diffusive-thermal model is used and\\u000d\\u000a\\u0009the calculations reported are based on Arrhenius-type chemistry.\\u000d\\u000a\\u0009Attention is focused on the influence of the magnitude of heat losses,\\u000d\\u000a\\u0009the channel width, and the mean flow velocity. Special attention

J. Daou; M. Matalon

2002-01-01

444

The gravitational heat conduction and the hierarchical structure in solar interior  

E-print Network

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, radiation region and convection region, in excellent agreement with the solar hierarchical structure. By generalizing the Fourier 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.

Zheng Yahui; Du Jiulin

2014-03-10

445

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

446

Multiply scaled constrained nonlinear equation solvers. [for nonlinear heat conduction problems  

NASA Technical Reports Server (NTRS)

To improve the numerical stability of nonlinear equation solvers, a partitioned multiply scaled constraint scheme is developed. This scheme enables hierarchical levels of control for nonlinear equation solvers. To complement the procedure, partitioned convergence checks are established along with self-adaptive partitioning schemes. Overall, such procedures greatly enhance the numerical stability of the original solvers. To demonstrate and motivate the development of the scheme, the problem of nonlinear heat conduction is considered. In this context the main emphasis is given to successive substitution-type schemes. To verify the improved numerical characteristics associated with partitioned multiply scaled solvers, results are presented for several benchmark examples.

Padovan, Joe; Krishna, Lala

1986-01-01

447

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

448

Heat conductivity from molecular chaos hypothesis in locally confined billiard systems  

E-print Network

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 demonstated by comparing our predictions to the results of numerical simulations performed on a new class of high-dimensional defocusing chaotic billiards.

Thomas Gilbert; Raphael Lefevere

2008-10-14

449

Heat conduction: a telegraph-type model with self-similar behavior of solutions II  

E-print Network

In our former study (J. Phys. A: Math. Theor. 43, (2010) 325210 or arXiv:1002.0999v1 [math-ph]) we introduced a modified Fourier-Cattaneo law and derived a non-autonomous telegraph-type heat conduction equation which has desirable self-similar solution. Now we present a detailed in-depth analysis of this model and discuss additional analytic solutions for different parameters. The solutions have a very rich and interesting mathematical structure due to various special functions.

I. F. Barna; R. Kersner

2010-09-30

450

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

451

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

452

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

453

Mathematical equations for heat conduction in the fins of air-cooled engines  

NASA Technical Reports Server (NTRS)

The problem considered in this report is that of reducing actual geometrical area of fin-cooling surface, which is, of course, not uniform in temperature, to equivalent cooling area at one definite temperature, namely, that prevailing on the cylinder wall at the point of attachment of the fin. This makes it possible to treat all the cooling surface as if it were part of the cylinder wall and 100 per cent effective. The quantities involved in the equations are the geometrical dimensions of the fin, thermal conductivity of the material composing it, and the coefficient of surface heat dissipation between the fin and the air streams.

Harper, R R; Brown, W B

1923-01-01

454

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

SciTech Connect

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. (Department of Physics and Solid State Science Center, University of California, Los Angeles, California 90024 (USA)); Brown, S.E. (Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (USA))

1990-02-01

455

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

456

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 were made at temperatures between 65 and 303 K with pressures between 0.1 and 70 MPa. The data cover the vapor, liquid, and supercritical gas phases for the three mixtures. The total reported points are 1066 for the air mixture (78.11 percent nitrogen, 20.97 percent oxygen, and 0.92 percent argon), 1058 for the 50 percent nitrogen, 50 percent oxygen mixture, and 864 for the 25 percent nitrogen, 75 oxygen mixture. Empirical thermal conductivity correlations are provided for the three mixtures.

Perkins, R. A.; Cieszkiewicz, M. T.

1991-01-01

457

Effects of preheating and highly heat-conductive brick on coke quality  

SciTech Connect

In replacing the coke ovens available currently, the introduction of a combined technique of a preheated coal charging method (preheating temperature:175 C) and the use of highly heat-conductive brick is under examination for raising the productivity of coke ovens. With such background, a study of the effects of this combined technique on the coke quality, especially the coke size was conducted. The experimental results revealed that the primary size of coke produced by the combined technique is noticeably larger than that of the coke made from wet coal and after five revolutions of drum (equivalent to mechanical impact given at a time of dropping from coke oven chamber to wharf), the coke size reduces even compared with an ordinary coke. This may be due to the fact that the coke produced by the combined technique includes a lot of fissures inside the coke lump.

Fukuda, K.; Arima, T. [Nippon Steel Corp., Chiba (Japan). Process Technology, Research Labs.

1995-12-31

458

Thermal Conductivity and Elastic Modulus Evolution of Thermal Barrier Coatings under High Heat Flux Conditions  

NASA Technical Reports Server (NTRS)

Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings (TBCs) under near-realistic temperature and thermal gradients that may he encountered in advanced engine systems. Thermal conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures. A significant thermal conductivity increase was observed during the laser simulated engine heat flux tests. For a 0.25 mm thick ZrO2-8%Y2O3 coating system, the overall thermal conductivity increased from the initial value of 1.0 W/m-K to 1. 15 W/m-K, 1. 19 W/m-K and 1.5 W/m-K after 30 hour testing at surface temperatures of 990C, 1100C, and 1320C. respectively. Hardness and modulus gradients across a 1.5 mm thick TBC system were also determined as a function of laser testing time using the laser sintering/creep and micro-indentation techniques. The coating Knoop hardness values increased from the initial hardness value of 4 GPa to 5 GPa near the ceramic/bond coat interface, and to 7.5 GPa at the ceramic coating surface after 120 hour testing. The ceramic surface modulus increased from an initial value of about 70 GPa to a final value of 125 GPa. The increase in thermal conductivity and the evolution of significant hardness and modulus gradients in the TBC systems are attributed to sintering-induced micro-porosity gradients under the laser-imposed high thermal gradient conditions. The test techniques provide a viable means for obtaining coating data for use in design, development, stress modeling, and life prediction for various thermal barrier coating applications.

Zhu, Dongming; Miller, Robert A.

1999-01-01

459

Measurement of in-plane thermal conductivity and heat capacity of separator in Li-ion cells using a transient DC heating method  

NASA Astrophysics Data System (ADS)

The separator is a critical, multi-functional component of a Li-ion cell that plays a key role in performance and safety during energy conversion and storage processes. Heat flow through the separator is important for minimizing cell temperature and avoiding thermal runaway. Despite the critical nature of thermal conduction through the separator, very little research has been reported on understanding and measuring the thermal conductivity and heat capacity of the separator. This paper presents first-ever measurements of thermal conductivity and heat capacity of the separator material. These measurements are based on thermal response to an imposed DC heating within a time period during which an assumption of a thermally semi-infinite domain is valid. Experimental data are in excellent agreement with the analytical model. Comparison between the two results in measurement of the in-plane thermal conductivity and heat capacity of the separator. Results indicate very low thermal conductivity of the separator. Measurements at an elevated temperature indicate that thermal conductivity and heat capacity do not change much with increasing temperature. Experimental measurements of previously unavailable thermal properties reported here may facilitate a better fundamental understanding of thermal transport in a Li-ion cell, and enhanced safety due to more accurate thermal prediction.

Vishwakarma, V.; Jain, A.

2014-12-01

460

Finite Element A Posteriori Error Estimation for Heat Conduction. Degree awarded by George Washington Univ.  

NASA Technical Reports Server (NTRS)

This research investigates residual-based a posteriori error estimates for finite element approximations of heat conduction in single-layer and multi-layered materials. The finite element approximation, based upon hierarchical modelling combined with p-version finite elements, is described with specific application to a two-dimensional, steady state, heat-conduction problem. Element error indicators are determined by solving an element equation for the error with the element residual as a source, and a global error estimate in the energy norm is computed by collecting the element contributions. Numerical results of the performance of the error estimate are presented by comparisons to the actual error. Two methods are discussed and compared for approximating the element boundary flux. The equilibrated flux method provides more accurate results for estimating the error than the average flux method. The error estimation is applied to multi-layered materials with a modification to the equilibrated flux method to approximate the discontinuous flux along a boundary at the material interfaces. A directional error indicator is developed which distinguishes between the hierarchical modeling error and the finite element error. Numerical results are presented for single-layered materials which show that the directional indicators accurately determine which contribution to the total error dominates.

Lang, Christapher G.; Bey, Kim S. (Technical Monitor)

2002-01-01

461

On the dynamical Rayleigh-Taylor instability in compressible viscous flows without heat conductivity  

E-print Network

We investigate the instability of a smooth Rayleigh-Taylor steady-state solution to compressible viscous flows without heat conductivity in the presence of a uniform gravitational field in a bounded domain $\\Omega\\subset{\\mathbb R}^3$ with smooth boundary $\\partial\\Omega$. We show that the steady-state is linearly unstable by constructing a suitable energy functional and exploiting arguments of the modified variational method. Then, based on the constructed linearly unstable solutions and a local well-posedness result of classical solutions to the original nonlinear problem, we further reconstruct the initial data of linearly unstable solutions to be the one of the original nonlinear problem and establish an appropriate energy estimate of Gronwall-type. With the help of the established energy estimate, we show that the steady-state is nonlinearly unstable in the sense of Hadamard by a careful bootstrap argument. As a byproduct of our analysis, we find that the compressibility has no stabilizing effect in the linearized problem for compressible viscous flows without heat conductivity.

Fei Jiang; Song Jiang

2014-03-20

462

Numerical solutions for the one-dimensional heat-conduction equation using a spreadsheet  

NASA Astrophysics Data System (ADS)

We show how to use a spreadsheet to calculate numerical solutions of the one-dimensional time-dependent heat-conduction equation. We find the spreadsheet to be a practical tool for numerical calculations, because the algorithms can be implemented simply and quickly without complicated programming, and the spreadsheet utilities can be used not only for graphics, printing, and file management, but also for advanced mathematical operations. We implement the explicit and the Crank-Nicholson forms of the finite-difference approximations and discuss the geological applications of both methods. We also show how to adjust these two algorithms to a nonhomogeneous lithosphere in which the thermal properties (thermal conductivity, density, and radioactive heat generation) change from the upper crust to the lower crust and to the mantle. The solution is presented in a way that can fit any spreadsheet (Lotus-123, Quattro-Pro, Excel). In addition, a Quattro-Pro program with macros that calculate and display the thermal evolution of the lithosphere after a thermal perturbation is enclosed in an appendix.

Gvirtzman, Zohar; Garfunkel, Zvi

1996-12-01

463

Advanced development of the boundary element method for steady-state heat conduction  

NASA Technical Reports Server (NTRS)

Considerable progress has been made in recent years toward advancing the state-of-the-art in solid mechanics boundary element technology. In the present work, much of this new technology is applied in the development of a general-purpose boundary element method (BEM) for steady-state heat conduction. In particular, the BEM implementation involves the use of higher-order conforming elements, self-adaptive integration and multi-region capability. Two- and three-dimensional, as well as axisymmetric analysis, are incorporated within a unified framework. In addition, techniques are introduced for the calculation of boundary flux, and for the inclusion of thermal resistance across interfaces. As a final extension, an efficient formulation is developed for the analysis of solid three-dimensional bodies with embedded holes. For this last class of problems, the new BEM formulation is particularly attractive, since use of the alternatives (i.e. finite element or finite difference methods) is not practical. A number of detailed examples illustrate the suitability and robustness of the present approach for steady-state heat conduction.

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

1989-01-01

464

The specific heat capacity and thermal conductivity of normal liquid /sup 3/He  

SciTech Connect

By observing the diffusion of a heat pulse along a 10-cm column of normal liquid /sup 3/He with the aid of two vibrating wire thermometers, it has been possible to measure the heat capacity C and thermal conductivity K of the liquid in the temperature range from T /sub c/ to 10 mK and at pressures of 0.21, 4.39, 9.97, 20.01, and 29.32 bar. By using a Pt NMR thermometer, an LCMN thermometer, and a /sup 3/He melting curve thermometer calibrated using the melting curve given by Greywall in 1983, a temperature scale has been established and (1) it has been shown that this melting curve is consistent in the temperature range 5-22 mK with the Korringa law for the Pt thermometer with a Korringa constant of 29.8 +/- 0.2 sec mK, (2) departures have been observed from the Curie-Weiss law for LCMN at low temperatures, and (3) values of the superfluid transition temperature have been obtained that are about 4% lower than the Helsinki values. The measured heat capacities agree well with those of Greywall, but values of KT are higher than those of Greywall and show more temperature dependence below 10mK. The implications for the present results of the very different melting curve given by Greywall in 1985 are discussed in an Appendix.

Mitchell, R.; Eastop, A.D.; Faraj, E.; Hook, J.R.

1986-07-01

465

Phenomenological Approach to Heat Conduction in a One-Dimensional Hard-Point Gas beyond Local Equilibrium  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulation data on stationary heat conduction in a one-dimensional binary hard-point gas are studied: We estimate the validity range of the local equilibrium assumption explicitly. The temperature profiles with the temperature jumps at the boundaries are analyzed consistently by a phenomenological theory beyond the local equilibrium assumption (extended thermodynamics). The agreement between the numerical result of the temperature profiles and its theoretical prediction is fairly well. The heat conductivity is analyzed in two limiting cases: We find that the exponent, which characterizes the divergence of the heat conductivity in a thermodynamic limit, depends on the mass ratio of two different constituent particles. We also find a power law relation between the heat conductivity and the mass ratio in a limit to the system where energy transport is in a ballistic mode.

Taniguchi, Shigeru; Nakamura, Masashi; Sugiyama, Masaru; Isobe, Masaharu; Zhao, Nanrong

2008-01-01

466

Visual and quantitative measurement of the temperature distribution of heat conduction process in glass based on digital holographic interferometry  

NASA Astrophysics Data System (ADS)

The temperature distribution of heat conduction process in transparent solid medium is visually and quantitatively measured based on digital holographic interferometry. A series of phase maps reflecting the temperature distribution of a glass sample during the heat conduction process are numerically reconstructed from the digital holograms. Then, based on the derived relationship between temperature variation and phase change, we obtained the full field temperature distribution of the glass sample by the method of sample point calibration. By seriating maps of the temperature distribution, a movie is produced to show the heat conduction phenomenon more vividly. What is more, based on the thermodynamic model of heat conduction, we numerically figured out the temperature distribution of the glass sample using the finite element algorithm. It turns out that the experimental results are consistent with the numerical simulation results very well.

Wang, Qian; Zhao, Jianlin; Jiao, Xiangyang; Di, Jianglei; Jiang, Hongzhen

2012-05-01

467

Modeling of piezoelectric ceramic vibrators including thermal effects. Part III. Bond graph model for one-dimensional heat conduction  

SciTech Connect

A new bond graph model for conduction heat transfer is developed, and applied to thermal energy balance in the piezoelectric thickness vibrator. In formulation of the heat conduction model, the mechanical and electrical effects are included. Hence, it can be directly applied to the temperature-dependent thickness vibrator. For the purpose of evaluation of the new method, one-dimensional heat conduction excluding other variable effects is compared with the results of the analytic solutions in simple cases. The simulation illustrates the validity and the accuracy of the model. Although the model is applied to the one-dimensional case only, the method can be easily used for general heat conduction problems. {copyright} {ital 1997 Acoustical Society of America.}

Moon, W.; Busch-Vishniac, I.J. [Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States)] [Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States)

1997-03-01

468

An inverse analysis to estimate linearly temperature dependent thermal conductivity components and heat capacity of an orthotropic medium  

Microsoft Academic Search

An inverse analysis is used to estimate linearly temperature dependent thermal conductivity components kx(T), ky(T) and specific heat capacity C(T) per unit volume for an orthotropic solid. Simulated measured transient temperature data are generated by adding random errors to the exact temperatures computed from the solution of the two-dimensional, direct transient heat conduction problem. An iterative procedure, based on minimizing

Y. Jarny

1995-01-01

469

Effect of convective heat transfer on thermal conductivity measurement under microgravity using a transient hot wire method  

Microsoft Academic Search

Measurements of thermal conductivity for mercury are performed under low gravitational condition of 0.1 to 0.01 g during the parabolic flight of an aircraft (Mitsubishi MU-300). Effects of convective heat transfer on thermal conductivity value of low Prandtl number melts measured by a transient hot wire method are discussed quantitatively. The critical Rayleigh number to suppress convective heat transfer is

Shin Nakamura; Taketoshi Hibiya; Fumio Yamamoto

1992-01-01

470

Computational aspects of temperature-based finite element technique for the phase-change heat conduction problem  

Microsoft Academic Search

Liquid–solid phase transition is accompanied by a latent heat release, both in isothermal and non-isothermal phase transformations. The latent heat, the discontinuous phase-change function, and the local exchange of field variables during phase-changes increase the difficulties for obtaining a solution for the Fourier heat conduction equation. Celentano et al. [3] (COO) proposed a temperature-based finite element model for solving the

Ashok Kumar Nallathambi; Eckehard Specht; Albrecht Bertram

2009-01-01

471

Estimates of conductive heat flow through bottom-simulating reflectors on the Hikurangi and southwest Fiordland continental margins, New Zealand  

Microsoft Academic Search

Bottom-simulating reflectors (BSRs) represent the base of the stability field for gas hydrates in shallow oceanic sediments. A simple conductive model is used to calculate surface heat flow through the Hikurangi and southwest Fiordland continental margins of New Zealand, based on the depths of BSRs. The results indicate mean uncorrected heat flows through the two regions of 37 ± 8

John Townend

1997-01-01

472

The Coupled Analysis of Electromagnetic Wave and Heat Conduction with Rotational Motion of Heated Target and Temperature-Dependent Complex Permittivity  

NASA Astrophysics Data System (ADS)

In order to evaluate the heated process of the target, S parameter, and initial design of cavity size in the furnaces for dielectric heating such as microwave oven, the coupled analysis of electromagnetic wave and heat conduction (EM-HC coupled analysis) is a useful tool for practical design. In this paper, valuable EM-HC coupled analysis method with rotational motion of heated target such as turntable and temperature-dependent complex permittivity by using edge-based finite element method is proposed. As a result of useful investigation of the proposed method, the effectiveness in tracing the detailed temperature rise of dielectric target is demonstrated.

Okamoto, Yoshifumi; Himeno, Ryutaro; Ushida, Kiminori; Ahagon, Akira; Fujiwara, Koji

473

Reaction of thermal laminar boundary layer to stepwise change in heat conduction and specific heat of the wall in the direction of flow  

SciTech Connect

The conjugate problem of nonsteady heat transfer between a laminar boundary layer with a pressure gradient and a wall with stepwise change in its thermophysical properties (heat conduction and volume specific heat) in the longitudinal direction is solved by the finite-difference method for an incompressible liquid and a wall whose internal surface is heat insulated. The results of the calculations show that the reaction of the thermal boundary layer to discontinuity in the thermophysical properties of the wall is nonunique and multi-parametric. Since these parameters determine the thickness of the thermal boundary layer it may be concluded that thin thermal boundary layers react more strongly than thick layers.

Sapelkin, V.A.; Sergeev, Yu.V.

1988-03-01

474

A stochastic analysis of steady and transient heat conduction in random media using a homogenization approach  

SciTech Connect

We present a new stochastic analysis for steady and transient one-dimensional heat conduction problem based on the homogenization approach. Thermal conductivity is assumed to be a random field K consisting of random variables of a total number N. Both steady and transient solutions T are expressed in terms of the homogenized solution (symbol) and its spatial derivatives (equation), where homogenized solution (symbol) is obtained by solving the homogenized equation with effective thermal conductivity. Both mean and variance of stochastic solutions can be obtained analytically for K field consisting of independent identically distributed (i.i.d) random variables. The mean and variance of T are shown to be dependent only on the mean and variance of these i.i.d variables, not the particular form of probability distribution function of i.i.d variables. Variance of temperature field T can be separated into two contributions: the ensemble contribution (through the homogenized temperature (symbol)); and the configurational contribution (through the random variable Ln(x)Ln(x)). The configurational contribution is shown to be proportional to the local gradient of (symbol). Large uncertainty of T field was found at locations with large gradient of (symbol) due to the significant configurational contributions at these locations. Numerical simulations were implemented based on a direct Monte Carlo method and good agreement is obtained between numerical Monte Carlo results and the proposed stochastic analysis.

Zhijie Xu

2014-07-01

475

Anomalous heat-kernel decay for random walk among bounded random conductances  

E-print Network

We consider the nearest-neighbor simple random walk on $\\Z^d$, $d\\ge2$, driven by a field of bounded random conductances $\\omega_{xy}\\in[0,1]$. The conductance law is i.i.d. subject to the condition that the probability of $\\omega_{xy}>0$ exceeds the threshold for bond percolation on $\\Z^d$. For environments in which the origin is connected to infinity by bonds with positive conductances, we study the decay of the $2n$-step return probability $P_\\omega^{2n}(0,0)$. We prove that $P_\\omega^{2n}(0,0)$ is bounded by a random constant times $n^{-d/2}$ in $d=2,3$, while it is $o(n^{-2})$ in $d\\ge5$ and $O(n^{-2}\\log n)$ in $d=4$. By producing examples with anomalous heat-kernel decay approaching $1/n^2$ we prove that the $o(n^{-2})$ bound in $d\\ge5$ is the best possible. We also construct natural $n$-dependent environments that exhibit the extra $\\log n$ factor in $d=4$. See also math.PR/0701248.

Noam Berger; Marek Biskup; Christopher E. Hoffman; Gady Kozma

2007-06-26

476

Measurement of the Electronic Thermal Conductance Channels and Heat Capacity of Graphene at Low Temperature  

NASA Astrophysics Data System (ADS)

The ability to transport energy is a fundamental property of the two-dimensional Dirac fermions in graphene. Electronic thermal transport in this system is relatively unexplored and is expected to show unique fundamental properties and to play an important role in future applications of graphene, including optoelectronics, plasmo