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1

An improved local radial point interpolation method for transient heat conduction analysis  

NASA Astrophysics Data System (ADS)

The smoothing thin plate spline (STPS) interpolation using the penalty function method according to the optimization theory is presented to deal with transient heat conduction problems. The smooth conditions of the shape functions and derivatives can be satisfied so that the distortions hardly occur. Local weak forms are developed using the weighted residual method locally from the partial differential equations of the transient heat conduction. Here the Heaviside step function is used as the test function in each sub-domain to avoid the need for a domain integral. Essential boundary conditions can be implemented like the finite element method (FEM) as the shape functions possess the Kronecker delta property. The traditional two-point difference method is selected for the time discretization scheme. Three selected numerical examples are presented in this paper to demonstrate the availability and accuracy of the present approach comparing with the traditional thin plate spline (TPS) radial basis functions.

Wang, Feng; Lin, Gao; Zheng, Bao-Jing; Hu, Zhi-Qiang

2013-06-01

2

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

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

Determination of thermal conductivities of Sn-Zn lead-free solder alloys with radial heat flow and Bridgman-type apparatus  

NASA Astrophysics Data System (ADS)

The variations of thermal conductivities of solid phases versus temperature for pure Sn, pure Zn and Sn-9 wt.% Zn, Sn-14 wt.% Zn, Sn-50 wt.% Zn, Sn-80 wt.% Zn binary alloys were measured with a radial heat flow apparatus. The thermal conductivity ratios of liquid phase to solid phase for the pure Sn, pure Zn and eutectic Sn-9 wt.% Zn alloy at their melting temperature are found with a Bridgman-type directional solidification apparatus. Thus, the thermal conductivities of liquid phases for pure Sn, pure Zn and eutectic Sn-9 wt.% Zn binary alloy at their melting temperature were evaluated by using the values of solid phase thermal conductivities and the thermal conductivity ratios of liquid phase to solid phase.

Meydaneri, Fatma; Saatçi, Buket; Gündüz, Mehmet; Özdemir, Mehmet

2013-11-01

5

Stirling Engine With Radial Flow Heat Exchangers  

NASA Technical Reports Server (NTRS)

Conflict between thermodynamical and structural requirements resolved. In Stirling engine of new cylindrical configuration, regenerator and acceptor and rejector heat exchangers channel flow of working gas in radial direction. Isotherms in regenerator ideally concentric cylinders, and gradient of temperature across regenerator radial rather than axial. Acceptor and rejector heat exchangers located radially inward and outward of regenerator, respectively. Enables substantial increase in power of engine without corresponding increase in diameter of pressure vessel.

Vitale, N.; Yarr, George

1993-01-01

6

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

7

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

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. 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

9

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

10

Heat transfer in cooled guide vanes. [of radial inflow turbine  

NASA Technical Reports Server (NTRS)

A numerical study to determine the temperature distribution in the guide vanes of a radial inflow turbine is presented. A computer program has been developed to calculate the temperature distribution when the vanes are cooled internally using a combination of impingement and film cooling techniques. The study is based on the use of the finite difference method in a two dimensional heat conduction problem. The results are then compared to determine the best cooling configuration for a certain coolant to primary mass flow ratio.

Tabakoff, W.; Kotwal, R.; Hamed, A.

1977-01-01

11

Thermal Diffusivity Measurement by a Radial Heat Flow Method.  

National Technical Information Service (NTIS)

A method is presented whereby the thermal diffusivity of a solid is measured by observing the temperature excursion which results from a radial flow of heat. The radial heat flow is produced by the instantaneous deposition of energy on a disk region of on...

A. B. Donaldson R. E. Taylor

1975-01-01

12

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

13

Analytical Solutions for Heat Conduction.  

National Technical Information Service (NTIS)

Green's functions are found for steady state heat conduction in a composite rectangular parallelepiped (RPP) and in a composite right circular cylinder (RCC) assuming no contact resistance. These Green's functions may then be used to provide analytical so...

S. K. Fraley

1976-01-01

14

Effective heat conduction in a configuration with nonoverlapped magnetic islands  

SciTech Connect

The effective radial heat conduction {kappa}{sub eff} in a plasma configuration with nonoverlapped magnetic island chains is assessed by applying an ''optimal path'' method. This approach implies that heat is transported predominantly along paths rendering the minimum temperature variation and is related to the principle of minimum entropy production. Paths combined of up to three radial sections and two segments aligned along magnetic field lines are considered. It is demonstrated that the enhancement of {kappa}{sub eff} over the level of perpendicular heat conduction {kappa}{sub perpendicular} arising due to flows along magnetic field lines is controlled only by the Chirikov parameter and by the value 4b{sub r}{sup 2}{kappa}{sub parallel}/{kappa}{sub perpendicular}, where b{sub r} is the relative amplitude of the radial field resonant harmonic and {kappa}{sub parallel} is the parallel heat conduction.

Gupta, A.; Tokar, M. Z. [Institut fuer Energieforschung - Plasmaphysik, Forschungszentrum Juelich, Association EURATOM-FZJ, Trilateral Euregio Cluster, Juelich (Germany)

2008-03-15

15

Heat Transfer Experiments in the Internal Cooling Passages of a Cooled Radial Turbine Rotor  

NASA Technical Reports Server (NTRS)

An experimental study was conducted (1) to experimentally measure, assess and analyze the heat transfer within the internal cooling configuration of a radial turbine rotor blade and (2) to obtain heat transfer data to evaluate and improve computational fluid dynamics (CFD) procedures and turbulent transport models of internal coolant flows. A 1.15 times scale model of the coolant passages within the NASA LERC High Temperature Radial Turbine was designed, fabricated of Lucite and instrumented for transient beat transfer tests using thin film surface thermocouples and liquid crystals to indicate temperatures. Transient heat transfer tests were conducted for Reynolds numbers of one-fourth, one-half, and equal to the operating Reynolds number for the NASA Turbine. Tests were conducted for stationary and rotating conditions with rotation numbers in the range occurring in the NASA Turbine. Results from the experiments showed the heat transfer characteristics within the coolant passage were affected by rotation. In general, the heat transfer increased and decreased on the sides of the straight radial passages with rotation as previously reported from NASA-HOST-sponsored experiments. The heat transfer in the tri-passage axial flow region adjacent to the blade exit was relatively unaffected by rotation. However, the heat transfer on one surface, in the transitional region between the radial inflow passage and axial, constant radius passages, decreased to approximately 20 percent of the values without rotation. Comparisons with previous 3-D numerical studies indicated regions where the heat transfer characteristics agreed and disagreed with the present experiment.

Johnson, B. V.; Wagner, J. H.

1996-01-01

16

Fabrication and test of radial grooved micro heat pipes  

Microsoft Academic Search

This paper describes the development of radial grooved micro heat pipes (MHPs) with a three-layer structure. The MHPs were designed to allow separation of the liquid and vapor flow to reduce the viscous shear force. The 5×5 cm2 MHP array was fabricated by using bulk micromachining and eutectic bonding techniques on 4-in. (100) silicon wafers. Experiments were undertaken to evaluate

Shung-Wen Kang; Sheng-Hong Tsai; Hong-Chih Chen

2002-01-01

17

Heat Conduction of Air in Nano Spacing  

Microsoft Academic Search

The scale effect of heat conduction of air in nano spacing (NS) is very important for nanodevices to improve their life and\\u000a efficiency. By constructing a special technique, the changes of heat conduction of air were studied by means of measuring\\u000a the heat conduction with heat conduction instrument in NS between the hot plate and the cooling plate. Carbon nanotubes

Yao-Zhong Zhang; Bo Zhao; Gai-Yan Huang; Zhi Yang; Ya-Fei Zhang

2009-01-01

18

Microscale heat conduction in dielectric thin films  

Microsoft Academic Search

Starting from fundamental principles, it is shown that heat conduction by phonons can be analyzed in radiative transfer. A general theory of heat conduction is developed, showing that the Fourier law is a limiting case for steady-state macroscale heat transport. Two cases of heat transport across and along a thin film are considered. For the transient case, the theory shows

A. Majumdar

1993-01-01

19

Heat Conduction in Three Dimensions.  

National Technical Information Service (NTIS)

An applications-oriented numerical solution to the heat diffusion equation in three dimensions, with local temperature dependence in the thermal parameters and including phase changes, has been developed. Comparisons with exact one-dimensional solutions a...

S. T. Hanley

1976-01-01

20

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

21

Asymmetric Heat Conduction in Nonlinear Systems  

NASA Astrophysics Data System (ADS)

Heat conduction is an old yet important problem. Since Fourier introduced the law bearing his name two hundred years ago, a first-principle derivation of this law from statistical mechanics is still lacking. Worse still, the validity of this law in low dimensions, and the necessary and sufficient conditions for its validity are still far from clear. In this talk I'll give a review of recent works done on this subject. I'll also report our latest work on asymmetric heat conduction in nonlinear systems. The study of heat condution is not only of theoretical interest but also of practical interest. The study of electric conduction has led to the invention of such important electric devices such as electric diodes and transistors. The study of heat conduction may also lead to the invention of thermal diodes and transistors in the future. Note from Publisher: This article contains the abstract only.

Hu, Bambi

2008-12-01

22

Heat Conductivity of Pure Oxide Ceramics.  

National Technical Information Service (NTIS)

The values of lamda (heat conductivity) for dense specimens of ceramics made from Al2O3, MgO, and BeO, measured by the methods of stationary and regular heat regimes, differ within the limits of experimental error. The lamda of specimens with similar dens...

I. G. Duderov D. N. Poluboyarinov

1969-01-01

23

Contact conductivity of cryogenic heat insulation materials  

Microsoft Academic Search

Results are presented of an experimental investigation by the method of the electrothermal analogy for the contact heat transfer in different kinds of cryogenic thermal insulation and empirical dependences are obtained that permit execution of a qualitative, and in a number of cases, even a quantitative estimate of the contribution of the contact conductivity to the total heat transport through

S. B. Mil'Man; M. G. Velikanova

1991-01-01

24

Leaf hydraulic conductance for a tank bromeliad: axial and radial pathways for moving and conserving water.  

PubMed

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

25

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.

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

2013-01-01

26

Transient Heat Conduction Simulation around Microprocessor Die  

NASA Astrophysics Data System (ADS)

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

Nishi, Koji

27

Local effects of longitudinal heat conduction in plate heat exchangers  

Microsoft Academic Search

In a plate heat exchanger, heat transfer from the hot to the cold fluid is a multi-dimensional conjugate problem, in which longitudinal heat conduction (LHC) along the dividing walls often plays some role and can not be neglected. Large-scale, or end-to-end, LHC is always detrimental to the exchanger’s effectiveness. On the contrary, if significant non-uniformities exist in the distribution of

Michele Ciofalo

2007-01-01

28

Radial heat flux limits in potassium heat pipes: An experimental and analytical investigation  

NASA Astrophysics Data System (ADS)

A radial flux limit of 147 W/sq cm at the wetted inner tube wall has been demonstrated with a Nb-1 percent Zr/K heat pipe, a flux 5 times greater than the previously accepted safe design level of 25 to 30 W/sq cm. The wick structure was an annular gap type fabricated from 100 times 100 mesh Nb-1 percent Zr screen. Rigorous fabrication and cleaning procedures are believed to be critical to good wetting, resulting in significantly reduced active nucleation site size and a higher boiling limit. The procedure used to clean this heat pipe included acid wash, Freon-TF degrease, ethanol wash, high-vacuum firing, and operation as a lithium heat pipe. A heat pipe boiling limit model, based on the active nucleation site radius, is described. An active nucleation site radius of 6 times 10(exp -6) m 2.4 times 10(exp -4) in. correlates the radial flux boiling limit measured in these tests.

Woloshun, K. A.; Sena, J. Tom; Keddy, E. S.; Merrigan, Michael A.

29

Asymmetric heat conduction in nonlinear lattices.  

PubMed

In this Letter, we conduct an extensive study of the two-segment Frenkel-Kontorova model. We show that the rectification effect of the heat flux reported in recent literature is possible only in the weak interfacial coupling limit. The rectification effect will be reversed when the properties of the interface and the system size change. These two types of asymmetric heat conduction are governed by different mechanisms though both are induced by nonlinearity. An intuitive physical picture is proposed to interpret the reversal of the rectification effect. Since asymmetric heat conduction depends critically on the properties of the interface and the system size, it is probably not an easy task to fabricate a thermal rectifier or thermal diode in practice. PMID:17025972

Hu, Bambi; Yang, Lei; Zhang, Yong

2006-09-22

30

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

31

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

32

Measurement of heat conduction through stacked screens.  

PubMed

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. PMID:11543366

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

1998-01-01

33

Determination of the heat transfer coefficients in transient heat conduction  

NASA Astrophysics Data System (ADS)

The determination of the space- or time-dependent heat transfer coefficient which links the boundary temperature to the heat flux through a third-kind Robin boundary condition in transient heat conduction is investigated. The reconstruction uses average surface temperature measurements. In both cases of the space- or time-dependent unknown heat transfer coefficient the inverse problems are nonlinear and ill posed. Least-squares penalized variational formulations are proposed and new formulae for the gradients are derived. Numerical results obtained using the nonlinear conjugate gradient method combined with a boundary element direct solver are presented and discussed.

Nho Hào, Dinh; Thanh, Phan Xuan; Lesnic, D.

2013-09-01

34

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

35

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

36

Electrohydrodynamic instability in an annular liquid layer with radial conductivity gradients  

NASA Astrophysics Data System (ADS)

In this paper, the electrohydrodynamic stability in an annular liquid layer with a radial electrical conductivity gradient is investigated. A weak shear flow arises from a constant pressure gradient in the axial direction. In the radial direction, an electric field is applied. The three-dimensional linear instability analysis is implemented to study the influence of the inner radius, electrical conductivity gradient, shear flow, and ionic diffusion on the dynamics of the fluid layer. It is found that the critical unstable mode may either be oscillatory or stationary. The system becomes more unstable as the dimensionless inner radius a increases. When the inner radius a is small, the critical unstable mode is stationary, while it is given by three-dimensional oblique waves when a is large. When the conductivity gradient is small, the critical unstable mode is the three-dimensional oblique wave, while when the conductivity gradient is large, it would switch to the stationary mode rather than the oscillatory mode. The system becomes more unstable when the Reynolds number is slightly increased from zero. Additionally, it is found that the electrical Schmidt number has dual effects. The liquid layer becomes either more unstable or stable as the electric Schmidt number increases.

Ding, Zijing; Wong, Teck Neng

2014-03-01

37

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

38

Radial Reactor-Heat Exchanger for Natural Gas Combustion in a Structured Porous Metal Catalyst Bed  

Microsoft Academic Search

A compact (0.01 m3 in volume) radial reactor for deep oxidation of methane (with a heat output of 16–30 kW) that is combined with an internal water heat exchanger is designed. The reactor contains the structured porous metal catalyst 5% (0.5% Pt\\/?-Al2O3) + 65% Ni + 5% Al. The reactor performance at different heat outputs is experimentally studied. It is

V. A. Kirillov; N. A. Kuzin; V. A. Kuz’min; V. B. Skomorokhov; A. B. Shigarov

2005-01-01

39

Impact of Radial Compression on the Conductance of Carbon Nanotube Field Effect Transistors  

NASA Astrophysics Data System (ADS)

The electronic behavior of semiconducting carbon nanotubes based CNTFET under the influence of radial deformation defect present in the channel is theoretically investigated using nonequilibrium Green's function method self-consistently coupled with three-dimensional electrostatics. It was found that deformation in the CNTFET channel composed of a small diameter semiconducting carbon nanotube can increase its conductance by a factor of 4 or more depending upon the average reduction in the C-C bond length after compression. This increase in CNTFET conductance is directly related to the movement of the electronic states toward the Fermi level when the tubes are squeezed. Furthermore, the device ON-OFF current ratio also decreases with increase in applied compression which makes it hard to switch-OFF the device.

Choudhary, Sudhanshu; Saini, Gaurav; Qureshi, S.

2014-01-01

40

Measurements of radial profiles of ion cyclotron resonance heating on the tandem mirror experiment  

SciTech Connect

A small Radial Energy Analyzer (REA) was used on the Tandem Mirror Experiment-Upgrade (TMX-U), at Lawrence Livermore National Laboratory, to investigate the radial profiles of ion temperature, density, and plasma potential during Ion Cyclotron Resonance Heating (ICRH). This analyzer indicates an increase in ion temperature from {approx}20 eV before ICRH to {approx}150 eV during ICRH, with {approx}60 kW of broadcast power. The REA measurements were cross-checked against other diagnostics on TMX-U and found to be consistent. The ion density measurement was compared to the line-density measured by microwave interferometry and found to agree within 10 to 20%. A radial integral of n{sub i}T{sub i} as measured by the REA shows good agreement with the diamagnetic loop measurement of plasma energy. The radial density profile is observed to broaden during the RF heating pulses, without inducing additional radial losses in the core plasma. The radial profile of plasma potential is seen to vary from axially peaked, to nearly flat, as the plasma conditions varied over the series of experiments. To relate the increase in ion temperature to power absorbed by the plasma, a power balance as a function of radius was performed. The RF power absorbed is set equal to the sum of the losses during ICRH, minus those without ICRH. This method accounts for more than 70% of the broadcast power using a simple power balance model. The measured radial profile of the RF heating was compared to the calculations of two codes, ANTENA and GARFIELD, to test their effectiveness as predictors of power absorption profiles for TMX-U.

Falabella, S.

1988-01-01

41

Measurements of radial profiles of ion cyclotron resonance heating on the Tandem Mirror Experiment-Upgrade  

SciTech Connect

A small Radial Energy Analyzer (REA) was used on the Tandem Mirror Experiment-Upgrade (TMX-U), at Lawerence Livermore National Laboratory, to investigate the radial profiles of ion temperature, density, and plasma potential during Ion Cyclotron Resonance Heating (ICRH). The probe has been inserted into the central-cell plasma at temperatures of 200 eV and densities of 3 x 10/sup 12/cm/sup /minus 3// without damage to the probe, or major degradation of the plasma. This analyzer has indicated an increase in ion temperature from near 20 eV before ICRH to near 150 eV during ICRH, with about 60 kW of broadcast power. The REA measurements were cross-checked against other diagnostics on TMX-U and found to be consistent. The ion density measurement was compared to the line-density measured by microwave interferometry and found to agree within 10 to 20%. A radial intergral of n/sub i/T/sub i/ as measured by the REA shows good agreement with the diamagnetic loop measurement of plasma energy. The radial density profile is observed to broaden during the RF heating pulses, without inducing additional radial losses in the core plasma. The radial profile of plasma is seen to vary from axially peaked, to nearly flat as the plasma conditions carried over the series of experiments. To relate the increase in ion temperature to power absorbed by the plasma, a power balance as a function of radius was performed. The RF power absorbed is set equal to the sum of the losses during ICRH, minus those without ICRH. This method accounts for more than 70% of the broadcast power using a simple power balance model. The measured radial profile of the RF heating was compared to the calculations of two codes, ANTENA and GARFIELD, to test their effectiveness as predictors of power absorption profiles for TMX-U. 62 refs., 63 figs., 7 tabs.

Falabella, S.

1988-05-11

42

Measurements of radial heat wave propagation in laser-produced exploding-foil plasmas  

SciTech Connect

Time-resolved, 2D images of x-ray emission from thin, laser-irradiated titanium foils are presented. The foils are irradiated with 0.35 [mu]m light at intensities of 1[times]10[sup 15] W/cm[sup 2] which produces a plasma with electron densities [le]10[sup 22] cm[sup [minus]3] and electron temperature of 3--4 keV. X-ray emission that is characteristic of the thermal heat front is observed to propagate radially outward from the heated region. Comparison of these measurements with 2D hydrodynamic simulations of the experiment suggests the radial heat flux to be about 3% of the free-streaming heat flux.

Montgomery, D.S.; Landen, O.L.; Drake, R.P.; Estabrook, K.G.; Baldis, H.A.; Batha, S.H.; Bradley, K.S.; Procassini, R.J. (Lawrence Livermore National Laboratory, Livermore, California 94551 (United States) Plasma Physics Research Institute, University of California Davis, Lawrence Livermore National Laboratory, Livermore, California 94551 (United States) Department of Applied Science, University of California Davis, Davis, California 95616 (United States))

1994-10-10

43

Measurements of radial heat wave propagation in laser-produced exploding-foil plasmas  

Microsoft Academic Search

Time-resolved, 2D images of x-ray emission from thin, laser-irradiated titanium foils are presented. The foils are irradiated with 0.35 mum light at intensities of 1×1015 W\\/cm2 which produces a plasma with electron densities <=1022 cm-3 and electron temperature of 3-4 keV. X-ray emission that is characteristic of the thermal heat front is observed to propagate radially outward from the heated

D. S. Montgomery; O. L. Landen; R. P. Drake; K. G. Estabrook; H. A. Baldis; S. H. Batha; K. S. Bradley; R. J. Procassini

1994-01-01

44

Calculations of Temperature, Conductive Heat Flux, and Heat Wave Velocities Due to Radiant Heating of Opaque Materials.  

National Technical Information Service (NTIS)

The analytic solutions of the one-dimensional Fourier conductive heat flux law and corresponding transient heat transfer equation have been used to calculate temperature, conductive heat flux, and their trajectories due to radiant heating of opaque materi...

A. Cohen

2011-01-01

45

2D divertor heat flux distribution using a 3D heat conduction solver in National Spherical Torus Experiment.  

PubMed

The divertor heat flux footprint in tokamaks is often observed to be non-axisymmetric due to intrinsic error fields, applied 3D magnetic fields or during transients such as edge localized modes. Typically, only 1D radial heat flux profiles are analyzed; however, analysis of the full 2D divertor measurements provides opportunities to study the asymmetric nature of the deposited heat flux. To accomplish this an improved 3D Fourier analysis method has been successfully applied in a heat conduction solver (TACO) to determine the 2D heat flux distribution at the lower divertor surface in the National Spherical Torus Experiment (NSTX) tokamak. This advance enables study of helical heat deposition onto the divertor. In order to account for heat transmission through poorly adhered surface layers on the divertor plate, a heat transmission coefficient, defined as the surface layer thermal conductivity divided by the thickness of the layer, was introduced to the solution of heat conduction equation. This coefficient is denoted as ? and a range of values were tested in the model to ensure a reliable heat flux calculation until a specific value of ? led to the constant total deposited energy in the numerical solution after the end of discharge. A comparison between 1D heat flux profiles from TACO and from a 2D heat flux calculation code, THEODOR, shows good agreement. Advantages of 2D heat flux distribution over the conventional 1D heat flux profile are also discussed, and examples of 2D data analysis in the study of striated heat deposition pattern as well as the toroidal degree of asymmetry of peak heat flux and heat flux width are demonstrated. PMID:23464209

Gan, K F; Ahn, J-W; Park, J-W; Maingi, R; McLean, A G; Gray, T K; Gong, X; Zhang, X D

2013-02-01

46

2D divertor heat flux distribution using a 3D heat conduction solver in National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

The divertor heat flux footprint in tokamaks is often observed to be non-axisymmetric due to intrinsic error fields, applied 3D magnetic fields or during transients such as edge localized modes. Typically, only 1D radial heat flux profiles are analyzed; however, analysis of the full 2D divertor measurements provides opportunities to study the asymmetric nature of the deposited heat flux. To accomplish this an improved 3D Fourier analysis method has been successfully applied in a heat conduction solver (TACO) to determine the 2D heat flux distribution at the lower divertor surface in the National Spherical Torus Experiment (NSTX) tokamak. This advance enables study of helical heat deposition onto the divertor. In order to account for heat transmission through poorly adhered surface layers on the divertor plate, a heat transmission coefficient, defined as the surface layer thermal conductivity divided by the thickness of the layer, was introduced to the solution of heat conduction equation. This coefficient is denoted as ? and a range of values were tested in the model to ensure a reliable heat flux calculation until a specific value of ? led to the constant total deposited energy in the numerical solution after the end of discharge. A comparison between 1D heat flux profiles from TACO and from a 2D heat flux calculation code, THEODOR, shows good agreement. Advantages of 2D heat flux distribution over the conventional 1D heat flux profile are also discussed, and examples of 2D data analysis in the study of striated heat deposition pattern as well as the toroidal degree of asymmetry of peak heat flux and heat flux width are demonstrated.

Gan, K. F.; Ahn, J.-W.; Park, J.-W.; Maingi, R.; McLean, A. G.; Gray, T. K.; Gong, X.; Zhang, X. D.

2013-02-01

47

Heat conduction in heterogeneous media and volumetric heating of oil shales by magnetic methods  

Microsoft Academic Search

The problem of volumetric heating of oil shales by electromagnetic methods is studied theoretically. This study includes both a detailed examination of heat conduction in composite media, and the development of a numerical model to describe the heating process. The effects of layering on heat conduction in oil shale materials is studied theoretically. A new solution to a heat conduction

Baker-Jarvis

1984-01-01

48

Induction heating of electrically conductive porous asphalt concrete  

Microsoft Academic Search

In this research, an electrically conductive porous asphalt concrete, used for induction heating, was prepared by adding electrically conductive filler (steel fibers and steel wool) to the mixture. The main purpose of this paper is to examine the electrical conductivity and the indirect tensile strength of this conductive porous asphalt concrete and prove that it can be heated via induction

Quantao Liu; Erik Schlangen; Álvaro García; Martin van de Ven

2010-01-01

49

Variable-Conductance Heat-Transfer Module  

NASA Technical Reports Server (NTRS)

Working lengths of heat pipes electronically controlled. Rate of heat transfer controlled by electrical heaters shorten effective working lengths of heat pipes. Concept not limited to right circular cylindrical shape. Concept adaptable to terrestrial instruments or processes in which atmospheres or fluids must be cooled and returned to instruments or processes at fixed lower temperatures.

Hewitt, D. R.

1984-01-01

50

The peridynamic formulation for transient heat conduction  

Microsoft Academic Search

In bodies where discontinuities, like cracks, emerge and interact, the classical equations for heat and mass transfer are not well suited. We propose a peridynamic model for transient heat (or mass) transfer which is valid when the body undergoes damage or evolving cracks. We use a constructive approach to find the peridynamic formulation for heat transfer and test the numerical

Florin Bobaru; Monchai Duangpanya

2010-01-01

51

Vibrations and nonuniform heating of a shaft in a radial bearing  

SciTech Connect

This article examines the problem of vibrations of the axis of a shaft in a radial bearing due to the imbalance of the system as a result of nonuniform heating of the shaft. For purposes of generality a simplified model of an ideal radial bearing is used; within its framework, various boundary-value problems are divided and linearized. The proposed methods of analysis make it possible in principle to find a correlation function between the oscillations of the shaft of a radial bearing and the perturbing force acting on it, between the perturbed flow in the layer of lubricant and these oscillations, and between the distribution of the shaft temperature and the properties of such a flow. Closing of the problem of unbalancing (which can be modeled as a result of a peculiar thermohydrodynamic unstable system) is effected with the aid of the solution of the independent problem of thermoelasticity.

Buevich, Yu.A.; L'vov, M.I.

1988-08-01

52

Transport of radial heat flux and second sound in fusion plasmas  

SciTech Connect

Simple flux-gradient relations that involve time delay and radial coupling are discussed. Such a formulation leads to a rather simple description of avalanches and may explain breaking of gyroBohm transport scaling. The generalization of the flux-gradient relation (i.e., constitutive relation), which involve both time delay and spatial coupling, is derived from drift-kinetic equation, leading to kinetic definitions of constitutive elements such as the flux of radial heat flux. This allows numerical simulations to compute these cubic quantities directly. The formulation introduced here can be viewed as an extension of turbulence spreading to include the effect of spreading of cross-phase as well as turbulence intensity, combined in such a way to give the flux. The link between turbulence spreading and entropy production is highlighted. An extension of this formulation to general quasi-linear theory for the distribution function in the phase space of radial position and parallel velocity is also discussed.

Guercan, Oe. D.; Berionni, V.; Hennequin, P.; Morel, P.; Vermare, L. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex (France); Diamond, P. H. [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of); CMTFO and CASS, UCSD, California 92093 (United States); Garbet, X.; Dif-Pradalier, G. [CEA, IRFM, F-13108 Saint Paul Lez Durance (France); Kosuga, Y. [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of)

2013-02-15

53

Statistical analysis as approach to conductive heat transfer modelling  

NASA Astrophysics Data System (ADS)

The main inspiration for article was the problem of high investment into installation of the building insulation. The question of its effectiveness and reliability also after the period of 10 or 15 years was the topic of the international research project carried out at the University of Prešov in Prešov and Vienna University of Technology entitled "Detection and Management of Risk Processes in Building Insulation" and numbered SRDA SK-AT-0008-10. To detect especially the moisture problem as risk process in the space between the wall and insulation led to construction new measuring equipment to test the moisture and temperature without the insulation destruction and this way to describe real situation in old buildings too. The further investigation allowed us to analyse the range of data in the amount of 1680 measurements and express conductive heat transfer using the methods of statistical analysis. Modelling comprises relationships of the environment properties inside the building, in the space between the wall and insulation and in ambient surrounding of the building. Radial distribution function also characterizes the connection of the temperature differences.

Antonyová, A.; Antony, P.

2013-04-01

54

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

NASA Astrophysics Data System (ADS)

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.; Diamond, P. H.; Dif-Pradalier, G.; Gürcan, Ã.-. D.

2014-05-01

55

Some observations on the historical development of conduction heat transfer  

NASA Astrophysics Data System (ADS)

An attempt is made to obtain historical perspectives on the development of the mathematical theory of heat conduction considering Newton's law of cooling (1701) and its close connection with Fourier's work from 1807 to 1822 resulting in his epoch-making treatise on "The Analytical Theory of Heat". Fourier was the principal architect of the heat conduction theory. Fourier's work established a new methodology for the formulation and solution of physical problems, based on partial differential equations and marked a major turning point in the history of physics. The developments in the periods 1822 to 1900 and 1900 to 1950 are also briefly reviewed as are the classical (analytical) and numerical methods of solution for heat conduction problems. The analogy in heat, momentum, and mass transfer for transport phenomena is discussed. A list of recent conduction heat transfer books is presented to show the scope of recent developments. Some observations on conduction heat transfer are noted.

Cheng, Kwo Chang

56

Heat transfer enhancement and pumping power in confined radial flows using nanoparticle suspensions (nanofluids)  

Microsoft Academic Search

This paper presents a numerical investigation of heat transfer enhancement capabilities of coolants with suspended nanoparticles (Al2O3 dispersed in water) inside a confined impinging jet cooling device. Steady, laminar radial flow of a nanofluid in a axis-symmetric configuration with axial coolant injection has been considered. A single phase fluid approach was adopted to numerically investigate the behavior of nanofluids in

Iulian Gherasim; Gilles Roy; Cong Tam Nguyen; Dinh Vo-Ngoc

2011-01-01

57

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

58

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

59

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

60

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

61

Interchangeable variable conductance heat pipes for sodium-sulfur batteries  

NASA Astrophysics Data System (ADS)

Sodium-sulfur batteries can provide electrical power to satellite instrumentation operating in geosynchronous-earth-orbit (GEO) and low-earth-orbit (LEO) conditions. While on orbit, the sodium-sulfur battery requires thermal management as the battery is cycled between discharge in solar eclipse and recharge in sunlight. As the battery discharges in solar eclipse waste heat is generated and the battery requires cooling. During recharge in sunlight the battery temperature needs to be maintained above 320 C. In this Phase 1 program, Thermacore developed and demonstrated a dual titanium/cesium heat pipe to provide passive, lightweight management of the battery during orbital cycling. The dual heat pipe concept uses both constant and variable conductance heat pipes. Constant conductance heat pipes are inserted between sodium-sulfur cells. The cells radiate to the constant conductance heat pipes and this energy is transferred to a variable conductance heat pipe and radiated to deep space.

Hartenstine, John R.

1991-08-01

62

A survey of heat conduction problems  

Microsoft Academic Search

Several forms of thermal conductivity apparatus are described which have been devised for the study of diverse materials ranging from a sheet of mica to a wall section weighing half a ton. The materials are broadly classified into four groups:(1) Materials of very low thermal conductivity, such as cold storage insulators. (2) Materials supplied in the form of thin sheets

Ezer Griffiths

1928-01-01

63

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

64

Application of Radial Basis Function Neural Networks to Odour Sensing Using a Broad Specifity Array of Conducting Polymers  

Microsoft Academic Search

Neural networks are increasingly being used to enhance the classification and recognition powers of data collected from sensory analysis. This paper details the effectiveness of an enhanced Radial Basis Function Neural Network combined with the outputs from an Electronic Nose using electrically conducting organic polymers as sensor materials. Robust performance and classification of data is demonstrated with data patterns from

Dong-hyun Lee; John S. Payne; Hyung-gi Byun; Krishna C. Persaud

1996-01-01

65

Analytical calculation of the magnetic-dipole field in a radially expanding and differentially rotating conducting medium  

Microsoft Academic Search

An electrodynamic problem of the solar wind is considered in the case when a sphere of radius R0 with a constant conductivity sigma1 and a magnetic dipole source in the center rotates with an angular velocity Omega1 parallel to the magnetic axis. At R greater than R0, there is specified a constant radial velocity of the expansion of the medium

A. I. Laptukhov; V. P. Shabanskii

1984-01-01

66

Manufacture of high heat conductivity resistant clay bricks containing perlite  

Microsoft Academic Search

Different methods have been investigated for achieving heat insulation in the buildings. Manufacturing of high heat conductivity resistant construction materials is an important part of these research efforts. Perlite is an extremely useful material for heat insulation and 70% of the world reserves are located in Turkey. Nearly 65% of the perlite produced today is consumed by the construction industry.

?lker Bekir Topçu; Burak I??kda?

2007-01-01

67

Spherical harmonic analysis of earth's conductive heat flow  

Microsoft Academic Search

A reappraisal of the international heat flow database has been carried out and the corrected data set was employed in spherical harmonic analysis of the conductive component of global heat flow. Procedures used prior to harmonic analysis include analysis of the heat flow data and determination of representative mean values for a set of discretized area elements of the surface

V. M. Hamza; R. R. Cardoso; C. F. Ponte Neto

2008-01-01

68

Phononic Heat Conduction in Disordered Crystals  

Microsoft Academic Search

We investigate the question as to whether disordered harmonic crystals in two and three dimensions have a finite thermal conductivity. A heuristic argument using localization theory and kinetic theory is given to estimate the system size dependence of the current. Numerical results testing these predictions are then discussed. The numerical studies are based on the Landauer formula using phonon transmission

Abhishek Dhar

2011-01-01

69

Truly meshless localized type techniques for the steady-state heat conduction problems for isotropic and functionally graded materials  

Microsoft Academic Search

A numerical solution of steady-state heat conduction problems is obtained using the strong form meshless point collocation (MPC) method. The approximation of the field variables is performed using the Moving Least Squares (MLS) and the local form of the multiquadrics Radial Basis Functions (LRBF). The accuracy and the efficiency of the MPC schemes (with MLS and LRBF approximations) are investigated

E. D. Skouras; G. C. Bourantas; V. C. Loukopoulos; G. C. Nikiforidis

2011-01-01

70

A criterion of applicability of the parabolic heat conduction equation  

NASA Astrophysics Data System (ADS)

A criterion ( K MCV) of applicability of the parabolic heat conduction equation to isotropic materials is proposed that quantitatively determines the conditional boundary between linear and nonlinear regimes of nonequilibrium thermodynamics in the one-dimensional formulation of some heat transfer problems. The criterion is related to the heat flux relaxation time ?r. Once this characteristic time is known, the condition K MCV = 0 implies validity of the parabolic heat conduction equation. If ?r is unknown, the adequacy of the parabolic heat conduction model can be judged from the absence of a temporal variation of the K MCV/?r ratio under the main condition that the heat source power is independent of the time.

Kostanovskiy, A. V.; Kostanovskaya, M. E.

2008-06-01

71

Measurements of radial heat wave propagation in laser-produced exploding-foil plasmas  

Microsoft Academic Search

Time-resolved, 2D images of x-ray emission from thin, laser-irradiated titanium foils are presented. The foils are irradiated with 0.35 [mu]m light at intensities of 1[times]10[sup 15] W\\/cm[sup 2] which produces a plasma with electron densities [le]10[sup 22] cm[sup [minus]3] and electron temperature of 3--4 keV. X-ray emission that is characteristic of the thermal heat front is observed to propagate radially

D. S. Montgomery; O. L. Landen; R. P. Drake; K. G. Estabrook; H. A. Baldis; S. H. Batha; K. S. Bradley; R. J. Procassini

1994-01-01

72

Numerical solutions of transient temperature and thermally induced stress distributions in a solid disk heated with radially periodic expanding and contracting ring heat flux  

Microsoft Academic Search

Thermal stresses are taken into consideration as important phenomena in many manufacturing processes and design applications. Moreover, moving heat source is frequently encountered in these processes. The aim of this study is to analyze the numerical solutions of transient temperature and thermally induced stress distributions in a solid steel disk heated with radially periodic expanding and contracting ring heat flux

Hüseyin Yap?c?; Gamze Ba?türk

2005-01-01

73

Heat conduction in deformable Frenkel-Kontorova lattices: Thermal conductivity and negative differential thermal resistance  

NASA Astrophysics Data System (ADS)

Heat conduction through the Frenkel-Kontorova lattices is numerically investigated in the presence of a deformable substrate potential. It is found that the deformation of the substrate potential has a strong influence on heat conduction. The thermal conductivity as a function of the shape parameter is nonmonotonic. The deformation can enhance thermal conductivity greatly, and there exists an optimal deformable value at which thermal conductivity takes its maximum. Remarkably, we also find that the deformation can facilitate the appearance of the negative differential thermal resistance.

Ai, Bao-Quan; Hu, Bambi

2011-01-01

74

Heat conduction in deformable Frenkel-Kontorova lattices: thermal conductivity and negative differential thermal resistance.  

PubMed

Heat conduction through the Frenkel-Kontorova lattices is numerically investigated in the presence of a deformable substrate potential. It is found that the deformation of the substrate potential has a strong influence on heat conduction. The thermal conductivity as a function of the shape parameter is nonmonotonic. The deformation can enhance thermal conductivity greatly, and there exists an optimal deformable value at which thermal conductivity takes its maximum. Remarkably, we also find that the deformation can facilitate the appearance of the negative differential thermal resistance. PMID:21405685

Ai, Bao-quan; Hu, Bambi

2011-01-01

75

Geometrically Unidimensional Heat Conduction in Melting and Solidification.  

National Technical Information Service (NTIS)

An analytical approximation method is given for the solution of one-dimensional heat-conduction problems involving simultaneous phase change in melting and solidification processes. The starting point is a polynomial expression for the temperature distrib...

F. Megerlin

1968-01-01

76

Kohlrausch Heat Conductivity Apparatus for Intermediate or Advanced Laboratory  

ERIC Educational Resources Information Center

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

Jensen, H. G.

1970-01-01

77

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

78

Sequential Regularization Solution of the Inverse Heat Conduction Problem.  

National Technical Information Service (NTIS)

The Inverse Heat Conduction Problem (IHCP) is defined and a sequential regularization solution is presented. Although the algorithm is developed specifically for the first-order regularization procedure, it can be extended to any order. Example calculatio...

J. V. Beck B. F. Blackwell C. R. St. Clair

1985-01-01

79

Monte Carlo Heat Conduction Using the Transport Equation Approximation.  

National Technical Information Service (NTIS)

The use of Monte Carlo radiation transport codes to solve heat conduction problems was shown to be applicable to steady state and time dependent multi-media problems. An improved method for treating problems with given surface temperature distributions is...

S. K. Fraley

1977-01-01

80

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 [Formula: see text] 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 [Formula: see text] 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

81

Spherical harmonic analysis of earth’s conductive heat flow  

Microsoft Academic Search

A reappraisal of the international heat flow database has been carried out and the corrected data set was employed in spherical\\u000a harmonic analysis of the conductive component of global heat flow. Procedures used prior to harmonic analysis include analysis\\u000a of the heat flow data and determination of representative mean values for a set of discretized area elements of the surface

V. M. Hamza; R. R. Cardoso; C. F. Ponte Neto

2008-01-01

82

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

83

Variable Conductance Heat Pipes from the Laboratory to Space.  

National Technical Information Service (NTIS)

Heat pipes were developed which can be used as (1) a variable conductance link between a heat source and sink which provides temperature stability; (2) a feedback control mechanism that acts to directly maintain the source at a constant temperature; (3) o...

J. P. Kirkpatrick

1973-01-01

84

Normal heat conductivity in chains capable of dissociation  

NASA Astrophysics Data System (ADS)

The paper considers the highly debated problem of convergence of heat conductivity in one-dimensional chains with asymmetric nearest-neighbor potential. We conjecture that the convergence may be promoted not by the mere asymmetry of the potential, but due to the possibility that the chain dissociates. In other terms, the attractive part of the potential function should approach a finite value as the distance between the neighbors grows. To clarify this point, we study the simplest model of this sort —a chain of linearly elastic rods with finite size. If the distance between the rod centers exceeds their size, the rods cease to interact. Formation of gaps between the rods is the only possible mechanism for scattering of the elastic waves. Heat conduction in this system turns out to be convergent. Moreover, an asymptotic behavior of the heat conduction coefficient for the case of large densities and relatively low temperatures obeys a simple Arrhenius-type law. In the limit of low densities, the heat conduction coefficient converges due to triple rod collisions. Numeric observations in both limits are grounded by analytic arguments. In a chain with Lennard-Jones nearest-neighbor potential the heat conductivity also saturates in a thermodynamic limit and the coefficient also scales according to the Arrhenius law for low temperatures. This finding points on a universal role played by the possibility of dissociation, as convergence of the heat conduction coefficient is considered.

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

2014-05-01

85

Heat transfer enhancement with the use of nanofluids in radial flow cooling systems considering temperature-dependent properties  

Microsoft Academic Search

Heat transfer enhancement capabilities of coolants with suspended metallic nanoparticles inside typical radial flow cooling systems are numerically investigated in this paper. The laminar forced convection flow of these nanofluids between two coaxial and parallel disks with central axial injection has been considered using temperature dependent nanofluid properties. Results clearly indicate that considerable heat transfer benefits are possible with the

Samy Joseph Palm; Gilles Roy; Cong Tam Nguyen

2006-01-01

86

Single-photon heat conduction in electrical circuits  

NASA Astrophysics Data System (ADS)

We study photonic heat conduction between two resistors coupled weakly to a single superconducting microwave cavity. At low enough temperature, the dominant 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 quantum bits coupled to cavities.

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

2012-02-01

87

Conduction phase change beneath insulated heated or cooled structures  

NASA Astrophysics Data System (ADS)

The problem of thawing beneath heated structures on permafrost (or cooled structures in non-permafrost zones) must be addressed if safe engineering designs are to be conceived. In general, there are no exact solutions to the problem of conduction heat transfer with phase change for practical geometries. The quasi-steady approximation is used here to solve the conductive heat transfer problem with phase change for insulated geometries including infinite strips, rectangular buildings, circular storage tanks, and buried pipes. Analytical solutions are presented and graphed for a range of parameters of practical importance.

Lunardini, V. J.

1982-08-01

88

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

89

Verification for transient heat conduction calculation of multilayer building constructions  

Microsoft Academic Search

Validation and verification of building simulation programs and load calculation programs is of continuing interest. Dynamic thermal behavior data, including conduction transfer function (CTF) coefficients, thermal response factors and periodic response factors, are used to calculate transient heat conduction through building constructions. Computational inaccuracy sometimes occurs in calculating CTF coefficients and response factors. In this paper, a method for verification

Youming Chen; Juan Zhou; Jeffrey D. Spitler

2006-01-01

90

Quantal Heating of Conducting Electrons with Discrete Spectrum  

SciTech Connect

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

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

2011-12-23

91

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

92

Thermal conductivity of metal cloth heat pipe wicks  

NASA Astrophysics Data System (ADS)

Experimental results on heat conduction through a metal cloth wick saturated with a liquid are determined and compared to results from both a new mean-gap-conductance model, based on the wick geometry, and the simple series model. The mean-gap-conductance model includes three-dimensional and contact conductance effects, and it evaluates the effects of the mesh geometry in addition to predicting the effective conductivity. This new model predicts the experimental data to within 10 percent, while the series model may be more than 40 percent in error. The present model is used to determine theoretical limits on the maximum and minimum conductivity enhancement as a function of geometric parameters, and to establish guidelines for the design of heat pipe wicks.

Phillips, J. R.; Chow, L. C.; Grosshandler, W. L.

1987-08-01

93

Pitch Angle Distribution Analysis from the CRRES MEA - Average Picture and Radial Diffusion versus Local Heating  

NASA Astrophysics Data System (ADS)

Variations in electron phasespace density at a particular location can be indicative of a specific energization or loss process. Determining the nature of that process as diffusive or local heating can be difficult to do. However, these processes can also leave different signatures on the pitch angle distributions (PADs) of a particle population, such that changes at a single location can give us important clues to the factors producing electron flux variations. Using data from the medium electron A instrument (MEA) on the CRRES satellite, a survey of PADs of energetic electrons is performed. The distributions are classified into three types (butterfly, 90-degree peaked, and flattop) based on the ratio of counts at 90 degrees and the average of the counts at 45 and 135 degrees. The categorizations are examined as a function of L-shell, localtime, orbit number and geomagnetic activity. The 90-degree peaked distributions tend to dominate on the dayside and in the lowest energy channel (153keV). Butterfly distributions are more prevalent at higher L-shells and on the nightside. During periods of moderate geomagnetic activity, we see an increase in butterfly distributions at L-shells greater than on the nightside and for 3.5 < L < 5.5 on the dayside. We also find significant differences in the average PAD before and after the great storm of March 24, 1991. Knowing the typical PAD types in a region, and the dependencies on other parameters, we can look for changes that might indicate a particular energization process is occurring. Radial diffusion tends to favor local 90-degree particles. As diffusion occurs, the pitch angle distribution becomes more 90-degree peaked, or transitions from one type of distribution to another, for example butterfly to flattop. We show examples of the diffusion of PADs at higher L-shells, consistent with radial diffusion, and examples inconsistent with radial diffusion at lower L-shells and near the plasmapause.

Gannon, J.; Li, X.; Heyndericks, D.

2005-12-01

94

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

95

The specific heat and the radial thermal expansion of bundles of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

The specific heat at constant pressure C(T) of bundles of single-walled carbon nanotubes (SWNTs) closed at their ends has been investigated in the temperature interval of 2-120 K. It is found that the curve C(T) has features near 5, 36, 80, and 100 K. The experimental results on the C(T) and the radial thermal expansion coefficient ?R(T) of bundles of SWNTs oriented perpendicular to the sample axis have been compared. It is found that the curves C(T) and ?R(T) exhibit a similar temperature behavior at T > 10 K. The temperature dependence of the Grüneisen coefficient ?(T) has been calculated. The curve ?(T) also has a feature near 36 K. Above 36 K the Grüneisen coefficient is practically independent of temperature (? ~ 4). Below 36 K, ?(T) decreases monotonically with lowering temperature and becomes negative at T < 6 K.

Bagatskii, M. I.; Barabashko, M. S.; Dolbin, A. V.; Sumarokov, V. V.; Sundqvist, B.

2012-06-01

96

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

97

Heat conduction in the Frenkel-Kontorova model.  

PubMed

Heat conduction is an old yet important problem. Since Fourier introduced the law bearing his name almost 200 years ago, a first-principle derivation of this simple law from statistical mechanics is still lacking. Worse still, the validity of this law in low dimensions, and the necessary and sufficient conditions for its validity are far from clear. In this paper we will review recent works on heat conduction in a simple nonintegrable model called the Frenkel-Kontorova model. The thermal conductivity of this model has been found to be finite. We will study the dependence of the thermal conductivity on the temperature and other parameters of the model such as the strength and the periodicity of the external potential. We will also discuss other related problems such as phase transitions and finite-size effects. The study of heat conduction is not only of theoretical interest but also of practical interest. We will show various recent designs of thermal rectifiers and thermal diodes by coupling nonlinear chains together. The study of heat conduction in low dimensions is also important to the understanding of the thermal properties of carbon nanotubes. PMID:15836296

Hu, Bambi; Yang, Lei

2005-03-01

98

Heat transfer in axially conducting flow and periodically contacting solids  

NASA Astrophysics Data System (ADS)

The effects of axial heat conduction on the temperature distribution and local Nusselt number in a fluid for forced convection in a circular tube subjected to various boundary conditions are investigated theoretically. Fully developed laminar flow inside a tube with an insulated upstream region followed by a uniformly heated downstream region. Two independent analytical methods are developed for the solution of this problem. The techniques are extended to solve problems with convective boundaries for the upstream and downstream regions. The cases of both a laminar and slug flow velocity model are considered. The results show that the axial heat conduction in the fluid significantly effects the bulk and wall temperatures and local Nusselt number in the thermal entrance region, with the effects becoming more pronounced at lower Peclet numbers. Also the results obtained with convective boundary conditions show that the external heat transfer coefficients significantly effect the temperature distribution, and hence the Nusselt number, in the thermal entrance region.

Vick, B.

1981-08-01

99

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

100

NON-FOURIER HEAT CONDUCTION PHENOMENA IN POROUS MATERIAL HEATED BY MICROSECOND LASER PULSE  

Microsoft Academic Search

Experiments on porous material heated by a microsecond laser pulse and the corresponding theoretical analysis are carried out. Some non-Fourier heat conduction phenomena are observed in the experimental sample. The experimental results indicate that only if the thermal disturbance is strong enough (i.e., the pulse duration is short enough and the pulse heat flux is great enough) is it possible

Fangming Jiang

2003-01-01

101

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

102

Effect of crosslink formation on heat conduction in amorphous polymers  

NASA Astrophysics Data System (ADS)

We performed molecular dynamics (MD) simulations on amorphous polyethylene (PE) and polystyrene (PS) in order to elucidate the effect of crosslinks between polymer chains on heat conduction. In each polymer system, thermal conductivities were measured for a range of crosslink concentration by using nonequilibrium MD techniques. PE comprised of 50 carbon atom long chains exhibited slightly higher conductivity than that of 250 carbon atom long chains at the standard state. In both cases for PE, crosslinking significantly increased conductivity and the increase was more or less proportional to the crosslink density. On the other hand, in the PS case, although the thermal conductivity increased with the crosslinking, the magnitude of change in thermal conductivity was relatively small. We attribute this difference to highly heterogeneous PS based network including phenyl side groups. In order to elucidate the mechanism for the increase of thermal conductivity with the crosslink concentration, we decomposed energy transfer into modes associated with various bonded and non-bonded interactions.

Kikugawa, Gota; Desai, Tapan G.; Keblinski, Pawel; Ohara, Taku

2013-07-01

103

Heat conduction in one-dimensional aperiodic quantum Ising chains  

NASA Astrophysics Data System (ADS)

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 Jm between the nearest-neighbor spins takes the two values JA and JB 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.

Li, Wenjuan; Tong, Peiqing

2011-03-01

104

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

105

Application of genetic algorithms in nonlinear heat conduction problems.  

PubMed

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

Kadri, Muhammad Bilal; Khan, Waqar A

2014-01-01

106

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

107

Computer Program For Variable-Conductance Heat Pipes  

NASA Technical Reports Server (NTRS)

VCHPDA provides accurate mathematical models of transient as well as steady-state performance of variable-conductance heat pipes over wide range of operating conditions. Applies to heat pipes with either cold, wicked or hot, nonwicked gas reservoirs and uses ideal-gas law and "flat-front" (negligible vapor diffusion) gas theory. Calculates length of gas-blocked region and temperature of vapor in active portion of heat pipe by solving set of nonlinear equations for conservation of energy and mass. Written in FORTRAN 77.

Antoniuk, D.

1992-01-01

108

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

109

Phase transitions and heat conduction in post-glacial rebound  

NASA Astrophysics Data System (ADS)

We have developed a method for including phase boundary conditions into post-glacial rebound models that allows for conduction of latent heat away from the boundary. This method returns the chemical boundary results if latent heat conducts away from the phase boundary too slowly to allow the transition to proceed, as is commonly argued. This is not necessarily the case, however. For example, the secular change of the geoid and the vertical uplift rates for phase boundaries with latent heat conduction can differ from the chemical boundary results by up to 10 and 15 per cent, respectively. When modelling the phase transition, we consider two scenarios: the latent heat is released either at a narrow boundary that separates the two phases or over a thick mixed region of the two phases. In the case where the phase transition occurs over a thick enough region (5-10 km), the final results are close to the results obtained by considering a phase boundary that ignores the release of latent heat completely. This thick boundary formulation also suggest that the phase boundaries could respond nearly instantaneously, changing both the elastic load and body Love numbers. However, we have not considered kinetics, the energetics of the mechanisms of the phase transitions, in this formulation. This work suggests a greater knowledge of the kinetics near equilibrium phase transitions is required. A naive calculation indicates that the kinetics will not be a significant factor for post-glacial rebound but will be a limiting factor for earth tides.

Tamisiea, M. E.; Wahr, J. M.

2002-05-01

110

Influence of heat bath on the heat conductivity in disordered anharmonic chain  

NASA Astrophysics Data System (ADS)

We study heat conduction in a one-dimensional disordered anharmonic chain with arbitrary heat bath by using extended Ford, Kac and Mazur (FKM) formulation, which satisfy the fluctuation-dissipation theorem. A simple formal expression for the heat conductivity ? is obtained, from which the asymptotic system-size (N) dependence is extracted. It shows ?˜N?. As a special case we give the expression that ?˜N1/2 for free boundaries, and ?˜ N-1/2 for fixed boundaries, from which we can get the conclusion that the momentum conservation is a key factor of the anomalous heat conduction. Comparing with different ?T, the heat conductivity shows large difference between the linear system and the nonlinear system.

Zhao, H.; Yi, L.; Liu, F.; Xu, B.

2006-11-01

111

Heat Conductivity of Polyatomic and Polar Gases and Gas Mixtures  

Microsoft Academic Search

A theory is presented which can be used for the practical calculation of the heat conductivity of polyatomic and polar gases and gas mixtures. For pure gases, the results are based on the Wang Chang—Uhlenbeck equations and involve no approximations, provided that a suitable definition of an internal diffusion coefficient is employed. This is compared with the known results for

L. Monchick; A. N. G. Pereira; E. A. Mason

1965-01-01

112

Thin-Film Conducting Microgrids as Transparent Heat Mirrors.  

National Technical Information Service (NTIS)

A new type of transparent heat mirror for solar-energy applications has been fabricated by chemically etching a Sn-doped In2O3 film to form a transparent conducting microgrid. For square openings 2.5 micrometers on a side, separated by lines 0.6 micromete...

J. C. Fan F. J. Bachner R. A. Murphy

1975-01-01

113

Identification of unknown parameters for heat conductivity equations  

Microsoft Academic Search

An algorithm for identification of unknown parameters of nonlinear heat conductivity equations is proposed. Solutions of equations observed with an error are input data of the algorithm. Finite dimensional approximations of input signals and their derivatives are used. The algorithm utilizes the idea of the direct minimization of the residual of equations written in an appropriate variational form. The convergence

N. D. Botkin

1995-01-01

114

Equivalence transformations and symmetries for a heat conduction model  

Microsoft Academic Search

In the framework of Extended Thermodynamics, we consider the unidimensional case of a non-linear system of partial differential equations describing the heat conduction in a rigid body and removing the well known paradox of thermal pulses propagating with infinite speed. Because of the strong non-linearity of the model we look for an invariant classification via equivalence transformations. Some general results

M. Torrisi; R. Tracinà

1998-01-01

115

Numerical investigation of laminar flow and heat transfer in a radial flow cooling system with the use of nanofluids  

Microsoft Academic Search

Nanofluids, because of their enhanced heat transfer capability as compared to normal water\\/glycol\\/oil based fluids, offer the engineer opportunities for development in areas where high heat transfer, low temperature tolerance and small component size are required. In this present paper, the hydrodynamic and thermal fields of a water–?Al2O3 nanofluid in a radial laminar flow cooling system are considered. Results indicate

Gilles Roy; Cong Tam Nguyen; Paul-René Lajoie

2004-01-01

116

Modeling of microconvection in a fluid between heat conducting solids  

NASA Astrophysics Data System (ADS)

Unsteady convection in a fluid under weak gravity is modeled. Convection in a rectangular domain elongated in the direction of gravity and enclosed between two heat-conducting solids is investigated in the case of heat insulation of the ends of the rectangle and the periodic heat flow through the outer boundaries of the solids. In this case, the condition of zero total heat flux is satisfied. Convective fluid motions are described using two mathematical models: the classical Oberbeck-Boussinesq model and the microconvection model for an isothermally incompressible fluid. Results of the numerical studies confirm the quantitative and qualitative differences between the flow characteristics calculated using the two convection models. Fluid particle trajectories are presented. Effects due to various physical characteristics of the problem are studied.

Goncharova, O. N.

2011-01-01

117

Variable conductance heat pipes from the laboratory to space  

NASA Technical Reports Server (NTRS)

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

Kirkpatrick, J. P.

1973-01-01

118

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

119

Two-dimensional heat conduction in metal, fluid composites  

NASA Astrophysics Data System (ADS)

Because the size and weight of main propulsion and auxiliary systems are inversely proportional to the ease in which heat or energy is exchanged, a major thrust of the research and development program of the U.S. Navy is toward the design and development of equipment that perform at higher efficiency with a reduction in size and weight. In particular, one area of great interest is the reduction in size and weight of steam condensers. The heat-transfer effectiveness is governed by the amount of surface and the overall resistance to the flow of heat. Filmwise condensation of steam on externally-finned tubes is a very complex process. Recent experiments have shown that enhancement ratios (ratio of steam-side heat-transfer coefficient to that of a smooth tube having the same diameter) exceeded the area enhancement produced by the fins. Moreover, the enhancement ratios for fully flooded tubes exceed the values predicted by a simple, one-dimensional conduction model by a factor of 2 to 4. A new two-dimensional conduction model was developed, which showed that the one-dimensional model overpredicted the two-dimensional results for high conductivity tube-metals such as copper by as much as 13%. The two-dimensional model also showed that variations in fin thickness or spacing can result in an overprediction by the one-dimensional model of the two-dimensional results by as much as twenty-two percent.

Gomori, M. A.

1985-12-01

120

Heat conduction in graphene: experimental study and theoretical interpretation  

NASA Astrophysics Data System (ADS)

We review the results of our experimental investigation of heat conduction in suspended graphene and offer a theoretical interpretation of its extremely high thermal conductivity. The direct measurements of the thermal conductivity of graphene were performed using a non-contact optical technique and special calibration procedure with bulk graphite. The measured values were in the range of ~3000-5300 W mK-1 near room temperature and depended on the lateral dimensions of graphene flakes. We explain the enhanced thermal conductivity of graphene as compared to that of bulk graphite basal planes by the two-dimensional nature of heat conduction in graphene over the whole range of phonon frequencies. Our calculations show that the intrinsic Umklapp-limited thermal conductivity of graphene grows with the increasing dimensions of graphene flakes and can exceed that of bulk graphite when the flake size is on the order of a few micrometers. The detailed theory, which includes the phonon-mode-dependent Gruneisen parameter and takes into account phonon scattering on graphene edges and point defects, gives numerical results that are in excellent agreement with the measurements for suspended graphene. Superior thermal properties of graphene are beneficial for all proposed graphene device applications.

Ghosh, S.; Nika, D. L.; Pokatilov, E. P.; Balandin, A. A.

2009-09-01

121

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

122

Heat conductance is strongly anisotropic for pristine silicon nanowires.  

PubMed

We compute atomistically the heat conductance for ultrathin pristine silicon nanowires (SiNWs) with diameters ranging from 1 to 5 nm. The room temperature thermal conductance is found to be highly anisotropic: wires oriented along the <110> direction have 50-75% larger conductance than wires oriented along the <100> and <111> directions. We show that the anisotropies can be qualitatively understood and reproduced from the bulk phonon band structure. Ab initio density functional theory (DFT) is used to study the thinnest wires, but becomes computationally prohibitive for larger diameters, where we instead use the Tersoff empirical potential model (TEP). For the smallest wires, the thermal conductances obtained from DFT and TEP calculations agree within 10%. The presented results could be relevant for future phonon-engineering of nanowire devices. PMID:18811212

Markussen, Troels; Jauho, Antti-Pekka; Brandbyge, Mads

2008-11-01

123

Heat conduction nanocalorimeter for pl-scale single cell measurements  

NASA Astrophysics Data System (ADS)

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

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

2002-03-01

124

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

125

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

126

Pressure recovery in a cylindrical heat pipe at high radial Reynolds numbers and at high Mach numbers  

SciTech Connect

The pressure recovery in a cylindrical heat pipe has been investigated. The experiments cover average radial Reynolds numbers between 5 and 150 and average Mach numbers up to the velocity of sound. During preliminary experiments in a cylindrical, gravity-assisted heat pipe at high Mach numbers large condensate flow instabilities were observed. As a consequence the heat pipe power varied strongly. Based on these observations an improved heat pipe design was made that resulted in steady operating conditions throughout the entire parameter range. This heat pipe is described. The pressure recovery was measured and compared with results from a two-dimensional analytical model for describing compressible vapor flow in heat pipes. Good agreement with the experimental data was found.

Haug, F.; Busse, C.A.

1985-01-01

127

Development of a high performance variable conductance heat pipe  

NASA Astrophysics Data System (ADS)

An all stainless steel bendable gas controlled variable conductance heat pipe (VCHP) has been developed and submitted to adverse environments, including life test. The heat carrier is ammonia, the capillary system a homogeneous wick structure, temperature control involves a cold wicked reservoir. This design presents excellent potential for high performance since, within a one centimeter diameter tube, a heat transport capability of 100 watt metre has been demonstrated. Its performance does not degrade when control gas is added to the working fluid. The gas control was designed to achieve a 5 degree temperature range, which was finally demonstrated after improvement of the VCHP design. Environmental and life tests demonstrated the rugginess of the developed VCHP.

Mathieu, J.-P.; Moschetti, B.; Savage, C. J.

1980-07-01

128

Low-temperature specific heat and thermal conductivity of glycerol  

Microsoft Academic Search

We have measured the thermal conductivity of glassy glycerol between 1.5 and 100 K, as well as the specific heat of both glassy and crystalline phases of glycerol between 0.5 and 25 K. We discuss both low-temperature properties of this typical molecular glass in terms of the soft-potential model. Our finding of an excellent agreement between its predictions and experimental

C. Talón; Q. W. Zou; M. A. Ramos; R. Villar; S. Vieira

2002-01-01

129

Heating of foods in space-vehicle environments. [by conductive heat transfer  

NASA Technical Reports Server (NTRS)

In extended space missions, foods will be heated to enhance the psychological as well as the physiological well-being of the crew. In the low-gravity space environment natural convection is essentially absent so that the heat transfer within the food is by conduction alone. To prevent boiling in reduced pressure environments the maximum temperature of the heating system is severely limited. The Skylab food-heating system utilizes a tray with receptables for the food containers. The walls of the receptacles are lined with thermally controlled, electrical-resistance, blanket-type heating elements. A finite difference model is employed to perform parametric studies on the food-heating system. The effects on heating time of the (1) thermophysical properties of the food, (2) heater power level, (3) initial food temperatures, (4) container geometry, and (5) heater control temperature are presented graphically. The optimal heater power level and container geometry are determined.

Bannerot, R. B.; Cox, J. E.; Chen, C. K.; Heidelbaugh, N. D.

1973-01-01

130

HEAT TRANSFER IN TRICKLE-BED REACTORS  

Microsoft Academic Search

The mechanism of radial heat transfer in two-phase flow through packed beds is examined. A model with 2 parameters: an effective radial thermal conductivity in the bed, ke, and a heat transfer coefficient, hw, at the wall, give a satisfactory interpretation of the radial temperature profile.ke was expressed in terms of a stagnant contribution, due to the heat conduction through

V. SPECCHIA; G. BALDI

1979-01-01

131

Conjugate mixed convection-conduction heat transfer in porous media  

NASA Astrophysics Data System (ADS)

This dessertation studies analytically the conjugate mixed-convection conduction heat transfer in porous media. Solutions for mixed convection flows about vertical plate and cylindrical fins embedded in a porous medium have been obtained by including the effects of interactions between the conduction in the solid boundaries (fins) and the convection in the boundary layer. It has been found that the governing parameters are the Prandtl number Pr, buoyancy force parameter Omega, convection conduction parameter Ncc, and the surface curvature parameter lambda. Extensive results for heat transfer characteristics are presented graphically and in tabular forms for the following ranges of parameters: 0.05 or = Pr or = 7.5, 0.0 or = omega or = 20.0, 0.0 or = Ncc 2.0 and 0.5 or = lambda or = 5.0. Many results were found to have trends similar to those for classical fluids. In particular, the local heat transfer coefficients for mixed convection flows were found not to decrease monotonically as usual, but instead, the coefficients decreased first, attained a minimum value and then increased with increasing streamwise distance. This behavior is attributable to an enhanced buoyancy force resulting from an increase in the wall-to-fluid temperature difference along the streamwise direction.

Lin, J. Y.

1985-12-01

132

Molecular Characterization of Radial Spoke Subcomplex Containing Radial Spoke Protein 3 and Heat Shock Protein 40 in Sperm Flagella of the Ascidian Ciona intestinalis  

PubMed Central

Members of the heat-shock protein (HSP)40 regulate the protein folding activity of HSP70 proteins and help the functional specialization of this molecular chaperone system in various types of cellular events. We have recently identified Hsp40 as a component of flagellar axoneme in the ascidian Ciona intestinalis, suggesting a correlation between Hsp40 related chaperone system and flagellar function. In this study, we have found that Ciona 37-kDa Hsp40 is extracted from KCl-treated axonemes with 0.5 M KI solution and comigrates with radial spoke protein (RSP)3 along with several proteins as a complex through gel filtration and ion exchange columns. Peptide mass fingerprinting with matrix-assisted laser desorption ionization/time of flight/mass spectrometry revealed that other proteins in the complex include a homolog of sea urchin spokehead protein (homolog of RSP4/6), a membrane occupation and recognition nexus repeat protein with sequence similarity with meichroacidin, and a functionally unknown 33-kDa protein. A spoke head protein, LRR37, is not included in the complex, suggesting that the complex constructs the stalk of radial spoke. Immunoelectron microscopy indicates that Hsp40 is localized in the distal portion of spoke stalk, possibly at the junction between spoke head and the stalk.

Satouh, Yuhkoh; Padma, Potturi; Toda, Toshifusa; Satoh, Nori; Ide, Hiroyuki; Inaba, Kazuo

2005-01-01

133

Thermal heat transport characterization for macroscale, microscale, and nanoscale heat conduction  

NASA Astrophysics Data System (ADS)

Several theoretical and experimental methods for predicting the thermal conductivity of thin dielectric films and carbon nanotubes are presented based on two schools of thought: (1) the physics of the Boltzmann Transport Equation (BTE), and (2) Molecular Dynamics (MD) simulations. First, in relation to models based on the BTE, this thesis highlights temporal and spatial scale issues by looking at a unified theory that bridges physical aspects presented in the Fourier and Cattaneo models. This newly developed unified model is the so called C- and F-Processes heat conduction model. The model introduces the dimensionless heat conduction model number which is the ratio of thermal conductivity of the fast heat carrier F-Processes to the total thermal conductivity comprised of both fast F-processes and slow heat carrier C-processes. Prior work has claimed that macroscopic heat transfer models cannot explain microscale heat transfer. First, this dissertation provides arguments by showing how the C-F model is able to extend the use of "macroscopic" constitutive relations for the prediction of thermal conductivity at the "microscopic" level for thin films, multilayer structures, and includes both dielectrics and metals. Second, the influence of external mechanical strain on the thermal conductivity of single-wall carbon nanotubes is studied using direct molecular dynamics simulations with Tersoff-Brenner potential for C-C interactions. Three types of external mechanical strain, namely, axial compression, tension, and torsion are studied. In all three cases, the thermal conductivity does not degrade much, i.e., it remains within 10% of the pristine nanotube values for lower applied strain below the values required for structural collapse. At higher applied strain, structural collapse occurs, and major reductions in the observed thermal conductivity for axially compressed and torsionally twisted tubes are observed.

Anderson, Christianne Vanessa Duim Ribeiro

134

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

135

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

136

Variable Conductance Heat Pipes for Radioisotope Stirling Systems  

NASA Technical Reports Server (NTRS)

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

Anderson, William G.; Tarau, Calin

2008-01-01

137

DSMC Convergence for Microscale Gas-Phase Heat Conduction  

NASA Astrophysics Data System (ADS)

The convergence of Bird's Direct Simulation Monte Carlo (DSMC) method is investigated for gas-phase heat conduction at typical microscale conditions. A hard-sphere gas is confined between two fully accommodating walls of unequal temperature. Simulations are performed for small system and local Knudsen numbers, so continuum flow exists outside the Knudsen layers. The ratio of the DSMC thermal conductivity to the Chapman-Enskog value in the central region is determined for over 200 combinations of time step, cell size, and number of computational molecules per cell. In the limit of vanishing error, this ratio approaches 1.000 to within the correlation uncertainty. In the limit of infinite computational molecules per cell, the difference from unity depends quadratically on time step and cell size as these quantities become small. The coefficients of these quadratic terms are in good agreement with Green-Kubo values found by Hadjiconstantinou, Garcia, and co-workers. These results demonstrate that DSMC can accurately simulate microscale gas-phase heat conduction. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

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

2004-11-01

138

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

139

Radiative Cooling and Heating and Thermal Conduction in M87  

NASA Astrophysics Data System (ADS)

The crisis of the standard cooling flow model brought about by Chandra and XMM-Newton observations of galaxy clusters has led to the development of several models that explore different heating processes in order to assess whether they can quench the cooling flow. Among the most appealing mechanisms are thermal conduction and heating through buoyant gas deposited in the intracluster medium (ICM) by active galactic nuclei (AGNs). We combine Virgo/M87 observations of three satellites (Chandra, XMM-Newton, and BeppoSAX) to inspect the dynamics of the ICM in the center of the cluster. Using the spectral deprojection technique, we derive the physical quantities describing the ICM and determine the extra heating needed to balance the cooling flow, assuming that thermal conduction operates at a fixed fraction of the Spitzer value. We assume that the extra heating is due to buoyant gas, and we fit the data using the model developed by Ruszkowski and Begelman. We derive a scale radius for the model of ~5 kpc, which is comparable with the M87 AGN jet extension, and a required luminosity of the AGN of afew×1042ergss-1, which is comparable to the observed AGN luminosity. We discuss a scenario in which the buoyant bubbles are filled with relativistic particles and magnetic field, which are responsible for the radio emission in M87. The AGN is supposed to be intermittent and to inject populations of buoyant bubbles through a succession of outbursts. We also study the X-ray-cool component detected in the radio lobes and suggest that it is structured in blobs that are tied to the radio buoyant bubbles.

Ghizzardi, Simona; Molendi, Silvano; Pizzolato, Fabio; De Grandi, Sabrina

2004-07-01

140

Specific heat and thermal conductivity of solid fullerenes  

NASA Astrophysics Data System (ADS)

Evidence is presented that the lattice vibrations of compacted C60/C70 fullerite microcrystals consist predominantly of localized modes. Vibrational motions of the rigid molecules ('buckyballs') have been identified as well as their internal vibrations. Debye waves play only a relatively minor role, except below about 4 K. By comparison with other crystalline materials, for these materials the Einstein model of the specific heat and thermal conductivity of solids, which is based on the assumption of atoms (in this case, buckyballs) vibrating with random phases, is in much better agreement with the measurements than the Debye model, which is based on collective excitations.

Olson, J. R.; Topp, K. A.; Pohl, R. O.

1993-02-01

141

Specific heat and thermal conductivity of solid fullerenes  

SciTech Connect

Evidence is presented that the lattice vibrations of compacted C[sub 60]/C[sub 70] fullerite microcrystals consist predominantly of localized modes. Vibrational motions of the rigid molecules (buckyballs) have been identified as well as their internal vibrations. Debye waves play only a relatively minor role, except below [approximately]4 kelvin. By comparison with other crystalline materials, for these materials the Einstein model of the specific heat and thermal conductivity of solids, which is based on the assumption of atoms (in this case, buckyballs) vibrating with random phases, is in much better agreement with the measurements than the Debye model, which is based on collective excitations.

Olson, J.R.; Topp, K.A.; Pohl, R.O. (Lab. of Atomic and Solid State Physics, Cornell Univ., Ithaca, NY (United States))

1993-02-19

142

Low-temperature specific heat and thermal conductivity of glycerol  

NASA Astrophysics Data System (ADS)

We have measured the thermal conductivity of glassy glycerol between 1.5 and 100 K, as well as the specific heat of both glassy and crystalline phases of glycerol between 0.5 and 25 K. We discuss both low-temperature properties of this typical molecular glass in terms of the soft-potential model. Our finding of an excellent agreement between its predictions and experimental data for these two independent measurements constitutes a robust proof of the capabilities of the soft-potential model to account for the low-temperature properties of glasses in a wide temperature range.

Talón, C.; Zou, Q. W.; Ramos, M. A.; Villar, R.; Vieira, S.

2002-01-01

143

A simple optical probe of transient heat conduction  

NASA Astrophysics Data System (ADS)

We use a laser beam and a stopwatch to investigate transient heat conduction in Plexiglas and glycerol samples chilled by ice water. The deflection of the laser beam is proportional to the thermal gradient in the sample. Measurements of the beam deflection allow us to calculate the thermal gradient as a function of time. Our empirical results fit the theoretical predictions very well and show an initial increase in the thermal gradient followed by a gradual decrease as the entire sample approaches the temperature of ice water. The procedure is simple and can be used as a lecture demonstration, an afternoon's experiment, or an extended investigation in an advanced laboratory course.

Brody, Jed; Andreae, Phillip; Robinson, C. Andrew

2010-05-01

144

Tunable single-photon heat conduction in electrical circuits  

NASA Astrophysics Data System (ADS)

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.

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

2012-07-01

145

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

146

Homogeneous Thermal Cloak with Constant Conductivity and Tunable Heat Localization  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

147

Heat conduction across monolayer and few-layer graphenes.  

PubMed

We report the thermal conductance G of Au/Ti/graphene/SiO(2) interfaces (graphene layers 1 ? n ? 10) typical of graphene transistor contacts. We find G ? 25 MW m(-2) K(-1) at room temperature, four times smaller than the thermal conductance of a Au/Ti/SiO(2) interface, even when n = 1. We attribute this reduction to the thermal resistance of Au/Ti/graphene and graphene/SiO(2) interfaces acting in series. The temperature dependence of G from 50 ? T ? 500 K also indicates that heat is predominantly carried by phonons through these interfaces. Our findings suggest that metal contacts can limit not only electrical transport but also thermal dissipation from submicrometer graphene devices. PMID:20923234

Koh, Yee Kan; Bae, Myung-Ho; Cahill, David G; Pop, Eric

2010-11-10

148

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.

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

2013-01-01

149

Long life heat conductive body for utilization of solar heat energy and water heater for making use of same  

SciTech Connect

A heat conductive body for use in apparatus for the heating of liquid by way of solar radiation incident on the conductive body is formed of a mixture of sand iron with a fiber-reinforced formable plastic material. A heater apparatus uses the inventive conductive body for maintaining a supply of heated water.

Sakamoto, Y.

1983-01-18

150

High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

151

Application of sensitivity coefficients for heat conduction problems  

SciTech Connect

In parameter estimation considerable insight is provided by examining sensitivity coefficients. This paper focuses on the use of sensitivity coefficients in connection with estimating thermal properties in the heat conduction equation. A general methodology for computing sensitivity coefficients can be an important design tool. The use of such a tool is demonstrated in this paper. A control volume, finite element program is used, and briefly described, to implement numerical sensitivity coefficient calculations. In this approach general problems can be studied. Several example problems are presented to demonstrate the insight gained from sensitivity coefficients. The problems are selected from experimental studies to characterize the thermal properties of carbon-carbon composite. Sensitivity coefficients show that in an experiment that is not well designed, additional materials in the experimental configuration can have a larger impact on the temperature than the material of interest. Two-dimensional configurations demonstrate that there can be isolated areas of insensitivity and the difficulty of estimating multiple parameters.

Dowding, K.J.; Blackwell, B.F.; Cochran, R.J.

1998-02-01

152

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

153

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

154

THERM: A three-dimensional transient heat conduction computer program  

SciTech Connect

THERM is a three-dimensional finite-element computer program for solving transient heat conduction problems. This report presents the techniques used to develop THERM. The theory described consists of a governing equation, boundary conditions, and an equivalent variational principle. The matrix equations used in THERM are derived using both vector and tensor analysis. These equations used finite-element approximations for the geometry and a finite-difference approximation for the time. THERM has finite-element formulations using both Cartesian or cylindrical coordinates. Several example problems are included to demonstrate that the THERM formulations are correct and that THERM can be used to solve meaningful problems. 7 refs., 4 figs., 6 tabs.

Cook, W.A.

1991-10-01

155

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

156

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

157

Thermal stresses due to a uniform heat flow past a circular hole with a radial edge crack  

SciTech Connect

The problem solved here is that of finding the stresses in an isotropic, linear, thermoelastic solid when a uniform heat flow is disturbed by the presence of an insulated circular hole with a radial edge crack. By superimposing a Mellin-transform solution of the equations of thermoelasticity on a Michell series solution the author reduces the problem to a pair of singular integral equations which are then solved numerically. The stress-intensity factors and crack-formation energies, quantities of interest to workers in fracture mechanics, are then calculated.

Edmonds, G.F.

1987-01-01

158

INFLUENCE OF MASHED POTATO DIELECTRIC PROPERTIES AND CIRCULATING WATER ELECTRIC CONDUCTIVITY ON RADIO FREQUENCY HEATING  

Microsoft Academic Search

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

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

159

Underground heat conduction near a spherical inhomogeneity: theory and applications  

NASA Astrophysics Data System (ADS)

A large underground inhomogeneity, such as a salt dome or cavity, is known to disturb the subsurface temperature field. Such anomalies appear in many geophysical surveys. Detection and knowledge of the magnitude of these disturbances is the objective of both near surface and deep borehole temperature surveys aimed at delineating the inhomogeneities. It also impacts surface temperature history analysis which reconstructs past climate change in an effort to study the recent global warming. This work is aimed at quantifying these effects by solving a problem of heat conduction in Earth's subsurface in the presence of a spherical inhomogeneity. Both the steady state temperature field pertaining to the constant geothermal gradient and the time dependent field caused by a surface jump in temperature are solved. A solution is derived for both cases as an infinite series of spherical harmonics and Bessel functions (in the Laplace domain) for the steady and unsteady problems, respectively. It is shown that an accurate solution can be achieved by a small number of terms. The results are illustrated and analysed for a given accuracy and for a few values of the governing parameters. The general solution can be simplified considerably for asymptotic values of the parameters. Comparison with the exact solution shows that these approximations are accurate for a wide range of parameter values. Some examples of applying the solution to the geophysical methods stated above are discussed. In the case of surface temperature surveys, an example showing good agreement between theoretical and measured heat flux above a salt diapir is given. Though the sphere is an idealized shape, the simplicity of the solution makes possible a general analysis toward gaining a better understanding of the process. Furthermore, it can be employed for preliminary assessment of the impact of a body and may serve as a benchmark for numerical solutions.

Rabinovich, A.; Dagan, G.; Miloh, T.

2012-06-01

160

Heat transport by conduction in the deep mantle  

NASA Astrophysics Data System (ADS)

At high mantle temperatures, the phonon (vibrational or lattice) component of thermal diffusivity is independent of T. Laser flash measurements, which isolate phonon transport, of mineral families show that the complex silicates (olivines, orthopyroxenes, clinopyroxenes, garnets) have D asymptoting to 0.7 mm2/s whereas simple oxides (spinel, MgO, quartz) have slightly higher values of 1 to 1.5 mm2/s, such that the impurites lower Dsat. Values in the lower mantle are hence controlled by pressure. Multiple measurements of olivine and MgO give d(ln D)/dP near 3%/GPa which are compatible with the damped harmonic oscillator model. This model predicts d(ln D)/dP = 1.7%/GPa for incompressible phases like perovskite. Data and model constrain values of D and k = density X heat capacity X D for the lower mantle. High temperatures also provide radiative transfer, for which the strong dependence on temperature, Fe-content, and grain-size supercede its weak pressure dependence. However, the small expected grainsize of ca 1 mm makes scattering important and calculated values of krad are similar for olivine, perovskite and garnet, despite the variation in absorption spectra. Roughly, krad is 0.5 W/m-K in the lower mantle increasing to 3 W/m-K the lowest mantle (layer D"), which is dwarfed by 60 W/m-K for klat of a perovskite dominated lower mantle. Magnesiowustite, if present, would further increase klat. Thus layer D" can carry immense power (100 TW) over a steep temperature gradient (1000 K over 200 km) and 3 TW, which is a likely value for core production, over an adiabatic D" layer. Thus, the efficiency of phonons in diffusing heat allows the lower mantle to conduct: convection in the lower mantle is not likely, other than in the form of weak Hadley-type unicells.

Hofmeister, A. M.

2008-05-01

161

HEAT TRANSFER TO AN ELECTRICALLY CONDUCTING FLUID FLOWING IN A CHANNEL WITH A TRANSVERSE MAGNETIC FIELD  

Microsoft Academic Search

An analysis is made of forced-convection heat transfer to laminar flow ; of an incompressible electrically conducting fluid between parallel plates. The ; plates are heated (or cooled) with a uniform wall heat flux, and heating within ; the fluid is present from viscous and electrical dissipations. The fluid enters ; the heated section of the channel with a uniform

M. Perlmutter; R. Siegel

1961-01-01

162

Effects of Magnetic Field on Entropy Generation in Flow and Heat Transfer due to a Radially Stretching Surface  

NASA Astrophysics Data System (ADS)

We investigate the effects of magnetic field on the entropy generation during fluid flow and heat transfer due to the radially stretching surface. The partial differential equations governing the flow and heat transfer phenomenon are transformed into nonlinear ordinary differential equations by using suitable similarity transformations. These equations are then solved by the homotopy analysis method and the shooting technique. The effects of the magnetic field parameter M and the Prandtl number Pr on velocity and the temperature profiles are presented. Moreover, influence of the magnetic field parameter M and the group parameter Br/? on the local entropy generation number Ns as well as the Bejan number Be are inspected. It is observed that the magnetic field is a strong source of entropy production in the considered problem.

Adnan Saeed, Butt; Asif, Ali

2013-02-01

163

Systems analysis of the inverse heat conduction problem  

NASA Astrophysics Data System (ADS)

The groundwork necessary for frequency domain analysis of solutions to the inverse heat conduction problem, using Laplace and z-transform techniques is presented. The solution is traced back through the direct solution methods used to generate the inverse solution, and draws heavily upon tranfer function concepts. Transformation methods from continuous time ladder network models to discrete time models are developed. The mathematical relationship between ladder network models and finite difference models is derived. In addition, a new procedure for generating errorless discrete time models from Fourier series solutions is presented. The frequency response of direct discrete time solutions and the impact on the stability and noise performance of inverse algorithms arising from these direct solutions is presented. Inverse algorithm methods are generalized according to their frequency domain structure, rather than time domain, which effectively decouples the algorithm classification from a direct solution. Precompensation filter concepts are introduced, and a frequency domain test for inverse algorithm stability is developed. Examples of Stolz's method and Beck's method are included. Results are discussed.

Manner, David Bruce

164

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

165

The Results of a Radial Divergent Tracer Experiment Conducted Over the Full Thickness of a Horizontally Fractured Dolomite  

NASA Astrophysics Data System (ADS)

In several recent field studies it was concluded that highly transmissive features are key to the movement of mass in horizontally-fractured bedrock aquifers. In many cases these features can be hydraulically identified in individual boreholes and correlated from borehole to borehole. The purpose of this investigation is to determine the relative role of these hydraulic features in transporting in the horizontal direction where the source of mass is distributed uniformly with depth. To explore this, a radial-divergent tracer experiment was conducted in a four-borehole array completed through a horizontally-fractured dolomite in Smithville, Ontario, Canada. The injection interval created by the dual packer injection system spanned over 8.6m vertically. This injection interval included several identified features located in the Upper Eramosa of the Lockport formation. Utilizing a fire hydrant as a water source, a flow field was established by injecting water at a rate of 21.4 L/min. After the flow field had been established, 500 L of Lissamine FF (a conservative fluorescent dye tracer at a concentration of 200mg/L) was injected at a rate of 23.25 L/min. To allow for a consistent flow field throughout the experiment, water was injected behind the tracer at 20.4 L/min. The sampling wells were fitted with a packer in order to isolate the entire Eramosa section. A submersible fluorometer outfitted with a pressure transducer was used to detect the arrival of tracer in the sampling wells. The pressure transducer was used to identify the exact depth where fluorescence signals were detected. Correlating the fluorescence signals at depth with hydraulically-identified features provided an in-situ measure that identified the role of each feature with respect to mass transport. Over 100 vertical fluorescent profiles were collected among the four wells, and the peak concentration profiles in each well exceeded 85 ppb. Preliminary analyses indicate that specific highly transmissive features carry more mass than other features of similar transmissivity. The data also indicates that each well exhibits a unique mass transport behaviour and unique fluorescent signature. The results of this experiment suggest that mass transport and the associated interactions are more complex than previously surmised.

Melaney, M. A.; Novakowski, K.

2005-12-01

166

An Experimental Study of a Radially Arranged Thin Film Heat Flux Gauge  

NASA Technical Reports Server (NTRS)

A new thin-film heat-flux gauge was designed and fabricated on three different substrate materials. Forty pairs of Pt-Pt/10% Rh thermocouple junctions were deposited in a circular pattern on the same plane of the substrate. Over the thermocouples, 5 and 10 micron thick thermal resistance layers were deposited to create a temperature gradient across those layers. Calibration and testing of these gauges were carried out in an arc-lamp calibration facility. The heat flux calculated from the gauge output is in good agreement with the value obtained from the pre-calibrated standard sensor. A CO2 laser was also used to test the steady-state and dynamic responses of the heat-flux gauge. During the steady-state test, the time constant for the heating period was 30 s. The frequency response of the heat-flux gauge was measured in the frequency domain using a CO2 laser and a chopper. The responses from an infrared detector and the heat-flux gauge were measured simultaneously and compared. It was found that the thin-film heat-flux gauge has a dynamic frequency response of 3 kHz.

Cho, Christoper S. K.; Fralick, Gustave C.; Bhatt, Hemanshu D.

1997-01-01

167

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

168

A meshless local boundary integral equation method for heat conduction analysis in nonhomogeneous solids  

Microsoft Academic Search

A local boundary integral equation method (LBIEM) with meshless approximation for heat conduction analysis in non?homogeneous solids is presented. A review of recent developments in advanced meshless LBIEM for 2?d, 3?d axisymmetric problems and microwave heating analysis is given. Both stationary and transient heat conduction problems are investigated in the paper. For transient problems both the Laplace transform technique and

Jan Sladek; Vladimir Sladek; Chuanzeng Zhang

2004-01-01

169

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

Microsoft Academic Search

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

Adrian Bejan

1997-01-01

170

The Effects of Axial Conduction in the Wall on Heat Transfer with Laminar Flow.  

National Technical Information Service (NTIS)

Wall conduction effects on steady-state laminar flow heat-transfer experiments are examined, and an analysis of heat transfer with axial conduction in the wall bounding a fluid in laminar flow is developed to determine the effects of the conduction in the...

E. J. Davis W. N. Gill

1969-01-01

171

Nongrey Radiant Heat Transfer Corrections to Thermal Conductivity Measurements.  

National Technical Information Service (NTIS)

A numerical investigation is presented to determine the influence of radiative transfer on experimental thermal conductivity measurements. The analysis is simplified by approximating the thermal conductivity test cell configuration by a parallel plate mod...

R. J. Latko W. Leidenfrost

1969-01-01

172

Heat flow in the laser-heated diamond anvil cell and the thermal conductivity of iron-bearing oxides and silicates at lower mantle pressures and temperatures  

NASA Astrophysics Data System (ADS)

The thermal conductivity of minerals in the lowermost mantle controls the total heat flow across the core-mantle boundary and is critical for the thermal evolution of the Earth. However, lower mantle thermal conductivity values and their pressure, temperature, and compositional dependencies are not well known. Here we present our recent progress combining 3D models of heat flow in the laser-heated diamond cell (LHDAC) with laboratory measurements of hotspot temperature distributions to assess the thermal conductivity of lower mantle minerals as a function of pressure and temperature. Using our numerical model of heat flow in the LHDAC, central hotspot temperature and radial and axial temperature gradients are calculated as a function of laser power, sample thermal conductivity, and sample geometry. For a given geometry, the relationship between peak sample temperature and laser power depends on the sample thermal conductivity. However, quantifying the experimental parameters sufficiently to precisely determine an absolute value of sample thermal conductivity is difficult. But relative differences in thermal conductivity are easily inferred by comparing the slopes of differing temperature vs. laser power curves measured on the same system. This technique can be used to measure the pressure dependence of thermal conductivity for minerals at lower mantle conditions. We confirm the effectiveness of this approach by measuring the pressure slope of thermal conductivity for MgO between 10 and 30 GPa. MgO retains the B1 phase throughout the experimental pressure range, and existing experimental measurements and theoretical calculations are in good agreement on the pressure- and temperature- dependence of the thermal conductivity of MgO. We also use this technique to measure the relative thermal conductivity of high pressure assemblages created from San Carlos olivine starting material. Both MgO and (Mg,Fe)2SiO4 materials show a shallower temperature vs. laser power slope as a function of pressure as expected for increasing thermal conductivity. In addition, olivine undergoes a series of phase transformations which changes its thermal behavior at upper mantle conditions (10-20 GPa) where olivine and wadsleyite are stable compared with lower mantle (25-30 GPa) conditions where the olivine transforms to a perovskite + oxide assemblage.

Rainey, E. S.; Kavner, A.; Hernlund, J. W.; Pilon, L.; Veitch, M.

2012-12-01

173

Theoretical analysis on efficient microwave heating of materials with various square cross sections in the presence of lateral and radial irradiation  

NASA Astrophysics Data System (ADS)

A theoretical analysis has been carried out to analyse the efficient heating process of long rectangular samples with various orientations of square cross sections in the presence of lateral and radial irradiation. Lateral irradiation represents the sample incident at one direction with the source at infinity whereas radial irradiation represents the situation where the sample is incident with microwave radiation from the coaxial cylindrical cavity at infinity. Electric field equations have been solved with a hypothetical circular domain which surrounds the square cross sections and facilitates the solution of field equations with the radiation boundary condition. The electric field and temperature have been solved using the finite element method for the composite domain. Generalized characteristics on power absorption and temperature distribution as functions of the wave number (Nw) and the penetration number (Np) have been obtained. Radial irradiation gives a larger power absorption for Nw <= 0.56 and either lateral or radial irradiation is favoured for Nw >= 0.56 based on various Np values. The aligned square cross section is found to give larger heating rates in the presence of dominant lateral irradiation. The detailed spatial distributions of power and temperature are extensively studied and the suitability of either radial or lateral irradiation for a specific cross section has been recommended. The large heating rate as well as minimal thermal runaway become the competing factors for the selection of a specific heating strategy. The case studies are demonstrated for high and low lossy substances (beef and bread).

Basak, Tanmay

2008-02-01

174

Evaluating new ways of conducting convective heat dissipation experiments with ventilated brake discs  

Microsoft Academic Search

A research on convective cooling from automotive brake discs has been conducted using an affordable way of experimentally modelling various vanes geometries. A standard gray iron ventilated brake disc with 30 radial vanes was used as a baseline design. This disc has been computationally modelled and good correlation has been obtained with experimental results. The new brake disc concept, an

Carlos H. Galindo-López

175

SPH Numerical Modeling for Ballistic-Diffusive Heat Conduction  

Microsoft Academic Search

The classic Fourier heat diffusion theory, in general, does not apply to micro\\/nanoscale or ultrafast thermal processes, where the mean free path of the heat carriers is comparable to the system size and\\/or typical times are comparable to the carrier relaxation time. For these processes, the ballistic-diffusive equation is a good alternative. In this context, the smoothed particle hydrodynamics (SPH)

Fangming Jiang; Antonio C. M. Sousa

2006-01-01

176

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  

Microsoft Academic Search

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

Ming-Ming Chen; Amir Faghri

1990-01-01

177

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

PubMed

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

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

2013-03-01

178

Constant of thermal heat conduction and stabilization of the bus bar conductor for superconducting accelerators  

SciTech Connect

Using the one-dimensional, time-independent conduction state, a constant of thermal heating conduction is given that brings about the known stabilization theorem and a closed expression for the bus bar to be cryogenically stable in superconducting accelerators.

Lopez, G.

1993-07-01

179

Prediction of heat transfer to a thin liquid film in plane and radially spreading flows  

SciTech Connect

The numerical solution of a thin film flow is difficult since the free surface geometry changes along the path of the flow, is unknown ahead of time, and cannot be fitted in a regular Cartesian or cylindrical coordinate system. Therefore, most theoretical studies in this area were related to the development of approximate analytical models (Faghri and Seban, 1981; Chaudhury, 1964). The finite-difference solution was attempted only for a falling film (Faghri and Payvar, 1979) where the film thickness could be approximated to be uniform. Recently, Rahman et al. (1990a) have developed a finite-difference solution method applicable for the fluid mechanics of thin film flows under zero and normal gravity. A body-fitted coordinate system was used where the free surface was approximated by a curve and iterated for the best possible solution. The present study is intended to incorporate the energy equation in the solution algorithm of Rahman et al. (1990a) to compute the heat transfer to a thin film in the presence or absence of gravity. In addition to the enhancement of the knowledge of thin film heat transfer, the results of the present study may be directly applicable to the design of space-based cooling systems.

Rahman, M.M.; Faghri, A.; Hankey, W.L. (Wright State Univ., Dayton, OH (USA)); Swanson, T.D. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

1990-08-01

180

Glass-Like Heat Conduction in Crystalline Semiconductors  

SciTech Connect

The thermal conductivity and structural properties of polycrystalline and single crystal semiconductor type-1 germanium clathrates are reported. Germanium clathrates exhibit thermal conductivities that are typical of amorphous materials. This behavior occurs in spite of their well-defined crystalline structure. The authors employ temperature dependent neutron diffraction data in investigating the displacements of the caged strontium atoms in Sr{sub 8}Ga{sub 16}Ge{sub 30} and their interaction with the polyhedral cages that entrap them. Their aim is to investigate the correlation between the structural properties and the low, glass-like thermal conductivity observed in this compound.

Nolas, G.S.; Cohn, J.L.; Chakoumakos, B.C.; Slack, G.A.

1999-06-13

181

A two-fluid model for relativistic heat conduction  

NASA Astrophysics Data System (ADS)

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.

2014-01-01

182

Approximate Method of Solving Nonlinear Heat Conduction Problems.  

National Technical Information Service (NTIS)

A method of solving nonlinear problems of high-temperature heat transfer is presented; it is based on the linearization of the basic process equation, starting from the condition of minimum rms error due to violating nonlinearity; in this, the nonlinear b...

V. V. Salomatov

1973-01-01

183

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

184

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

185

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

186

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

187

On the heat conduction problem and a design principle for plasma arc furnace  

Microsoft Academic Search

In this paper a plane heat conduction problem with variable coefficients of heat conductivity K(T) is analysed with given electric power supplied to the plasma arc. The governing equation for unknown temperature distribution is a nonlinear one with a ? function as its nonhomogeneous term. To make the problem attractable by the method of separation of variables, a set of

Rong Sheng

1984-01-01

188

A new stochastic approach to transient heat conduction modeling with uncertainty  

Microsoft Academic Search

We present a generalized polynomial chaos algorithm for the solution of transient heat conduction subject to uncertain inputs, i.e. random heat conductivity and capacity. The stochastic input and solution are represented spectrally by the orthogonal polynomial functionals from the Askey scheme, as a generalization of the original polynomial chaos idea of Wiener [Am. J. Math. 60 (1938) 897]. A Galerkin

Dongbin Xiu; George Em Karniadakis

2003-01-01

189

Phonon heat conduction in nano and microporous thin films  

NASA Astrophysics Data System (ADS)

In this dissertation, the phonon size effect in the experimental and theoretical studies of random and periodic porous media are reported. First, a literature review on the past modeling studies on porous media are presented that covers both the earlier works that use the traditional effective medium approach and the few existing recent works that consider the low-dimensional effects. Next, the experimental characterization of the cross-plane thermal conductivity of randomly nano-porous bismuth thin films is presented. Fabricated in search for more efficient thermoelectric materials, the nanoporous bismuth films use nano-scale pores to impede phonon transport more than electron transport. Their cross-plane thermal conductivity characterization using the differential 3o technique revealed an order-of-magnitude reduction in the thermal conductivity values of the porous bismuth over those of non-porous bismuth films and a potential for the independent tuning of their electrical conductivity and thermal conductivity, but the defect-laden structure was difficult to model. Therefore, a new study was undertaken that focused on simpler periodic micro-porous single-crystal silicon membranes. A batch of such membranes were fabricated from both a plain silicon wafer and a silicon-on-insulator wafer using MEMS techniques, including bulk chemical etching and deep-reactive ion etching. The resulting samples contained periodically arranged pores of controlled dimension and orientation, but the pore dimension and orientation was varied from sample to sample to experimentally isolate the phonon size effect due to pore boundary scattering. The in-plane thermal conductivity of the microporous silicon membranes is characterized by a modified version of Volklein's DC method. The resulting thermal conductivity reduction in porous films compared to the solid silicon film strongly suggest phonon size effect. The three-dimensional phonon transport in porous silicon membranes were modeled using the Monte Carlo method to yield an equivalent solution to the three-dimensional Boltzmann transport equation. Since the focus of the modeling is the effect of pore boundary scattering on phonon transport, a simplified view of gray-body medium is studied. The thermal conductivity result predicts a thermal conductivity reduction in porous silicon films compared to solid silicon films by an amount beyond that predicted from porosity and comparable to that observed in experiments.

Song, David Won-Jun

190

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

191

Heat Transfer with Axial Conduction in Triangular Ducts Filled with Saturated Porous Materials  

Microsoft Academic Search

The study reports the contribution of axial conduction in heat transfer to flow passing through triangular porous passages. The problem under consideration uses the H2 boundary condition; that is, locally constant wall heat flux. Because of the geometrical asymmetry, nonorthogonal boundary conditions can exist and this makes the determination of heat transfer more demanding. The porous medium is fully saturated

Abhishek Banerjee; A. Haji-Sheikh; Seiichi Nomura

2012-01-01

192

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

193

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

194

Bem Solution to Transient Free Convective Heat Transfer in a Viscous, Electrically Conducting, and Heat Generating Fluid  

Microsoft Academic Search

The nonlinear partial differential equations for the transient free convective heat transfer in a viscous, electrically conducting, and heat-generating fluid past a vertical porous plate in the presence of free stream oscillations are solved by the boundary element method (BEM). Time-dependent fundamental solutions are employed in a time marching scheme to resolve the field variables. Numerical results are compared with

K. Vajravelu; A. Kassab; A. Hadjinicolaou

1996-01-01

195

DYNAMIC RESPONSE OF A ROD DUE TO A MOVING HEAT SOURCE UNDER THE HYPERBOLIC HEAT CONDUCTION MODEL  

Microsoft Academic Search

The dynamic thermal and elastic behavior of a rod due to a moving heat source are investigated. The hyperbolic heat conduction model is used for the prediction of the temperature history. Thermally induced displacements and stresses are determined. An analytical–numerical technique based on the Laplace transformation and the Riemann-sum approximation is used to calculate the temperature, displacement and stress distributions

N. S. AL-HUNITI; M. A. AL-NIMR; M. NAJI

2001-01-01

196

Phonon Transport in Graphene: Umklapp Quenching and Heat Conduction  

NASA Astrophysics Data System (ADS)

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

Balandin, Alexander

2009-11-01

197

Symmetry analysis of a heat conduction model for heat transfer in a longitudinal rectangular fin of a heterogeneous material  

NASA Astrophysics Data System (ADS)

We consider a heat conduction model arising in transient heat transfer through longitudinal fins of a heterogeneous (functionally graded) material. In this case, the thermal conductivity depends on the spatial variable. The heat transfer coefficient depends on the temperature and is given by the power law function. The resulting nonlinear partial differential equation is analyzed using both classical and nonclassical symmetry techniques. Both the transient state and the steady state result in a number of exotic symmetries being admitted by the governing equation. Furthermore, nonclassical symmetries are also admitted. Both classical and nonclassical symmetry analysis results in some useful reductions and some remarkable exact solutions are constructed.

Moitsheki, Raseelo J.; Bradshaw-Hajek, Bronwyn H.

2013-09-01

198

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

199

Numerical simulation of heat conduction in a random ballistic deposited grain aggregate  

NASA Astrophysics Data System (ADS)

A numerical simulation of heat conduction in a grain aggregate is carried out to determine the packing fraction (the spatial fraction occupied by grains or 1-porosity) dependence of the thermal conductivity of the aggregate. Arrangements of grains are given by random ballistic deposition. It is found that the packing fraction dependence is well approximated by an exponential function. The number of contacts between grains is the crucial quantity in the conduction, and its packing fraction dependence is exponential. Heat conduction is found to be anisotropic, where the conduction along the deposition direction is more efficient than that perpendicular to the deposition direction.

Sirono, Sin-Iti

2014-01-01

200

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

201

Soil profile method for soil thermal diffusivity, conductivity and heat flux: Comparison to soil heat flux plates  

NASA Astrophysics Data System (ADS)

Diffusive heat flux at the soil surface is commonly determined as a mean value over a time period using heat flux plates buried at some depth (e.g., 5-8 cm) below the surface with a correction to surface flux based on the change in heat storage during the corresponding time period in the soil layer above the plates. The change in heat storage is based on the soil temperature change in the layer over the time period and an estimate of the soil thermal heat capacity that is based on soil water content, bulk density and organic matter content. One- or multiple-layer corrections using some measure of mean soil temperature over the layer depth are common; and in some cases the soil water content has been determined, although rarely. Several problems with the heat flux plate method limit the accuracy of soil heat flux values. An alternative method is presented and this flux gradient method is compared with soil heat flux plate measurements. The method is based on periodic (e.g., half-hourly) water content and temperature sensing at multiple depths within the soil profile and a solution of the Fourier heat flux equation. A Fourier sine series is fit to the temperature at each depth and the temperature at the next depth below is simulated with a sine series solution of the differential heat flux equation using successive approximation of the best fit based on changing the thermal diffusivity value. The best fit thermal diffusivity value is converted to a thermal conductivity value using the soil heat capacity, which is based on the measured water content and bulk density. A statistical analysis of the many data resulting from repeated application of this method is applied to describe the thermal conductivity as a function of water content and bulk density. The soil heat flux between each pair of temperature measurement depths is computed using the thermal conductivity function and measured water contents. The thermal gradient method of heat flux calculation compared well to values determined using heat flux plates and calorimetric correction to the soil surface; and it provided better representation of the surface spatiotemporal variation of heat flux and more accurate heat flux values. The overall method resulted in additional important knowledge including the water content dynamics in the near-surface soil profile and a soil-specific function relating thermal conductivity to soil water content and bulk density.

Evett, Steven R.; Agam, Nurit; Kustas, William P.; Colaizzi, Paul D.; Schwartz, Robert C.

2012-12-01

202

Heat conduction in driven Frenkel-Kontorova lattices: thermal pumping and resonance.  

PubMed

Heat conduction through the Frenkel-Kontorova chain under the influence of an ac driving force applied locally at one boundary is studied by nonequilibrium molecular dynamics simulations. We observe the occurrence of thermal resonance, namely, there exists a value of the driving frequency at which the heat flux takes its maximum value. The resonance frequency is determined by the dynamical parameters of the model, which has been numerically explored. Remarkably, the heat can be pumped from the low-temperature heat bath to the high temperature one by suitably adjusting the frequency of the ac driving force. By examining effects of the driving amplitude on heat conduction, we show that the amplitude threshold for nonlinear supratransmission is absent when the system is in contact with heat baths, namely, the heat flux smoothly increases with the increasing of amplitude. PMID:20365714

Ai, Bao-quan; He, Dahai; Hu, Bambi

2010-03-01

203

Heat conduction in driven Frenkel-Kontorova lattices: Thermal pumping and resonance  

NASA Astrophysics Data System (ADS)

Heat conduction through the Frenkel-Kontorova chain under the influence of an ac driving force applied locally at one boundary is studied by nonequilibrium molecular dynamics simulations. We observe the occurrence of thermal resonance, namely, there exists a value of the driving frequency at which the heat flux takes its maximum value. The resonance frequency is determined by the dynamical parameters of the model, which has been numerically explored. Remarkably, the heat can be pumped from the low-temperature heat bath to the high temperature one by suitably adjusting the frequency of the ac driving force. By examining effects of the driving amplitude on heat conduction, we show that the amplitude threshold for nonlinear supratransmission is absent when the system is in contact with heat baths, namely, the heat flux smoothly increases with the increasing of amplitude.

Ai, Bao-Quan; He, Dahai; Hu, Bambi

2010-03-01

204

Heat flux cloaking, focusing, and reversal in ultra-thin composites considering conduction-convection effects  

NASA Astrophysics Data System (ADS)

Experimental results are presented for heat flux cloaking, focusing, and reversal in ultra-thin anisotropic composites. A two-material system is utilized in the device design, which features an annular region for heat flow control. The effective thermal conductivity layout of the composite is specified through logical combination of the base material constituents. Heat transfer considering conduction-convection is numerically predicted and experimentally verified via infrared thermography. A Biot number analysis reveals the significance of high rates of convection for large-area planar devices, while the experimental results indicate the feasibility of such heat flow control techniques for advanced electronics applications involving natural convection.

Dede, Ercan M.; Nomura, Tsuyoshi; Schmalenberg, Paul; Seung Lee, Jae

2013-08-01

205

Heat transport and conduction layers in gravity-assisted heat pipes  

NASA Astrophysics Data System (ADS)

The steady state performance and the limiting heat transport capability of gravity-assisted screen-wicked heat pipes with a liquid overfill are discussed in the present work. A semi-empirical correlation between the maximum heat flux density, or maximum heat transport rate, and various influence parameters, viz. tilt angle, fill charge, number of screen mesh layers, screen mesh size, operating temperature, heat pipe diameter and evaporator length, is derived. Moreover, the heat transfer phenomenon within the heat pipe as well as the effect of the screen structure on the bubble growth process is thoroughly investigated. Finally, the work confirms the complexity of the influence of screen mesh size and of the multiple-layer screen mesh configuration on the wall superheat required for the nucleation of the first bubbles, on the capillary force and on the wick porosity.

Nguyen-Chi, H.

1980-02-01

206

Experimental Thermal Conductivity, Thermal Diffusivity, and Specific Heat Values of Argon and Nitrogen.  

National Technical Information Service (NTIS)

Experimental measurements of thermal conductivity and thermal diffusivity as obtained in a transient hot-wire apparatus for argon and nitrogen are reported. Values of the specific heat are calculated from these measured values and the density associated w...

H. M. Roder R. A. Perkins C. A. Nieto de Castro

1988-01-01

207

Thermal conductivity of cementitious grouts for geothermal heat pumps. progress report fy 1997.  

National Technical Information Service (NTIS)

The thermal conductivity of cementitious grouts was investigated in order to determine suitability of these materials for grouting vertical boreholes used with geothermal heat pump systems. In addition, other relevant physical and mechanical properties we...

Allan

1997-01-01

208

The Thermal Conductivity Measurements of Solid Samples by Heat Flux Differantial Scanning Calorimetry  

NASA Astrophysics Data System (ADS)

The thermal conductivity of polyvinylchloride (PVC), polysytrene (PS) and polypropylene (PP) were measured by heat flux DSC. Our results are in good agreement with the results observed by different methods.

Kök, M.; Aydo?du, Y.

2007-04-01

209

[Effect of an ultrahigh-frequency electromagnetic field on the heat conductivity of experimental biological tissue].  

PubMed

It has been established that heat conductivity was markedly increased after UHF-irradiation. The combined use of UHF-irradiation and cryogenic destruction is 30-40 times as effective as cryogenic destruction alone. PMID:3337877

Ten, Iu V; Shafranov, V V; Repalov, V A; Kozhevnikov, V A; Mazokhin, V N

1988-01-01

210

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

211

Specific heat and thermal conductivity of superionic conductors in the superionic phase  

Microsoft Academic Search

The temperature dependences of the specific heat and the thermal conductivity of crystalline superionic conductors LnF3 (Ln = La, Ce, Pr), Li2B4O7 and ?-LiIO3 in the superionic phase have been investigated experimentally. The specific heat C\\u000a p and the thermal conductivity K are observed to increase monotonically over a wide range of temperatures above the Debye temperature ?D. This increase

A. É. Aliev; V. F. Krivorotov; P. K. Khabibullaev

1997-01-01

212

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

Microsoft Academic Search

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

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

2000-01-01

213

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

214

Identification of a moving boundary for a heat conduction problem in a multilayer medium  

Microsoft Academic Search

In this paper, we give a uniqueness theorem for the moving boundary of a heat problem in a composite medium. Through solving\\u000a the Cauchy problem of heat equation in each subdomain, we finally find an approximation to the moving boundary for one-dimensional\\u000a heat conduction problem in a multilayer medium. The numerical scheme is based on the use of the method

Y. S. LiT; T. Wei

2010-01-01

215

On the Conduction and Convection Heat Transfer From Lightweight Advanced Heat Sinks  

Microsoft Academic Search

Seamless advancements in the electronics industry lead to high heat fluxes from very limited thermal real estates. Use of natural convection air cooling is of interest to meet some of the low flux cooling needs, while active cooling techniques via liquid or forced convection are the methods of choice. In natural convection heat transfer applications, the components used for cooling

M. Baris Dogruoz; Mehmet Arik

2010-01-01

216

NUMERICAL ANALYSIS OF TWO DIMENSIONAL HEAT CONDUCTIVITY IN STEADY STATE REGIME  

Microsoft Academic Search

Solving the differential equation of the heat conduction the temperature in each point of the body can be determined. However, in the case of bodies with boundary surface of sophisticated geometry no analytic method can be used. In this case the use of numerical methods becomes necessary. The finite element method is based on the integral equation of the heat

Ioan SÂRBU

217

Longwave ultrasound and conductive heating increase functional ankle mobility in asymptomatic subjects  

Microsoft Academic Search

AimsThis study aimed to compare the thermal effects of longwave ultrasound (LWUS) and conductive heating (hot water bottle—HWB) on ankle mobility using a non-injured Achilles tendon (AT) model. These two modalities represent a clinical and a home variation of heat treatment.

Adam Meakins; Tim Watson

2006-01-01

218

Spectral Element Approach for Coupled Radiative and Conductive Heat Transfer in Semitransparent Medium  

Microsoft Academic Search

A spectral element method is presented to solve coupled radiative and conductive heat transfer problems in multidimensional semitransparent medium. The solution of radiative energy source is based on a second order radiative transfer equation. Both the second order radiative transfer equation and the heat diffusion equation are discretized by spec- tral element approach. Four various test problems are taken as

J. M. Zhao; L. H. Liu

2007-01-01

219

Coupled boundary element method and finite difference method for the heat conduction in laser processing  

Microsoft Academic Search

This paper is presented as a way to model transient heat conduction in a 3-D axisymmetric case where large rates of heat fluxes are applied on the surfaces as done in the case of laser processing. This would result in large temperature gradients in a small area irradiated by the laser on the incident surface that could also reach melting

Sirilath J. DeSilva; Cho Lik Chan

2008-01-01

220

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

Microsoft Academic Search

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

J. Sladek; V. Sladek; Ch. Zhang

2003-01-01

221

Convective mechanism for inhibition of heat conduction in laser produced plasmas  

SciTech Connect

In laser-produced plasmas, the laser energy is absorbed only below and up to the critical density. For laser fusion applications, this energy must be transported beyond the corona via electron thermal conduction towards colder, higher density regions of the target to heat up material and cause ablation, which in turn generates an inward pressure to compress the fusion fuel. If the heat conduction is inhibited, the consequences will be a weaker ablation and therefore a weaker implosion. For many years now, the inhibition of heat conduction, i.e., the reduction of heat conduction relative to classical conduction, in laser-produced plasmas at relevant irradiances has been apparent from the large body of experimental evidence. Many mechanisms, such as dc magnetic fields, ion acoustic turbulence, and Weibel instabilities, have been proposed to be the cause of inhibition of heat conduction. Even improved calculations of the classical heat flux have been carried out to solve this problem. Nevertheless, no single one of the above mentioned mechanisms can explain the large inhibition observed in the experiments.

Lee, P.H.Y.; Willi, O.; Trainor, R.J.

1984-06-27

222

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

223

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

224

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

225

The effects of heat conduction on the vaporization of liquid invading superheated permeable rock  

SciTech Connect

We examine the role of conductive and convective heat transfer in the vaporization of liquid as it slowly invades a superheated permeable rock. For very slow migration, virtually all of the liquid vaporizes. As the liquid supply rate increases beyond the rate of heat transfer by thermal conduction, a decreasing fraction of the liquid can vaporize. Indeed, for sufficiently high flow rates, the fraction vaporizing depends solely on the superheat of the rock, and any heat transfer from the superheated region is negligible. These results complement earlier studies of vaporization under very high injection rates, in which case the dynamic vapour pressure reduces the mass fraction vaporizing to very small values.

Woods, Andrew, W.; Fitzgerald, Shaun D.

1996-01-24

226

Combined heat transfer of radiation and conduction in stacked radiation shields for vacuum insulation panels  

Microsoft Academic Search

Combined heat transfer of radiation and conduction considering depthwise conduction phenomena in stacked radiation shields for vacuum insulation panels (VIPs) having an artificial core structure is investigated. The purpose of this study is to establish a reliable analysis method for actual shield design. A one-dimensional problem is first analyzed. Actual two-dimensional problem is simplified for theoretical modeling and the depthwise

Choonghyo Jang; Jongmin Kim; Tae-Ho Song

2011-01-01

227

COMBINED CONDUCTION AND RADIATION HEAT TRANSFER IN PLANE-PARALLEL PACKED BEDS WITH VARIABLE POROSITY  

Microsoft Academic Search

The primary concern of this study deals with the prediction of thermal performance of packed beds with variable porosity. Combined conduction and radiation heat transfer in plane-parallel packed beds of spherical particles was investigated numerically. The effects of variable porosity, effective thermal conductivity, and thermal radiation were taken into account. The method for radiative transfer equation was based on the

JHY-WEN WU; HSIN-SEN CHU

1999-01-01

228

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

229

Electrical Conductivity during XPS of Heated PMMA: Detection of Core Line and Valence Band Tacticity Effects.  

National Technical Information Service (NTIS)

Electrical conductivity during the XPS of approximately 100 nm thick films of PMMA on silicon was induced by heating to above 100 degrees C. Rapid x-ray induced depolymerization set in at about the same temperature. The electrical conductivity allowed acq...

G. Beamson D. T. Clark D. S. L. Law

1998-01-01

230

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

PubMed

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

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

2013-11-13

231

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

232

Meshless approach for coupled radiative and conductive heat transfer in one-dimensional graded index medium  

NASA Astrophysics Data System (ADS)

A meshless local Petrov Galerkin (MLPG) approach is employed for solving the coupled radiative and conductive heat transfer in a one-dimensional slab with graded index media. The angular distribution term in discrete ordinate equation of radiative transfer within a one-dimensional graded index slab is discretized by a step scheme, and the meshless approach for radiative transfer is based on the discrete ordinate equation. A moving least-squares approximation is used to construct the shape function. Two particular test cases for coupled radiative and conductive heat transfer within a one-dimensional graded index slab are examined to verify this new approximate method. The temperatures and the radiative heat fluxes are obtained. The results are compared with the other benchmark approximate solutions. By comparison, the results show that the MLPG approach has a good accuracy in solving the coupled radiative and conductive heat transfer in one-dimensional graded index media.

Liu, L. H.; Tan, J. Y.; Li, B. X.

2006-09-01

233

An Experimental-Numerical Evaluation of Thermal Contact Conductance in Fin-Tube Heat Exchangers  

NASA Astrophysics Data System (ADS)

The contact between fin collar and tube surface of a fin-tube heat exchanger is secured through mechanical expansion of tubes. However, the characteristics of heat transfer through the interfaces between the tubes and fins have not been clearly understood because the interfaces consist partially of metal-to-metal contact and partially of air. The objective of the present study is to develop a new method utilizing an experimental-numerical method for the estimation of the thermal contact resistance between the fin collar and tube surface and to evaluate the factors affecting the thermal contact resistance in a fin-tube heat exchanger. In this study, heat transfer characteristics of actual heat exchanger assemblies have been tested in a vacuum chamber using water as an internal fluid, and a finite difference numerical scheme has been employed to reduce the experimental data for the evaluation of the thermal contact conductance. The present study has been conducted for fin-tube heat exchangers of tube diameter of 7mm with different tube expansion ratios, fin spacings, and fin types. The results show, with an appropriate error analysis, that these parameters as well as hydrophilic fin coating affect notably the thermal contact conductance. It has been found out that the thermal contact resistance takes fairly large portion of the total thermal resistance in a fin-tube heat exchanger and it turns out that careful consideration is needed in a manufacturing process of heat exchangers to reduce the thermal contact resistance.

Kim, Chang Nyung; Jeong, Jin; Youn, Baek; Kil, Seong Ho

234

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

PubMed

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

Kondaraju, Sasidhar; Lee, Joon Sang

2011-01-01

235

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.

2011-01-01

236

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

237

The role of percolation and sheet dynamics during heat conduction in poly-dispersed graphene nanofluids  

NASA Astrophysics Data System (ADS)

A thermal transport mechanism leading to the enhanced thermal conductivity of graphene nanofluids has been proposed. The graphene sheet size is postulated to be the key to the underlying mechanism. Based on a critical sheet size derived from Stokes-Einstein equation for the poly-dispersed nanofluid, sheet percolation and Brownian motion assisted sheet collisions are used to explain the heat conduction. A collision dependant dynamic conductivity considering Debye approximated volumetric specific heat due to phonon transport in graphene has been incorporated. The model has been found to be in good agreement with experimental data.

Dhar, Purbarun; Sen Gupta, Soujit; Chakraborty, Saikat; Pattamatta, Arvind; Das, Sarit K.

2013-04-01

238

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

SciTech Connect

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

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

1989-12-12

239

Simple heat treatment for fabrication of carbonaceous layer-coated microelectrodes and conductive stainless steels  

NASA Astrophysics Data System (ADS)

A simple heat treatment was used to fabricate carbonaceous layer-coated electrodes: micro-ring electrodes and conductive stainless steel. Substrates of sharpened quartz capillaries or type-316 stainless steel plates were put in an alumina boat with powder of petroleum pitch A240F separately and heated at 1073-1273 K in a flow of nitrogen or argon. By this treatment, both of the substrates were coated with a uniform carbonaceous layer of several hundred nano-meters in thickness. The electric conductivity of the layer was improved by increases in temperature and period of the heating. The quartz glass-capillary covered with the conductive layer was modified to a needle-type microelectrode by coating with an insulating polymer and baring the tip. At least a dozen carbon micro-ring electrodes with an outer radius of about 1 ?m were successfully prepared by the simple heat treatment. On the other hand, the carbonaceous layer formed on type-316 stainless steel showed relatively poor conductivity due to the formation of oxides in the layer. However, the conductivity was improved by electroplating of nickel on the substrate before the heating. The carbonaceous layer-coated stainless steel showed good corrosion resistance in sulphuric acid.

Fushimi, K.; Ono, A.; Matsushita, K.; Kumagai, H.; Konno, H.

2011-07-01

240

Surface Heat Loss on Venus due to the Heat Capacities of Thermal Conductivity and Hot-Spot/Corona Volcanism  

NASA Astrophysics Data System (ADS)

A lot of different approaches have been performed in the literature to estimate the surface heat flow on Venus. Estimates based on parameterized convection solutions resulted in values between 15 and 50 mW m-2, in contrast to global scaling from Earth, which results in a distinctively higher amount of heat loss (between ca. 60 and 70 mW m-2) as shown by Phillips R. J. et al. (1997). In our estimate we have considered the capacities of main lithospheric heat transport mechanisms on Venus. On Earth their contribution to the total heat loss is small, because plate-recycling is the most dominant factor. But since the MAGELLAN radar surface mapping mission and theoretical calculations which have shown that presently plate-recycling is not able to be operative on Venus (Leitner J. J. and Firneis M. G. (2005)), the Venusian surface heat loss is only characterized by thermal conductivity and hot-spot/Corona volcanism. Under consideration of the different thermic parameters of the Venusian interior we have calculated the amount of heat loss due to thermal conductivity to be 33.5 mW m-2. The present contribution of hot-spot volcanism, which we have found on Venus to be manifested in the form of Corona-volcanism (under consideration of presumably active or at least in the recent past active sources), yields a quota of 6.0 ± 1.4 mW m-2. A result, which corresponds well with the estimation of the quota of Corona heat loss on Venus given by Stofan E. R. al el. (2001). With this prior estimate we were able to determine the present heat loss on Venus to be 39.5 ± 3.0 mW m-2.

Leitner, J. J.; Firneis, M. G.

2005-04-01

241

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

242

High heat flux Kapitza conductance of technical copper with several different surface preparations  

NASA Astrophysics Data System (ADS)

Kapitza conductance values of technical copper with different surface treatments and for heat fluxes of up to 6 W cm -2 are reported. Five different surface preparations were studied: a, polished with 0.3 ?m alumina powder; b, oxidized at room temperature in air for a period of one month; c, oxidized in air at 200°C for 40 min; d, coated with 50-50 PbSn solder; e, coated with a layer of GE7031 varnish. The variation of surface temperature with heat flux as well as the limiting values of Kapitza conductance for small temperature difference are determined. Relative to the polished samples, it is observed that the baked and solder coated samples have higher conductances and that the samples oxidized in the atmosphere show lower conductances. The surface temperature of the varnished samples is controlled mostly by the low thermal conductivity of the varnish.

Kashani, A.; Van Sciver, S. W.

243

In Situ Determination of BCC-, FCC- and HPC-Iron Textures at Simultaneous High- Pressure and -Temperature by Means of the Resistive Heated Radial Diffraction Diamond Anvil Cell (RH-RD-DAC): Implications for the iron core.  

NASA Astrophysics Data System (ADS)

Radial diffraction in the diamond anvil cell (DAC) has long been used to determine the stress state of materials under non-hydrostatic compression. This technique is also a major tool to investigate textures and infer deformation mechanisms in the earth mantle and core. However, most of these experiments have been conducted at ambient temperatures and therefore the results of these measurements may be difficult to extrapolate to the deep Earth. Here, we present texture data collected at HPCAT sector 16 BMD of the Advanced Photon Source during the plastic deformation of BCC-, FCC- and HPC-iron at simultaneous high-pressure and temperature in the new Resistive Heated Radial Diffraction Diamond Anvil Cell (RH-RD-DAC). Initial results from Rietveld refinements in MAUD indicate that BCC- iron develops a mixed {100} and {111} texture that remains active during heating. Latter is compatible with previous observations on BCC-iron and interpreted as slip along {110}<111>. Texture obtained after formation of FCC-iron at simultaneous high- pressure and temperatures show a pronounced maximum at {110} with minima at {100} and {111}. This texture is typical for FCC metals in compression with slip on {111}<110>. Processing of the HCP-iron textures at high-pressure and -temperature are under way. We will discuss the implications that the experimental results have for the deformation mechanisms of iron at pressure temperature conditions of the inner core.

Liermann, H.; Merkel, S.; Miyagi, L.; Wenk, H.; Shen, G.; Cynn, H.; Evans, W. J.

2008-12-01

244

Thermal characterization of micro/nanoscale conductive and non-conductive wires based on optical heating and electrical thermal sensing  

NASA Astrophysics Data System (ADS)

In this work, a technique based on optical heating and electrical thermal sensing (OHETS) is developed to characterize the thermophysical properties of one-dimensional micro/nanoscale conductive and non-conductive wires. In this method, the to-be-measured thin wire is suspended over two electrodes and is irradiated with a periodically modulated laser beam. The laser beam induces a periodical temperature variation in the wire/tube, which will lead to a periodical change in its electrical resistance. A dc current is applied to the sample, and the resulting periodical voltage variation over the wire is measured and used to extract the thermophysical properties of the wire/tube. A 25.4 µm thick platinum wire is used as the reference sample to verify this technique. Sound agreement is obtained between the measured thermal conductivity and the reference value. Applying the OHETS technique, the thermal diffusivity of conductive single-wall carbon nanotube (SWCNT) bundles and non-conductive human hair and cloth fibres are measured. For non-conductive wires, a thin (~nm) metallic film is coated at the outside of the wire for electrical thermal sensing. The measured thermal diffusivities for three different SWCNT bundles are 2.98 × 10-5 m2 s-1, 4.41 × 10-5 m2 s-1 and 6.64 × 10-5 m2 s-1. These values are much less than the thermal diffusivity of graphite in the layer direction. For human hair and microscale cloth fibres, our experiments show that their thermal diffusivities are at the level of 10-6 m2 s-1.

Hou, Jinbo; Wang, Xinwei; Guo, Jiaqi

2006-08-01

245

Heat diode effect and negative differential thermal conductance across nanoscale metal-dielectric interfaces  

NASA Astrophysics Data System (ADS)

Controlling heat flow by phononic nanodevices has received significant attention recently because of its fundamental and practical implications. Elementary phononic devices such as thermal rectifiers, transistors, and logic gates are essentially based on two intriguing properties: heat diode effect and negative differential thermal conductance. However, little is known about these heat transfer properties across metal-dielectric interfaces, especially at nanoscale. Here we analytically resolve the microscopic mechanism of the nonequilibrium nanoscale energy transfer across metal-dielectric interfaces, where the inelastic electron-phonon scattering directly assists the energy exchange. We demonstrate the emergence of heat diode effect and negative differential thermal conductance in nanoscale interfaces and explain why these novel thermal properties are usually absent in bulk metal-dielectric interfaces. These results will generate exciting prospects for the nanoscale interfacial energy transfer, which should have important implications in designing hybrid circuits for efficient thermal control and open up potential applications in thermal energy harvesting with low-dimensional nanodevices.

Ren, Jie; Zhu, Jian-Xin

2013-06-01

246

Thermal conductivity, heat capacity, and thermal diffusivity of selected commercial AlN substrates  

SciTech Connect

The thermal transport properties of four commercially available AlN substrates have been investigated using a combination of steady-state and transient techniques. Measurements of thermal conductivity using a guarded longitudinal heat flow apparatus are in good agreement with published room temperature data (in the range 130-170 W {center dot} m{sup {minus}1} {center dot} K{sup {minus}1}). Laser flash diffusivity measurements combined with heat capacity data yielded anomalously low results. This was determined to be an experimental effect for which a method of correction is presented. Low-temperature measurements of thermal conductivity and heat capacity are used to probe the mechanisms that limit the thermal conductivity in AlN.

Dinwiddie, R.B.; Whittaker, A.J.; Onn, D.G. (Univ. of Delaware, Newark (USA))

1989-09-01

247

Combined parameter and function estimation in heat transfer with application to contact conductance  

NASA Astrophysics Data System (ADS)

This paper discusses parameter estimation, function estimation, and a combination of the two. An example of parameter estimation is the determination of thermal conductivity of solids from transient temperature measurements. An example of function estimation is the inverse heat conduction problem, which uses transient temperature measurements to determine the surface heat flux history. The examples used herein involve the determination of the thermal contact conductance. Two sets of very good data are analyzed. One set of steady-state data was obtained by Antonetti and Eid (1987). The other set was obtained by Moses and Johnson (1986) under transient conditions for periodic contact. Both sets of data are used to illustrate parameter, function, and combined estimation. It is demonstrated that the proposed methods are more powerful then commonly accepted methods. Many other heat transfer problems can be treated using the proposed techniques.

Beck, J. V.

1988-11-01

248

Heat transfer through a multifoil insulation system by radiation and gaseous conduction - Analytical and experimental investigations  

NASA Astrophysics Data System (ADS)

Heat transfer through a 302-stainless steel multifoil insulation system under the flight conditions similar to that of an Unmanned Hypersonic Vehicle (UHV) was examined by both analysis and experiment. The analytical model considered both thermal radiation between two adjacent foils and gaseous heat conduction through the gas medium contained in the foil spacing. Temperature predictions from the pretest analysis agreed well with the test data under vacuum environment and gas pressures greater than 1.0 mm Hg. For intermediate pressures around 0.2 mm Hg, however, the pretest analytical model was found to slightly overpredict thermal radiation and underpredict gaseous heat conduction. The radiation and gaseous conduction parameters were therefore correlated using the test data. With the new correlations, agreement with the test and computed temperatures was excellent for all pressures.

Kang, C. S.; Hinton, J. F.; McNamara, R. C.

1989-01-01

249

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

250

Transient heat transfer measurements using thermochromic liquid crystal: lateral-conduction error  

Microsoft Academic Search

Thermochromic liquid crystal (TLC) can be used to measure the surface temperature in transient heat transfer experiments. Knowing the time at which the TLC changes colour, hence knowing the surface temperature at that time, it is possible to calculate the heat transfer coefficient, h, and the analytical one-dimensional solution of Fourier’s conduction equation for a semi-infinite wall is often used

James R. Kingsley-Rowe; Gary D. Lock; J. Michael Owen

2005-01-01

251

Specific heat and thermal conductivity of ionic conductors and chalcogenide glasses at low temperatures  

Microsoft Academic Search

Measurements of specific heat in the temperature range 1–40 K for four chalcogen amorphous alloys (Se1-x-Tex)1-ySby and of thermal conductivity for three samples of superionic glasses (AgI)x (Ag2O2B2O3)1-x between 1 and 10 K are reported. The anomalous measured specific heat is interpreted in terms of phonon localization. The values obtained for the parameter L characterizing the length of this localization

A. Avogadro; S. Aldrovandi; G. Carini; A. Siri

1989-01-01

252

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

NASA Astrophysics Data System (ADS)

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

Talmage, G.

1994-05-01

253

Specific heat and quantized thermal conductance of single-walled boron nitride nanotubes  

NASA Astrophysics Data System (ADS)

The thermal properties of single-walled boron nitride nanotubes are calculated. It is found that boron nitride nanotubes have a larger specific heat than that of carbon nanotubes. The fitting formulas for diameter and chirality dependence of specific heat at 300 K are given. Moreover, thermal conductance of single-walled boron nitride nanotubes exhibits a universal quantization at low temperature, which is independent of the diameter and chirality of nanotubes.

Xiao, Y.; Yan, X. H.; Cao, J. X.; Ding, J. W.; Mao, Y. L.; Xiang, J.

2004-05-01

254

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

255

Combined resistive and laser heating technique for in situ radial X-ray diffraction in the diamond anvil cell at high pressure and temperature  

NASA Astrophysics Data System (ADS)

To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a Liermann-type diamond anvil cell with radial diffraction geometry (rDAC) was redesigned and developed for synchrotron X-ray diffraction experiments at beamline 12.2.2 of the Advanced Light Source. The rDAC, equipped with graphite heating arrays, allows simultaneous resistive and laser heating while the material is subjected to high pressure. The goals are both to extend the temperature range of external (resistive) heating and to produce environments with lower temperature gradients in a simultaneously resistive- and laser-heated rDAC. Three different geomaterials were used as pilot samples to calibrate and optimize conditions for combined resistive and laser heating. For example, in Run#1, FeO was loaded in a boron-mica gasket and compressed to 11 GPa then gradually resistively heated to 1007 K (1073 K at the diamond side). The laser heating was further applied to FeO to raise temperature to 2273 K. In Run#2, Fe-Ni alloy was compressed to 18 GPa and resistively heated to 1785 K (1973 K at the diamond side). The combined resistive and laser heating was successfully performed again on (Mg0.9Fe0.1)O in Run#3. In this instance, the sample was loaded in a boron-kapton gasket, compressed to 29 GPa, resistive-heated up to 1007 K (1073 K at the diamond side), and further simultaneously laser-heated to achieve a temperature in excess of 2273 K at the sample position. Diffraction patterns obtained from the experiments were deconvoluted using the Rietveld method and quantified for lattice preferred orientation of each material under extreme conditions and during phase transformation.

Miyagi, Lowell; Kanitpanyacharoen, Waruntorn; Raju, Selva Vennila; Kaercher, Pamela; Knight, Jason; MacDowell, Alastair; Wenk, Hans-Rudolf; Williams, Quentin; Alarcon, Eloisa Zepeda

2013-02-01

256

Equilibration and Universal Heat Conduction in Fermi-Pasta-Ulam Chains  

NASA Astrophysics Data System (ADS)

It is shown numerically that for Fermi-Pasta-Ulam (FPU) chains with alternating masses and heat baths at slightly different temperatures at the ends, the local temperature (LT) on small scales behaves paradoxically in steady state. This expands the long established problem of equilibration of FPU chains. A well-behaved LT appears to be achieved for equal mass chains; the thermal conductivity is shown to diverge with chain length N as N1/3, relevant for the much debated question of the universality of one-dimensional heat conduction. The reason why earlier simulations have obtained systematically higher exponents is explained.

Mai, Trieu; Dhar, Abhishek; Narayan, Onuttom

2007-05-01

257

Conducting-probe AFM nanoscale joule heating yields charge-density-wave transition detection.  

PubMed

Several layered transition-metal dichalcogenides are studied using conducting probe AFM aiming to investigate the probe-mediated thermal processes likely to arise in the probe-substrate vicinity due to the high-current densities involved. A signature of local heating is found in the shape of current-potential (i/V) curves. The latter allows straightforward detection of a charge-density-wave (CDW) transition for 1T-TaSe(2) samples exhibiting it above room temperature. This is an illustration of a new use of conducting probe AFM to investigate solid-state bulk characteristics owing to a distinctive nanoscale Joule heating. PMID:16706457

Schneegans, Olivier; Moradpour, Alec; Wang, Kang; Leblanc, Annie; Molinié, Philippe

2006-05-25

258

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

NSDL National Science Digital Library

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

Robison, David

259

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

260

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

261

Electrical conductivity of carbonaceous chondrites and electric heating of meteorite parent bodies  

NASA Technical Reports Server (NTRS)

Electromagnetic heating of rock-forming materials most probably was an important process in the early history of the solar system. Electrical conductivity experiments of representative materials such as carbonaceous chondrites are necessary to obtain data for use in electromagnetic heating models. With the assumption that carbon was present at grain boundaries in the material that comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance using the T-Tauri model of Sonett and Herbert (1977). The results are discussed.

Duba, AL

1987-01-01

262

An investigation on the conduction and convection heat transfer from advanced heat sinks  

Microsoft Academic Search

In natural convection applications, the components used for cooling may represent a significant portion of the overall weight of the system. Consequently, advanced materials are of interest in such applications, as they may substantially reduce the total size and the weight of the system. Many of these advanced materials have anisotropic thermo physical properties, hence the control of thermal conductivity

M. Baris Dogruoz; M. Arik

2008-01-01

263

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

SciTech Connect

A numerical study has been conducted for natural convection heat transfer for air from two vertically separated horizontal heated cylinders confined to a rectangular enclosure having vertical walls of finite conductances and horizontal walls at the heat sink temperature. The interaction between convection in the fluid filled cavity and conduction in the vertical walls is investigated. Results have been obtained for Rayleigh numbers, Ra, between 10{sup 3} and 10{sup 6}, dimensionless wall-fluid thermal conductivity ratio {alpha} between 0.2 and 1,000.0 and dimensionless wall thickness {bar W} between 0.25 and 1.375. Results indicate that the Nusselt number along the vertical wall-fluid interface is a complex function of both Ra and {bar {alpha}}. In general, the relative heat removal contribution by conduction in the wall through the top horizontal surface {eta}{sub N} decreases with Ra while that for the bottom surface {eta}{sub S} increases. For 0.2 {le} {alpha} {le} 5.0, {eta}{sub S} is nearly independent of Ra. Moreover, for Ra {ge} 10{sup 5}, 0.2 {le} {bar {alpha}} {le} 5.0 and 0.25 {le} {bar W} {le} 1.375, {eta}{sub S} is independent of {bar {alpha}} while {eta}{sub N} tends to zero with increasing {bar {alpha}}.

Lacroix, M.; Joyeux, A. [Univ. de Sherbrooke, Quebec (Canada). Dept. de Genie Mecanique] [Univ. de Sherbrooke, Quebec (Canada). Dept. de Genie Mecanique

1996-01-01

264

Effective Thermal Conductivity Measurement and Heat Transfer Enhancement of Metal Hydride Bed for Heat Driven Type Refrigerator  

NASA Astrophysics Data System (ADS)

A series of study has been performed on the metal hydride beds of Ti0.15Zr0.85Cr0.9Fe0.6Ni0.2Mn0.3Cu0.05 (MH-1, using for heat source), Ti0.73Zr0.27Cr1.2Fe0.3Ni0.1Mn0.4Cu0.05 (MH-2, using for cooling load) to measure the effective thermal conductivities. The effective thermal conductivities of MH alloy bed in hydrogen and helium have been examined. Experiment results show that pressure has great influence on effective thermal conductivity in low pressure range. And that influence decreases rapidly with increase of gas pressure. The reason is at low pressure, the mean free path of gas becomes greater than effective thickness of gas film which is important to the heat transfer mechanism. Then, carbon fiber has been used to try to enhance the poor thermal conductivity of MH alloy bed. Three types, two insert methods and three weight percentages of carbon fiber have been examined and compared. The highest effective thermal conductivity has been reached with carbon fiber which has second higher thermal conductivity, and highest weight percentage. This method has acquired 5.4 times higher thermal conductivity than pure metal hydride beds with quite low quantity of additives, only 1.7 wt % of carbon fiber. This is a good result comparing to other method which can reach higher effective thermal conductivity but needs much higher percentage of additives too.

Bae, Sang-Chul; Matsuishi, Yukino; Monde, Masanori; Katsuta, Masafumi

265

Thermal conductivity and elastic modulus evolution of thermal barrier coatings under high heat flux conditions  

Microsoft Academic Search

Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings\\u000a (TBCs) under near-realistic temperature and thermal gradients that may be encountered in advanced engine systems. Thermal\\u000a conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures.\\u000a A significant thermal conductivity increase was observed during

Dongming Zhu; Robert A. Miller

2000-01-01

266

A meshless model for transient heat conduction in functionally graded materials  

Microsoft Academic Search

A meshless numerical model is developed for analyzing transient heat conduction in non-homogeneous functionally graded materials\\u000a (FGM), which has a continuously functionally graded thermal conductivity parameter. First, the analog equation method is used\\u000a to transform the original non-homogeneous problem into an equivalent homogeneous one at any given time so that a simpler fundamental\\u000a solution can be employed to take the

H. Wang; Q. H. Qin; Y. L. Kang

2006-01-01

267

Development of an Algorithm to Predict Vertical Heat Transfer Through Ceiling\\/Floor Conduction  

Microsoft Academic Search

This paper describes a new algorithm of the Consolidated Fire Growth and Smoke Transport (CFAST) fire model and compares the results with data from real-scale fire tests conducted aboard the ex-USS Shadwell, the U.S. Navy's Research and Development Damage Control Platform. The new phenomenon modeled in this work is the conduction of heat in the vertical direction. The Shadwell tests

J. L. Bailey; W. W. Jones; P. A. Tatem; G. P. Forney

1998-01-01

268

A peridynamic formulation for transient heat conduction in bodies with evolving discontinuities  

NASA Astrophysics Data System (ADS)

We introduce a multidimensional peridynamic formulation for transient heat-transfer. The model does not contain spatial derivatives and uses instead an integral over a region around a material point. By construction, the formulation converges to the classical heat transfer equations in the limit of the horizon (the nonlocal region around a point) going to zero. The new model, however, is suitable for modeling, for example, heat flow in bodies with evolving discontinuities such as growing insulated cracks. We introduce the peridynamic heat flux which exists even at sharp corners or when the isotherms are not smooth surfaces. The peridynamic heat flux coincides with the classical one in simple cases and, in general, it converges to it in the limit of the peridynamic horizon going to zero. We solve test problems and compare results with analytical solutions of the classical model or with other numerical solutions. Convergence to the classical solutions is seen in the limit of the horizon going to zero. We then solve the problem of transient heat flow in a plate in which insulated cracks grow and intersect thus changing the heat flow patterns. We also model heat transfer in a fiber-reinforced composite and observe transient but steep thermal gradients at the interfaces between the highly conductive fibers and the low conductivity matrix. Such thermal gradients can lead to delamination cracks in composites from thermal fatigue. The formulation may be used to, for example, evaluate effective thermal conductivities in bodies with an evolving distribution of insulating or permeable, possibly intersecting, cracks of arbitrary shapes.

Bobaru, Florin; Duangpanya, Monchai

2012-04-01

269

Magnetosphere-ionosphere coupling through E region turbulence: 2. Anomalous conductivities and frictional heating  

NASA Astrophysics Data System (ADS)

Global magnetospheric MHD codes using ionospheric conductances based on laminar models systematically overestimate the cross-polar cap potential during storm time by up to a factor of 2. At these times, strong DC electric fields penetrate to the E region and drive plasma instabilities that create turbulence. This plasma density turbulence induces nonlinear currents, while associated electrostatic field fluctuations result in strong anomalous electron heating. These two effects will increase the global ionospheric conductance. On the basis of the theory of nonlinear currents developed by Dimant and Oppenheim [2011], this paper derives the correction factors describing turbulent conductivities and calculates turbulent frictional heating rates. Estimates show that during strong geomagnetic storms the inclusion of anomalous conductivity can double the total Pedersen conductance. This may help explain the overestimation of the cross-polar cap potentials by existing MHD codes. The turbulent conductivities and frictional heating presented in this paper should be included in global magnetospheric codes developed for predictive modeling of space weather.

Dimant, Y. S.; Oppenheim, M. M.

2011-09-01

270

Local Heat Transfer for the Evaporation of a Laminar Falling Liquid Film on a Cylinder: Experimental, Numerical, and Inverse Heat Conduction Analysis  

Microsoft Academic Search

This article presents the experimental, numerical, and inverse heat conduction (IHCP) analysis of the evaporation heat transfer of a falling liquid film on a horizontal cylinder. The two-dimensional IHCP is solved in order to determine the surface temperature, local heat flux, and local heat transfer coefficient for the sheet flow. The local surface temperature is used as the boundary condition

H. Louahlia-Gualous; L. El Omari

2006-01-01

271

The role of diabatic heating, torques and stabilities in forcing the radial-vertical circulation within cyclones part ii: case study of extratropical and tropical cyclones  

NASA Astrophysics Data System (ADS)

Utilizing Eliassen's concepts, the forcing of the isentropic azimuthally-averaged mass-weighted radial-vertical circulation by diabatic heating and torques within an extratropical cyclone and a typhoon was studied through numerical simulations based on the linear diagnostic equation derived previously. The structure of the forcing associated with diabatic heating and torques was determined from quasi-Lagrangian diagnostic analyses of actual case studies. The two cyclones studied were the Ohio extratropical cyclone of 25-27 January 1978 and typhoon Nancy of 18-23 September 1979. The Ohio cyclone, which formed over the Gulf Coast and moved through Ohio and eastern Michigan, was one of the most intense storms with blizzard conditions to ever occur in this region. Typhoon Nancy which occurred over the South China Sea during the FGGE year was selected since relatively high quality assimilated data were available. Within the Ohio cyclone, the dominant internal processes forcing the mean circulation with embedded relatively strong hydrodynamic stability were the pressure torque associated with baroclinic (asymmetric) structure and the horizontal eddy angular momentum transport associated with the typical S-shaped thermal and wind structures of self-development. Within typhoon Nancy, the dominant internal process forcing the mean circulation with embedded weak hydrodynamic stability was the latent heat release. This analysis shows that the simulated azimuthally-averaged mass-weighted radial motions within these two cyclones agree quite well with the “ observed? azimuthally-averaged mass-weighted radial motions. This isentropic numerical study also provides insight into the relatively important internal forcing processes and the trade off between forcing and stability within both extratropical and tropical cyclones.

Yuan, Zhuojian; Johnson, Donald R.

1998-12-01

272

Conductivity  

NSDL National Science Digital Library

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

Integrated Teaching And Learning Program

273

Direct determination of plasma fibrinogen levels by heat precipitation. A comparison of the technique against thrombin clottable fibrinogen with spectrophotometry and radial immuno-diffusion.  

PubMed

We have studied the Thorp method for precipitation of fibrinogen from diluted plasma, using a specific buffer (pH 6.3) at 56 degrees C, and the preferred anticoagulant (EDTA). Nephelometric or turbidimetric measurements of the precipitate were compared with the results obtained by radial immunodiffusion, or by thrombin clotting, of fibrinogen. In the absence of prior proteolysis (as indicated by the presence of fibrinogen and fibrin degradation products), correlations between the methods were excellent (r > 0.99). We conclude that the method of heat precipitation, which is simple to operate and inexpensive, gives results equally as good as the more difficult and time-consuming techniques. PMID:6783348

Desvignes, P; Bonnet, P

1981-02-19

274

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

SciTech Connect

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 mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss.

Ida, K.; Funaba, H.; Kado, S.; Narihara, K.; Tanaka, K.; Takeiri, Y.; Nakamura, Y.; Ohyabu, N.; Yamazaki, K.; Yokoyama, M. (and others)

2001-06-04

275

A simplified approach for heat conduction analysis of CNT-based nano-composites  

Microsoft Academic Search

The unique thermal properties of carbon nanotubes (CNT) may offer possibilities for the development of fundamentally new composite materials. Numerical simulation for such CNT-based composites usually demands extremely large and expensive computer resources. In preliminary computations, temperature distribution in the CNT has been turned out to be almost uniform, due to its exceptionally high heat conductivity in comparison with the

Jianming Zhang; Masataka Tanaka; Toshiro Matsumoto

2004-01-01

276

Electrohydrodynamic linear stability of finitely conducting flows through porous fluids with mass and heat transfer  

Microsoft Academic Search

In this work, a linear stability analysis is used to investigate a capillary surface waves between two horizontal finite fluid layers. The system is acted upon by a vertical periodic electric field. The problem examines few representatives of porous media. It is also includes finite conductivity, mass and heat transfer. It is assumed that the basic flow is two-dimensional streaming

Galal M. Moatimid; Mahmoud H. Obied Allah

2010-01-01

277

Heat transfer by conduction and radiation in one-dimensional planar medium using the differential approximation  

Microsoft Academic Search

The combined conduction and radiation heat transfer problem for a gray planar medium between two diffuse, isothermal infinite parallel plates is considered using the differential approximation. The P-1 and P-3 spherical harmonics approximations for the intensity distribution are used. In addition, isotropic scattering and uniform volumetric generation terms are included. The governing energy equations developed using the P-1 and P-3

A. C. Ratzel; J. R. Howell

1981-01-01

278

Nonlinear thermal bending response of FGM plates due to heat conduction  

Microsoft Academic Search

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

Hui-Shen Shen

2007-01-01

279

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

280

Penalty-finite element methods in conduction and convection heat transfer  

Microsoft Academic Search

It is pointed out that the coupled conduction and convection phenomenon due to the buoyancy-driven flow inside a closed enclosure subjected to differential side heating is commonly encountered in many practically important engineering problems. Some of the problems are related to the thermal insulation of buildings, cooling of electronic equipment, and general circulation of planetary atmospheres. The present investigation is

J. N. Reddy

1983-01-01

281

Discussion of Heat Flow Meter Apparatus Calibration and Traceability Issues for Thermal Conductivity Measurements  

Microsoft Academic Search

During a period where both North American and International product markets are opening, the issue of calibration traceability has become a sig mficant issue in the calibration of heat flow meters [1,2] used in thermal conductivity measurements on insulation materials. This paper will discuss the approach of the Production Support Services Laboratory of Owens Corning\\/Fiberglas Canada Inc. in addressing traceability

J. A. Scott; R. W. Bell

1994-01-01

282

Coupled deformation, filtration, and heat-conduction processes in media with disoriented quasi-spheroidal pores  

SciTech Connect

Using the random function method we determine the effective thermoelastic properties of a saturated porous medium with disoriented quasi-spheroidal pores. On the basis of the functional dependence obtained for the parameters averaged over the macrovolume and phases we construct the equations of coupled deformation, filtration, and heat-conduction processes in a saturated porous medium.

Khoroshun, L.P.; Shikula, E.N.

1994-08-01

283

Analysis of Transient Heat Conduction in 3D Anisotropic Functionally Graded Solids, by the MLPG Method  

Microsoft Academic Search

A meshless method based on the local Petrov-Galerkin approach is proposed for the solution of steady-state and transient heat conduction problems in a continuously non- homogeneous anisotropic medium. The Laplace transform is used to treat the time dependence of the variables for transient problems. The an- alyzed domain is covered by small subdomains with a simple geometry. A weak formulation

J. Sladek; V. Sladek; C. L. Tan; S. N. Atluri

2008-01-01

284

Transient heat conduction analysis using the MLPG method and modified precise time step integration method  

Microsoft Academic Search

The meshless local Petrov–Galerkin (MLPG) method in conjunction with the modified precise time step integration method in the time domain is proposed for transient heat conduction analysis in this paper. The MLPG method is often referred to as a truly meshless method because it requires no elements or background cells for either field interpolation or background integration. Local weak forms

Qing-Hua Li; Shen-Shen Chen; Guang-Xiao Kou

2011-01-01

285

Transient heat conduction analysis using the MLPG method and modified precise time step integration method  

NASA Astrophysics Data System (ADS)

The meshless local Petrov-Galerkin (MLPG) method in conjunction with the modified precise time step integration method in the time domain is proposed for transient heat conduction analysis in this paper. The MLPG method is often referred to as a truly meshless method because it requires no elements or background cells for either field interpolation or background integration. Local weak forms are developed using weighted residual method locally from the partial differential equation of transient heat conduction. In order to simplify the treatment of essential boundary conditions, the natural neighbour interpolation (NNI) is employed for the construction of trial functions. Moreover, the three-node triangular FEM shape functions are taken as test functions to reduce the order of integrands involved in domain integrals. The semi-discrete heat conduction equation is solved numerically with modified precise time step integration method in the time domain. The availability and accuracy of the present method for transient heat conduction analysis are tested through numerical examples.

Li, Qing-Hua; Chen, Shen-Shen; Kou, Guang-Xiao

2011-04-01

286

Specific heat and thermal conductivity of UCu4+ x Al8- x compounds  

NASA Astrophysics Data System (ADS)

We report on thermal conductivity and specific heat measurements for eight UCu4+ x Al8- x compounds (0 ? x ? 2.0) as a function of temperature and magnetic field. For this series of compounds, previous magnetic and transport studies indicated a transition from magnetic to a non-magnetic heavy fermion state near x cr ? 1.15. This paper presents supplementary specific heat and thermal conductivity studies. The ratio of the specific heat over temperature C/T data on the non magnetic compound with x cr ? 1.15 show logarithmic dependence with T, a hallmark of non-Fermi liquid (NFL) behavior due to the proximity of a quantum critical point. Compounds with higher Cu content ( x > x cr ) exhibit unusual temperature scaling in the specific heat possibly due to an increase in disorder between Cu and Al. Thermal conductivity data show stark contrast in the behaviors between the magnetic ( x = 0.5) and non-magnetic compound ( x = 1.75). Our results confirm that a simple free-electron picture is inadequate for the description of the low-temperature thermal conductivity properties in non-magnetic UCu4+ x Al8- x compounds.

Nasreen, F.; Torikachvili, M. S.; Kothapalli, K.; Kohama, Y.; Zapf, V. S.; Nakotte, H.

2013-05-01

287

Bianchi VI0 electric type cosmological models in General Relativity with stiff fluid and heat conduction  

NASA Astrophysics Data System (ADS)

The paper consists of some exact tilted solutions for a homogeneous Bianchi type VI0 universe. The material distribution is taken to be a stiff fluid with heat conduction. The physical and kinematical parameters have also been calculated to discuss the models in detail.

Roy, S. R.; Banerjee, S. K.

1996-01-01

288

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.

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

2011-01-01

289

Transient Coupled Radiation and Conduction Heat Transfer in a Scattering Layer of ARLEN  

Microsoft Academic Search

ARLEN is a heat-resistant, modified polyamide with a high melting point and a rigidity level comparable to super engineering plastics. It possesses strong dimensional stability and is widely used in engineering and high-temperature applications. At elevated temperatures, radiative transfer becomes important, and transient temperature responses, including radiation, can be significantly different from those by conduction alone. This work considers transient

Parham Sadooghi

2006-01-01

290

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

291

Finite element simulation of warm deep drawing of aluminium alloy sheet when accounting for heat conduction  

Microsoft Academic Search

The deformation behaviour and the temperature change in cylindrical deep drawing of an aluminium alloy sheet at elevated temperatures are simulated by the combination of the rigid-plastic and the heat conduction finite element methods. The comparison with the experimental results shows that the forming limits and the necking sites are successfully predicted by the simulation. It is clarified that the

H. Takuda; K. Mori; I. Masuda; Y. Abe; M. Matsuo

2002-01-01

292

COYOTE: a finite-element computer program for nonlinear heat-conduction problems  

SciTech Connect

COYOTE is a finite element computer program designed for the solution of two-dimensional, nonlinear heat conduction problems. The theoretical and mathematical basis used to develop the code is described. Program capabilities and complete user instructions are presented. Several example problems are described in detail to demonstrate the use of the program.

Gartling, D.K.

1982-10-01

293

Effects of Axial Heat Conduction in the Metal Wall of a Detonator Delay Element  

Microsoft Academic Search

We investigate the effect of axial heat conduction in the metal wall of a detonator delay element on the speed of a deflagration wave. An axisymmetric time dependent model is formulated in which the reaction rate is described by a single step kinetic equation. Numerical solutions are obtained and it is found that the flame speed is reduced below its

A. H. C. NORGROVE; A. F. JONES; J. A. KING-HELE

1994-01-01

294

Application of the Hybrid Differential Transform-Finite Difference Method to Nonlinear Transient Heat Conduction Problems  

Microsoft Academic Search

This article presents a hybrid differential transformation-finite difference method to analyze nonlinear transient heat conduction problems. The differential transformation technique is used to transform the governing equations from the time domain into the spectrum domain, followed by use of the finite difference method to formulate discretized iteration equations appropriate for rapid computation. Numerical examples provide reasonable results that well explain

Hsin-Ping Chu; Cheng-Ying Lo

2008-01-01

295

Thermal stability of superconductors under the effect of a two-dimensional hyperbolic heat conduction model  

Microsoft Academic Search

The thermal stability of superconductor is numerically investigated under the effect of a two-dimensional hyperbolic heat conduction model. Two types of superconductor wires are considered, Types II and I. The thermal stability of superconductor wires under the effect of different design, geometrical and operating conditions is studied. The Effect of the time rate of change of the disturbance and the

M. Al-Odat; M. A. Al-Nimr; M. Hamdan

2002-01-01

296

End effects of heat conduction in circular cylinders of functionally graded materials and laminated composites  

Microsoft Academic Search

Heat conduction in circular cylinders of functionally graded materials and laminated composites is studied with emphasis on the end effects. By means of matrix algebra and eigenfunction expansion, the decay length that characterizes the end effects on the thermal filed is evaluated and the 2D solution as a useful approximation assessed.

Jiann-Quo Tarn; Yung-Ming Wang

2004-01-01

297

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

NASA Astrophysics Data System (ADS)

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 three media with known thermal properties shows the uncertainty of measurements to be about 2%. The reproducibility is 0.5% for the thermal-conductivity measurements and 2% for the thermal-diffusivity measurements. Thermal properties were measured in dog, pig, rabbit, and human tissues. The tissues included kidney, spleen, liver, brain, heart, lung, pancreas, colon cancer, and breast cancer. Thermal properties were measured for 65 separate tissue samples at 3, 10, 17, 23, 30, 37, and 45°C. The results show that the temperature coefficient of biomaterials approximates that of water.

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

1985-05-01

298

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

299

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

NASA Astrophysics Data System (ADS)

Glass-ceramic is prepared by heat treatment of melt quenched 14Li2O-9Al2O3-38TiO2-39P2O5 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 LiTi2(PO4)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; Soman, Swati; Kulkarni, Ajit R.

2014-04-01

300

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

PubMed

Previous experimental studies have shown that NAPL will be removed when it is contacted by steam. However, in full-scale operations, steam may not contact the NAPL directly and this is the situation addressed in this study. A two-dimensional intermediate scale sand box experiment was performed where an organic contaminant was emplaced below the water table at the interface between a coarse and a fine sand layer. Steam was injected above the water table and after an initial heating period the contaminant was recovered at the outlet. The experiment was successfully modeled using the numerical code T2VOC and the dominant removal mechanism was identified to be heat conduction induced boiling of the separate phase contaminant. Subsequent numerical modeling showed that this mechanism was insensitive to the porous medium properties and that it could be evaluated by considering only one-dimensional heat conduction. PMID:15240173

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

2004-08-01

301

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

302

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

2014-05-28

303

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

304

Ballistic-diffusive heat conduction at nanoscale: GENERIC approach [rapid communication  

NASA Astrophysics Data System (ADS)

Heat conduction in nanosize systems has to be studied in settings involving microscopic details that are not seen in the classical Fourier theory. G. Chen has suggested [Phys. Rev. Lett. 86 (2001) 2297] a combination of the Cattaneo setting in which the velocity of the heat propagation is finite and the kinetic theory setting in which phonons are seen as heat carriers. In this Letter we show that if the Cattaneo and the kinetic theories are combined in a way that preserves the structure expressing their compatibility with thermodynamics (GENERIC structure) then both the Cattaneo and the kinetic equations become modified. The modified Cattaneo equations involve the term introduced by Chen and, in addition, new terms that are nonlinear in quantities that disappear at equilibrium. The kinetic equation is modified by new terms involving gradients of the heat flux and the local temperature.

Grmela, M.; Lebon, G.; Dauby, P. C.; Bousmina, M.

2005-05-01

305

Development of highly effective cryogenic printed circuit heat exchanger (PCHE) with low axial conduction  

NASA Astrophysics Data System (ADS)

This paper presents the results of an experimental investigation of the thermal and hydraulic performance of a printed circuit heat exchanger (PCHE) for use in the cryogenic temperature region. Compact PCHEs with multiple corrugated, longitudinal flow microchannels were fabricated using chemical etching and diffusion bonding to evaluate their thermal and hydraulic performance. The testing of the PCHEs was conducted with helium gas at cryogenic temperatures. The pressure drop and thermal effectiveness values obtained from the measured pressures and temperatures are discussed. The thermal performance was predominantly affected by the axial conduction heat transfer in the low Reynolds number ranges of theses experiments. A simple performance calculation model is presented, and the effectiveness calculated from the model is compared with the experimental data. The design of the cryogenic PCHE was then modified to reduce axial conduction losses.

Baek, Seungwhan; Kim, Jin-Hyuck; Jeong, Sangkwon; Jung, Jeheon

2012-07-01

306

Improving the conductivity of hole injection layer by heating PEDOT:PSS  

NASA Astrophysics Data System (ADS)

Poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonic acid) (PEDOT:PSS) is a common material of hole injection layer used in polymer light emitting diodes (PLEDs) and organic solar cells. It can improve the efficiency of the charge collection at the anode. It has been reported that adding glycerol to PEDOT:PSS could increase the conductivity and improve the efficiency of PLEDs and organic solar cells. However, it is less noticed that the conductivity could be improved when the solution of PEDOT was heated before deposition. Here we experimented different concentrations of glycerol into PEDOT:PSS to make G-PEDOT:PSS solution, and heated the G-PEDOT:PSS solution at different temperatures before deposition. The solutions are then spin-coated on the glass and annealed at 140 °C. The conductivity was then measured and compared. The experiments showed that the conductivity of pure PEDOT:PSS slightly increased for 2-3 times, while the G-PEDOT:PSS increased over two orders of magnitudes. The conductivity increased with the heating temperature before deposition. The enhancement of the conductivity of the G-PEDOT:PSS film was higher than that of the pure PEDOT:PSS film. The overall conductivity increase for over three orders of magnitude. The reason is because the high temperature causes the glycerol and PEDOT:PSS to mix evenly. This is helpful for the swelling and aggregation of colloidal PEDOT-rich particles, forming a highly conductive network. When G-PEDOT:PSS resistance is reduced, it may not only increase the hole collection ability, but also replace ITO as the anode layer due to its advantages of low production cost and high work function.

Tsai, Kao-Hua; Shiu, Shu-Chia; Lin, Ching-Fuh

2008-08-01

307

The time fractional heat conduction equation in the general orthogonal curvilinear coordinate and the cylindrical coordinate systems  

NASA Astrophysics Data System (ADS)

In this paper a time fractional Fourier law is obtained from fractional calculus. According to the fractional Fourier law, a fractional heat conduction equation with a time fractional derivative in the general orthogonal curvilinear coordinate system is built. The fractional heat conduction equations in other orthogonal coordinate systems are readily obtainable as special cases. In addition, we obtain the solution of the fractional heat conduction equation in the cylindrical coordinate system in terms of the generalized H-function using integral transformation methods. The fractional heat conduction equation in the case 0heat conduction equation (?=1) and the Localized heat conduction equation (??0). Finally, numerical results are presented graphically for various values of order of fractional derivative.

Jiang, Xiaoyun; Xu, Mingyu

2010-09-01

308

Heat conductivities of insulation mats based on water glass bonded non-textile hemp or flax fibres  

Microsoft Academic Search

Heat insulation mats based on water glass bonded non-textile flax and hemp fibres were fabricated via a pilot plant, and their heat conductivities investigated. Under the influence of various factors like moisture content, water sorption and diffusion processes, fibre characteristics and heat radiation as well as thickness and apparent density, heat conductivities in the range of 0.0392–0.0484 W\\/mK for flax fibre

B. Grohe

2004-01-01

309

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

310

Transient temperature distributions in simple conducting bodies steadily heated through a laminar boundary layer  

NASA Technical Reports Server (NTRS)

An analysis is made of the transient heat-conduction effects in three simple semi-infinite bodies: the flat insulated plate, the conical shell, and the slender solid cone. The bodies are assumed to have constant initial temperatures and, at zero time, to begin to move at a constant speed and zero angle of attack through a homogeneous atmosphere. The heat input is taken as that through a laminar boundary layer. Radiation heat transfer and transverse temperature gradients are assumed to be zero. The appropriate heat-conduction equations are solved by an iteration method, the zeroeth-order terms describing the situation in the limit of small time. The method is presented and the solutions are calculated to three orders which are sufficient to give reasonably accurate results when the forward edge has attained one-half the total temperature rise (nose half-rise time). Flight Mach number and air properties occur as parameters in the result. Approximate expressions for the extent of the conduction region and nose half-rise times as functions of the parameters of the problem are presented. (author)

Parker, Hermon M

1953-01-01

311

A Spatially-Analytical Scheme for Surface Temperatures and Conductive Heat Fluxes in Urban Canopy Models  

NASA Astrophysics Data System (ADS)

In the urban environment, surface temperatures and conductive heat fluxes through solid media (roofs, walls, roads and vegetated surfaces) are of paramount importance for the comfort of residents (indoors) and for microclimatic conditions (outdoors). Fully discrete numerical methods are currently used to model heat transfer in these solid media in parametrisations of built surfaces commonly used in weather prediction models. These discrete methods usually use finite difference schemes in both space and time. We propose a spatially-analytical scheme where the temperature field and conductive heat fluxes are solved analytically in space. Spurious numerical oscillations due to temperature discontinuities at the sublayer interfaces can be avoided since the method does not involve spatial discretisation. The proposed method is compared to the fully discrete method for a test case of one-dimensional heat conduction with sinusoidal forcing. Subsequently, the analytical scheme is incorporated into the offline version of the current urban canopy model (UCM) used in the Weather Research and Forecasting model and the new UCM is validated against field measurements using a wireless sensor network and other supporting measurements over a suburban area under real-world conditions. Results of the comparison clearly show the advantage of the proposed scheme over the fully discrete model, particularly for more complicated cases.

Wang, Zhi-Hua; Bou-Zeid, Elie; Smith, James A.

2011-02-01

312

Variation of thermal conductivity and heat flux at the Earth's core mantle boundary  

NASA Astrophysics Data System (ADS)

The two convective systems that dominate Earth's internal dynamics meet at the boundary between the rocky mantle and metallic liquid core. Energy transfer between processes driving plate tectonics and the geodynamo is controlled by thermal conduction in the lowermost mantle (D?). We use atomic scale simulations to determine the thermal conductivity of MgSiO3 perovskite and post-perovskite under D? conditions and probe how these two convective systems interact. We show that the thermal conductivity of post-perovskite (?12 W/mK) is 50% larger than that of perovskite under the same conditions (?8.5 W/mK) and is anisotropic, with conductivity along the a-axis being 40% higher than conductivity along the c-axis. This enhances the high heat flux into cold regions of D? where post-perovskite is stable, strengthening the feedback between convection in the core and mantle. Reminiscent of the situation in the lithosphere, there is potential for deformation induced texturing associated with mantle convection to modify how the mantle is heated from below. We test this by coupling our atomic scale results to models of texture in D? and suggest that anisotropic thermal conductivity may help to stabilise the roots of mantle plumes over their protracted lifetime.

Ammann, Michael W.; Walker, Andrew M.; Stackhouse, Stephen; Wookey, James; Forte, Alessandro M.; Brodholt, John P.; Dobson, David P.

2014-03-01

313

Lattice Boltzmann study on size effect with geometrical bending on phonon heat conduction in a nanoduct  

NASA Astrophysics Data System (ADS)

Phonon heat transport based on the Boltzmann transport equation (BTE) in a free standing, bent duct with characteristic dimension down to the nanoscale is investigated through the lattice Boltzmann (LB) method. Both the thermal excited transverse and longitudinal phonons are considered. The collision term in BTE is approximated by the relaxation time approximation. Both diffusive and specular phonon scatterings at duct surfaces are considered. An analytical expression for thermal conductivity suitable for an infinitely long, straight duct with constant properties is derived. Results show that the size effect depends strongly on the Knudsen number. For large Knudsen number, heat transport is mainly dominated by the ballistics that results in strong size effect, and vice versa. For the bent duct more phonons take the passageway near the inner corner of the bending region where higher local thermal conductivity is expected. Although the specular boundary scattering introduces no change in the bulk quantities for a straight duct, it, however, brings in the geometric influence as the duct is bent. Compared to the straight duct, the bent duct has the supremacy in conducting heat as the Knudsen number is small. Conversely the straight duct presents higher conductivity when the Knudsen number is large. By the present LB method, jumps in macroscopic quantities, occurring at boundary and wall surface, can be calculated naturally and straightforwardly.

Jiaung, Wen-Shu; Ho, Jeng-Rong

2004-02-01

314

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

315

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

USGS Publications Warehouse

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

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

1956-01-01

316

Heat conduction from hot plate to photoresist on top of wafer including heat loss to the environment  

NASA Astrophysics Data System (ADS)

Post exposure bake (PEB) process among the lithography steps is important for making good patterns when the chemically amplified resist is used. During the PEB, the de-protection reaction and the acid diffusion are determined by bake temperature and time. One of the key factors that determine the de-protection and acid diffusion is the initial temperature rising inside the photoresist. The time delay due to the temperature rising from the room temperature to the pre-set bake temperature is the main cause of line width variation. It is very important to control 1~2 nm line width variation for patterns of 32 nm and below. This variation mainly comes from PEB temperature and time of the resist on top of the multi-stacking silicon wafer on hot plate. In order to predict the accurate PEB temperature and time applied to the resist, we studied heat transfer from hot plate to the resist on top of the silicon wafer. We calculated boundary temperature values of each layer and compared the change of temperature caused by different kinds and thicknesses of sublayers including antireflection coating and resist. In order to predict bake temperature, we have to consider the heat loss which was made by the temperature differences with surrounding air, conductivity difference of various layer, and nitrogen purge during the PEB process. Therefore, heat loss to the environment is included to solve real heat conduction problem in the hot plate of the track system. We also found that the resultant line width was changed by small temperature variation, stack thickness and layer numbers.

Jung, Minhee; Kim, Sarah; Kim, Do Wan; Oh, Hye-Keun

2009-12-01

317

Development and test of the ESTEC Variable Conductance Heat Pipe (VCHP) experiment flown on SPAS-01  

NASA Astrophysics Data System (ADS)

A shuttle-borne experiment demonstrated the 0-g performance of a stainless steel-ammonia variable conductance heat pipe (VCHP) with cold, wicked reservoir. The experiment consisted of the heat pipe, with simulated load, attached to a solid aluminum radiator. The load was controlled in steps up to the estimated maximum heat transport capability of 25 W to explore the temperature control characteristic of the VCHP and investigate its start-up capability. The same test sequence was employed in 1-g and 0-g environments. The experiment flew twice the second flight exploring the heat-transport capability further, and overcoming effects of thermal inertia seen during earlier tests. The VCHP shows 5% higher heat-transport capability in the 0-g environment, while the start-up performance was unaffected, the VCHP being able to start up in a single step to virtually full load in both environments. An excess of liquid was determined from the results, and redistribution of this liquid affected the performance at high heat loads.

Savage, C. J.; Wilson, R. J.; Aalders, B. G. M.; Burke, W. R.

1987-02-01

318

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

319

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

320

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

321

Graphite-Fiber Heat Radiators  

NASA Technical Reports Server (NTRS)

Heat radiators of proposed type feature thermally conductive fibers protruding from metallic surfaces to provide increased heat-dissipation surface areas. Free of leaks and more reliable than radiators incorporating heat pipes. Also lightweight and relatively inexpensive. Radial graphite fibers carry heat away from spherical shell and radiate heat into space. Radiators prove useful on Earth in special industrial and scientific applications involving dissipation of heat in vacuum or in relatively still air.

Phillips, Wayne M.

1995-01-01

322

Heat characteristic analysis of a conduction cooling toroidal-type SMES magnet  

NASA Astrophysics Data System (ADS)

This paper analyzed the heat characteristics of a conduction cooling toroidal-type SMES magnet. The authors designed and manufactured a conduction cooling toroidal-type SMES magnet which consists of 30 double pancake coils. One (a single pancake coil) of a double pancake coil is arranged at an angle of 6° from each other. The shape of the toroidal-type SMES magnet was designed by a 3D CAD program. The heat invasion was investigated under no-load condition and the thermal characteristic of the toroidal-type SMES magnet was analyzed using the Finite Elements Method program. Both the analyzed and the experiment results are compared and discussed in detail.

Kim, K. M.; Kim, A. R.; Kim, J. G.; Kim, D. W.; Park, M.; Yu, I. K.; Eom, B. Y.; Sim, K.; Kim, S. H.; Shon, M. H.; Kim, H. J.; Bae, H. J.; Seong, K. C.

2010-11-01

323

Energy relaxation times in metal films from the response of electrical conductivity to periodic heating  

NASA Astrophysics Data System (ADS)

Heating of a metal film with a weak oscillating heat source leads to oscillations of the electron temperature Te. Because of the temperature dependence of phonon contribution to electrical conductivity, the oscillations of Te result in oscillations of voltage across the current-carrying film. Using the equation for Te and the expression for the phonon contribution to the electrical conductivity, we have found the connection of the frequency dependence of the amplitude of the voltage oscillations across the film with the time of electron-phonon collisions (?e) and the mean phonon escape time from the film to the substrate (?es). Renormalization of electron-phonon interaction by impurities and defects is considered phenomenologically. It is discussed how the times ?e and ?es can be found experimentally using the peculiarities of the frequency dependence of the voltage oscillations across the film.

Bezuglyj, A. I.; Shklovskij, V. A.

2014-06-01

324

Oscillatory conductive heat transfer for a fiber in an ideal gas  

NASA Technical Reports Server (NTRS)

A description of the thermal effects created by placing a cylindrical fiber in an inviscid, ideal gas, through which an acoustic wave propagates, is presented. The fibers and the gas have finite heat capacities and thermal conductivities. Expressions for the temperature distribution in the gas and in the material are determined. The temperature distribution is caused by pressure oscillations in the gas which, in turn, are caused by the passage of an acoustic wave. The relative value of a dimensionless parameter is found to be indicative of whether the exact or approximate equations should be used in the solution. This parameter is a function of the thermal conductivities and heat capacities of the fiber and gas, the acoustic frequency, and the fiber diameter.

Kuntz, H. L.; Perreira, N. D.

1985-01-01

325

Specific heat and thermal conductivity of ferromagnetic magnons in Yttrium Iron Garnet  

NASA Astrophysics Data System (ADS)

The specific heat and thermal conductivity of an insulating ferrimagnet Y3Fe5O12 (Yttrium Iron Garnet, YIG) single crystal were measured down to 50 mK. The ferromagnetic magnon specific heat Cm shows a characteristic T1.5-dependence down to 0.77 K. Below 0.77 K, a downward deviation is observed, which is attributed to the magnetic dipole-dipole interaction with typical magnitude of 10^{-4}\\ \\text{eV} . The ferromagnetic magnon thermal conductivity \\kappa_m does not show the characteristic T2-dependence below 0.8 K. To fit the \\kappa_m data, both magnetic defect scattering effect and dipole-dipole interaction are taken into account. These results provide a complete picture of the thermodynamic and thermal transport properties of the low-lying ferromagnetic magnons.

Pan, B. Y.; Guan, T. Y.; Hong, X. C.; Zhou, S. Y.; Qiu, X.; Zhang, H.; Li, S. Y.

2013-08-01

326

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

NASA Technical Reports Server (NTRS)

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

Antoniuk, D.; Luedke, E. E.

1978-01-01

327

Hamiltonian dynamics of thermostated systems: two-temperature heat-conducting phi4 chains.  

PubMed

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 "phi4" 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 to model correctly the flow of heat. PMID:17477595

Hoover, Wm G; Hoover, Carol G

2007-04-28

328

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

329

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

330

A computational method for solving a class of coupled conductive-radiative heat transfer problems  

Microsoft Academic Search

The PN method, also called the spherical harmonics method, is used along with Hermite cubic splines to define an iterative technique for solving a class of nonlinear problems in radiative transfer. Anisotropic scattering and specularly and diffusely reflecting boundaries are allowed for the steady-state, combined-mode, conductive-radiative, heat transfer problem considered. Computational aspects of the technique are discussed, and the method

C. E. Siewert; J. R. Thomas Jr.

1991-01-01

331

Topology optimization of heat conduction problems using the finite volume method  

Microsoft Academic Search

This note addresses the use of the finite volume method (FVM) for topology optimization of a heat conduction problem. Issues\\u000a pertaining to the proper choice of cost functions, sensitivity analysis, and example test problems are used to illustrate\\u000a the effect of applying the FVM as an analysis tool for design optimization. This involves an application of the FVM to problems

A. Gersborg-Hansen; M. P. Bendsøe; O. Sigmund

2006-01-01

332

Improved analytical solution for inverse heat conduction problems on thermally thick and semi-infinite solids  

Microsoft Academic Search

Analytical solutions to inverse heat conduction problems with a far-field boundary condition are derived for one- and two-dimensional problems using a Laplace transform technique. Accuracy of the predictions is improved by superposition of successive corrections to the function used to approximate the measured data. Long-term history of high frequency modes in both time and space is neglected noting that these

P. L. Woodfield; M. Monde; Y. Mitsutake

2006-01-01

333

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

334

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

335

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

336

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

337

Nonstationary heat conduction in one-dimensional models with substrate potential  

NASA Astrophysics Data System (ADS)

The paper investigates nonstationary heat conduction in one-dimensional models with substrate potential. To establish universal characteristic properties of the process, we explore three different models: Frenkel-Kontorova (FK), phi4+ (?4+), and phi4- (?4-). Direct numeric simulations reveal in all these models a crossover from oscillatory decay of short-wave perturbations of the temperature field to smooth diffusive decay of the long-wave perturbations. Such behavior is inconsistent with the parabolic Fourier equation of heat conduction and clearly demonstrates the necessity for hyperbolic corrections in the phenomenological description of the heat conduction process. The crossover wavelength decreases with an increase in the average temperature. The decay patterns of the temperature field almost do not depend on the amplitude of the perturbations, so the use of linear evolution equations for the temperature field is justified. In all models investigated, the relaxation of thermal perturbations is exponential, contrary to a linear chain, where it follows a power law. The most popular lowest-order hyperbolic generalization of the Fourier law, known as the Cattaneo-Vernotte or telegraph equation, is also not valid for the description of the observed behavior of the models with the substrate potential, since the characteristic relaxation time in an oscillatory regime strongly depends on the excitation wavelength. For some of the models, this dependence seems to obey a simple scaling law.

Gendelman, O. V.; Shvartsman, R.; Madar, B.; Savin, A. V.

2012-01-01

338

Heat conduction in one-dimensional lattices with on-site potential.  

PubMed

The process of heat conduction in one-dimensional lattices with on-site potential is studied by means of numerical simulation. Using the discrete Frenkel-Kontorova, phi(4), and sinh-Gordon models we demonstrate that contrary to previously expressed opinions the sole anharmonicity of the on-site potential is insufficient to ensure the normal heat conductivity in these systems. The character of the heat conduction is determined by the spectrum of nonlinear excitations peculiar for every given model and therefore depends on the concrete potential shape and the temperature of the lattice. The reason is that the peculiarities of the nonlinear excitations and their interactions prescribe the energy scattering mechanism in each model. For sine-Gordon and phi(4) models, phonons are scattered at a dynamical lattice of topological solitons; for sinh-Gordon and for phi(4) in a different parameter regime the phonons are scattered at localized high-frequency breathers (in the case of phi(4) the scattering mechanism switches with the growth of the temperature). PMID:12786351

Savin, A V; Gendelman, O V

2003-04-01

339

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

340

Conditions for Aeronomic Applicability of the Classical Electron Heat Conduction Formula  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

341

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

SciTech Connect

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

Xu, Zhijie

2012-07-01

342

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

343

Computations of the three-dimensional flow and heat transfer within a coolant passage of a radial turbine blade  

NASA Technical Reports Server (NTRS)

A numerical code is developed for computing three-dimensional, turbulent, compressible flow within coolant passages of turbine blades. The code is based on a formulation of the compressible Navier-Stokes equations in a rotating frame of reference in which the velocity dependent variable is specified with respect to the rotating frame instead of the inertial frame. The algorithm employed to obtain solutions to the governing equation is a finite-volume LU algorithm that allows convection, source, as well as diffusion terms to be treated implicitly. In this study, all convection terms are upwind differenced by using flux-vector splitting, and all diffusion terms are centrally differenced. This paper describes the formulation and algorithm employed in the code. Some computed solutions for the flow within a coolant passage of a radial turbine are also presented.

Shih, T. I.-P.; Roelke, R. J.; Steinthorsson, E.

1991-01-01

344

Review and comparison of nanofluid thermal conductivity and heat transfer enhancements.  

SciTech Connect

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 and convective heat transfer of nanofluids relative to conventional heat transfer fluids, and assessments were made as to the state-of-the-art of verified parametric trends and magnitudes. Pertinent parameters of particle volume concentration, particle material, particle size, particle shape, base fluid material, temperature, additive, and acidity were considered individually, and experimental results from multiple research groups were used together when assessing results. To this end, published research results from many studies were recast using a common parameter to facilitate comparisons of data among research groups and to identify thermal property and heat transfer trends. The current state of knowledge is presented as well as areas where the data are presently inconclusive or conflicting. Heat transfer enhancement for available nanofluids is shown to be in the 15-40% range, with a few situations resulting in orders of magnitude enhancement.

Yu, W.; France, D. M.; Routbort, J. L.; Choi, S. U.S.; Energy Systems; Univ. of Illinois at Chicago; Korea Inst. of Energy Research

2008-05-01

345

Entropy and Nonlinear Nonequilibrium Thermodynamic Relation for Heat Conducting Steady States  

NASA Astrophysics Data System (ADS)

Among various possible routes to extend entropy and thermodynamics to nonequilibrium steady states (NESS), we take the one which is guided by operational thermodynamics and the Clausius relation. In our previous study, we derived the extended Clausius relation for NESS, where the heat in the original relation is replaced by its "renormalized" counterpart called the excess heat, and the Gibbs-Shannon expression for the entropy by a new symmetrized Gibbs-Shannon-like expression. Here we concentrate on Markov processes describing heat conducting systems, and develop a new method for deriving thermodynamic relations. We first present a new simpler derivation of the extended Clausius relation, and clarify its close relation with the linear response theory. We then derive a new improved extended Clausius relation with a "nonlinear nonequilibrium" contribution which is written as a correlation between work and heat. We argue that the "nonlinear nonequilibrium" contribution is unavoidable, and is determined uniquely once we accept the (very natural) definition of the excess heat. Moreover it turns out that to operationally determine the difference in the nonequilibrium entropy to the second order in the temperature difference, one may only use the previous Clausius relation without a nonlinear term or must use the new relation, depending on the operation (i.e., the path in the parameter space). This peculiar "twist" may be a clue to a better understanding of thermodynamics and statistical mechanics of NESS.

Komatsu, Teruhisa S.; Nakagawa, Naoko; Sasa, Shin-Ichi; Tasaki, Hal

2011-01-01

346

The impact of subcontinuum gas conduction on topography measurement sensitivity using heated atomic force microscope cantilevers  

SciTech Connect

Nanometer-scale topographical imaging using heated atomic force microscope (AFM) cantilevers, referred to here as thermal sensing AFM (TSAFM), is a promising technology for high resolution topographical imaging of nanostructured surfaces. Heated AFM cantilevers were developed for high-density data storage, where the heated cantilever tip can form and detect 20 nm indents made in a thermoplastic polymer. The scan height of the cantilever heater platform is typically near 500 nm, but could be made much smaller to improve reading sensitivity. Under atmospheric conditions the continuum models used in previous studies to model the gas phase heat transfer are invalid for the smallest operating heights. The present study uses a molecular model of subcontinuum heat transfer coupled with a finite difference simulation to predict the behavior of a TSAFM system. A direct simulation Monte Carlo model and a kinetic theory based macromodel are separately developed and used to model subcontinuum gas conduction. For the working gas (argon) the simple macromodel is found to be accurate and is used to predict cantilever operation. This systems-level modeling approach for TSAFM operation can aid data interpretation and seeks to improve microcantilever design.

Masters, Nathan D.; Ye Wenjing; King, William P. [Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States)

2005-10-01

347

[Calculation of thermal protein changes in food with heat conduction. Determination of reaction rate and activation heat].  

PubMed

The velocity constant k of protein changes is commonly determined by heating as abruptly as possible to a given temperature for various periods. Its dependence on temperature or activation heat is deduced from the k value determinations at different temperatures, using the ARRHENIUS diagram. In contrast to this, the authors determined the k and E values in a temperature field for a constant reaction time. This is done directly in the foodstuff which is introduced (in ball form) into a bath of constant temperature. In case of foodstuffs with mere heat conduction, there are in the interior innumerable spherical shells subjected to the same thermal stress which increases from within towards the exterior. Thermal protein changes (such as the thermal coagulation of egg white and muscle proteins and the formation of metmyochromogen) which can be visualized directly or, in case of enzymatic denaturation, indirectly by colour reactions, using the presence-absence method, may be observed if the ball is cut in half. This procedure (termed "change-over method" by the authors) permits to calculate the unknown k and E values from the radius of the visible inner circle. (This applied also to cylindrical forms.) Since this method allows to estimate approximately these reaction kinetic constants directly in the foodstuff under conditions encountered in practice, it is in many cases better suited for simulating, calculating, or optimizing desirable or undesirable protein changes occurring during thermal processing than the mere model experiment with abrupt heating which does not reproduce the changes in the reaction medium occuring during the slow increase or decrease in temperature. PMID:1226205

Herrmann, J; Brennig, K; Nour, S

1975-01-01

348

Solving transient conduction and radiation heat transfer problems using the lattice Boltzmann method and the finite volume method  

Microsoft Academic Search

The lattice Boltzmann method (LBM) was used to solve the energy equation of a transient conduction–radiation heat transfer problem. The finite volume method (FVM) was used to compute the radiative information. To study the compatibility of the LBM for the energy equation and the FVM for the radiative transfer equation, transient conduction and radiation heat transfer problems in 1-D planar

Subhash C.. Mishra; Hillol K. Roy

2007-01-01

349

NaK Variable Conductance Heat Pipe for Radioisotope Stirling Systems  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

350

Thermal-contact-conductance measurement for high-heat-load optics components at SPring-8  

NASA Astrophysics Data System (ADS)

Thermal contact in water-cooling or cryogenic cooling-cooling condition is used for forming a high-heat-load component at the synchrotron radiation beamline. In SPring-8, for example, cryogenic cooling is used for silicon monochromator crystal with an indium insertion metal at the interface between a copper block and a silicon crystal. To reduce the strain on the silicon crystal with a low contact pressure and a high thermal conductivity, we require a silicon-indium-copper system and an alternative insertion material such as a graphite foil. To measure the thermal contact conductance in a quick measurement cycle under various thermal-contact conditions, we improve the thermal-contact-conductance measurement system in terms of the setup facilitation, precise temperature measurement, and thermal insulation around a sample.

Takeuchi, T.; Tanaka, M.; Senba, Y.; Ohashi, H.; Goto, S.

2011-09-01

351

Radial plasma measurements and calculations in the center of a three-meter laser-heated theta pinch. Final report  

SciTech Connect

Experimental results are reported on the process of density minimum creation and maintenance in the center of a 3-m-long laser-heated fast solenoid. These results are correlated with one-dimensional magnetohydrodynamic calculations and scaling laws are developed for both heating efficiency and for the length of time a density minimum could be maintained against diffusive processes. Both absorption and diffusion are classical and the density minimum maintenance time scales linearly with the plasma line density. Small laser-beam diameters result in long density minimum maintenance times, but also introduce heating inefficiencies due to the non-uniform illumination. In the present experiments, the plasma energy decay time is governed by thermal diffusion to a cold edge layer produced by small amounts of entrapped wall impurity.

Lowenthal, D.D.; Quimby, D.C.; Hoffman, A.L.

1983-05-01

352

Radial Plasma Measurements and Calculations in the Center of a Three-Meter Laser-Heated theta Pinch. Final Report.  

National Technical Information Service (NTIS)

Experimental results are reported on the process of density minimum creation and maintenance in the center of a 3-m-long laser-heated fast solenoid. These results are correlated with one-dimensional magnetohydrodynamic calculations and scaling laws are de...

D. D. Lowenthal D. C. Quimby A. L. Hoffman

1983-01-01

353

Critical heat flux prediction by using radial basis function and multilayer perceptron neural networks: A comparison study  

Microsoft Academic Search

Critical heat flux (CHF) is an important parameter for the design of nuclear reactors. Although many experimental and theoretical researches have been performed, there is not a single correlation to predict CHF because it is influenced by many parameters. These parameters are based on fixed inlet, local and fixed outlet conditions. Artificial neural networks (ANNs) have been applied to a

Nima Vaziri; Alireza Hojabri; Ali Erfani; Mehrdad Monsefi; Behnam Nilforooshan

2007-01-01

354

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

SciTech Connect

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

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

1980-12-01

355

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

356

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

357

Kinetic Study of the Effect of Gravity on the Heat Conductivity  

NASA Astrophysics Data System (ADS)

We consider a steady heat transfer problem between two parallel plates under a uniform gravity field perpendicular to them when the length scale of temperature variation is comparable to the mean free path of the gas molecules. We analyze this problem numerically on the basis of kinetic theory. Our aim is to investigate the general relation holding among the relevant macroscopic quantities where the direct effect of the boundaries are negligible and to clarify the effect of gravity on this relation. Our numerical results show: (i) At any point in this region, a relation -q/G=?? holds, where q is the heat flux, G is the local temperature gradient, ? is the heat conductivity in the absence of gravity. The factor ?, which is a measure of the deviation from the well-known Fourier law, is determined only by a local Knudsen number and a local Froude number. (ii) ? is greater than 1 when the heat flux is parallel to the gravity field, while it is less than 1 when both vectors are antiparallel. Comparisons with an asymptotic analysis as well as with Padé approximants are also made.

Doi, T.; Santos, A.; Tij, M.

1999-11-01

358

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

NASA Astrophysics Data System (ADS)

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 measured at Fargo, North Dakota. We spectrally decompose each of these temperature time series to determine the amplitude and phase of the annual signal at each depth. Conductive heat transport of a harmonic temperature signal in a homogeneous medium is characterized theoretically by exponential amplitude attenuation and linear phase shift with depth. We show that transport of the annual signal in the soil at Fargo follows these theoretical characterizations of conduction closely: the depth dependence of both the natural logarithm of the amplitude and the phase shift are highly linear. Interval wave velocities and thermal diffusivities calculated as functions of depth suggest a diffusivity gradient in the upper meter of the soil. We estimate the annual signal at the ground surface by extrapolating amplitude and phase shift regression lines upward to the surface. We compare this estimate of the annual signal at the ground surface to the annual signal contained in the SAT and show the ground surface signal to be attenuated ˜20% and negligibly phase shifted relative to the SAT.

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

2003-09-01

359

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

SciTech Connect

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

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

1998-11-01

360

Thermal conductivity of EB-PVD thermal barrier coatings evaluated by a steady-state laser heat flux technique  

Microsoft Academic Search

The thermal conductivity of electron beam-physical vapor deposited (EB-PVD) ZrO2–8 wt.%Y2O3 thermal barrier coatings was determined by a steady-state laser heat flux technique. Thermal conductivity change kinetics of the EB-PVD ceramic coatings were also obtained in real time, at high temperatures, under the laser high heat flux, long-term test conditions. The thermal conductivity increase due to micro-pore sintering and the

Dongming Zhu; Robert A. Miller; Ben A. Nagaraj; Robert W. Bruce

2001-01-01

361

Phonon heat conduction in nanostructures 1 Based on a paper presented as a plenary talk at Eurotherm Seminar No. 57 “Microscale Heat Transfer”, Poitiers, France, July 8–10, 1998. 1  

Microsoft Academic Search

Phonon heat conduction mechanisms in nanostructures may differ significantly from those in macrostructures. In this paper, we illustrate the fundamental differences between heat conduction in nanostructures and macrostructures based on examples we have been working on, including particularly heat conduction in superlattices, nanowires, and nanoparticles. The prospects of control heat conduction in nanostructures through phonon engineering are discussed. Examples are

Gang Chen

2000-01-01

362

Heat conduction in the nonlinear response regime: Scaling, boundary jumps, and negative differential thermal resistance  

NASA Astrophysics Data System (ADS)

We report a numerical study on heat conduction in one-dimensional homogeneous lattices in both the linear and the nonlinear response regime, with a comparison among three prototypical nonlinear lattice models. In the nonlinear response regime, negative differential thermal resistance (NDTR) can occur in both the Frenkel-Kontorova model and the ?4 model. In the Fermi-Pasta-Ulam- ? model, however, only positive differential thermal resistance can be observed, as shown by a monotonous power-law dependence of the heat flux on the applied temperature difference. In general, it was found that NDTR can occur if there is nonlinearity in the onsite potential of the lattice model. It was also found that the regime of NDTR becomes smaller as the system size increases, and eventually vanishes in the thermodynamic limit. For the ?4 model, a phenomenological description of the size-induced crossover from the existence to the nonexistence of a NDTR regime is provided.

He, Dahai; Ai, Bao-Quan; Chan, Ho-Kei; Hu, Bambi

2010-04-01

363

Heat conduction in the nonlinear response regime: scaling, boundary jumps, and negative differential thermal resistance.  

PubMed

We report a numerical study on heat conduction in one-dimensional homogeneous lattices in both the linear and the nonlinear response regime, with a comparison among three prototypical nonlinear lattice models. In the nonlinear response regime, negative differential thermal resistance (NDTR) can occur in both the Frenkel-Kontorova model and the phi4 model. In the Fermi-Pasta-Ulam- beta model, however, only positive differential thermal resistance can be observed, as shown by a monotonous power-law dependence of the heat flux on the applied temperature difference. In general, it was found that NDTR can occur if there is nonlinearity in the onsite potential of the lattice model. It was also found that the regime of NDTR becomes smaller as the system size increases, and eventually vanishes in the thermodynamic limit. For the phi4 model, a phenomenological description of the size-induced crossover from the existence to the nonexistence of a NDTR regime is provided. PMID:20481701

He, Dahai; Ai, Bao-quan; Chan, Ho-Kei; Hu, Bambi

2010-04-01

364

Nonequilibrium temperature and thermometry in heat-conducting phi4 models.  

PubMed

We analyze temperature and thermometry for simple nonequilibrium heat-conducting models. We also 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 phi4 models investigated here the mechanical temperature closely approximates the local thermodynamic equilibrium temperature. There is a significant difference between the kinetic temperature and nonlocal configurational temperature. Neither obeys the predictions of extended irreversible thermodynamics. Overall, we find that the kinetic temperature, as modeled and imposed by the Nosé-Hoover thermostats developed in 1984, provides the simplest means for simulating, analyzing, and understanding nonequilibrium heat flows. PMID:18517575

Hoover, Wm G; Hoover, Carol G

2008-04-01

365

The improved element-free Galerkin method for three-dimensional transient heat conduction problems  

NASA Astrophysics Data System (ADS)

With the improved moving least-squares (IMLS) approximation, an orthogonal function system with a weight function is used as the basis function. The combination of the element-free Galerkin (EFG) method and the IMLS approximation leads to the development of the improved element-free Galerkin (IEFG) method. In this paper, the IEFG method is applied to study the partial differential equations that control the heat flow in three-dimensional space. With the IEFG technique, the Galerkin weak form is employed to develop the discretized system equations, and the penalty method is applied to impose the essential boundary conditions. The traditional difference method for two-point boundary value problems is selected for the time discretization. As the transient heat conduction equations and the boundary and initial conditions are time dependent, the scaling parameter, number of nodes and time step length are considered in a convergence study.

Zhang, Zan; Wang, JianFei; Cheng, YuMin; Liew, Kim Meow

2013-08-01

366

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

367

Fully coupled heat conduction and deformation analyses of visco-elastic solids  

NASA Astrophysics Data System (ADS)

Visco-elastic materials are known for their capability of dissipating energy. This energy is converted into heat and thus changes the temperature of the materials. In addition to the dissipation effect, an external thermal stimulus can also alter the temperature in a visco-elastic body. The rate of stress relaxation (or the rate of creep) and the mechanical and physical properties of visco-elastic materials, such as polymers, vary with temperature. This study aims at understanding the effect of coupling between the thermal and mechanical response that is attributed to the dissipation of energy, heat conduction, and temperature-dependent material parameters on the overall response of visco-elastic solids. The non-linearly visco-elastic constitutive model proposed by Schapery (Further development of a thermodynamic constitutive theory: stress formulation, 1969, Mech. Time-Depend. Mater. 1:209-240, 1997) is used and modified to incorporate temperature- and stress-dependent material properties. This study also formulates a non-linear energy equation along with a dissipation function based on the Gibbs potential of Schapery (Mech. Time-Depend. Mater. 1:209-240, 1997). A numerical algorithm is formulated for analyzing a fully coupled thermo-visco-elastic response and implemented it in a general finite-element (FE) code. The non-linear stress- and temperature-dependent material parameters are found to have significant effects on the coupled thermo-visco-elastic response of polymers considered in this study. In order to obtain a realistic temperature field within the polymer visco-elastic bodies undergoing a non-uniform heat generation, the role of heat conduction cannot be ignored.

Khan, Kamran A.; Muliana, Anastasia H.

2012-11-01

368

Measurement of the radial temperature distribution of the heated spot produced by a focused laser beam using an optical pyrometer.  

PubMed

A method is described for the evaluation of the Gaussian curve parameters needed for the description of the temperature distribution of the heated spot produced on a target substrate by a well-focused laser beam, using an optical pyrometer to read the weighted average temperatures from two distinct distances. The parameter so found gave a calculated distribution curve in excellent agreement with experimental determinations of that distribution. PMID:20332849

Hendricks, L J; Zobrist, S P

1981-05-15

369

Heat transfer in rotating serpentine passages with trips skewed to the flow  

Microsoft Academic Search

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips, skewed at 45 deg to the flow direction, were machined on the leading and trailing surfaces of the radial

B. V. Johnson; J. H. Wagner; G. D. Steuber; F. C. Yeh

1994-01-01

370

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

371

Heat conduction and Fourier's law by consecutive local mixing and thermalization.  

PubMed

We present a first-principles study of heat conduction in a class of models which exhibit a new multistep local thermalization mechanism which gives rise to Fourier's law. Local thermalization in our models occurs as the result of binary collisions among locally confined gas particles. We explore the conditions under which relaxation to local equilibrium, which involves no energy exchange, takes place on time scales shorter than that of the binary collisions which induce local thermalization. The role of this mechanism in multiphase material systems such as aerogels is discussed. PMID:18764167

Gaspard, P; Gilbert, T

2008-07-11

372

Graphene-diamond hybrid structure as spin-polarized conducting wire with thermally efficient heat sinks  

NASA Astrophysics Data System (ADS)

We have theoretically investigated electronic, magnetic, and thermal properties of a graphene-diamond hybrid structure consisting of a graphene nanoribbon with zigzag edges connected to diamond surfaces. From the first-principles calculation, we found that the hybrid structure is stable and that the ferro-magnetically ordered edge state appears around the graphene-diamond. On the other hand, from the non-equilibrium molecular dynamics simulations, we found that the thermal conductance at the interface between the graphene and diamond is 7.01 +/- 0.05 GWm-2K-1 at the room temperature, which is much larger than that for covalently bonded interface between carbon nanotube and silicon. Thus, we propose that the hybrid structure is a potential candidate for spin-polarized conducting wires with thermally efficient heat sinks.

Shiga, Takuma; Konabe, Satoru; Shiomi, Junichiro; Yamamoto, Takahiro; Maruyama, Shigeo; Okada, Susumu

2012-06-01

373

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

374

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

375

A new heat propagation velocity prevails over Brownian particle velocities in determining the thermal conductivities of nanofluids  

NASA Astrophysics Data System (ADS)

An alternative insight is presented concerning heat propagation velocity scales in predicting the effective thermal conductivities of nanofluids. The widely applied Brownian particle velocities in published literature are often found too slow to describe the relatively higher nanofluid conductivities. In contrast, the present model proposes a faster heat transfer velocity at the same order as the speed of sound, rooted in a modified kinetic principle. In addition, this model accounts for both nanoparticle heat dissipation as well as coagulation effects. This novel model of effective thermal conductivities of nanofluids agrees well with an extended range of experimental data.

Kihm, Kenneth D.; Chon, Chan Hee; Lee, Joon Sik; Choi, Stephen Us

2011-04-01

376

A new heat propagation velocity prevails over Brownian particle velocities in determining the thermal conductivities of nanofluids  

PubMed Central

An alternative insight is presented concerning heat propagation velocity scales in predicting the effective thermal conductivities of nanofluids. The widely applied Brownian particle velocities in published literature are often found too slow to describe the relatively higher nanofluid conductivities. In contrast, the present model proposes a faster heat transfer velocity at the same order as the speed of sound, rooted in a modified kinetic principle. In addition, this model accounts for both nanoparticle heat dissipation as well as coagulation effects. This novel model of effective thermal conductivities of nanofluids agrees well with an extended range of experimental data.

2011-01-01

377

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

378

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

379

Dissipation and entropy production in deterministic heat conduction of quasi-one-dimensional systems  

NASA Astrophysics Data System (ADS)

We explore the consequences of a deterministic microscopic thermostat-reservoir contact mechanism. With different temperature reservoirs at each end of a two-dimensional system, a heat current is produced and the system has an anomalous thermal conductivity. The microscopic form for the local heat flux vector is derived and both the kinetic and potential contributions are calculated. The total heat flux vector is shown to satisfy the continuity equation. The properties of this nonequilibrium steady state are studied as functions of system size and temperature gradient, identifying key scaling relations for the local fluid properties and separating bulk and boundary effects. The local entropy density calculated from the local equilibrium distribution is shown to be a very good approximation to the entropy density calculated directly from the velocity distribution even for systems that are far from equilibrium. The dissipation and kinetic entropy production and flux are compared quantitatively and the differing mechanisms discussed within the Bhatnagar-Gross-Krook approximation. For equal-temperature reservoirs the entropy production near the reservoir walls is shown to be proportional to the local phase space contraction calculated from the tangent space dynamics. However, for unequal temperatures, the connection between local entropy production and local phase space contraction is more complicated.

Morriss, Gary P.; Truant, Daniel P.

2013-06-01

380

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

381

Dissipation and entropy production in deterministic heat conduction of quasi-one-dimensional systems.  

PubMed

We explore the consequences of a deterministic microscopic thermostat-reservoir contact mechanism. With different temperature reservoirs at each end of a two-dimensional system, a heat current is produced and the system has an anomalous thermal conductivity. The microscopic form for the local heat flux vector is derived and both the kinetic and potential contributions are calculated. The total heat flux vector is shown to satisfy the continuity equation. The properties of this nonequilibrium steady state are studied as functions of system size and temperature gradient, identifying key scaling relations for the local fluid properties and separating bulk and boundary effects. The local entropy density calculated from the local equilibrium distribution is shown to be a very good approximation to the entropy density calculated directly from the velocity distribution even for systems that are far from equilibrium. The dissipation and kinetic entropy production and flux are compared quantitatively and the differing mechanisms discussed within the Bhatnagar-Gross-Krook approximation. For equal-temperature reservoirs the entropy production near the reservoir walls is shown to be proportional to the local phase space contraction calculated from the tangent space dynamics. However, for unequal temperatures, the connection between local entropy production and local phase space contraction is more complicated. PMID:23848664

Morriss, Gary P; Truant, Daniel P

2013-06-01

382

Similarity solution for the flow behind a shock wave in a non-ideal gas with heat conduction and radiation heat-flux in magnetogasdynamics  

NASA Astrophysics Data System (ADS)

The propagation of a spherical (or cylindrical) shock wave in a non-ideal gas with heat conduction and radiation heat-flux, in the presence of a spacially decreasing azimuthal magnetic field, driven out by a moving piston is investigated. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient ?R are assumed to vary with temperature and density. The gas is assumed to have infinite electrical conductivity and to obey a simplified van der Waals equation of state. The shock wave moves with variable velocity and the total energy of the wave is non-constant. Similarity solutions are obtained for the flow-field behind the shock and the effects of variation of the heat transfer parameters, the parameter of the non-idealness of the gas, both, decreases the compressibility of the gas and hence there is a decrease in the shock strength. Further, it is investigated that with an increase in the parameters of radiative and conductive heat transfer the tendency of formation of maxima in the distributions of heat flux, density and isothermal speed of sound decreases. The pressure and density vanish at the inner surface (piston) and hence a vacuum is form at the center of symmetry. The shock waves in conducting non-ideal gas with conductive and radiative heat fluxes can be important for description of shocks in supernova explosions, in the study of central part of star burst galaxies, nuclear explosion, chemical detonation, rupture of a pressurized vessels, in the analysis of data from exploding wire experiments, and cylindrically symmetric hypersonic flow problems associated with meteors or reentry vehicles, etc. The findings of the present works provided a clear picture of whether and how the non-idealness parameter, conductive and radiative heat transfer parameters and the magnetic field affect the flow behind the shock front.

Nath, G.; Vishwakarma, J. P.

2014-05-01

383

Thermomechanical coupling, heat conduction and director rotation in cholesteric liquid crystals studied by molecular dynamics simulation.  

PubMed

The lack of a centre of inversion in a cholesteric liquid crystal allows linear cross couplings between thermodynamic forces and fluxes that are polar vectors and pseudovectors, respectively. This makes it possible for a temperature gradient parallel to the cholesteric axis to induce a torque that rotates the director, a phenomenon known as the Lehmann effect or thermomechanical coupling. The converse is also possible: a torque applied parallel to the cholesteric axis rotates the director and drives a heat flow. In order to study this phenomenon, nonequilibrium molecular dynamics simulation algorithms and Green-Kubo relations evaluated by equilibrium molecular dynamics simulation have been used to calculate the Leslie coefficient, i.e. the cross coupling coefficient between the temperature gradient and the director angular velocity, for a model system composed of soft prolate ellipsoids of revolution interacting via the Gay-Berne potential augmented by a chiral interaction potential causing the formation of a cholesteric phase. It is found that the Leslie coefficient is two orders of magnitudes smaller than other transport coefficients such as the heat conductivity and the twist viscosity, so that very long simulations are required to evaluate it. The Leslie coefficient decreases with the pitch but it has not been possible to determine the exact functional dependence of this coefficient on the pitch. Since very long simulations have been performed to evaluate the Leslie coefficient, very accurate values have been obtained for the twist viscosity and the heat conductivity as a by-product and it is found that they are very similar to the values of the corresponding quantities in the achiral nematic phase that arises when the pitch goes to infinity. PMID:23223192

Sarman, Sten; Laaksonen, Aatto

2013-03-14

384

Determination of thermal conductivity from specific heat and thermal diffusivity measurements of plasma-sprayed cermets  

SciTech Connect

The thermal conductivities of three plasma-sprayed cermets have been determined over the temperature range 23-630 degrees C from the measurement of the specific heat, thermal diffusivity, and density. These cermets are mixtures of Al and SiC prepared by plasma spray deposition and are being considered for various applications in magnetic confinement fusion devices. The samples consisted of three compositions: 61 vol% Al/39 vol% SiC, 74 vol% Al/26 vol% SiC, and 83 vol% Al/17 vol% SiC. The specific heat was determined by differential scanning calorimetry through the Al melt transition up to 720/sup 0/C, while the thermal diffusivity was determined using the laser flash technique up to 630/sup 0/C. The linear thermal expansion was measured and used to correct the diffusivity and density values. The thermal diffusivity showed a significant increase after thermal cycling due to a reduction in the intergrain contact resistance, increasing from 0.4 to 0.6 cm /SUP 2./ S/sup -1/ at 160/sup 0/C. However, effective medium theory calculations indicated that the thermal conductivities of both the Al and the SiC were below the ideal defect-free limit even after high-temperature cycling. The specific heat measurements showed suppressed melting points in the plasmasprayed cermets. The 39 vol% SiC began a melt endotherm at 577/sup 0/C, which peaked in the 640-650/sup 0/C range depending on the sample thermal history. Chemical and X-ray diffraction analysis indicated the presence of free silicon in the cermet and in the SiC powder, which resulted in a eutectic Al/Si alloy.

Roth, E.P.; Smith, M.F.; Hanley, H.J.M.; Cezairliyan, A.

1986-03-01

385

Heat transfer from horizontal tubes in pool boiling: influence of three-dimensional heat conduction in the wall of the evaporator tube—a finite element analysis  

Microsoft Academic Search

In pool boiling, the electrically heated tube releases the energy non-uniformly to the liquid, due to different surface roughness\\u000a and flowing liquid. The heat transfer coefficient therefore varies with axial and azimuthal position on the tube. Hence a\\u000a finite element analysis has been carried out on a horizontal 1in. copper tube for evaporation in pool boiling for three-dimensional\\u000a conduction heat

C. Ranganayakulu; Gerhard Herres

2006-01-01

386

MONTE CARLO RESEARCH SERIES: GAMMA HEATING STUDY NO. 1: GAMMA HEATING RATE DENSITY RADIAL VARIATION IN A CORE CELL FOR THREE FUEL CYLINDER SPACINGS  

Microsoft Academic Search

ABS>A hypothetical reactor core is presented in which right cylindrical ; fuel regions sre positioned at the core corners of equilateral, space-filling, ; parallelograms. The average gamma heating rate density in each of a set of ; concentric annular regions, centered on a fuel cylinder, is presented for three ; different fuel cylinder separation distances. The fuel cylinder radius, fuel

J. R. Jr. Beeler; R. H. Nelson; R. G. Herrmann

1957-01-01

387

Heat Conduction to Photoresist on Top of Wafer during Post Exposure Bake Process: II. Application  

NASA Astrophysics Data System (ADS)

Chemically amplified resists are used for 248 nm, 193 nm, immersion and extreme ultraviolet (UV) lithography. Among many process steps, post exposure bake (PEB) is the key process to make the desired small line width and critical dimension control. During PEB, the de-protection reaction and acid diffusion are determined by bake temperature and time. One of the key factors that determines the de-protection and acid diffusion is the initial temperature rising of the hot plate. The unpredictable temperature rising to the pre-set temperature is the main cause of line width variation. In order to predict the accurate PEB temperature and time dependency to the line width, the heat transfer from the hot plate to the resist on top of the silicon wafer is studied. Numerical approach is used to solve the heat conduction problem. Only the boundary temperature values are needed to solve this conduction, the information inside each layer is not required. We calculated the temperature rising characteristics of the photoresist on top of the several layers of the mask. The air conductivity, air gap, number of layers underneath the resist, thickness of the wafer, thickness of the layer including the resist, and different kind of layers are varied to see the characteristics of the bake temperature rising. We showed that there was small temperature difference at photoresist among the layer stack and thickness variation, even though it was very small. There is a strong possibility that this small PEB temperature difference would cause serious critical dimension (CD) control problem.

Oh, Hye-Keun; Kim, Do Wan; Lee, Ji-Eun

2008-11-01

388

Effect of variable thermal conductivity and viscosity on single phase convective heat transfer in slip flow  

NASA Astrophysics Data System (ADS)

For a variety of fields in which micro-mechanical systems and electronic components are used, fluid flow and heat transfer at the microscale needs to be understood and modeled with an acceptable reliability. In general, models are prepared by making some extensions to the conventional theories by including the scaling effects that become important for microscale. Some of these effects are; axial conduction, viscous dissipation, and rarefaction. In addition to these effects, temperature variable thermal conductivity and viscosity may become important in microscale gas flows due to the high temperature gradients that may exist in the fluid. For this purpose, simultaneously developing, single phase, laminar and incompressible air flow in a microtube and in the micro gap between parallel plates is numerically analyzed. Navier-Stokes and energy equations are solved and the variation of Nusselt number along the channel is presented in tabular and graphical forms as a function of Knudsen, Peclet, and Brinkman numbers, including temperature variable thermal conductivity and viscosity.

Kakaç, Sad?k; Yaz?c?o?lu, Alm?la G.; Gözükara, Arif Cem

2011-08-01

389

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, plasmonics, and ultrasensitive bolometry. Here, we present measurements of bipolar thermal conductances due to electron diffusion and electron-phonon coupling and infer the electronic specific heat, with a minimum value of 10kB (10-22J/K) per square micron. We test the validity of the Wiedemann-Franz law and find that the Lorenz number equals 1.32×(?2/3)(kB/e)2. The electron-phonon thermal conductance has a temperature power law T2 at high doping levels, and the coupling parameter is consistent with recent theory, indicating its enhancement by impurity scattering. We demonstrate control of the thermal conductance by electrical gating and by suppressing the diffusion channel using NbTiN superconducting electrodes, which sets the stage for future graphene-based single-microwave photon detection.

Fong, Kin Chung; Wollman, Emma E.; Ravi, Harish; Chen, Wei; Clerk, Aashish A.; Shaw, M. D.; Leduc, H. G.; Schwab, K. C.

2013-10-01

390

Heat capacity, enthalpy of mixing, and thermal conductivity of Hg(1-x)Cd(x)Te pseudobinary melts  

NASA Technical Reports Server (NTRS)

Heat capacity and enthalpy of mixing of Hg(1-x)Cd(x)Te pseudobinary melts were calculated assuming an associated solution model for the liquid phase. The thermal conductivity of the pseudobinary melts for x = 0, 0.05, 0.1, and 0.2 was then calculated from the heat capacity values and the experimental values of thermal diffusivity and density for these melts. The thermal conductivity for the pseudobinary solid solution is also discussed.

Su, Ching-Hua

1986-01-01

391

Numerical study of the modeling error in the online input estimation algorithm used for inverse heat conduction problems (IHCPs)  

NASA Astrophysics Data System (ADS)

A numerical investigation has been conducted to study the effect of modeling error in the state equation on the performance of the online input estimation algorithm in its application to the inverse heat conduction problems. This modeling error is used as a tuning parameter known as the stabilizing parameter in the online input estimation algorithm of the inverse heat conduction problems. Three different cases which cover most forms of the boundary heat flux functions have been considered. These cases are: square wave, triangular wave and mixed wave heat fluxes. The investigation has been carried for a one dimensional inverse heat conduction problem. Temperature measurements required for the inverse algorithm was generated by using a numerical solution of the direct heat conduction problem employing the three boundary heat flux functions. The most important finding of this investigation is that a robust range of the stabilizing parameter has been found which achieves the desired trade-off between the filter tracking ability and its sensitivity to measurement errors. For all three considered cases, it has been found that there is a common optimal value of the stabilizing parameter at which the estimate bias is minimal. This finding is very important for practical applications since this parameter is unknown practically and this study provides a needed guidance for assuming this parameter. The effect of changing other important parameters in the online input estimation algorithm on its performance has also been studied in this investigation.

Ali, S. K.; Hamed, M. S.; Lightstone, M. F.

2008-11-01

392

Dual Phase Lag Heat Conduction and Thermoelastic Properties of a Semi-Infinite Medium Induced by Ultrashort Pulsed Laser  

Microsoft Academic Search

In this work the uncopled thermoelastic model based on the Dual Phase Lag (DPL) heat conduction equation is used to investigate the thermoelastic properties of a semi-infinite medium induced by a homogeneously illuminating ultrashort pulsed laser heating. The exact solution for the temperature, the displacement and the stresses distributions ob- tained analytically using the separation of variables method (SVM) hybrid

Ibrahim A. Abdallah

393

Treatment of material discontinuity in two meshless local Petrov-Galerkin (MLPG) formulations of axisymmetric transient heat conduction  

Microsoft Academic Search

SUMMARY We use two meshless local Petrov-Galerkin (MLPG) formulations to analyse heat conduction in a bimetallic circular disk. The continuity of the normal component of the heat flux at the interface between two materials is satisfied either by the method of Lagrange multipliers or by using a jump function. The convergence of the H 0 and H 1 error norms

R. C. Batra; M. Porfiri; D. Spinello

2004-01-01

394

CTRUMP: Its development and use in solution of problems of conduction heat flow in solid state devices  

Microsoft Academic Search

The TRUMP program, developed by Arthur Edwards of the Lawrence Radiation Laboratory, has been adapted for use on the IBM 360\\/44, under the name CTRUMP. Modifications were made to enable calculations of three-dimensional heat flow in solid state devices, as a result of internal conduction and internal heat generation with constant boundary conditions. CTRUMP was then used to calculate temperature

R. L. Bastile; H. Domingos

1975-01-01

395

Optimal design and measurement of the effective thermal conductivity of a powder using a crenel heating excitation  

Microsoft Academic Search

This paper presents an experimental optimal design of a photothermal radiometry method using a crenel heating excitation. This method is used for the determination of the effective thermal conductivity of a powder in imperfect contact with a coating, and in presence of convective heat losses. The parameter identification is performed by the minimization of the ordinary least squares objective function

Fethi Albouchi; Mourad Fetoui; Fabrice Rigollet; Mohamed Sassi; Sassi Ben Nasrallah

2005-01-01

396

Development of a measurement technique for highly conductive CVD diamonds and analysis of uncertanties due to 3D heat losses  

Microsoft Academic Search

Thermal spreaders have been of interest over the last few decades. Heat pipes, Thermal Pyrolytic Graphite (TPG), and other graphite-based materials have been commonly used for enhancing the thermal performance. This study will start for a discussion of Chemical Vapor Deposition (CVD) of diamond manufacturing to enable high conductivity plates for heat spreading. Later attention will be turned to absolute

Mehmet Arik; Ri Li; Kristian Andreini; Jared Crosby; Dave Shaddock; Huseyin Kizil

2010-01-01

397

Thermal Vacuum Test Performance of the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) Variable Conductance Heat Pipe Assembly  

NASA Technical Reports Server (NTRS)

The Hubble Space Telescope (HST) is one of NASA s premier astronomical observatories. A unique design feature of the spacecraft is its capacity to be serviced and refurbished on-orbit. Repairs to the HST are made during events called Servicing Missions (SM). The SM consists of several phases that include: shuttle launch, ascent, rendezvous with HST, grapple, Extra Vehicular Activity (EVA) servicing, redeployment of the HST, shuttle entry and landing. The purpose of a SM is to upgrade the HST scientific capabilities and to repair or replace failed equipment. The benefit of the SM is to enhance the scientific capability of the HST and to extend its operational lifetime to a decade or more. Extra Vehicular Activity (EVA) days, the crew will replace the Wide Field Planetary Camera II (WFPCII) with the Wide Field Camera 3 (WFC3). The HST slot for these instruments is the "-V3 Radial Instrument" position. Servicing Mission 4 (SM-4) is currently scheduled for Spring 2005. During one of the five The WFC3 contains both Ultraviolet and Infrared detectors. Due to the differing thermal requirements for these items and their associated assemblies, the WFC3 contains several thermal subsystems within the instrument enclosure. One of these subsystems is the Variable Conductance Heat Pipe (VCHP) assembly. contains an integral constant conductance heat pipe (CCHP); a variable conductance heat pipe (VCHP); and a VCHP reservoir radiator (offset from the main WFC3 external radiator). The VCHP condenser utilizes the main WFC3 external radiator to reject its heat to space. The WFC3 VCHP assembly consists of the Optical Bench Cold Plate (OBCP), which The primary challenge for the VCHP assembly is to maintain the OBCP at -5 C +/- 2 C for various heat loads while subject to a 90-minute orbit cycling environment which ranges from 0 C to -143 C. Key components that provide active control include a 10 W heater system, the reservoir, and a proportional controller. This paper summarizes the overall thermal vacuum test program for the VCHP assembly. This includes performance during the 90-minute orbit cycling case, maximum capacity case, and cold system shut down case. The test was conducted in Building 7, Chamber #237 at the NASA/Goddard Space Flight Center. It lasted approximately fourteen days, from 5-28-02 to 6-10-02. Included in this paper is a comparison of the results with thermal model temperature predictions.

Cleveland, Paul E.; Buchko, Matthew T.; Stavely, Richard A.; Simpson, Alda (Technical Monitor)

2002-01-01

398

Conductive heat transfer from an isothermal magma chamber and its application to the measured heat flow distribution from mount hood, Oregon  

USGS Publications Warehouse

A steady-state solution for heat transfer from an isothermal, spherical magma chamber, with an imposed regional geothermal gradient far from the chamber, is developed. The extensive published heat-flow data set for Mount Hood, Oregon, is dominated by conductive heat transfer in the deeper parts of most drill holes and provides an ideal application of such a model. Magma-chamber volumes or depths needed to match the distribution of heat-flow data are larger or shallower than those inferred from geologic evidence.

Nathenson, Menuel; Tilling, Robert, I.

1993-01-01

399

Inverse analysis of thermal conductivities in transient non-homogeneous and non-linear heat conductions using BEM based on complex variable differentiation method  

NASA Astrophysics Data System (ADS)

This paper presents a new inverse analysis approach to sensitivity analysis and material property identification in transient non-homogeneous and non-linear heat conduction Boundary Element Method (BEM) analysis based on Complex Variable Differentiation Method (CVDM). In this approach, the material properties are taken as the optimization variables, and the sensitivity coefficients are computed by CVDM. The advantages of using CVDM are that the computation of partial derivatives of an implicit function is reduced to function calculation in a complex domain, and the parameter sensitivity coefficients can be determined in a more accurate way than the traditional Finite Difference Method (FDM). Based on BEM and CVDM in evaluation of the sensitivity matrix of heat flux, the parameter such as thermal conductivity can be accurately identified. Six numerical examples are given to demonstrate the potential of the proposed approach. The results indicate that the presented method is efficient for identifying the thermal conductivity with single or multiple parameters.

Yu, XiaoChun; Bai, YuGuang; Cui, Miao; Gao, XiaoWei

2013-05-01

400

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

SciTech Connect

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 packages currently exist for such applications, ranging in sophistication from the large, general purpose, commercial codes, such as COMSOL, COSMOSWorks, ABAQUS and TSS to codes written by individuals for specific problem applications. The original purpose for developing the finite element code described here, COYOTE, was to bridge the gap between the complex commercial codes and the more simplistic, individual application programs. COYOTE was designed to treat most of the standard conduction problems of interest with a user-oriented input structure and format that was easily learned and remembered. Because of its architecture, the code has also proved useful for research in numerical algorithms and development of thermal analysis capabilities. This general philosophy has been retained in the current version of the program, COYOTE, Version 5.0, though the capabilities of the code have been significantly expanded. A major change in the code is its availability on parallel computer architectures and the increase in problem complexity and size that this implies. The present document describes the theoretical and numerical background for the COYOTE program. This volume is intended as a background document for the user's manual. Potential users of COYOTE are encouraged to become familiar with the present report and the simple example analyses reported in before using the program. The theoretical and numerical background for the finite element computer program, COYOTE, is presented in detail. COYOTE is designed for the multi-dimensional analysis of nonlinear heat conduction problems. A general description of the boundary value problems treated by the program is presented. The finite element formulation and the associated numerical methods used in COYOTE are also outlined. Instructions for use of the code are documented in SAND2010-0714.

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

2010-03-01

401

Application of the two-dimensional differential transform method to heat conduction problem for heat transfer in longitudinal rectangular and convex parabolic fins  

NASA Astrophysics Data System (ADS)

In this article, approximate analytical (series) solutions for the temperature distribution in a longitudinal rectangular and convex parabolic fins with temperature dependent thermal conductivity and heat transfer coefficient are derived. The transient heat conduction problem is solved for the first time using the two-dimensional differential transform method (2D DTM). The effects of some physical parameters such as the thermo-geometric parameter, exponent and thermal conductivity gradient on temperature distribution are studied. Furthermore, we study the temperature profile at the fin tip.

Ndlovu, Partner L.; Moitsheki, Raseelo J.

2013-10-01

402

Effect of the time window on the heat-conduction information filtering model  

NASA Astrophysics Data System (ADS)

Recommendation systems have been proposed to filter out the potential tastes and preferences of the normal users online, however, the physics of the time window effect on the performance is missing, which is critical for saving the memory and decreasing the computation complexity. In this paper, by gradually expanding the time window, we investigate the impact of the time window on the heat-conduction information filtering model with ten similarity measures. The experimental results on the benchmark dataset Netflix indicate that by only using approximately 11.11% recent rating records, the accuracy could be improved by an average of 33.16% and the diversity could be improved by 30.62%. In addition, the recommendation performance on the dataset MovieLens could be preserved by only considering approximately 10.91% recent records. Under the circumstance of improving the recommendation performance, our discoveries possess significant practical value by largely reducing the computational time and shortening the data storage space.

Guo, Qiang; Song, Wen-Jun; Hou, Lei; Zhang, Yi-Lu; Liu, Jian-Guo

2014-05-01

403

High Conductivity Carbon-Carbon Heat Pipes for Light Weight Space Power System Radiators  

NASA Technical Reports Server (NTRS)

Based on prior successful fabrication and demonstration testing of a carbon-carbon heat pipe radiator element with integral fins this paper examines the hypothetical extension of the technology via substitution of high thermal conductivity composites which would permit increasing fin length while still maintaining high fin effectiveness. As a result the specific radiator mass could approach an ultimate asymptotic minimum value near 1.0 kg/m2, which is less than one fourth the value of present day satellite radiators. The implied mass savings would be even greater for high capacity space and planetary surface power systems, which may require radiator areas ranging from hundreds to thousands of square meters, depending on system power level.

Juhasz, Albert J.

2008-01-01

404

Passive amplification of the pyroelectric current in thin films on a heat-conducting substrate  

SciTech Connect

We show both theoretically and experimentally that passive amplification of the pyroelectric current takes place when modulated radiation is recorded by a pyroelectric detector in some range of modulation frequencies. The amplification effect manifests itself in the fact that the current generated by a thin pyroelectric film lying on a massive heat-conducting substrate exceeds that in a freely suspended film. We use a ferroelectric 70:30 P(VDF-TrFE) copolymer, a crystalline guanidine pyroelectric, and a 70:30 composition of an achiral liquid-crystal polymer and its monomer PM6R14n-M6R14n to illustrate the frequency dependence of the pyroelectric current.

Yablonskii, S. V., E-mail: yablonskii2005@yandex.r [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Soto-Bustamante, E. A., E-mail: esotobrasil2005@gmail.co [Universidad de Chile 1058 (Chile)

2010-11-15

405

Response-coefficient method for heat-conduction transients with time-dependent inputs  

NASA Technical Reports Server (NTRS)

A theoretical overview of the response coefficient method for heat conduction transients with time-dependent input forcing functions is presented with a number of illustrative applications. The method may be the most convenient and economical if the same problem is to be solved many times with different input-time histories or if the solution time is relatively long. The method is applicable to a wide variety of problems, including irregular geometries, position-dependent boundary conditions, position-dependent physical properties, and nonperiodic irregular input histories. Nonuniform internal energy generation rates within the structure can also be handled by the method. The area of interest is long-time solutions, in which initial condition is unimportant, and not the early transient period. The method can be applied to one dimensional problems in cartesian, cylindrical, and spherical coordinates as well as to two dimensional problems in cartesian and cylindrical coordinates.

Ceylan, Tamer

1993-01-01

406

Steady-state heat conduction in multilayered composite plates and shells  

NASA Technical Reports Server (NTRS)

A study is made of a predictor-corrector procedure for the accurate determination of the temperature and heat flux distributions in thick multilayered composite plates and shells. A linear through-the-thickness temperature distribution is used in the predictor phase. The functional dependence of temperature on the thickness coordinate is then calculated a posteriori and used in the corrector phase. Extensive numerical results are presented for linear steady-state heat conduction problems, showing the effects of variation in the geometric and lamination parameters on the accuracy of the thermal response predictions of the predictor-corrector approach. Both antisymmetrically laminated anisotropic plates and multilayered orthotropic cylinders are considered. The solutions are assumed to be periodic in the surface coordinates. For each problem the standard of comparison is taken to be the analytic three-dimensional solution based on treating each layer as a homogeneous anisotropic medium. The potential of the predictor-corrector approach for predicting the thermal response of multilayered plates and shells with complicated geometry is discussed.

Noor, A. K.; Burton, W. S.

1991-01-01

407

Interaction of Radiation with Conduction Heat Transfer in the Presence of Variable Property Non-Gray Carbon Dioxide Gas  

Microsoft Academic Search

The current study addresses the mathematical modelling aspects of coupled conductive and radiative heat transfer in the presence of variable property non-gray Carbon dioxide gas within a two-dimensional square enclosure. The walls of the enclosure are considered to be opaque, diffuse and gray. The participating medium is bounded by isothermal vertical walls and insulated horizontal walls. Thermal conductivity and absorption

S. K. Mahapatra

2001-01-01

408

Thermal Conductivity of Advanced Ceramic Thermal Barrier Coatings Determined by a Steady-State Laser Heat-Flux Approach  

NASA Technical Reports Server (NTRS)

The development of low conductivity and high temperature capable thermal barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity under future high-performance and low-emission engine heat-flux conditions. In this paper, a unique steady-state CO2 laser (wavelength 10.6 microns) heat-flux approach is described for determining the thermal conductivity and conductivity deduced cyclic durability of ceramic thermal and environmental barrier coating systems at very high temperatures (up to 1700 C) under large thermal gradients. The thermal conductivity behavior of advanced thermal and environmental barrier coatings for metallic and Si-based ceramic matrix composite (CMC) component applications has also been investigated using the laser conductivity approach. The relationships between the lattice and radiation conductivities as a function of heat flux and thermal gradient at high temperatures have been examined for the ceramic coating systems. The steady-state laser heat-flux conductivity approach has been demonstrated as a viable means for the development and life prediction of advanced thermal barrier coatings for future turbine engine applications.

Zhu, Dong-Ming; Miller, Robert A.

2004-01-01

409

Nanoparticle synergies in modifying thermal conductivity for heat exchanger in condensing boilers  

NASA Astrophysics Data System (ADS)

The heat exchanger we are using for condensing boilers is mainly made from aluminum alloys and stainless steel. However, the metal is relatively expensive and corrosion together with maintenance is also a big problem. Therefore, we have developed a new design and material which contain carbon black, carbon nanotube, aluminum oxide and graphene as additives in polypropylene. When multiple types of particles can be melt blended simultaneously and synergies can be achieved, imparting particles to the nanocomposite, achieved much higher thermal conductivity rather than single additive. Here we show the flame retardant nanocomposite which can pass the UL-94-V0 vertical burning test, perform nice in Cone Calorimetry Test and has relatively good mechanical properties. SEM images of the blend show that the Carbon nanobute and other additives well dispersed within the polymer matrix which match our computational calculation for getting the percolation to achieve thermal conductivity around 1.5W/m.K rather than 0.23W/m.K as pure polypropylene.

Yang, Kai; He, Shan; Butcher, Thomas; Trojanowski, Rebecca; Sun, Ning; Gersappe, Dilip; Rafailovich, Miriam

2013-03-01

410

Conductive Sphere in a Radio Frequency Field: Theory and Applications to Positioners, Heating, and Noncontact Measurements  

NASA Technical Reports Server (NTRS)

An electrically conductive spherical sample located in an electromagnetic field excited by rf (radio frequency) current in a system of coaxial coils is treated theoretically. Maxwell's equations are solved exactly and all integrals in the formulas for the fields are evaluated analytically for the case where the sphere is on the axis and the coil system is modeled by a stack of filamentary circular loops. Formulas are also derived for electromagnetic force exerted on the sphere, excess impedance in the coil system due to the presence of the sphere, and power absorbed by the sphere. All integrals in those formulas have been evaluated analytically. Force measurements are presented and they are in excellent agreement with the new theory. A low-power electromagnetic levitator that is accurately described by the theory has been demonstrated and is discussed. Experimental measurements of excess impedance are presented and compared with theory, and those results are used to demonstrate an accurate noncontact method for determining electrical conductivity. Theoretical formulas for power absorption are evaluated numerically and their usefulness in both rf heating and in making noncontact measurements of a number of thermophysical properties of materials is discussed.

Jackson, H. W.; Watkins, J. L.; Chung, S.; Wagner, P.

1996-01-01

411

The effects of conduction, convection, and radiation on the thermodynamic environment surrounding a heat-generating waste package  

SciTech Connect

The thermodynamic environment surrounding a heat-generating waste package can play an important role in the performance of a high-level radioactive waste repository. However, rigorous models of heat transfer are often compromised in near-drift simulations. Convection and radiation are usually ignored or approximated so that simpler conduction models can be used. This paper presents numerical simulations that explicitly model conduction, convection, and radiation in an empty drift following emplacement of a heat-generating waste package. Temperatures and relative humidities are determined at various locations within the drift. Comparisons are made between different models of heat transfer, and the relative effects of each heat transfer mode on the thermodynamic environment of the waste package are examined.

Ho, Clifford K.; Francis, N.D.

1996-01-01

412

Analytical method of calculating temperature differences for rectangular heat-releasing elements in the body of a homogeneous heat-conducting rectangular plate with heat removal from its edges  

Microsoft Academic Search

An analytical method has been presented for calculating average temperature differences for rectangular heat-releasing elements located in the body of a rectangular homogeneous thin heat-conducting plate relative to its edges with the same temperature. A stationary problem for the cases of heat removal from one, two, three, and four edges of such a plate has been considered.

V. Z. Kokotov; A. A. Meyer; I. É. Kvint

2007-01-01

413

Micro heat pipes in low temperature cofire ceramic (LTCC) substrates  

Microsoft Academic Search

With projected power densities above 100 W\\/cm2 for devices, new methods for thermal management from the heat generation at the die to heat removal to the ambient must be addressed. By integrating micro heat pipes directly within the ceramic substrate, effective thermal conductivity for spreading heat in both radial and axial directions was achieved. New materials and processes were developed

W. Kinzy Jones; Yanqing Liu; Mingcong Gao

2003-01-01

414

Sensitivity of the interpretation of the experimental ion thermal diffusivity to the determination of the ion conductive heat flux  

NASA Astrophysics Data System (ADS)

A moments equation formalism for the interpretation of the experimental ion thermal diffusivity from experimental data is used to determine the radial ion thermal conduction flux that must be used to interpret the measured data. It is shown that the total ion energy flux must be corrected for thermal and rotational energy convection, for the work done by the flowing plasma against the pressure and viscosity, and for ion orbit loss of particles and energy, and expressions are presented for these corrections. Each of these factors is shown to have a significant effect on the interpreted ion thermal diffusivity in a representative DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] discharge.

Stacey, W. M.

2014-04-01

415

Thermal Conductive Heat Transfer and Partial Melting of Volatiles in Icy Moons, Asteroids, and Kuiper Belt Objects (Invited)  

NASA Astrophysics Data System (ADS)

Thermal gradients within conductive layers of icy satellite and asteroids depend partly on heat flow, which is related to the secular decay of radioactive isotopes, to heat released by chemical phase changes, by conversion of gravitational potential energy to heat during differentiation, tidal energy dissipation, and to release of heat stored from prior periods. Thermal gradients are also dependent on the thermal conductivity of materials, which in turn depends on their composition, crystallinity, porosity, crystal fabric anisotropy, and details of their mixture with other materials. Small impurities can produce lattice defects and changes in polymerization, and thereby have a huge influence on thermal conductivity, as can cage-inclusion (clathrate) compounds. Heat flow and thermal gradients can be affected by fluid phase advection of mass and heat (in oceans or sublimating upper crusts), by refraction related to heterogeneities of thermal conductivity due to lateral variations and composition or porosity. Thermal profiles depend also on the surface temperature controlled by albedo and climate, surface relief, and latitude, orbital obliquity and surface insolation, solid state greenhouses, and endogenic heating of the surface. The thermal state of icy moon interiors and thermal gradients can be limited at depth by fluid phase advection of heat (e.g., percolating meteoric methane or gas emission), by the latent heat of phase transitions (melting, solid-state transitions, and sublimation), by solid-state convective or diapiric heat transfer, and by foundering. Rapid burial of thick volatile deposits can also affect thermal gradients. For geologically inactive or simple icy objects, most of these controls on heat flow and thermal gradients are irrelevant, but for many other icy objects they can be important, in some cases causing large lateral and depth variations in thermal gradients, large variations in heat flow, and dynamically evolving thermal states. Many of these processes result in transient thermal states and hence rapid evolution of icy body interiors. Interesting heat-flow phenomena (approximated as steady-state thermal states) have been modeled in volatile-rich main belt asteroids, Io, Europa, Enceladus, Titan, Pluto, and Makemake (2005 FY9). Thermal conditions can activate geologic processes, but the occurrence of geologic activity can fundamentally alter the thermal conductivity and elasticity of icy objects, which then further affects the distribution and type of subsequent geologic activity. For example, cryoclastic volcanism on Enceladus can increase solid-state greenhouse heating of the upper crust, reduce thermal conductivity, and increase retention of heat and spur further cryovolcanism. Sulfur extrusion on Io can produce low-thermal-conductivity flows, high thermal gradients, basal melting of the flows, and lateral extrusion and spreading of the flows or formation of solid-crusted lava lakes. Impact formation of regoliths and fine-grained dust deposits on large asteroids may generate local variations in thermal gradients. Interior heating and geologic activity can either (1) emplace low-conductivity materials on the surface and cause further interior heating, or (2) drive metamorphism, sintering, and volatile loss, and increase thermal conductivity and cool the object. Thus, the type and distribution of present-day geologic activity on icy worlds is dependent on geologic history. Geology begets geology.

Kargel, J. S.; Furfaro, R.

2013-12-01

416

Opposite ReD-dependencies of nanofluid (Al2O3) thermal conductivities between heating and cooling modes  

NASA Astrophysics Data System (ADS)

The dynamic thermal conductivities of nanofluids (Al2O3) in heating or cooling under fully developed laminar flow conditions show opposite dependence on Reynolds numbers, i.e., the dynamic conductivities under the heating conditions increase with increasing ReD but under the cooling conditions, the dynamic conductivities decrease with increasing ReD. Furthermore, the dynamic conductivities for cooling are higher than those for heating, and the thermal conductivities of stationary nanofluids with uniform distributions fall between these two values, for the entire tested ReD range from 300 to 800. We believe that the main reason for this distinction is because of the drastically different cross-sectional nanoparticle concentration distributions that are in turn attributed to the opposite thermophoretic behavior near the tube wall between heating and cooling. The near-wall nanoparticle concentrations for cooling are substantially higher than those for heating; however, the stationary nanofluid with no thermophoresis maintains its uniform concentration in the middle between the two concentrations.

Su Na, Young; David Kihm, Kenneth; Sik Lee, Joon

2012-08-01

417

Heat transfer 1982; Proceedings of the Seventh International Conference, Technische Universitaet Muenchen, Munich, West Germany, September 6-10, 1982. Volume 2 - General papers: Conduction, natural convection, environmental heat transfer, radiation  

Microsoft Academic Search

Theoretical, numerical, and experimental investigations into problems of heat transfer are reported. Attention is given to numerical solutions to conduction occurring in heat generation, heat conduction in composites, and in heat exchangers, as well as to temperature dependent thermal properties in phase change materials. Natural convection is explored in terms of layered fluids, nongray gases, and spherical containment vessels. Environmental

U. Grigull; J. Straub; E. Hahne; K. Stephan

1982-01-01

418

Electrical resistivity and thermal conductivity of liquid Fe alloys at high P and T, and heat flux in Earth's core  

PubMed Central

Earth’s magnetic field is sustained by magnetohydrodynamic convection within the metallic liquid core. In a thermally advecting core, the fraction of heat available to drive the geodynamo is reduced by heat conducted along the core geotherm, which depends sensitively on the thermal conductivity of liquid iron and its alloys with candidate light elements. The thermal conductivity for Earth’s core is very poorly constrained, with current estimates based on a set of scaling relations that were not previously tested at high pressures. We perform first-principles electronic structure computations to determine the thermal conductivity and electrical resistivity for Fe, Fe–Si, and Fe–O liquid alloys. Computed resistivity agrees very well with existing shock compression measurements and shows strong dependence on light element concentration and type. Thermal conductivity at pressure and temperature conditions characteristic of Earth’s core is higher than previous extrapolations. Conductive heat flux near the core–mantle boundary is comparable to estimates of the total heat flux from the core but decreases with depth, so that thermally driven flow would be constrained to greater depths in the absence of an inner core.

de Koker, Nico; Steinle-Neumann, Gerd; Vlcek, Vojtech

2012-01-01

419

Crossover from Fermi-Pasta-Ulam to normal diffusive behavior in heat conduction through open anharmonic lattices.  

PubMed

We study heat conduction in one-, two-, and three-dimensional anharmonic lattices connected to stochastic Langevin heat baths. The interatomic potential of the lattices is double-well type, i.e., V(DW)(x)=k(2)x(2)/2+k(4)x(4)/4 with k(2)<0 and k(4)>0. We observe two different temperature regimes of transport: a high-temperature regime where asymptotic length dependence of nonequilibrium steady state heat current is similar to the well-known Fermi-Pasta-Ulam lattices with an interatomic potential, V(FPU)(x)=k(2)x(2)/2+k(4)x(4)/4 with k(2),k(4)>0, and a low-temperature regime where heat conduction is most likely diffusive normal, satisfying Fourier's law. We present our simulation results for different temperature regimes in all dimensions. PMID:23214524

Roy, Dibyendu

2012-10-01

420

Fast transient thermal analysis of non-fourier heat conduction using tikhonov well-conditioned asymptotic waveform evaluation.  

PubMed

Non-Fourier heat conduction model with dual phase lag wave-diffusion model was analyzed by using well-conditioned asymptotic wave evaluation (WCAWE) and finite element method (FEM). The non-Fourier heat conduction has been investigated where the maximum likelihood (ML) and Tikhonov regularization technique were used successfully to predict the accurate and stable temperature responses without the loss of initial nonlinear/high frequency response. To reduce the increased computational time by Tikhonov WCAWE using ML (TWCAWE-ML), another well-conditioned scheme, called mass effect (ME) T-WCAWE, is introduced. TWCAWE with ME (TWCAWE-ME) showed more stable and accurate temperature spectrum in comparison to asymptotic wave evaluation (AWE) and also partial Pade AWE without sacrificing the computational time. However, the TWCAWE-ML remains as the most stable and hence accurate model to analyze the fast transient thermal analysis of non-Fourier heat conduction model. PMID:25019096

Rana, Sohel; Kanesan, Jeevan; Reza, Ahmed Wasif; Ramiah, Harikrishnan

2014-01-01

421

Fast Transient Thermal Analysis of Non-Fourier Heat Conduction Using Tikhonov Well-Conditioned Asymptotic Waveform Evaluation  

PubMed Central

Non-Fourier heat conduction model with dual phase lag wave-diffusion model was analyzed by using well-conditioned asymptotic wave evaluation (WCAWE) and finite element method (FEM). The non-Fourier heat conduction has been investigated where the maximum likelihood (ML) and Tikhonov regularization technique were used successfully to predict the accurate and stable temperature responses without the loss of initial nonlinear/high frequency response. To reduce the increased computational time by Tikhonov WCAWE using ML (TWCAWE-ML), another well-conditioned scheme, called mass effect (ME) T-WCAWE, is introduced. TWCAWE with ME (TWCAWE-ME) showed more stable and accurate temperature spectrum in comparison to asymptotic wave evaluation (AWE) and also partial Pade AWE without sacrificing the computational time. However, the TWCAWE-ML remains as the most stable and hence accurate model to analyze the fast transient thermal analysis of non-Fourier heat conduction model.

Reza, Ahmed Wasif

2014-01-01

422

Transient radiative and conductive heat transfer in non-gray semitransparent two-dimensional media with mixed boundary conditions  

Microsoft Academic Search

This paper is devoted to transient heat transfer involving radiation and conduction. Considering a non-gray purely absorbing\\u000a media, the radiative heat transfer equation (RTE) is solved iteratively with the Discrete Ordinates Method (DOM) using an\\u000a exponential differencing scheme. The energy balance equation is used to compute temperature at each time step with the Crank–Nicholson\\u000a technique. Energy equation is coupled to

Lacroix David; Berour Nacer; Boulet Pascal; Jeandel Gérard

2006-01-01

423

Non-gray radiative and conductive heat transfer in single and double glazing solar collector glass covers  

Microsoft Academic Search

A rigorous model for the radiative heat transfer combined with the conduction and the convection has been applied for a solar collector glazing. The glass cover is analysed as a non-gray plane-parallel medium subjected to solar and thermal irradiation in one-dimensional case, using the radiation element method by ray emission model. The model allows the calculation of the steady-state heat

Khoukhi Maatouk

2006-01-01

424

Estimation of Surface Heat Flux and Surface Temperature during Inverse Heat Conduction under Varying Spray Parameters and Sample Initial Temperature  

PubMed Central

An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27?mm and thickness (mm) 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2?MPa to 1.8?MPa, while sample initial temperature varied from 600°C to 900°C. Beck's sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF) within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024?MW/m2 was estimated for a thickness of 8.5?mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8?MPa.

Aamir, Muhammad; Liao, Qiang; Zhu, Xun; Aqeel-ur-Rehman; Wang, Hong

2014-01-01

425

Compressive pressure dependent anisotropic effective thermal conductivity of granular beds  

Microsoft Academic Search

In situ planetary thermal conductivity measurements are typically made using a long needle-like probe, which measures effective\\u000a thermal conductivity in the probe’s radial (horizontal) direction. The desired effective vertical thermal conductivity for\\u000a heat flow calculations is assumed to be the same as the measured effective horizontal thermal conductivity. However, it is\\u000a known that effective thermal conductivity increases with increasing compressive

Daniel Garrett; Heng Ban

426

The coupling problem of ablation and heat-conduction in thermo-protective calculation of solid rocket nozzle  

Microsoft Academic Search

The coupling calculation method of ablation and the temperature field of the silica-phenolics lining in the divergent portion of solid rocket nozzles is discussed. The unsteady liquid layer ablative model of this lining, in which liquid, charred and pyrolitic layers are formed under high temperature, is used. The transient heat conductive model in cylindrical coordinate system is used for calculation

Honqing He; Jinlan Tang

1992-01-01

427

Analysis of combined conduction and radiation heat transfer in presence of participating medium by the development of hybrid method  

Microsoft Academic Search

The current study addresses the mathematical modeling aspects of coupled conductive and radiative heat transfer in the presence of absorbing, emitting and isotropic scattering gray medium within two-dimensional square enclosure. A blended method where the concepts of modified differential approximation employed by combining discrete ordinate method and spherical harmonics method, has been developed for modeling the radiative transport equation. The

S. K. Mahapatra; B. K. Dandapat; A. Sarkar

2006-01-01

428

Heat Transfer and Effective Thermal Conductivity Analyses in Carbon-Based Foams for Use in Thermal Protection Systems  

Microsoft Academic Search

The applicability of carbon-based foams as an insulation material in the thermal protection systems (TPSs) of space vehicles is considered using a physical analysis and computer modelling. The heat transfer through the foam is considered through its solid phase and the gas residing in the foam pores via conduction and radiation. As the cellular structure of the foam prevents a

M Grujicic; C L Zhao; S B Biggers; J M Kennedy; D R Morgan

2005-01-01

429

An improved iterative method for solving a class of coupled conductive-radiative heat-transfer problems  

Microsoft Academic Search

Newton's method of iteration is used along with the PN method, also called the spherical-harmonics method, and Hermite cubic splines to develop an iterative solution to a class of nonlinear problems in radiative transfer. Anisotropic scattering and specularly and diffusely reflecting boundaries are allowed for the steady-state, combined-mode, conductive-radiative, heat-transfer problem considered.

C. E. Siewert

1995-01-01

430

Heat transfer by conduction and radiation in a one-dimensional planar medium using the differential approximation  

Microsoft Academic Search

The combined conduction and radiation heat transfer problem for a gray planar medium between two diffuse, isothermal infinite parallel plates is considered using the differential aproximation. e P-1 and P-3 spherical harmonics approximations for the intensity distribution are used. In addition, isotropic scattering and uniform volumetric generation terms are included. The governing energy equations developed using the P-1 and P-3

A. C. Ratzel; J. R. Howell

1981-01-01

431

Analysis of coupled conduction and radiation heat transfer in presence of participating medium- using a hybrid method  

Microsoft Academic Search

The current study addresses the mathematical modeling aspects of coupled conductive and radiative heat transfer in presence of absorbing, emitting and isotropic scattering gray medium within two-dimensional square enclosure. The walls of the enclosure are considered to be opaque, diffuse and gray. The enclosure comprised of isothermal vertical walls and ins