THERM3D: A boundary element computer program for transient heat conduction problems
M. S. Ingber
1994-01-01
The computer code THERM3D implements the direct boundary element method (BEM) to solve transient heat conduction problems in arbitrary three dimensional domains. This particular implementation of the BEM avoids performing time consuming domain integrations by approximating a 'generalized forcing function' in the interior of the domain with the use of radial basis functions. An approximate particular solution is then constructed,
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
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
NASA Astrophysics Data System (ADS)
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
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.
THERM3D: A boundary element computer program for transient heat conduction problems
NASA Astrophysics Data System (ADS)
Ingber, M. S.
1994-02-01
The computer code THERM3D implements the direct boundary element method (BEM) to solve transient heat conduction problems in arbitrary three dimensional domains. This particular implementation of the BEM avoids performing time consuming domain integrations by approximating a 'generalized forcing function' in the interior of the domain with the use of radial basis functions. An approximate particular solution is then constructed, and the original problem is transformed into a sequence of Laplace problems. The code is capable of handling a large variety of boundary conditions including isothermal, specified flux, convection, radiation, and combined convection and radiation conditions. The computer code is benchmarked by comparisons with analytic and finite element results.
J. Sladek; V. Sladek; Ch. Hellmich; J. Eberhardsteiner
2007-01-01
The meshless local Petrov–Galerkin method is used to analyze transient heat conduction in 3-D axisymmetric solids with continuously inhomogeneous and anisotropic material properties. A 3-D axisymmetric body is created by rotation of a cross section around an axis of symmetry. Axial symmetry of geometry and boundary conditions reduces the original 3-D boundary value problem into a 2-D problem. The cross
Conducting Polymer 3D Microelectrodes
Sasso, Luigi; Vazquez, Patricia; Vedarethinam, Indumathi; Castillo-León, Jaime; Emnéus, Jenny; Svendsen, Winnie E.
2010-01-01
Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained showed uniformity and good adhesion to both horizontal and vertical surfaces. Electrodes in combination with metal/conducting polymer materials have been characterized by cyclic voltammetry and the presence of the conducting polymer film has shown to increase the electrochemical activity when compared with electrodes coated with only metal. An electrochemical characterization of gold/polypyrrole electrodes showed exceptional electrochemical behavior and activity. PC12 cells were finally cultured on the investigated materials as a preliminary biocompatibility assessment. These results show that the described electrodes are possibly suitable for future in-vitro neurological measurements. PMID:22163508
1D-to-3D transition of phonon heat conduction in polyethylene using molecular dynamics simulations
Henry, Asegun
The thermal conductivity of nanostructures generally decreases with decreasing size because of classical size effects. The axial thermal conductivity of polymer chain lattices, however, can exhibit the opposite trend, ...
1D-to-3D transition of photon heat conduction in polyethylene using molecular dynamics simulations
Henry, Asegun Sekou Famake
2009-01-01
Experiments have demonstrated that the mechanical stretching of bulk polyethylene can increase its thermal conductivity by more than two orders of magnitude, from 0.35 W/mK to over 40W/mK, which is comparable to steel. ...
3D Thermal Modeling for Planetary Heat Flow Measurements
NASA Astrophysics Data System (ADS)
Siegler, M. A.; Smrekar, S. E.; Platt, J.; Paige, D. A.; Williams, J.
2013-12-01
We report on a variety of new modeling approaches for interpreting Lunar and Martian geothermal heat flow data. Heat Flow measurements aim to inform us of the global radiogenic composition, but are often complicated by local and regional effects. Interpretation of the Apollo Heat Flow measurements, new geothermal heat flow constraints from LRO, and the upcoming InSight mission to Mars depend heavily on our ability to model 3-dimensional heat transport through the crust. Past modeling of these problems has relied on analytic approximations and 1-dimensional studies. Recent computing developments, such as 3D finite element models, allow us to re-examine some of these problems in unprecedented detail. In this presentation, we hope to provide an overview of the need for and utility of such modeling in interpreting heat flow on terrestrial bodies. We will present on progress using 3D conduction models examining the Apollo Heat Flow Experiment. This includes a study of the cause of a slow steady warming in the Apollo Heat Flow Experiment data that has been unresolved for nearly 40 years (Langseth et al., 1976; Grott et al., 2010). We will examine the implications for the composition of the lunar interior (Siegler et al., 2013). We will examine the ability to derive new heat flow values from recent Diviner Lunar Radiometer measurements in the polar regions of the Moon (Siegler et al., 2012). Once deemed impossible due to our inability to separate the effects of lateral heat flux (Lachenbruch, 1965), interpretation of these measurements require a detailed understanding of lateral heat flow from nearby warmer regions. Finally, we will present on 3D thermal modeling of the InSight landing site on both a regional and local scale. Near the crustal dichotomy boundary and one of the largest igneous provinces on Mars, interpretation of InSight heat flow values will depend greatly on our understanding of regional effects on 3D heat flow. Additionally, we introduce efforts toward examining effects of local heat disturbances (such as shadowing and removal of dust) caused by the lander itself and how these may affect our first geothermal measurements from Mars.
Carlos F. Matt; Manuel E. Cruz
2008-01-01
This article presents a numerical scheme, based on an isoparametric second-order finite-element discretization of the unit cell heat conduction problem, to calculate the effective thermal conductivity of composite materials with general 3-D microstructures and interfacial thermal resistance. Representative numerical results for the effective conductivity of ordered arrays of spheres, prolate ellipsoids of revolution, and finite-length circular cylinders are presented and,
3D conductive nanocomposite scaffold for bone tissue engineering
Shahini, Aref; Yazdimamaghani, Mostafa; Walker, Kenneth J; Eastman, Margaret A; Hatami-Marbini, Hamed; Smith, Brenda J; Ricci, John L; Madihally, Sundar V; Vashaee, Daryoosh; Tayebi, Lobat
2014-01-01
Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D) ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene) poly(4-styrene sulfonate) (PEDOT:PSS), in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent microscope. Increasing the concentration of the conductive polymer in the scaffold enhanced the cell viability, indicating the improved microstructure of the scaffolds or boosted electrical signaling among cells. These results show that these conductive scaffolds are not only structurally more favorable for bone tissue engineering, but also can be a step forward in combining the tissue engineering techniques with the method of enhancing the bone healing by electrical stimuli. PMID:24399874
3D conductive nanocomposite scaffold for bone tissue engineering.
Shahini, Aref; Yazdimamaghani, Mostafa; Walker, Kenneth J; Eastman, Margaret A; Hatami-Marbini, Hamed; Smith, Brenda J; Ricci, John L; Madihally, Sundar V; Vashaee, Daryoosh; Tayebi, Lobat
2014-01-01
Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D) ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene) poly(4-styrene sulfonate) (PEDOT:PSS), in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent microscope. Increasing the concentration of the conductive polymer in the scaffold enhanced the cell viability, indicating the improved microstructure of the scaffolds or boosted electrical signaling among cells. These results show that these conductive scaffolds are not only structurally more favorable for bone tissue engineering, but also can be a step forward in combining the tissue engineering techniques with the method of enhancing the bone healing by electrical stimuli. PMID:24399874
Heat Transfer Boundary Conditions in the RELAP5-3D Code
Richard A. Riemke; Cliff B. Davis; Richard R. Schultz
2008-05-01
The heat transfer boundary conditions used in the RELAP5-3D computer program have evolved over the years. Currently, RELAP5-3D has the following options for the heat transfer boundary conditions: (a) heat transfer correlation package option, (b) non-convective option (from radiation/conduction enclosure model or symmetry/insulated conditions), and (c) other options (setting the surface temperature to a volume fraction averaged fluid temperature of the boundary volume, obtaining the surface temperature from a control variable, obtaining the surface temperature from a time-dependent general table, obtaining the heat flux from a time-dependent general table, or obtaining heat transfer coefficients from either a time- or temperature-dependent general table). These options will be discussed, including the more recent ones.
Conduction heat transfer solutions
NASA Astrophysics Data System (ADS)
Vansant, J. H.
1980-03-01
A collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc., are presented. 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.
Coolant side heat transfer with rotation: User manual for 3D-TEACH with rotation
NASA Technical Reports Server (NTRS)
Syed, S. A.; James, R. H.
1989-01-01
This program solves the governing transport equations in Reynolds average form for the flow of a 3-D, steady state, viscous, heat conducting, multiple species, single phase, Newtonian fluid with combustion. The governing partial differential equations are solved in physical variables in either a Cartesian or cylindrical coordinate system. The effects of rotation on the momentum and enthalpy calculations modeled in Cartesian coordinates are examined. The flow of the fluid should be confined and subsonic with a maximum Mach number no larger than 0.5. This manual describes the operating procedures and input details for executing a 3D-TEACH computation.
Temperature distributions in the laser-heated diamond anvil cell from 3-D numerical modeling
Rainey, E. S. G.; Kavner, A. [Department of Earth and Space Sciences, University of California, Los Angeles, California 90095 (United States); Hernlund, J. W. [Department of Earth and Planetary Science, University of California, Berkeley, California 94720 (United States); Earth-Life Science Institute, Megoro, Tokyo 152-8551 (Japan)
2013-11-28
We present TempDAC, a 3-D numerical model for calculating the steady-state temperature distribution for continuous wave laser-heated experiments in the diamond anvil cell. TempDAC solves the steady heat conduction equation in three dimensions over the sample chamber, gasket, and diamond anvils and includes material-, temperature-, and direction-dependent thermal conductivity, while allowing for flexible sample geometries, laser beam intensity profile, and laser absorption properties. The model has been validated against an axisymmetric analytic solution for the temperature distribution within a laser-heated sample. Example calculations illustrate the importance of considering heat flow in three dimensions for the laser-heated diamond anvil cell. In particular, we show that a “flat top” input laser beam profile does not lead to a more uniform temperature distribution or flatter temperature gradients than a wide Gaussian laser beam.
3D coupled heat and mass transfer processes at the scale of sedimentary basisn
NASA Astrophysics Data System (ADS)
Cacace, M.; Scheck-Wenderoth, M.; Kaiser, B. O.
2014-12-01
We use coupled 3D simulations of fluid, heat, and transport based on a 3D structural model of a complex geological setting, the Northeast German Basin (NEGB). The geological structure of the NEGB is characterized by a relatively thick layer of Permian Zechstein salt, structured in differnet diapirs (up to 5000 m thick) and pillows locally reaching nearly the surface. Salt is thermally more conductive than other sediments, hydraulically impervious but highly solvable. Thus salt structures have first order influence on the temperature distribution, the deep flow regime and the salinity of groundawater bearing aquifers. In addition, the post-Permian sedimentary sequence is vertically subdivided into several aquifers and aquitards. The shallow Quaternary to late Tertiary freshwater aquifer is separated from the underlying Mesozoic saline aquifers by an embedded Tertiary clay enriched aquitard (Rupelian Aquitard). An important feature of this aquitard is that hydraulic connections between the upper and lower aquifers exist in areas where the Rupelian Aquitard is missing (hydrogeological windows). By means of 3D numerical simulations we explore the role of heat conduction, pressure, and density driven groundwater flow as well as fluid viscosity-related and salinity-dependent effects on the resulting flow and temperature fields. Our results suggest that the regional temperature distribution within the basin results from interactions between regional pressure forces and thermal diffusion locally enhanced by thermal conductivity contrasts between the different sedimentary rocks with the highly conductive salt. Buoyancy forces triggered by temperature-dependent fluid density variations affect only locally the internal thermal configuration. Locations, geometry, and wavelengths of convective thermal anomalies are mainly controlled by the permeability field and thickness values of the respective geological layers. Numerical results from 3D thermo-haline numerical simulations suggest that hydrogeological windows act as preferential domains of hydraulic interconnectivity between the different aquifers at depth, and enable vigorous heat and mass transport which causes a mixing of warm and saline groundwater with cold and less saline groundwater within both aquifers.
NASA Astrophysics Data System (ADS)
Yang, R.; Song, A.; Li, X. D.; Lu, Y.; Yan, R.; Xu, B.; Li, X.
2014-10-01
A 3D reconstruction solution to ultrasound Joule heat density tomography based on acousto-electric effect by deconvolution is proposed for noninvasive imaging of biological tissue. Compared with ultrasound current source density imaging, ultrasound Joule heat density tomography doesn't require any priori knowledge of conductivity distribution and lead fields, so it can gain better imaging result, more adaptive to environment and with wider application scope. For a general 3D volume conductor with broadly distributed current density field, in the AE equation the ultrasound pressure can't simply be separated from the 3D integration, so it is not a common modulation and basebanding (heterodyning) method is no longer suitable to separate Joule heat density from the AE signals. In the proposed method the measurement signal is viewed as the output of Joule heat density convolving with ultrasound wave. As a result, the internal 3D Joule heat density can be reconstructed by means of Wiener deconvolution. A series of computer simulations set for breast cancer imaging applications, with consideration of ultrasound beam diameter, noise level, conductivity contrast, position dependency and size of simulated tumors, have been conducted to evaluate the feasibility and performance of the proposed reconstruction method. The computer simulation results demonstrate that high spatial resolution 3D ultrasound Joule heat density imaging is feasible using the proposed method, and it has potential applications to breast cancer detection and imaging of other organs.
3D and NDT using scanning from heating
NASA Astrophysics Data System (ADS)
Belkacemi, M.; Stolz, C.; Aubreton, O.
2015-04-01
A nondestructive inspection method using an infrared detection system is presented in this paper; the system uses a YAG laser as excitation point. The material thermal response to this excitation is processed for the detection of volume defects, this technique integrated into a 3D scanning system allows us to get a 3D scan of the object as well as defects detection.
Effects of Heat Loss on the Performance of Micro-Scale 3-D Supersonic Nozzles
NASA Astrophysics Data System (ADS)
Kujawa, Jeffrey; Hitt, Darren
2003-11-01
The performance optimization of supersonic micro-nozzles is a key element in the design of MEMS-based microthrusters for the next generation of miniaturized satellites ("nanosats"). Owing to the large surface area-to-volume ratio on the microscale and the high conductivity of typical substrate materials, heat transfer effects are expected to be significant. This has been corroborated by thermal measurements performed on microthruster prototypes at NASA/Goddard Space Flight Center. To detail the heat transfer and quantify its impact on thruster performance, 2-D and 3-D numerical simulations of the supersonic micro-nozzle flow with insulated and conductive wall boundaries are performed. Geometry and flow parameters are based on the NASA/Goddard H2O2 monopropellant prototype microthruster. Both steady-state and transient thruster operations are considered. The 3-D steady flow results indicate that heat losses approaching 20enthalpy are possible in comparison to an adiabatic wall assumption, resulting in a 10generation.
Variable conductance heat pipe technology
NASA Technical Reports Server (NTRS)
Marcus, B. D.; Edwards, D. K.; Anderson, W. T.
1973-01-01
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.
Paris-Sud XI, Université de
Numerical computation of 3D heat transfer in complex parallel convective exchangers using convective heat exchangers that handles possibly complex input/output con- ditions as well as connection between pipes. It is based on a spectral method that allows to re-cast three-dimensional heat exchangers
Zhang, Jun
Iterative Solution and Finite Difference Approximations to 3D Microscale Heat Transport Equationinfinite interval. Dai and Nassar [4] considered the numerical solution of the microscale heat transport equation [25]. Numerical solution techniques for more general doublelayered thin film heat transfer problems
A simple, low-cost conductive composite material for 3D printing of electronic sensors.
Leigh, Simon J; Bradley, Robert J; Purssell, Christopher P; Billson, Duncan R; Hutchins, David A
2012-01-01
3D printing technology can produce complex objects directly from computer aided digital designs. The technology has traditionally been used by large companies to produce fit and form concept prototypes ('rapid prototyping') before production. In recent years however there has been a move to adopt the technology as full-scale manufacturing solution. The advent of low-cost, desktop 3D printers such as the RepRap and Fab@Home has meant a wider user base are now able to have access to desktop manufacturing platforms enabling them to produce highly customised products for personal use and sale. This uptake in usage has been coupled with a demand for printing technology and materials able to print functional elements such as electronic sensors. Here we present formulation of a simple conductive thermoplastic composite we term 'carbomorph' and demonstrate how it can be used in an unmodified low-cost 3D printer to print electronic sensors able to sense mechanical flexing and capacitance changes. We show how this capability can be used to produce custom sensing devices and user interface devices along with printed objects with embedded sensing capability. This advance in low-cost 3D printing with offer a new paradigm in the 3D printing field with printed sensors and electronics embedded inside 3D printed objects in a single build process without requiring complex or expensive materials incorporating additives such as carbon nanotubes. PMID:23185319
NASA Astrophysics Data System (ADS)
Antonini Alves, Thiago; Santos, Paulo H. D.; Barbur, Murilo A.
2015-09-01
In this research, the temperatures of threedimensional (3D) protruding heaters mounted on a conductive substrate in a horizontal rectangular channel with laminar airflow are related to the independent power dissipation in each heater by using a matrix G + with invariant coefficients, which are dimensionless. These coefficients are defined in this study as the conjugate influence coefficients (g +) caused by the forced convection- conduction nature of the heaters' cooling process. The temperature increase of each heater in the channel is quantified to clearly identify the contributions attributed to the self-heating and power dissipation in the other heaters (both upstream and downstream). The conjugate coefficients are invariant with the heat generation rate in the array of heaters when assuming a defined geometry, invariable fluid and flow rate, and constant substrate and heater conductivities. The results are numerically obtained by considering three 3D protruding heaters on a twodimensional (2D) array by ANSYS/Fluent™ 15.0 software. The conservation equations are solved by a coupled procedure within a single calculation domain comprising of solid and fluid regions and by considering a steady state laminar airflow with constant properties. Some examples are shown, indicating the effects of substrate thermal conductivity and Reynolds number on conjugate influence coefficients.
Estimation of the thermal conductivity of hemp based insulation material from 3D tomographic images
NASA Astrophysics Data System (ADS)
El-Sawalhi, R.; Lux, J.; Salagnac, P.
2015-09-01
In this work, we are interested in the structural and thermal characterization of natural fiber insulation materials. The thermal performance of these materials depends on the arrangement of fibers, which is the consequence of the manufacturing process. In order to optimize these materials, thermal conductivity models can be used to correlate some relevant structural parameters with the effective thermal conductivity. However, only a few models are able to take into account the anisotropy of such material related to the fibers orientation, and these models still need realistic input data (fiber orientation distribution, porosity, etc.). The structural characteristics are here directly measured on a 3D tomographic image using advanced image analysis techniques. Critical structural parameters like porosity, pore and fiber size distribution as well as local fiber orientation distribution are measured. The results of the tested conductivity models are then compared with the conductivity tensor obtained by numerical simulation on the discretized 3D microstructure, as well as available experimental measurements. We show that 1D analytical models are generally not suitable for assessing the thermal conductivity of such anisotropic media. Yet, a few anisotropic models can still be of interest to relate some structural parameters, like the fiber orientation distribution, to the thermal properties. Finally, our results emphasize that numerical simulations on 3D realistic microstructure is a very interesting alternative to experimental measurements.
3D fabrication of all-polymer conductive microstructures by two photon polymerization.
Kurselis, Kestutis; Kiyan, Roman; Bagratashvili, Victor N; Popov, Vladimir K; Chichkov, Boris N
2013-12-16
A technique to fabricate electrically conductive all-polymer 3D microstructures is reported. Superior conductivity, high spatial resolution and three-dimensionality are achieved by successive application of two-photon polymerization and in situ oxidative polymerization to a bi-component formulation, containing a photosensitive host matrix and an intrinsically conductive polymer precursor. By using polyethylene glycol diacrylate (PEG-DA) and 3,4-ethylenedioxythiophene (EDOT), the conductivity of 0.04 S/cm is reached, which is the highest value for the two-photon polymerized all-polymer microstructures to date. The measured electrical conductivity dependency on the EDOT concentration indicates percolation phenomenon and a three-dimensional nature of the conductive pathways. Tunable conductivity, biocompatibility, and environmental stability are the characteristics offered by PEG-DA/EDOT blends which can be employed in biomedicine, MEMS, microfluidics, and sensorics. PMID:24514677
Validation of Heat Transfer and Film Cooling Capabilities of the 3-D RANS Code TURBO
NASA Technical Reports Server (NTRS)
Shyam, Vikram; Ameri, Ali; Chen, Jen-Ping
2010-01-01
The capabilities of the 3-D unsteady RANS code TURBO have been extended to include heat transfer and film cooling applications. The results of simulations performed with the modified code are compared to experiment and to theory, where applicable. Wilcox s k-turbulence model has been implemented to close the RANS equations. Two simulations are conducted: (1) flow over a flat plate and (2) flow over an adiabatic flat plate cooled by one hole inclined at 35 to the free stream. For (1) agreement with theory is found to be excellent for heat transfer, represented by local Nusselt number, and quite good for momentum, as represented by the local skin friction coefficient. This report compares the local skin friction coefficients and Nusselt numbers on a flat plate obtained using Wilcox's k-model with the theory of Blasius. The study looks at laminar and turbulent flows over an adiabatic flat plate and over an isothermal flat plate for two different wall temperatures. It is shown that TURBO is able to accurately predict heat transfer on a flat plate. For (2) TURBO shows good qualitative agreement with film cooling experiments performed on a flat plate with one cooling hole. Quantitatively, film effectiveness is under predicted downstream of the hole.
A quasi-3D analysis of the thermal performance of a flat heat pipe
G. Carbajal; C. B. Sobhan; G. P. “Bud” Peterson; D. T. Queheillalt; Haydn N. G. Wadley
2007-01-01
The thermal performance of a flat heat pipe thermal spreader has been described by a quasi-3D mathematical model and numerically modeled. An explicit finite volume method with under-relaxation was used for computations in the vapor phase. This was combined with a relatively small time step for the analysis. The physical problem consisted of an evaporator surface that was transiently heated
Rapid prototyping of electrically conductive components using 3D printing technology
J. Czy?ewski; P. Burzy?ski; K. Gawe?; J. Meisner
2009-01-01
A method of rapid prototyping of electrically conductive components is described. The method is based on 3D printing technology. The prototyped model is made of plaster-based powder bound layer-by-layer by an inkjet printing of a liquid binder. The resulting model is highly porous and can be impregnated by various liquids. In a standard prototyping process, the model is impregnated by
FURN3D: A computer code for radiative heat transfer in pulverized coal furnaces
Ahluwalia, R.K.; Im, K.H.
1992-08-01
A computer code FURN3D has been developed for assessing the impact of burning different coals on heat absorption pattern in pulverized coal furnaces. The code is unique in its ability to conduct detailed spectral calculations of radiation transport in furnaces fully accounting for the size distributions of char, soot and ash particles, ash content, and ash composition. The code uses a hybrid technique of solving the three-dimensional radiation transport equation for absorbing, emitting and anisotropically scattering media. The technique achieves an optimal mix of computational speed and accuracy by combining the discrete ordinate method (S[sub 4]), modified differential approximation (MDA) and P, approximation in different range of optical thicknesses. The code uses spectroscopic data for estimating the absorption coefficients of participating gases C0[sub 2], H[sub 2]0 and CO. It invokes Mie theory for determining the extinction and scattering coefficients of combustion particulates. The optical constants of char, soot and ash are obtained from dispersion relations derived from reflectivity, transmissivity and extinction measurements. A control-volume formulation is adopted for determining the temperature field inside the furnace. A simple char burnout model is employed for estimating heat release and evolution of particle size distribution. The code is written in Fortran 77, has modular form, and is machine-independent. The computer memory required by the code depends upon the number of grid points specified and whether the transport calculations are performed on spectral or gray basis.
FURN3D: A computer code for radiative heat transfer in pulverized coal furnaces
Ahluwalia, R.K.; Im, K.H.
1992-08-01
A computer code FURN3D has been developed for assessing the impact of burning different coals on heat absorption pattern in pulverized coal furnaces. The code is unique in its ability to conduct detailed spectral calculations of radiation transport in furnaces fully accounting for the size distributions of char, soot and ash particles, ash content, and ash composition. The code uses a hybrid technique of solving the three-dimensional radiation transport equation for absorbing, emitting and anisotropically scattering media. The technique achieves an optimal mix of computational speed and accuracy by combining the discrete ordinate method (S{sub 4}), modified differential approximation (MDA) and P, approximation in different range of optical thicknesses. The code uses spectroscopic data for estimating the absorption coefficients of participating gases C0{sub 2}, H{sub 2}0 and CO. It invokes Mie theory for determining the extinction and scattering coefficients of combustion particulates. The optical constants of char, soot and ash are obtained from dispersion relations derived from reflectivity, transmissivity and extinction measurements. A control-volume formulation is adopted for determining the temperature field inside the furnace. A simple char burnout model is employed for estimating heat release and evolution of particle size distribution. The code is written in Fortran 77, has modular form, and is machine-independent. The computer memory required by the code depends upon the number of grid points specified and whether the transport calculations are performed on spectral or gray basis.
Methodology for the Assessment of 3D Conduction Effects in an Aerothermal Wind Tunnel Test
NASA Technical Reports Server (NTRS)
Oliver, Anthony Brandon
2010-01-01
This slide presentation reviews a method for the assessment of three-dimensional conduction effects during test in a Aerothermal Wind Tunnel. The test objectives were to duplicate and extend tests that were performed during the 1960's on thermal conduction on proturberance on a flat plate. Slides review the 1D versus 3D conduction data reduction error, the analysis process, CFD-based analysis, loose coupling method that simulates a wind tunnel test run, verification of the CFD solution, Grid convergence, Mach number trend, size trends, and a Sumary of the CFD conduction analysis. Other slides show comparisons to pretest CFD at Mach 1.5 and 2.16 and the geometries of the models and grids.
A Numerical Study on the Thermal Conductivity of 3D Woven C/C Composites at High Temperature
NASA Astrophysics Data System (ADS)
Shigang, Ai; Rujie, He; Yongmao, Pei
2015-03-01
Experimental data for Carbon/Carbon (C/C) constituent materials are combined with a three dimensional steady state heat transfer finite element analysis to demonstrate the average in-plane and out-of-plane thermal conductivities (TCs) of C/C composites. The finite element analysis is carried out at two distinct length scales: (a) a micro scale comparable with the diameter of carbon fibres and (b) a meso scale comparable with the carbon fibre yarns. Micro-scale model calculate the TCs at the fibre yarn scale in the three orthogonal directions (x, y and z). The output results from the micro-scale model are then incorporated in the meso-scale model to obtain the global TCs of the 3D C/C composite. The simulation results are quite consistent with the theoretical and experimental counterparts reported in references. Based on the numerical approach, TCs of the 3D C/C composite are calculated from 300 to 2500 K. Particular attention is given in elucidating the variations of the TCs with temperature. The multi-scale models provide an efficient approach to predict the TCs of 3D textile materials, which is helpful for the thermodynamic property analysis and structure design of the C/C composites.
NASA Astrophysics Data System (ADS)
Xu, Hongmei; Wang, Huachun; Wu, Chenping; Lin, Na; Soomro, Abdul Majid; Guo, Huizhang; Liu, Chuan; Yang, Xiaodong; Wu, Yaping; Cai, Duanjun; Kang, Junyong
2015-06-01
Transparent conducting film occupies an important position in various optoelectronic devices. To replace the costly tin-doped indium oxide (ITO), promising materials, such as metal nanowires and graphene, have been widely studied. Moreover, a long-pursued goal is to consolidate these two materials together and express their outstanding properties simultaneously. We successfully achieved a direct 3D coating of a graphene layer on an interlacing Cu nanosilks network by the low pressure chemical vapor deposition method. High aspect ratio Cu nanosilks (13 nm diameter with 40 ?m length) were synthesized through the nickel ion catalytic process. Large-size, transparent conducting film was successfully fabricated with Cu nanosilks ink by the imprint method. A magnetic manipulator equipped with a copper capsule was used to produce high Cu vapor pressure on Cu nanosilks and realize the graphene 3D-coating. The coated Cu@graphene nanosilks network achieved high transparency, low sheet resistance (41 Ohm sq-1 at 95% transmittance) and robust antioxidant ability. With this technique, the transfer process of graphene is no longer needed, and a flexible, uniform and high-performance transparent conducting film could be fabricated in unlimited size.Transparent conducting film occupies an important position in various optoelectronic devices. To replace the costly tin-doped indium oxide (ITO), promising materials, such as metal nanowires and graphene, have been widely studied. Moreover, a long-pursued goal is to consolidate these two materials together and express their outstanding properties simultaneously. We successfully achieved a direct 3D coating of a graphene layer on an interlacing Cu nanosilks network by the low pressure chemical vapor deposition method. High aspect ratio Cu nanosilks (13 nm diameter with 40 ?m length) were synthesized through the nickel ion catalytic process. Large-size, transparent conducting film was successfully fabricated with Cu nanosilks ink by the imprint method. A magnetic manipulator equipped with a copper capsule was used to produce high Cu vapor pressure on Cu nanosilks and realize the graphene 3D-coating. The coated Cu@graphene nanosilks network achieved high transparency, low sheet resistance (41 Ohm sq-1 at 95% transmittance) and robust antioxidant ability. With this technique, the transfer process of graphene is no longer needed, and a flexible, uniform and high-performance transparent conducting film could be fabricated in unlimited size. Electronic supplementary information (ESI) available: Photographs, transmission spectra, Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) images. See DOI: 10.1039/c5nr01711d
Comparison of Conductances derived from IDA3D and TIMEGCM with GUVI
NASA Astrophysics Data System (ADS)
Reynolds, A. S.; Crowley, G. W.; Bust, G. S.; Paxton, L.; Christensen, A.; Secan, J.; Smith, R.
2006-12-01
The Global Ultraviolet Imager (GUVI) instrument on the TIMED satellite measures various auroral parameters including the energy and flux distributions, which can then be used to estimate auroral conductances. In this paper, we compare GUVI conductances with those obtained from an ionospheric data assimilation imaging algorithm. The comparison is focused on the Alaska region, where five tomographic receivers collected data during the November 6 14, 2004 study period, which contained both quiet days and a large magnetic storm. The receivers were arrayed across Central Alaska from ~ 60 70 degrees of latitude. The Ionospheric Data Assimilation Three-Dimensional (IDA3D) tomographic imaging algorithm was run for this period using the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIMEGCM) as a background model, driven by convection and precipitation patterns obtained from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure. In addition to the Alaska tomography data, IDA3D also ingested ground-based GPS data, low earth orbiting (LEO) satellite GPS occultation data and over-satellite electron content data, in-situ measurements of electron density from DMSP and CHAMP, incoherent scatter radar data and ionosonde data. IDA3D was run twice for the study period, with 5 minute cadence. The first run ingested all the data except the Alaska tomography data. The second run used all the data, including the Alaska tomography data. The study shows the value of the tomography data, and the kind of detailed ionospheric structure that can be obtained from IDA3D, which is particularly useful in complex highly structured situations.
NASA Astrophysics Data System (ADS)
Castro, M. C.; Patriarche, D.; Goblet, P.
2004-12-01
The conceptual and practical gains achieved by expanding a 2-D finite element model [Castro and Goblet, 2003] to a true 3-D one through an application in the Carrizo aquifer and surrounding formations in southwestern Texas are investigated through a series of groundwater flow and 4He transport simulations. Such a 3-D model represents 4 formations, covers a surface area of ˜7000 km2, and comprises more than 5 million elements. 3-D simulations allow for a more detailed and accurate definition of the heterogeneities of the system, by specifically identifying and differentiating processes that directly impact the three-dimensional hydraulic conductivity field. It is shown that while hydraulic conductivity decreases exponentially along the regional groundwater flow direction, such decrease is better described as a function of depth rather than recharge distance. This relationship reflects the combined influences of differential compaction of the media as well as down-dip lithological change. The intrinsic permeability derived from this relationship agrees with field information. In addition, our relationship intrinsic permeability-depth derived from the obtained hydraulic conductivity field in the 3-D model domain for depths < 2 km is in agreement with that one proposed by Saar and Manga [2004] for the Oregon Cascades volcanic setting, as well as that proposed by Manning and Ingebritsen [1999]. These findings suggest that large-scale permeability evolution with depth is, to a large extent, independent of the type of medium. The 4He external flux value for which calibration of the 3-D transport model was achieved is 1.5×10-15 mol m-2rock s-1. Calculated hydraulic conductivities vary from 5×10-4 to 3.1×10-8 m s-1 in the Carrizo aquifer from the outcrop to the discharge area. Results also suggest that the solution for groundwater flow simulations based on calibration of hydraulic heads depends on the ratio between hydraulic conductivities of different formations, showing that an infinite number of solutions are available for calibration of 3-D groundwater flow models. Understanding how geological processes directly affect the 3-D hydraulic conductivity field at the regional scale is essential not only to hydrogeological applications, but also at improving our understanding of the Earth\\'{ }s crust and mantle dynamics by allowing for a more accurate quantification of helium and heat fluxes. Castro M. C., and Goblet P. (2003). Calibration of regional groundwater flow models - working toward a better understanding of site-specific systems. Water Resour. Res., 39(6), 1172, doi:10.1029/2002WR001653. Manning C. E., and Ingebritsen S. E. (1999). Permeability of the continental crust; implications of geothermal data and metamorphic systems. Rev. Geophys., 37(1), p. 127-150. Saar M. O., and Manga M. (2004). Depth dependence of permeability in the Oregon Cascades inferred from hydrogeologic, thermal, seismic, and magmatic modeling constraints. J. Geophys. Res., 109(B4), B04204, doi:10.1029/2003JB002855.
Turbomachinery Heat Transfer and Loss Modeling for 3D Navier-Stokes Codes
NASA Technical Reports Server (NTRS)
DeWitt, Kenneth; Ameri, Ali
2005-01-01
This report's contents focus on making use of NASA Glenn on-site computational facilities,to develop, validate, and apply models for use in advanced 3D Navier-Stokes Computational Fluid Dynamics (CFD) codes to enhance the capability to compute heat transfer and losses in turbomachiney.
Jia, Jingjing; Sun, Xinying; Lin, Xiuyi; Shen, Xi; Mai, Yiu-Wing; Kim, Jang-Kyo
2014-06-24
Cellular-structured graphene foam (GF)/epoxy composites are prepared based on a three-step fabrication process involving infiltration of epoxy into the porous GF. The three-dimensional (3D) GF is grown on a Ni foam template via chemical vapor deposition. The 3D interconnected graphene network serves as fast channels for charge carriers, giving rise to a remarkable electrical conductivity of the composite, 3 S/cm, with only 0.2 wt % GF. The corresponding flexural modulus and strength increase by 53 and 38%, respectively, whereas the glass transition temperature increases by a notable 31 °C, compared to the solid neat epoxy. The GF/epoxy composites with 0.1 wt % GF also deliver an excellent fracture toughness of 1.78 MPa·m(1/2), 34 and 70% enhancements against their "porous" epoxy and solid epoxy counterparts, respectively. These observations signify the unrivalled effectiveness of 3D GF relative to 1D carbon nanotubes or 2D functionalized graphene sheets as reinforcement for polymer composites without issues of nanofiller dispersion and functionalization prior to incorporation into the polymer. PMID:24848106
Pattern transformation of heat-shrinkable polymer by three-dimensional (3D) printing technique.
Zhang, Quan; Yan, Dong; Zhang, Kai; Hu, Gengkai
2015-01-01
A significant challenge in conventional heat-shrinkable polymers is to produce controllable microstructures. Here we report that the polymer material fabricated by three-dimensional (3D) printing technique has a heat-shrinkable property, whose initial microstructure can undergo a spontaneous pattern transformation under heating. The underlying mechanism is revealed by evaluating internal strain of the printed polymer from its fabricating process. It is shown that a uniform internal strain is stored in the polymer during the printing process and can be released when heated above its glass transition temperature. Furthermore, the internal strain can be used to trigger the pattern transformation of the heat-shrinkable polymer in a controllable way. Our work provides insightful ideas to understand a novel mechanism on the heat-shrinkable effect of printed material, but also to present a simple approach to fabricate heat-shrinkable polymer with a controllable thermo-structural response. PMID:25757881
Xu, Hongmei; Wang, Huachun; Wu, Chenping; Lin, Na; Soomro, Abdul Majid; Guo, Huizhang; Liu, Chuan; Yang, Xiaodong; Wu, Yaping; Cai, Duanjun; Kang, JunYong
2015-06-28
Transparent conducting film occupies an important position in various optoelectronic devices. To replace the costly tin-doped indium oxide (ITO), promising materials, such as metal nanowires and graphene, have been widely studied. Moreover, a long-pursued goal is to consolidate these two materials together and express their outstanding properties simultaneously. We successfully achieved a direct 3D coating of a graphene layer on an interlacing Cu nanosilks network by the low pressure chemical vapor deposition method. High aspect ratio Cu nanosilks (13 nm diameter with 40 ?m length) were synthesized through the nickel ion catalytic process. Large-size, transparent conducting film was successfully fabricated with Cu nanosilks ink by the imprint method. A magnetic manipulator equipped with a copper capsule was used to produce high Cu vapor pressure on Cu nanosilks and realize the graphene 3D-coating. The coated Cu@graphene nanosilks network achieved high transparency, low sheet resistance (41 Ohm sq(-1) at 95% transmittance) and robust antioxidant ability. With this technique, the transfer process of graphene is no longer needed, and a flexible, uniform and high-performance transparent conducting film could be fabricated in unlimited size. PMID:26018299
An End-to-End Approach to Making Self-Folded 3D Surface Shapes by Uniform Heating
Demaine, Erik
a 3D geometric specification using print-and-fold processes. We have pre- viously demonstratedAn End-to-End Approach to Making Self-Folded 3D Surface Shapes by Uniform Heating Byoungkwon An, Robert J. Wood and Daniela Rus Abstract-- This paper presents an end-to-end approach for creating 3D
3-D thermal modelling applied to stress-induced anisotropy of thermal conductivity
H. Pron; C. Bissieux
2004-01-01
The present work consists in the development of a three-dimensional model of heat diffusion in orthotropic media, based on numerical Fourier transforms, and taking into account the extent of the source. This model has been applied, together with a Gauss–Newton parameter estimation procedure, to identify the components of the conductivity tensor of a steel bar under uniaxial loading. Few percent
Toward A 3-D Picture of Hydraulic Conductivity With Multilevel Slug Tests
NASA Astrophysics Data System (ADS)
McElwee, C. D.; McElwee, C. D.; Ross, H. C.
2001-12-01
The GEMS (Geohydrologic Experiment and Monitoring Site) field area has been established (in the Kansas River valley near Lawrence, Kansas) for a variety of reasons relating to research and teaching in hydrogeology at the University of Kansas. Over 70 wells have been installed for various purposes. The site overlies an alluvial aquifer with a total thickness of about 70 feet. The water table is typically about 20 feet below the surface, giving a total saturated thickness of about 50 feet. The upper part of the aquifer is finer material consisting of silt and clay. Typically, the lower 35 feet of the aquifer is sand and gravel. A number of wells through out the site are fully screened through the sand and gravel aquifer. Some of these fully screened wells are larger diameters; however, most wells are constructed of 2 inch PVC casing. Slug tests are widely used in hydrogeology to measure hydraulic conductivity. Over the last several years we have been conducting research to improve the slug test method. We have previously reported the detailed structure of hydraulic conductivity that can be seen in a 5 inch well (McElwee and Zemansky, EOS, v. 80, no. 46, p. F397, 1999) at this site, using multilevel slug tests. The existing 2 inch, fully screened wells are spread out over the site and offer the opportunity for developing a 3-D picture of the hydraulic conductivity distribution. However, it is difficult to develop a system that allows multilevel slug tests to be done accurately and efficiently in a 2 inch well. This is especially true in regions of very high hydraulic conductivity, where the water velocity in the casing will be relatively high. The resistance caused by frictional forces in the equipment must be minimized and a model taking account of these forces must be used. We have developed a system (equipment, software, and technique) for performing multilevel slug tests in 2 inch wells. Some equipment configurations work better than others. The data that we have been able to obtain look promising for delineating the spatial change in hydraulic conductivity over the site. The preliminary data definitely indicate significant changes over the area. With improvements in well installation, such as direct push and other techniques, it might be quite feasible to develop a 3-D picture of hydraulic conductivity over an area using multilevel slug tests in fully screened wells.
New transfer functions for probing 3-D mantle conductivity from ground and sea
NASA Astrophysics Data System (ADS)
Püthe, Christoph; Kuvshinov, Alexey; Olsen, Nils
2014-05-01
The C-response is a conventional transfer function in global electromagnetic induction research and is classically determined from local observations of magnetic variations in the vertical and the horizontal components. Its estimation and interpretation rely on the assumptions that the source of the considered variations is well approximated by a large-scale symmetric (magnetospheric) ring current that can be described by a single spherical harmonic, P10, and that conductivity in the Earth is only a function of depth. However, there is growing evidence for a more complex structure of the magnetospheric source. We investigate the variability of C-responses due to non-P10 contributions to the source. We show that this variability, which we denote as 'source effect' (as opposed to the well-known ocean effect), is significant and persists at all periods. If inverting estimated C-responses for mantle conductivity, this source effect will inevitably be mistaken for conductivity anomalies. To overcome the problem connected with the assumptions for deriving C-responses, we introduce new transfer functions that relate the local vertical component of the magnetic variation to different spherical harmonic coefficients describing the magnetospheric source. The latter are derived from observations of magnetic variations in the horizontal components. The new transfer functions are subsequently estimated with a robust multivariate data analysis tool. By analyzing 16 years of data, collected at the global network of geomagnetic observatories, we demonstrate that the new transfer functions exhibit a significant increase in coherence compared to C-responses, especially at high latitudes. The concept is easily extended to other data types. For example, by relating the voltage variations in abandoned submarine telecommunication cables to spherical harmonic coefficients in the same way as described above, one can define yet another array of transfer functions. In spite of the fact that the newly introduced transfer functions allow for a consistent treatment of a complex spatial structure of the source, the sparse and irregular distribution of geomagnetic observatories and submarine cables impedes a reliable inversion of these data for 3-D mantle conductivity on a global scale. However, in combination with matrix Q-responses estimated from Swarm satellite data, the new transfer functions can be used to probe the 3-D conductivity structure of Earth's mantle.
M. Bahrami ENSC 388 (F09) Steady Conduction Heat Transfer 1 Steady Heat Conduction
Bahrami, Majid
M. Bahrami ENSC 388 (F09) Steady Conduction Heat Transfer 1 Steady Heat Conduction In thermodynamics, we considered the amount of heat transfer as a system the process takes. In heat transfer, we are more concerned about the rate of heat transfer. The basic
NASA Astrophysics Data System (ADS)
López-Ruiz, G.; Bravo-Castillero, J.; Brenner, R.; Cruz, M. E.; Guinovart-Díaz, R.; Pérez-Fernández, L. D.; Rodríguez-Ramos, R.
2015-07-01
Improved variational bounds for the effective conductivity of a matrix-inclusion conductive periodic composite are obtained. The studied composite is macroscopically anisotropic with nonuniform interfacial thermal resistance between isotropic phases. The homogenization theory is applied to a three-dimensional heat conduction problem which is stated in terms of nondimensional parameters. The Biot number is explicitly given in the variational formulation of the local problems and in the related minimization problems. The approach is based on the Lipton-Vernescu variational principles which allow to derive narrower bounds by incorporating more detailed morphological information. The bounds depend on the concentration and the conductivity of each phase, the periodic distribution and the shape of the inclusions, the Biot number and the nonuniform interfacial resistance.
Finite-Difference Algorithm for Simulating 3D Electromagnetic Wavefields in Conductive Media
NASA Astrophysics Data System (ADS)
Aldridge, D. F.; Bartel, L. C.; Knox, H. A.
2013-12-01
Electromagnetic (EM) wavefields are routinely used in geophysical exploration for detection and characterization of subsurface geological formations of economic interest. Recorded EM signals depend strongly on the current conductivity of geologic media. Hence, they are particularly useful for inferring fluid content of saturated porous bodies. In order to enhance understanding of field-recorded data, we are developing a numerical algorithm for simulating three-dimensional (3D) EM wave propagation and diffusion in heterogeneous conductive materials. Maxwell's equations are combined with isotropic constitutive relations to obtain a set of six, coupled, first-order partial differential equations governing the electric and magnetic vectors. An advantage of this system is that it does not contain spatial derivatives of the three medium parameters electric permittivity, magnetic permeability, and current conductivity. Numerical solution methodology consists of explicit, time-domain finite-differencing on a 3D staggered rectangular grid. Temporal and spatial FD operators have order 2 and N, where N is user-selectable. We use an artificially-large electric permittivity to maximize the FD timestep, and thus reduce execution time. For the low frequencies typically used in geophysical exploration, accuracy is not unduly compromised. Grid boundary reflections are mitigated via convolutional perfectly matched layers (C-PMLs) imposed at the six grid flanks. A shared-memory-parallel code implementation via OpenMP directives enables rapid algorithm execution on a multi-thread computational platform. Good agreement is obtained in comparisons of numerically-generated data with reference solutions. EM wavefields are sourced via point current density and magnetic dipole vectors. Spatially-extended inductive sources (current carrying wire loops) are under development. We are particularly interested in accurate representation of high-conductivity sub-grid-scale features that are common in industrial environments (borehole casing, pipes, railroad tracks). Present efforts are oriented toward calculating the EM responses of these objects via a First Born Approximation approach. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Information filtering via weighted heat conduction algorithm
Jian-Guo Liu; Qiang Guo; Yi-Cheng Zhang
2011-01-01
In this paper, by taking into account effects of the user and object correlations on a heat conduction (HC) algorithm, a weighted heat conduction (WHC) algorithm is presented. We argue that the edge weight of the user–object bipartite network should be embedded into the HC algorithm to measure the object similarity. The numerical results indicate that both the accuracy and
NASA Astrophysics Data System (ADS)
Harlander, U.; Wright, G. B.; Egbers, C.
2012-04-01
In the earth's atmosphere baroclinic instability is responsible for the heat and momentum transport from low to high latitudes. In the fifties, Raymond Hide used a rather simple laboratory experiment to study such vortices in the lab. The experiment is comprised by a cooled inner and heated outer cylinder mounted on a rotating platform, which mimics the heated tropical and cooled polar regions of the earth's atmosphere. The experiment shows rich dynamics that have been studied by varying the radial temperature difference and the rate of annulus revolution. At the Brandenburg University of Technology (BTU) Cottbus the differentially heated rotating annulus is a reference experiment of the DFG priority program 'MetStröm'. The 3D structure of the annulus flow field has been numerically simulated but, to our knowledge, has not been measured in the laboratory. In the present paper we use novel interpolation techniques to reconstruct the 3D annulus flow field from synchronous Particle Image Velocimetry (PIV) and Infrared Thermography (IRT) measurements. The PIV system is used to measure the horizontal velocity components at 40, 60, 80, 100, and 120 mm above the bottom. The uppermost level is thus 15 mm below the fluid's surface. The surface temperature is simultaneously measured by an infrared (IR) camera. The PIV and infrared cameras have been mounted above the annulus and they co-rotate with the annulus. From the PIV observations alone a coherent 3D picture of the flow cannot be constructed since the PIV measurements have been taken at different instants of time. Therefore a corresponding IR image has been recorded for each PIV measurement. These IR images can be used to reconstruct the correct phase of the measured velocity fields. Each IR and PIV image for which t>0 is rotated back to the position at t=0. Then all surface waves have the same phase. In contrast, the PIV velocity fields generally have different phases since they have been taken at different vertical levels. From these rotated fields, a 3D flow field can be reconstructed that is an approximation to the true 3D flow. The PIV measurements of the horizontal velocity fields do not line up on a nice grid. We therefore use a mesh-free reconstruction method based on radial basis functions (RBFs). Additionally, we employ a filtering strategy for dealing with the noise in the measured velocity fields.
ALE3D Simulation of Heating and Violence in a Fast Cookoff Experiment with LX-10
McClelland, M A; Maienschein, J L; Howard, W M; Nichols, A L; deHaven, M R; Strand, O T
2006-06-26
We performed a computational and experimental analysis of fast cookoff of LX-10 (94.7% HMX, 5.3% Viton A) confined in a 2 kbar steel tube with reinforced end caps. A Scaled-Thermal-Explosion-eXperiment (STEX) was completed in which three radiant heaters were used to heat the vessel until ignition, resulting in a moderately violent explosion after 20.4 minutes. Thermocouple measurements showed tube temperatures as high as 340 C at ignition and LX-10 surface temperatures as high as 279 C, which is near the melting point of HMX. Three micro-power radar systems were used to measure mean fragment velocities of 840 m/s. Photonics Doppler Velocimeters (PDVs) showed a rapid acceleration of fragments over 80 {micro}s. A one-dimensional ALE3D cookoff model at the vessel midplane was used to simulate the heating, thermal expansion, LX-10 decomposition composition, and closing of the gap between the HE (High Explosive) and vessel wall. Although the ALE3D simulation terminated before ignition, the model provided a good representation of heat transfer through the case and across the dynamic gap to the explosive.
NASA Astrophysics Data System (ADS)
Bellmann, M. P.; Lindholm, D.; Sørheim, E. A.; Mortensen, D.; M'Hamdi, M.
2013-11-01
A heat transfer model of a semi-industrial induction furnace has been build, using a 3D finite element model in order to analyze the entire process cycle, based on the heating, melting, solidification and cooling phases of a multi-crystalline square ingot. In the modeling of the entire process, heat transfer phenomena such as radiation and conduction in the furnace have been taken into account. A PID (Proportional Integral Differential) control algorithm has been implemented into the model for adjusting the power input in the heaters, so that the heater temperature is kept at prescribed time-varying values. The furnace model and the PID control algorithm are validated by temperature measurements from a crystallization experiment. Subsequently the validated model was used to investigate the melt flow field and its impact on the solid-liquid interface shape.
NASA Astrophysics Data System (ADS)
Courbet, C.; DICK, P.; Lefevre, M.; Wittebroodt, C.; Matray, J.; Barnichon, J.
2013-12-01
In the framework of its research on the deep disposal of radioactive waste in shale formations, the French Institute for Radiological Protection and Nuclear Safety (IRSN) has developed a large array of in situ programs concerning the confining properties of shales in their underground research laboratory at Tournemire (SW France). One of its aims is to evaluate the occurrence and processes controlling radionuclide migration through the host rock, from the disposal system to the biosphere. Past research programs carried out at Tournemire covered mechanical, hydro-mechanical and physico-chemical properties of the Tournemire shale as well as water chemistry and long-term behaviour of the host rock. Studies show that fluid circulations in the undisturbed matrix are very slow (hydraulic conductivity of 10-14 to 10-15 m.s-1). However, recent work related to the occurrence of small scale fractures and clay-rich fault gouges indicate that fluid circulations may have been significantly modified in the vicinity of such features. To assess the transport properties associated with such faults, IRSN designed a series of in situ and laboratory experiments to evaluate the contribution of both diffusive and advective process on water and solute flux through a clay-rich fault zone (fault core and damaged zone) and in an undisturbed shale formation. As part of these studies, Modular Mini-Packer System (MMPS) hydraulic testing was conducted in multiple boreholes to characterize hydraulic conductivities within the formation. Pressure data collected during the hydraulic tests were analyzed using the nSIGHTS (n-dimensional Statistical Inverse Graphical Hydraulic Test Simulator) code to estimate hydraulic conductivity and formation pressures of the tested intervals. Preliminary results indicate hydraulic conductivities of 5.10-12 m.s-1 in the fault core and damaged zone and 10-14 m.s-1 in the adjacent undisturbed shale. Furthermore, when compared with neutron porosity data from borehole logging, porosity varies by a factor of 2.5 whilst hydraulic conductivity varies by 2 to 3 orders of magnitude. In addition, a 3D numerical reconstruction of the internal structure of the fault zone inferred from borehole imagery has been built to estimate the permeability tensor variations. First results indicate that hydraulic conductivity values calculated for this structure are 2 to 3 orders of magnitude above those measured in situ. Such high values are due to the imaging method that only takes in to account open fractures of simple geometry (sine waves). Even though improvements are needed to handle more complex geometry, outcomes are promising as the fault damaged zone clearly appears as the highest permeability zone, where stress analysis show that the actual stress state may favor tensile reopening of fractures. Using shale samples cored from the different internal structures of the fault zone, we aim now to characterize the advection and diffusion using laboratory petrophysical tests combined with radial and through-diffusion experiments.
Raj, Kovummal Govind; Joy, Pattayil Alias
2015-06-28
The changes in the electrical transport properties and mechanism of conduction in disordered carbon, with the extent of graphitization, are studied and discussed. With heat treatment induced graphitic ordering, the electrical properties are considerably modified, inducing a crossover from strong localization to weak localization behavior. Accordingly, the conduction mechanism is modified from the 3-dimensional variable range hopping (3D VRH) model to the 2-dimensional weak localization (2D WL) model. Results show that carrier-carrier and carrier-phonon interactions play major roles in developing the weak localization behavior with the extent of graphitization. PMID:26035227
3D finite element model of RF heating: novel nonablative cutaneous therapy
NASA Astrophysics Data System (ADS)
Pham, Linda; Pope, Karl A.
2003-06-01
This study presents a finite element model of a non-ablative RF tissue heating system for dermatological applications. The Thermage ThermaCool TC System consists of a capacitively coupled treatment tip, handpiece, RF generator, and cryogen delivery system. Various electrode geometries were created to generate uniform thermal profiles at specific depths in the tissue. The optimal thermal treatment depth for a clinical indication is influenced by factors such as tissue thickness for a given anatomical location, the desired target for heating in that tissue, and anesthesia factors. Electrodes of ¼, 1, and 1½cm2 area were evaluated for depth of treatment. A 3D multi-physics finite element model was developed to simulate RF heating in tissue. The program coupled electrical and thermal models to predict the electric field produced and the consequent heating. The electrical portion of the model was verified using an electric field mapping system. The thermal section of the model was confirmed via thermocouple measurements for cooling and infrared imaging measurements for RF heating. The FEM model produced electrical and thermal predictions that were verified with experimental measurements. The finite element model shows significant potential as a predictive R&D tool to assist in RF electrode design and reduce product development time.
Information filtering via biased heat conduction
NASA Astrophysics Data System (ADS)
Liu, Jian-Guo; Zhou, Tao; Guo, Qiang
2011-09-01
The process of heat conduction has recently found application in personalized recommendation [Zhou , Proc. Natl. Acad. Sci. USA PNASA60027-842410.1073/pnas.1000488107107, 4511 (2010)], which is of high diversity but low accuracy. By decreasing the temperatures of small-degree objects, we present an improved algorithm, called biased heat conduction, which could simultaneously enhance the accuracy and diversity. Extensive experimental analyses demonstrate that the accuracy on MovieLens, Netflix, and Delicious datasets could be improved by 43.5%, 55.4% and 19.2%, respectively, compared with the standard heat conduction algorithm and also the diversity is increased or approximately unchanged. Further statistical analyses suggest that the present algorithm could simultaneously identify users' mainstream and special tastes, resulting in better performance than the standard heat conduction algorithm. This work provides a creditable way for highly efficient information filtering.
Information filtering via biased heat conduction.
Liu, Jian-Guo; Zhou, Tao; Guo, Qiang
2011-09-01
The process of heat conduction has recently found application in personalized recommendation [Zhou et al., Proc. Natl. Acad. Sci. USA 107, 4511 (2010)], which is of high diversity but low accuracy. By decreasing the temperatures of small-degree objects, we present an improved algorithm, called biased heat conduction, which could simultaneously enhance the accuracy and diversity. Extensive experimental analyses demonstrate that the accuracy on MovieLens, Netflix, and Delicious datasets could be improved by 43.5%, 55.4% and 19.2%, respectively, compared with the standard heat conduction algorithm and also the diversity is increased or approximately unchanged. Further statistical analyses suggest that the present algorithm could simultaneously identify users' mainstream and special tastes, resulting in better performance than the standard heat conduction algorithm. This work provides a creditable way for highly efficient information filtering. PMID:22060533
A boundary element method with surface conductive absorbers for 3-D analysis of nanophotonics
Zhang, Lei, Ph. D. Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
2010-01-01
Fast surface integral equation (SIE) solvers seem to be ideal approaches for simulating 3-D nanophotonic devices, as these devices generate fields both in an interior channel and in the infinite exterior domain. However, ...
Conductive-bridging random access memory: challenges and opportunity for 3D architecture.
Jana, Debanjan; Roy, Sourav; Panja, Rajeswar; Dutta, Mrinmoy; Rahaman, Sheikh Ziaur; Mahapatra, Rajat; Maikap, Siddheswar
2015-01-01
The performances of conductive-bridging random access memory (CBRAM) have been reviewed for different switching materials such as chalcogenides, oxides, and bilayers in different structures. The structure consists of an inert electrode and one oxidized electrode of copper (Cu) or silver (Ag). The switching mechanism is the formation/dissolution of a metallic filament in the switching materials under external bias. However, the growth dynamics of the metallic filament in different switching materials are still debated. All CBRAM devices are switching under an operation current of 0.1 ?A to 1 mA, and an operation voltage of ±2 V is also needed. The device can reach a low current of 5 pA; however, current compliance-dependent reliability is a challenging issue. Although a chalcogenide-based material has opportunity to have better endurance as compared to an oxide-based material, data retention and integration with the complementary metal-oxide-semiconductor (CMOS) process are also issues. Devices with bilayer switching materials show better resistive switching characteristics as compared to those with a single switching layer, especially a program/erase endurance of >10(5) cycles with a high speed of few nanoseconds. Multi-level cell operation is possible, but the stability of the high resistance state is also an important reliability concern. These devices show a good data retention of >10(5) s at >85°C. However, more study is needed to achieve a 10-year guarantee of data retention for non-volatile memory application. The crossbar memory is benefited for high density with low power operation. Some CBRAM devices as a chip have been reported for proto-typical production. This review shows that operation current should be optimized for few microamperes with a maintaining speed of few nanoseconds, which will have challenges and also opportunities for three-dimensional (3D) architecture. PMID:25977660
Conductive-bridging random access memory: challenges and opportunity for 3D architecture
NASA Astrophysics Data System (ADS)
Jana, Debanjan; Roy, Sourav; Panja, Rajeswar; Dutta, Mrinmoy; Rahaman, Sheikh Ziaur; Mahapatra, Rajat; Maikap, Siddheswar
2015-04-01
The performances of conductive-bridging random access memory (CBRAM) have been reviewed for different switching materials such as chalcogenides, oxides, and bilayers in different structures. The structure consists of an inert electrode and one oxidized electrode of copper (Cu) or silver (Ag). The switching mechanism is the formation/dissolution of a metallic filament in the switching materials under external bias. However, the growth dynamics of the metallic filament in different switching materials are still debated. All CBRAM devices are switching under an operation current of 0.1 ?A to 1 mA, and an operation voltage of ±2 V is also needed. The device can reach a low current of 5 pA; however, current compliance-dependent reliability is a challenging issue. Although a chalcogenide-based material has opportunity to have better endurance as compared to an oxide-based material, data retention and integration with the complementary metal-oxide-semiconductor (CMOS) process are also issues. Devices with bilayer switching materials show better resistive switching characteristics as compared to those with a single switching layer, especially a program/erase endurance of >105 cycles with a high speed of few nanoseconds. Multi-level cell operation is possible, but the stability of the high resistance state is also an important reliability concern. These devices show a good data retention of >105 s at >85°C. However, more study is needed to achieve a 10-year guarantee of data retention for non-volatile memory application. The crossbar memory is benefited for high density with low power operation. Some CBRAM devices as a chip have been reported for proto-typical production. This review shows that operation current should be optimized for few microamperes with a maintaining speed of few nanoseconds, which will have challenges and also opportunities for three-dimensional (3D) architecture.
NASA Astrophysics Data System (ADS)
Püthe, Christoph; Kuvshinov, Alexey
2014-05-01
We present a novel 3-D frequency-domain inversion scheme to recover 3-D mantle conductivity from satellite magnetic data, for example, provided by the Swarm mission. The scheme is based on the inversion of a new set of electromagnetic transfer functions, which form an array that we denote as matrix Q-response and which relate external (inducing) and internal (induced) coefficients of the spherical harmonic expansion of the time-varying magnetic field of magnetospheric origin. This concept overcomes the problems associated with source determination inherent to recent schemes based on direct inversion of internal coefficients. Matrix Q-responses are estimated from time-series of external and internal coefficients with a newly elaborated multivariate analysis scheme. An inversion algorithm that deals with matrix Q-responses has been developed. In order to make the inversion tractable, we elaborated an adjoint approach to compute the data misfit gradient and parallelized the numerical code with respect to frequencies and elementary sources, which describe the external part of the magnetic field of magnetospheric origin. Both parts of the scheme have been verified with realistic test data. Special attention is given to the issue of correlated noise due to undescribed sources.
North Cascadia heat flux and fluid flow from gas hydrates: Modeling 3-D topographic effects
NASA Astrophysics Data System (ADS)
Li, Hong-lin; He, Tao; Spence, George D.
2014-01-01
The bottom-simulating reflector (BSR) of gas hydrate is well imaged from two perpendicular seismic grids in the region of a large carbonate mound, informally called Cucumber Ridge off Vancouver Island. We use a new method to calculate 3-D heat flow map from the BSR depths, in which we incorporate 3-D topographic corrections after calibrated by the drilling results from nearby (Integrated) Ocean Drilling Program Site 889 and Site U1327. We then estimate the associated fluid flow by relating it to the topographically corrected heat flux anomalies. In the midslope region, a heat flux anomaly of 1 mW/m2 can be associated with an approximate focused fluid flow rate of 0.09 mm/yr. Around Cucumber Ridge, high rates of focused fluid flow were observed at steep slopes with values more than double the average regional diffusive fluid discharge rate of 0.56 mm/yr. As well, in some areas of relatively flat seafloor, the focused fluid flow rates still exceeded 0.5 mm/yr. On the seismic lines the regions of focused fluid flow were commonly associated with seismic blanking zones above the BSR and sometimes with strong reflectors below the BSR, indicating that the faults/fractures provide high-permeability pathways for fluids to carry methane from BSR depths to the seafloor. These high fluid flow regions cover mostly the western portion of our area with gas hydrate concentration estimations of ~6% based on empirical correlations from Hydrate Ridge in south off Oregon, significantly higher than previously recognized values of ~2.5% in the eastern portion determined from Site U1327.
The Conduction of Heat through Cryogenic Regenerative Heat Exchangers
NASA Astrophysics Data System (ADS)
Superczynski, W. F.; Green, G. F.
2006-04-01
The need for improved regenerative cryocooler efficiency may require the replacement of conventional matrices with ducts. The ducts can not be continuous in the direction of temperature gradient when using conventional materials to prevent unacceptable conduction losses. However, this discontinuity creates a complex geometry to model and determine conduction losses. Chesapeake Cryogenics, Inc. has designed, fabricated and tested an apparatus for measuring the heat conduction through regenerative heat exchangers implementing different matrices. Data is presented for stainless steel photo etched disk, phophorus-bronze embossed ribbon coils and screens made of both stainless steel and phosphorus-bronze. The heat conduction was measured with the regenerators evacuated and pressurized with helium gas. In this test apparatus, helium gas presence increased the heat leak significantly. A description of the test apparatus, instrumentation, experimental methods and data analysis are presented.
The effect of anisotropic heat transport on magnetic islands in 3-D configurations
Schlutt, M. G.; Hegna, C. C.
2012-08-15
An analytic theory of nonlinear pressure-induced magnetic island formation using a boundary layer analysis is presented. This theory extends previous work by including the effects of finite parallel heat transport and is applicable to general three dimensional magnetic configurations. In this work, particular attention is paid to the role of finite parallel heat conduction in the context of pressure-induced island physics. It is found that localized currents that require self-consistent deformation of the pressure profile, such as resistive interchange and bootstrap currents, are attenuated by finite parallel heat conduction when the magnetic islands are sufficiently small. However, these anisotropic effects do not change saturated island widths caused by Pfirsch-Schlueter current effects. Implications for finite pressure-induced island healing are discussed.
Anisotropic heat transport in integrable and chaotic 3-D magnetic fields
Del-Castillo-Negrete, Diego B [ORNL] [ORNL; Blazevski, D. [University of Texas, Austin] [University of Texas, Austin; Chacon, Luis [ORNL] [ORNL
2012-01-01
A study of anisotropic heat transport in 3-D chaotic magnetic fields is presented. The approach is based on the recently proposed Lagrangian-Green s function (LG) method in Ref. [1] that allows an efficient and accurate integration of the parallel transport equation applicable to general magnetic fields with local or non-local parallel flux closures. We focus on reversed shear magnetic field configurations known to exhibit separatrix reconnection and shearless transport barriers. The role of reconnection and magnetic field line chaos on temperature transport is studied. Numerical results are presented on the anomalous relaxation of radial temperature gradients in the presence of shearless Cantori partial barri- ers. Also, numerical evidence of non-local effective radial temperature transport in chaotic fields is presented. Going beyond purely parallel transport, the LG method is generalized to include finite perpendicular diffusivity, and the problem of temperature flattening inside a magnetic island is studied.
Jong Young Kim; Jung Kyu Park; Sei Kwang Hahn; Tai Hun Kwon; Dong-Woo Cho
2009-01-01
The flow behavior model for 3D scaffold fabrication in the polymer deposition process by the heating method was developed for enhanced efficiency of the deposition process. The analysis of the polymer flow property is very important in the fabrication process of precise micro-structures such as scaffolds. In this study, a deposition model considering fluid mechanics and heat transfer phenomena was
Compact pulsed laser having improved heat conductance
NASA Technical Reports Server (NTRS)
Yang, L. C. (inventor)
1977-01-01
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.
NASA Astrophysics Data System (ADS)
Jalali, A.; Hulsen, M. A.; Norouzi, M.; Kayhani, M. H.
2013-05-01
This paper presents a numerical simulation of the developing flow and heat transfer of a viscoelastic fluid in a rectangular duct. In fully developed flow of a viscoelastic fluid in a non-circular duct, secondary flows normal to the flow direction are expected to enhance the rate of heat and mass transfer. On the other hand, properties such as viscosity, thermal conductivity, specific heat and relaxation time of the fluid are a function of temperature. Therefore, we developed a numerical model which solves the flow and energy equation simultaneously in three dimensional form. We included several equations of state to model the temperature dependency of the fluid parameters. The current paper is one of the first studies which present a 3D numerical simulation for developing viscoelastic duct flow that takes the dependency of flow parameters to the temperature into account. The rheological constitutive equation of the fluid is a common form of the Phan-Thien Tanner (PTT) model, which embodies both influences of elasticity and shear thinning in viscosity. The governing equations are discretized using the FTCS finite difference method on a staggered mesh. The marker-and-cell method is also employed to allocate the parameters on the staggered mesh, and static pressure is calculated using the artificial compressibility approach during the numerical simulation. In addition to report the results of flow and heat transfer in the developing region, the effect of some dimensionless parameters on the flow and heat transfer has also been investigated. The results are in a good agreement with the results reported by others in this field.
Single-mode heat conduction by photons.
Meschke, Matthias; Guichard, Wiebke; Pekola, Jukka P
2006-11-01
The thermal conductance of a single channel is limited by its unique quantum value G(Q), as was shown theoretically in 1983. This result closely resembles the well-known quantization of electrical conductance in ballistic one-dimensional conductors. Interestingly, all particles-irrespective of whether they are bosons or fermions-have the same quantized thermal conductance when they are confined within dimensions that are small compared to their characteristic wavelength. The single-mode heat conductance is particularly relevant in nanostructures. Quantized heat transport through submicrometre dielectric wires by phonons has been observed, and it has been predicted to influence cooling of electrons in metals at very low temperatures due to electromagnetic radiation. Here we report experimental results showing that at low temperatures heat is transferred by photon radiation, when electron-phonon as well as normal electronic heat conduction is frozen out. We study heat exchange between two small pieces of normal metal, connected to each other only via superconducting leads, which are ideal insulators against conventional thermal conduction. Each superconducting lead is interrupted by a switch of electromagnetic (photon) radiation in the form of a DC-SQUID (a superconducting loop with two Josephson tunnel junctions). We find that the thermal conductance between the two metal islands mediated by photons indeed approaches the expected quantum limit of G(Q) at low temperatures. Our observation has practical implications-for example, for the performance and design of ultra-sensitive bolometers (detectors of far-infrared light) and electronic micro-refrigerators, whose operation is largely dependent on weak thermal coupling between the device and its environment. PMID:17093446
NASA Astrophysics Data System (ADS)
Dvoynishnikov, Sergey
2014-08-01
A method for steam turbines 3D geometry optical control for effective heat power equipment quality improvement is proposed. It is shown that technical characteristics of the developed optical phase triangulation method for precision contactless geometry diagnostics of steam turbines meet modern requirements to 3D geometry measuring instruments and are perspective for further development. It is shown that used phase step method provides measurement error less than 0.024% of measurement range.
Conductivity of rf-heated plasma
Fisch, N.J.
1984-05-01
The electron velocity distribution of rf-heated plasma may be so far from Maxwellian that Spitzer conductivity no longer holds. A new conductivity for such plasmas is derived and the result can be put in a remarkably general form. The new expression should be of great practical value in examining schemes for current ramp-up in tokamaks by means of lower-hybrid or other waves.
Smoothed particle hydrodynamics: Applications to heat conduction
J. H. Jeong; M. S. Jhon; J. S. Halow; J. van Osdol
2003-01-01
In this paper, we modify the numerical steps involved in a smoothed particle hydrodynamics (SPH) simulation. Specifically, the second order partial differential equation (PDE) is decomposed into two first order PDEs. Using the ghost particle method, consistent estimation of near-boundary corrections for system variables is also accomplished. Here, we focus on SPH equations for heat conduction to verify our numerical
Extremal structures of multiphase heat conducting composites
Cherkaev, Andrej
Extremal structures of multiphase heat conducting composites A.V. Cherkaev \\Lambda L.V. Gibiansky y April 19, 1995 Abstract In this paper we construct microstructures of multiphase composites with un be easily genÂ eralized for the threeÂdimensional composites with arbitrary number of phases. 1 Introduction
Heat conductivity of a pion gas
Antonio Dobado Gonzalez; Felipe J. Llanes-Estrada; Juan M. Torres Rincon
2007-02-13
We evaluate the heat conductivity of a dilute pion gas employing the Uehling-Uehlenbeck equation and experimental phase-shifts parameterized by means of the SU(2) Inverse Amplitude Method. Our results are consistent with previous evaluations. For comparison we also give results for an (unphysical) hard sphere gas.
NASA Astrophysics Data System (ADS)
Guerreiro, Nuno; Haberreiter, Margit; Hansteen, Viggo; Schmutz, Werner
2015-04-01
We study the properties of the small-scale heating events in the solar atmosphere in the nano flare and micro flare energy scale using 3D MHD simulations. We put forward a method to identify and track the heating events in time to study their life times, frequency distributions and spectral signatures. These results aim to better understand the observations from future space missions such as the EUI and SPICE instruments onboard Solar Orbiter and improve our knowledge of the role of small-scale heating events in the heating of the corona.
NASA Astrophysics Data System (ADS)
Malesa, M.; Kujawi?ska, M.; Malowany, K.; Siwek, B.
2013-04-01
In the paper we present implementation of 3D DIC method for in-situ diagnostic measurements of expansion bellows in heating chambers. The simultaneous measurements of a supply and a return pipeline were carried out in a heating chamber in Warsaw at the peak of the heating season in cooperation with Dalkia Warszawa. Results of the measurements enabled assessment of the risk of failure of expansion bellows. In-situ measurements were preceded by feasibility tests carried out in the Institute of Heat Engineering of Warsaw University of Technology. Potential implementations and a direction of future works are discussed in conclusions.
Interfacial Heat Conduction in Modern Semiconductor Nanostructures
NASA Astrophysics Data System (ADS)
Goodson, Kenneth
2015-03-01
Heat conduction through interfaces in electronic nanostructures grows more important with the dimensional scaling trends throughout the semiconductor industry. The complexity of interfacial transport has increased owing to frequent examples of severe lattice mismatch and strain, boundaries with nanoscale non-planar features and, in some cases, the critical role of electron-phonon interactions. This talk will describe measurements and modeling of phonon heat conduction through interfaces in some of the latest semiconductor nanotechnologies and feature a range of material combinations. Examples include GaN-diamond and silicon-diamond composites, chalcogenide-metal multilayers, metal-semiconductor nanolayer stacks, and nonplanar interfaces in modern nanotransistors and interconnect structures. Applications range from conventional CMOS electronics and phase change memory to quantum cascade lasers and RF amplifiers for satellites.
Sengupta, Parijat; Bellotti, Enrico
2015-10-14
The zero gap surface states of a 3D-topological insulator host highly mobile Dirac fermions with spin locked to the momentum. The high mobility attributed to the absence of back scattering is reduced in the presence of impurities on the surface. In particular, we discuss and compare scattering times for localised impurities on the surface, scattering between states of opposite helicity located on different surfaces coupled through a hybridisation potential and the role of magnetic impurities. Magnetic impurities give rise to an additional spin suppression factor. The role of warped bands and their influence on topological factors that can enhance the overall surface mobility is examined. Finally, employing a linearised Boltzmann equation approach, surface conductivity calculations for Dirac fermions in a 3D TI is outlined. PMID:26402336
The optical conductivity of quasicrystals: evidence of a Weyl semimetal with 3D Dirac spectrum
NASA Astrophysics Data System (ADS)
Timusk, Thomas; Carbotte, Jules; Homes, Christopher; Basov, Dimitri; Sharapov, Sergei
2013-03-01
The optical conductivity of quasicrystals is characterized by an absence of the Drude peak and a conductivity that rises linearly over a wide range of frequencies. The absence of the Drude peak has been attributed to a pseudogap at the Fermi surface but a detailed explanation of the linear behavior has not been found. This unusual behavior is seen in all icosahedral quasicrystal families and their periodic approximants. A simple model that assumes that the entire Fermi surface is gapped, with the exception at a finite set of Dirac points, fits the data. There is no evidence of a semiconducting gap in any of the materials suggesting that the massless Dirac spectrum is protected by topology leading to a Weyl semimetal. The model gives rise to a linear conductivity with only one parameter, the Fermi velocity. In accord with this picture decagonal quasicrystals should have a frequency independent conductivity, without a Drude peak. This is in accord with the experimental data as well.
A phase-field method for 3D simulation of two-phase heat transfer , H. Babaee a
Dong, Suchuan "Steven"
A phase-field method for 3D simulation of two-phase heat transfer X. Zheng a , H. Babaee a , S are imposed on either side of this surface. For numerical simulation of two-phase flow systems with sharp Particle Hydrodynamics (SPH) has also been successfully used in modeling two-phase flow system. The SPH
NASA Astrophysics Data System (ADS)
Gasch, Caley K.; Hengl, Tomislav; Gräler, Benedikt; Meyer, Hanna; Magney, Troy; Brown, David J.
2015-04-01
Dynamic soil data collected using automated sensor networks can facilitate our understanding of soil processes, but highly dimensional data may be difficult to analyze in a manner that incorporates correlation in properties through 3-dimensions and time (3D+T). We demonstrate two approaches to making continuous predictions of dynamic soil properties from fixed point observations. For this analysis, we used the Cook Farm data set, which includes hourly measurements of soil volumetric water content, temperature, and electrical conductivity at 42 points and five depths, collected over five years. We compare performance of two modeling frameworks. In the first framework we used random forest algorithms to fit a 3D+T regression model to make predictions of all three soil variables from 2- and 3-dimensional, temporal, and spatio-temporal covariates. In the second framework we developed a 3D+T kriging model after detrending the observations for depth-dependent seasonal effects. The results show that both models accurately predicted soil temperature, but the kriging model outperformed the regression model according to cross-validation; it explained 37%, 96%, and 16% of the variability in water content, temperature, and electrical conductivity respectively versus 34%, 93%, and 4% explained by the random forest model. The full random forest regression model had high goodness-of-fit for all variables, which was reduced in cross-validation. Temporal model components (i.e. day of the year) explained most of the variability in observations. The seamless predictions of 3D+T data produced from this analysis can assist in understanding soil processes and how they change through a season, under different land management scenarios, and how they relate to other environmental processes.
Equilibrium molecular dynamics study of heat conduction in octane
Wang, Yi Jenny
2015-01-01
Fluids are important components in heat transfer systems. Understanding heat conduction in liquids at the atomic level would allow better design of liquids with specific heat transfer properties. However, heat transfer in ...
Intermittent Dissipation and Heating in 3D Kinetic Plasma Turbulence W. H. Matthaeus,1
Shay, Michael
of reduced dimensionality models, reduced physics models, or very small kinetic scale systems [4; published 30 April 2015) High resolution, fully kinetic, three dimensional (3D) simulation of collisionless such a complete 3D kinetic model. An important feature of plasma turbulence found in some reduced kinetic
NASA Astrophysics Data System (ADS)
Semenov, Alexey; Kuvshinov, Alexey
2012-12-01
The global 3-D electrical conductivity distribution in the mantle (in the depth range between 400 and 1600 km) is imaged by inverting C-responses estimated on a global net of geomagnetic observatories. Very long time-series (up to 51 years; 1957-2007) of hourly means of three components of the geomagnetic field from 281 geomagnetic observatories are collected and analysed. Special attention is given to data processing in order to obtain unbiased C-responses with trustworthy estimates of experimental errors in the period range from 2.9 to 104.2 d. After careful inspection of the obtained C-responses the data from 119 observatories are chosen for the further analysis. Squared coherency is used as a main quality indicator to detect (and then to exclude from consideration) observatories with a large noise-to-signal ratio. During this analysis we found that—along with the C-responses from high-latitude observatories (geomagnetic latitudes higher than 58°)—the C-responses from all low-latitude observatories (geomagnetic latitudes below 11°) also have very low squared coherencies, and thus cannot be used for global induction studies. We found that the C-responses from the selected 119 mid-latitude observatories show a huge variability both in real and imaginary parts, and we investigated to what extent the ocean effect can explain such a scatter. By performing the systematic model calculations we conclude that: (1) the variability due to the ocean effect is substantial, especially at shorter periods, and it is seen for periods up to 40 d or so; (2) the imaginary part of the C-responses is to a larger extent influenced by the oceans; (3) two types of anomalous C-response behaviour associated with the ocean effect can be distinguished; (4) to accurately reproduce the ocean effect a lateral resolution of 1°× 1° of the conductance distribution is needed, and (5) the ocean effect alone does not explain the whole variability of the observed C-responses. We also detected that part of the variability in the real part of the C-responses is due to the auroral effect. In addition we discovered that the auroral effect in the C-responses reveals strong longitudinal variability, at least in the Northern Hemisphere. Europe appears to be the region with smallest degree of distortion compared with North America and northern Asia. We found that the imaginary part of the C-responses is weakly affected by the auroral source, thus confirming the fact that in the considered period range the electromagnetic (EM) induction from the auroral electrojet is small. Assuming weak dependence of the auroral signals on the Earth's conductivity at considered periods, and longitudinal variability of the auroral effect, we developed a scheme to correct the experimental C-responses for this effect. With these developments and findings in mind we performed a number of regularized 3-D inversions of our experimental data in order to detect robust features in the recovered 3-D conductivity images. Although differing in details, all our 3-D inversions reveal a substantial level of lateral heterogeneity in the mantle at the depths between 410 and 1600 km. Conductivity values vary laterally by more than one order of magnitude between resistive and conductive regions. The maximum lateral variations of the conductivity have been detected in the layer at depths between 670 and 900 km. By comparing our global 3-D results with the results of independent global and semi-global 3-D conductivity studies, we conclude that 3-D conductivity mantle models produced so far are preliminary as different groups obtain disparate results, thus complicating quantitative comparison with seismic tomography or/and geodynamic models. In spite of this, our 3-D EM study and most other 3-D EM studies reveal at least two robust features: reduced conductivity beneath southern Europe and northern Africa, and enhanced conductivity in northeastern China.
Albedo and heat transport in 3-D model simulations of the early Archean climate
NASA Astrophysics Data System (ADS)
Kienert, H.; Feulner, G.; Petoukhov, V.
2013-08-01
At the beginning of the Archean eon (ca. 3.8 billion years ago), the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun paradox" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-D model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. In order to do so, we have appropriately modified an intermediate complexity climate model that couples a statistical-dynamical atmosphere model (involving parameterizations of the dynamics) to an ocean general circulation model and a thermodynamic-dynamic sea-ice model. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth"). We find a reduction in meridional heat transport compared to today, which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterization of the ice-albedo feedback for 1-D model simulations of the early Archean and thus the faint young Sun problem.
Brosten, T.R.; Day-Lewis, F. D.; Schultz, G.M.; Curtis, G.P.; Lane, J.W.
2011-01-01
Electromagnetic induction (EMI) instruments provide rapid, noninvasive, and spatially dense data for characterization of soil and groundwater properties. Data from multi-frequency EMI tools can be inverted to provide quantitative electrical conductivity estimates as a function of depth. In this study, multi-frequency EMI data collected across an abandoned uranium mill site near Naturita, Colorado, USA, are inverted to produce vertical distribution of electrical conductivity (EC) across the site. The relation between measured apparent electrical conductivity (ECa) and hydraulic conductivity (K) is weak (correlation coefficient of 0.20), whereas the correlation between the depth dependent EC obtained from the inversions, and K is sufficiently strong to be used for hydrologic estimation (correlation coefficient of -0.62). Depth-specific EC values were correlated with co-located K measurements to develop a site-specific ln(EC)-ln(K) relation. This petrophysical relation was applied to produce a spatially detailed map of K across the study area. A synthetic example based on ECa values at the site was used to assess model resolution and correlation loss given variations in depth and/or measurement error. Results from synthetic modeling indicate that optimum correlation with K occurs at ~0.5m followed by a gradual correlation loss of 90% at 2.3m. These results are consistent with an analysis of depth of investigation (DOI) given the range of frequencies, transmitter-receiver separation, and measurement errors for the field data. DOIs were estimated at 2.0??0.5m depending on the soil conductivities. A 4-layer model, with varying thicknesses, was used to invert the ECa to maximize available information within the aquifer region for improved correlations with K. Results show improved correlation between K and the corresponding inverted EC at similar depths, underscoring the importance of inversion in using multi-frequency EMI data for hydrologic estimation. ?? 2011.
A fast technique applied to the analysis of Resistive Wall Modes with 3D conducting structures
Rubinacci, Guglielmo [Ass. EURATOM/ENEA/CREATE, DIEL, Universita degli Studi di Napoli, Federico II (Italy); Ventre, Salvatore [Ass. EURATOM/ENEA/CREATE, DAEIMI, Universita degli Studi di Cassino, Via Di Biasio 43, 03043 Cassino (Italy); Villone, Fabio [Ass. EURATOM/ENEA/CREATE, DAEIMI, Universita degli Studi di Cassino, Via Di Biasio 43, 03043 Cassino (Italy)], E-mail: villone@unicas.it; Liu, Yueqiang [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)
2009-03-20
This paper illustrates the development of a 'fast' technique for the analysis of Resistive Wall Modes (RWMs) in fusion devices with three-dimensional conducting structures, by means of the recently developed CarMa code. Thanks to its peculiar features, the computational cost scales almost linearly with the number of discrete unknowns. Some large scale problems are solved in configurations of interest for the International Thermonuclear Experimental Reactor (ITER)
Al-Alfy, I M; Nabih, M A
2013-03-01
A 3D block of radiogenic heat production was constructed from the subsurface total gamma ray logs of Bahariya Formation, Western Desert, Egypt. The studied rocks possess a range of radiogenic heat production varying from 0.21 ?Wm(-3) to 2.2 ?Wm(-3). Sandstone rocks of Bahariya Formation have higher radiogenic heat production than the average for crustal sedimentary rocks. The high values of density log of Bahariya Formation indicate the presence of iron oxides which contribute the uranium radioactive ores that increase the radiogenic heat production of these rocks. The average radiogenic heat production produced from the study area is calculated as 6.3 kW. The histogram and cumulative frequency analyses illustrate that the range from 0.8 to 1.2 ?Wm(-3) is about 45.3% of radiogenic heat production values. The 3D slicing of the reservoir shows that the southeastern and northeastern parts of the study area have higher radiogenic heat production than other parts. PMID:23291561
Phonon heat conduction in layered anisotropic crystals
NASA Astrophysics Data System (ADS)
Minnich, A. J.
2015-02-01
The thermal properties of anisotropic crystals are of both fundamental and practical interest, but transport phenomena in anisotropic materials such as graphite remain poorly understood because solutions of the Boltzmann equation often assume isotropy. Here, we extend an analytic solution of the transient, frequency-dependent Boltzmann equation to highly anisotropic solids and examine its predictions for graphite. We show that this simple model predicts key results, such as long c -axis phonon mean free paths and a negative correlation of cross-plane thermal conductivity with in-plane group velocity, that were previously observed with computationally expensive molecular-dynamics simulations. Further, using our analytic solution, we demonstrate a method to reconstruct the anisotropic mean free path spectrum of crystals with arbitrary dispersion relations without any prior knowledge of their harmonic or anharmonic properties using observations of quasiballistic heat conduction. These results provide a useful analytic framework to understand thermal transport in anisotropic crystals.
NASA Astrophysics Data System (ADS)
Haddag, B.; Kagnaya, T.; Nouari, M.; Cutard, T.
2013-01-01
Modelling machining operations allows estimating cutting parameters which are difficult to obtain experimentally and in particular, include quantities characterizing the tool-workpiece interface. Temperature is one of these quantities which has an impact on the tool wear, thus its estimation is important. This study deals with a new modelling strategy, based on two steps of calculation, for analysis of the heat transfer into the cutting tool. Unlike the classical methods, considering only the cutting tool with application of an approximate heat flux at the cutting face, estimated from experimental data (e.g. measured cutting force, cutting power), the proposed approach consists of two successive 3D Finite Element calculations and fully independent on the experimental measurements; only the definition of the behaviour of the tool-workpiece couple is necessary. The first one is a 3D thermomechanical modelling of the chip formation process, which allows estimating cutting forces, chip morphology and its flow direction. The second calculation is a 3D thermal modelling of the heat diffusion into the cutting tool, by using an adequate thermal loading (applied uniform or non-uniform heat flux). This loading is estimated using some quantities obtained from the first step calculation, such as contact pressure, sliding velocity distributions and contact area. Comparisons in one hand between experimental data and the first calculation and at the other hand between measured temperatures with embedded thermocouples and the second calculation show a good agreement in terms of cutting forces, chip morphology and cutting temperature.
Information filtering via weighted heat conduction algorithm
NASA Astrophysics Data System (ADS)
Liu, Jian-Guo; Guo, Qiang; Zhang, Yi-Cheng
2011-06-01
In this paper, by taking into account effects of the user and object correlations on a heat conduction (HC) algorithm, a weighted heat conduction (WHC) algorithm is presented. We argue that the edge weight of the user-object bipartite network should be embedded into the HC algorithm to measure the object similarity. The numerical results indicate that both the accuracy and diversity could be improved greatly compared with the standard HC algorithm and the optimal values reached simultaneously. On the Movielens and Netflix datasets, the algorithmic accuracy, measured by the average ranking score, can be improved by 39.7% and 56.1% in the optimal case, respectively, and the diversity could reach 0.9587 and 0.9317 when the recommendation list equals to 5. Further statistical analysis indicates that, in the optimal case, the distributions of the edge weight are changed to the Poisson form, which may be the reason why HC algorithm performance could be improved. This work highlights the effect of edge weight on a personalized recommendation study, which maybe an important factor affecting personalized recommendation performance.
Panchagnula, Mahesh
ME 6010 CONDUCTION HEAT TRANSFER 1998 Catalog Data: ME 6010. Conduction Heat Transfer. Lec. 3. Cr. 3. Conduction in steady, periodic, and transient systems; analytical and numerical techniques. Prerequisite: Math 4510, ME 3710 Textbook: S. Kakac and Y. Yener, Heat Conduction, Taylor & Francis Coordinator
Effects of Heat Treatment on the Tensile Behavior and Damage Evolution of a 3d C/sic Composite
NASA Astrophysics Data System (ADS)
Wang, Yiqiang; Zhang, Litong; Cheng, Laifei
The tensile responses and the associated damage evolutions of a 3D C/SiC composite with and without heat treatment on the fiber preforms were compared. The results show that the composite without heat treatment exhibits a largely non-linear stress-strain behavior up to rupture as well as a lower strength and a strain-to-failure. The damage evolution characterized by acoustic emission indicates the composite failures in the region of matrix cracking multiplication. However, the composite with heat treatment has a larger strength and a strain-to-failure, and the damage evolution indicates that the composite had experienced the region of matrix cracking saturation and then fiber bundle pull-out just prior to final failure. Microstructural observations on the fractured specimens revealed the interfacial bonding between fibers and matrix becomes weaker after heat treatment.
Nonintegrability and the Fourier heat conduction law.
Chen, Shunda; Wang, Jiao; Casati, Giulio; Benenti, Giuliano
2014-09-01
We study in momentum-conserving systems, how nonintegrable dynamics may affect thermal transport properties. As illustrating examples, two one-dimensional (1D) diatomic chains, representing 1D fluids and lattices, respectively, are numerically investigated. In both models, the two species of atoms are assigned two different masses and are arranged alternatively. The systems are nonintegrable unless the mass ratio is one. We find that when the mass ratio is slightly different from one, the heat conductivity may keep significantly unchanged over a certain range of the system size and as the mass ratio tends to one, this range may expand rapidly. These results establish a new connection between the macroscopic thermal transport properties and the underlying dynamics. PMID:25314422
CONRAD: Heat conduction-radiation code, part 1
J. A. Fillo; R. Benenati; J. R. Powell
1976-01-01
A computer code is developed for two-dimensional, nonsteady heat conduction in heterogeneous, anisotropic solids with nonuniform volumetric internal heating. Thermal radiation and arbitrary heat flux boundary conditions are accommodated. Coolant tubes are taken into account by prescribing fluid temperatures and heat transfer coefficients. With regard to coolant tubes, allowance was made for: (1) heat capacitance in the tube wall, coolant
Constructing a model of 3D radiogenic heat production in Ireland
NASA Astrophysics Data System (ADS)
Willmot Noller, N. M.; Daly, J. S.
2012-04-01
Heat production values in the crust and mantle rock inform heat flow density data to provide crucial information about the structure of the Earth's lithosphere. In addition, accurate models of horizontal and vertical distribution of heat production can help to define geothermal exploration targets. Low-enthalpy district scale space heating and Enhanced Geothermal Systems (EGS) using hot, dry rock may provide sustainable energy resources in regions currently perceived as having low geothermal energy potential. Ireland is located within stable lithosphere, unaffected by recent tectonism and volcanism, and has an estimated heat flow range below the measured global continental average. Nevertheless, borehole data indicate that heat production is variable across the island, with anomalously high rates observed, for example, in Cavan, Meath and Antrim. Data coverage is, however, poor. Radioactive isotopic decay generates heat in rock. By using established heat production constants and known concentrations of unstable isotopes of uranium, thorium and potassium, along with rock density values, a heat production rate in ?W m -3 is obtained. With the objective of compiling the first comprehensive database of information about the Irish lithosphere, in three dimensions, the authors present here initial results obtained from published and unpublished whole-rock major and trace element analyses. The presence of systematic trends correlating heat production to properties such as age and lithology are also investigated. Offering insight into the vertical component of heat production distribution, Irish xenoliths emplaced in Lower Carboniferous volcanics are regarded as a reliable proxy for the present-day lower crust. Their geochemical composition gives heat production values that are higher than expected for the depths indicated by their thermobarometric data, suggesting that heat production rates do not simply reduce with depth.
Induction heating of electrically conductive porous asphalt concrete
Quantao Liu; Erik Schlangen; Álvaro García; Martin van de Ven
2010-01-01
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
NASA Astrophysics Data System (ADS)
Meqbel, N. M.; Egbert, G. D.; Kelbert, A.
2011-12-01
Long period (10-20,000 s) magnetotelluric (MT) data are being acquired in a series of temporary arrays deployed across the continental United States through the EMScope component of EarthScope. MT deployments in 2006-2011 have acquired data at 325 sites on an approximately regular grid, with the same nominal spacing as the USArray broadband seismic transportable array (~70 km). The MT sites span a rectangular area from NW Washington to NW Colorado. Here we present results of a 3-D inversion of the full data set. A number of conductive and resistive features appear consistently in the crust and upper mantle in essentially all of a large suite of 3-D inverse solutions. Extensive areas of high conductivity are found in the lower crust (up to a depth of ~ 40 km) beneath the Basin & Range in southeastern Oregon, as imaged by Patro and Egbert (2008). In our new model, this feature extends further to the south and to the east, where it merges with somewhat deeper (uppermost mantle) conductivities beneath the Yellowstone-Snake River Plain. This deeper feature, which extends from Yellowstone to the SW into northeastern Nevada, coincides with the track of the Yellowstone hotspot discussed e.g., in Smith et. al. (2008). The lower crust and the uppermost mantle in the northeastern part of the domain, covering the area from eastern Washington to Montana and continuing south to Wyoming, is generally resistive, with a few localized exceptions. This resistive zone coincides with high velocities discussed and interpreted, e.g., by Yang et. al. (2008) as thick, stable Proterozoic lithosphere. A number of large-scale anomalous features also appear consistently in the upper mantle, at depths of ~ 50 km to 300 km. Most striking is a zone of high resistivity on the western edge of the domain, beneath western Oregon, Washington and northern California in the area occupied by oceanic lithosphere of the Juan de Fuca Plate, which has subducted beneath the relatively more conductive continental mantle. Another striking feature is a layer of relatively high conductivity at an average depth of ~ 170 km extending from the back-arc of the subduction zone to cover almost the entire eastern portion of the model domain. We interpret this layer as the electrical asthenosphere. The inferred asthenosphere shallows significantly to the west, rising to very shallow depths in the back-arc, and appearing to connect into high conductivities in the upper mantle (and lower crust) found beneath the Cascade arc. Shallow back-arc conductivities are highest in Washington state, where conductivities peak near a depth of ~ 70 km and continue dipping to the SE, ultimately connecting into the broader asthenospheric conductive layer. Overall this anomaly is consistent with models suggesting the presence of shallow convecting asthenosphere in the Washington back-arc. Two elliptical "holes", with locally higher resistivities, appear in the broad asthenospheric conductor. Interestingly, one of these encircles the modern Yellowstone caldera, centered near where slow seismic anomalies have been interpreted as evidence for a deep mantle plume (e.g., Yuan and Dueker, 2005). The second, less pronounced asthenospheric "hole" lies beneath the border between Idaho and Nevada.
Modeling a Printed Circuit Heat Exchanger with RELAP5-3D for the Next Generation Nuclear Plant
Not Available
2010-12-01
The main purpose of this report is to design a printed circuit heat exchanger (PCHE) for the Next Generation Nuclear Plant and carry out Loss of Coolant Accident (LOCA) simulation using RELAP5-3D. Helium was chosen as the coolant in the primary and secondary sides of the heat exchanger. The design of PCHE is critical for the LOCA simulations. For purposes of simplicity, a straight channel configuration was assumed. A parallel intermediate heat exchanger configuration was assumed for the RELAP5 model design. The RELAP5 modeling also required the semicircular channels in the heat exchanger to be mapped to rectangular channels. The initial RELAP5 run outputs steady state conditions which were then compared to the heat exchanger performance theory to ensure accurate design is being simulated. An exponential loss of pressure transient was simulated. This LOCA describes a loss of coolant pressure in the primary side over a 20 second time period. The results for the simulation indicate that heat is initially transferred from the primary loop to the secondary loop, but after the loss of pressure occurs, heat transfers from the secondary loop to the primary loop.
NASA Astrophysics Data System (ADS)
Umar Alkali, Adam; Lenggo Ginta, Turnad; Majdi Abdul-Rani, Ahmad
2015-04-01
This paper presents a 3D transient finite element modelling of the workpiece temperature field produced during the travelling heat sourced from oxyacetylene flame. The proposed model was given in terms of preheat-only test applicable during thermally enhanced machining using the oxyacetylene flame as a heat source. The FEA model as well as the experimental test investigated the surface temperature distribution on 316L stainless steel at scanning speed of 100mm/min, 125mm/min 160mm/min, 200mm/min and 250mm/min. The parametric properties of the heat source maintained constant are; lead distance Ld =10mm, focus height Fh=7.5mm, oxygen gas pressure Poxy=15psi and acetylene gas pressure Pacty=25psi. An experimental validation of the temperature field induced on type 316L stainless steel reveal that temperature distribution increases when the travelling speed decreases.
Gustavsen, Arild; Arasteh, Dariush; Jelle, Bjorn Petter; Curcija, Charlie; Kohler, Christian
2008-09-11
While window frames typically represent 20-30% of the overall window area, their impact on the total window heat transfer rates may be much larger. This effect is even greater in low-conductance (highly insulating) windows that incorporate very low-conductance glazing. Developing low-conductance window frames requires accurate simulation tools for product research and development. Based on a literature review and an evaluation of current methods of modeling heat transfer through window frames, we conclude that current procedures specified in ISO standards are not sufficiently adequate for accurately evaluating heat transfer through the low-conductance frames. We conclude that the near-term priorities for improving the modeling of heat transfer through low-conductance frames are: (1) Add 2D view-factor radiation to standard modeling and examine the current practice of averaging surface emissivity based on area weighting and the process of making an equivalent rectangular frame cavity. (2) Asses 3D radiation effects in frame cavities and develop recommendation for inclusion into the design fenestration tools. (3) Assess existing correlations for convection in vertical cavities using CFD. (4) Study 2D and 3D natural convection heat transfer in frame cavities for cavities that are proven to be deficient from item 3 above. Recommend improved correlations or full CFD modeling into ISO standards and design fenestration tools, if appropriate. (5) Study 3D hardware short-circuits and propose methods to ensure that these effects are incorporated into ratings. (6) Study the heat transfer effects of ventilated frame cavities and propose updated correlations.
GENERALIZED HEAT CONDUCTION CODE FOR THE IBM704 COMPUTER
T. B. Fowler; E. R. Volk
1959-01-01
A generalized heat conduction code, GHT, has been anitten as an IBM-704 ; code. This code solves steadystate and\\/or transient heat conduction problems in ; three-dimensional geometry. The method used in GHT is numerical integration of ; the appropriate fixitedifference equations. Boundary temperatures and heat ; generation may be a function of position and\\/or time. Material properties and ; film
Fourth order discretization of anisotropic heat conduction operator
Natalia Krasheninnikova; Luis Chacon
2008-01-01
In magnetized plasmas, heat conduction plays an important role in such processes as energy confinement, turbulence, and a number of instabilities. As a consequence of the presence of a magnetic field, heat transport is strongly anisotropic, with energy flowing preferentially along the magnetic field direction. This in turn results in parallel and perpendicular heat conduction coefficients being separated by orders
Numerical simulation of the heat conduction in electrical cables
R. ?iegis; A. Ilgevi?ius; H. Liess; M. Meil?nas; O. Subo?
2007-01-01
The modelling of the heat conduction in electrical cables is a complex mathematical problem. To get a quantitative description of the thermo?electrical characteristics in the electrical cables, one requires a mathematical model for it. It must involve the different physical phenomena occurring in the electrical cables, i.e. heat conduction, convection and radiation effects, description of heat sources due to current
Signatures of small-scale heating events in EUV spectral lines as modeled from 3D MHD simulations
NASA Astrophysics Data System (ADS)
Guerreiro, Nuno; Haberreiter, Margit; Hansteen, Viggo; Curdt, Werner; Schmutz, Werner
2014-05-01
We aim at understanding the implications of small scale heating events in the solar atmosphere for the variations of the solar spectral irradiance. We present a technique for identification and characterization of these events in 3D simulations of the solar atmosphere. An accurate property determination of these events in time and space will help us to understand how spectral lines, in particular in the EUV, respond to them and which kind of spectral signatures one would expect to find in observations as from SOHO/SUMER and eventually from future space missions, as for example observations by SPICE on board Solar Orbiter.
NASA Astrophysics Data System (ADS)
Brykina, Irina G.
2014-12-01
The three-dimensional hypersonic rarefied gas flow over blunt bodies in the transitional flow regime is studied. The 3D thin viscous shock layer equations are solved by the asymptotic method developed for low Re numbers. The simple analytical solution is obtained for heat transfer and skin friction coefficients as functions of flow parameters and body geometry parameters. The values of these coefficients approach their values in the free molecular flow at unit accommodation coefficient as Reynolds number tends to zero. Comparison with DSMC solutions is carried out.
NASA Astrophysics Data System (ADS)
Vinsard, G.; Dufour, S.; Saatdjian, E.; Mota, J. P. B.
2015-04-01
Chaotic advection can effectively enhance the heat transfer rate between a boundary and fluids with high Prandtl number. These fluids are usually highly viscous and thus turbulent agitation is not a viable solution since the energy required to mix the fluid would be prohibitive. Here, we analyze previously obtained results on chaotic advection and heat transfer in two similar 2-D periodic flows and on their corresponding 3-D periodic flows when an axial velocity component is superposed. The two flows studied are the flow between eccentric rotating cylinders and the flow between confocal ellipses. For both of these flows the analysis is simplified because the Stokes equations can be solved analytically to obtain a closed form solution. For both 2-D periodic flows, we show that chaotic heat transfer is enhanced by the displacement of the saddle point location during one period. Furthermore, the enhancement by chaotic advection in the elliptical geometry is approximately double that obtained in the cylindrical geometry because there are two saddle points instead of one. We also explain why, for high eccentricity ratios, there is no heat transfer enhancement in the cylindrical geometry. When an axial velocity component is added to both of these flows so that they become 3-D, previous work has shown that there is an optimum modulation frequency for which chaotic advection and heat transfer enhancement is a maximum. Here we show that the optimum modulation frequency can be derived from results without an axial flow. We also explain by physical arguments other previously unanswered questions in the published data.
Inverse Heat Conduction Using Measured Back Surface Temperature and Heat Flux
Zhang, Yuwen
Inverse Heat Conduction Using Measured Back Surface Temperature and Heat Flux Jianhua Zhou, Yuwen.2514/1.40549 In the high-energy laser heating of a target, the temperature and heat flux at the heated surface on the measured temperature and/or the heat flux at the accessible (back) surface. In this study, the one
Transient Effects on Heat Conduction in Sliding Bodies
T. C. Kennedy; S. Traiviratana
2004-01-01
The finite-element method is used to study transient heat conduction in two bodies sliding over one another with frictional heat generated at the contact interface. Temperature profiles and heat partition distributions are determined for three cases: two-dimensional conduction between two semi-infinite sliding bodies in contact over an infinite strip, three-dimensional conduction between two semi-infinite sliding bodies in contact over a
3-D TRANSIENT SIMULATION OF A FLAT CAPPILARY HEAT PIPE VIA AN INTERFACE TRACKING METHOD
H. A. Machado
In capillary and micro heat pipes the internal porous media is replaced by a capillary groove, yielding a meniscus formed by the liquid phase. The meniscus height varies along the groove length, from the condenser section to the evaporator section, and the difference between the pressures in each extremity is responsible for pumping the liquid. Such devices have been employed
Numerical study of flow and heat transfer in 3D serpentine channels using colocated grids
Chintada, Sailesh Raju
1998-01-01
Reynolds number (Re=200). Periodically fully developed flow and heat transfer in serpentine channels were salved for different geometry parameters, for different Reynolds numbers and for two different Prandtl numbers ( 0.7 and 7.0 for air and water...
Grant L. Hawkes; James E. OBrien; Greg Tao
2011-01-01
A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in an internally manifolded planar solid oxide electrolysis cell (SOEC) stack. This design is being evaluated at the Idaho National Laboratory for hydrogen production from nuclear power and process heat. Mass, momentum, energy, and species conservation and transport are provided
Scalable 3D bicontinuous fluid networks: polymer heat exchangers toward artificial organs.
Roper, Christopher S; Schubert, Randall C; Maloney, Kevin J; Page, David; Ro, Christopher J; Yang, Sophia S; Jacobsen, Alan J
2015-04-17
A scalable method for fabricating architected materials well-suited for heat and mass exchange is presented. These materials exhibit unprecedented combinations of small hydraulic diameters (13.0-0.09 mm) and large hydraulic-diameter-to-thickness ratios (5.0-30,100). This process expands the range of material architectures achievable starting from photopolymer waveguide lattices or additive manufacturing. PMID:25753365
3D Numerical Simulation of Turbulent Buoyant Flow and Heat Transport in a Curved Open Channel
Technology Transfer Automated Retrieval System (TEKTRAN)
A three-dimensional buoyancy-extended version of kappa-epsilon turbulence model was developed for simulating the turbulent flow and heat transport in a curved open channel. The density- induced buoyant force was included in the model, and the influence of temperature stratification on flow field was...
Control of heat source in a heat conduction problem
NASA Astrophysics Data System (ADS)
Lyashenko, V.; Kobilskaya, E.
2014-11-01
The mathematical model of thermal processes during the heat treatment of a moving axisymmetric environment, for example wire. is considered. The wire is heated by internal constantly or periodically operating heat source. It is presented in the form of initial-boundary value problem for the unsteady heat equation with internal constantly or periodically operating heat source. The purpose of the work is the definition of control parameter of temperature field of a moving area, which is heated by internal heat source. The control parameters are determined by solving a nonlocal problem for the heat equation. The problem of getting an adequate temperature distribution throughout the heating area is considered. Therefore, a problem of heat source control is solved, in particular, control by electric current. Control of the heat source allows to maintain the necessary, from a technological point of view, temperature in the heating area. In this paper, to find additional information about the source of heat. The integral condition is used in the control problem. Integral condition, which is considered in the work, determines the energy balance of the heating zone and connects the desired temperature distribution in the internal points of area with temperatures at the boundaries. Control quality in an extremum formulation of the problem is assessed using the quadratic functional. In function space, from a physical point of view, proposed functional is the absolute difference between the actual emission of energy and absorbed energy in the heating zone. The absorbed energy is calculated by solving of the boundary value problem. Methods of determining the control parameters of temperature field are proposed. The resulting problem is solved by iterative methods. At different physical conditions, numerical calculations are carried out, control parameters of the heat treatment process are obtained.
Theory and design of variable conductance heat pipes
NASA Technical Reports Server (NTRS)
Marcus, B. D.
1972-01-01
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.
NASA Astrophysics Data System (ADS)
Fullea, J.; Muller, M. R.; Jones, A. G.
2012-04-01
Little is known of Ireland's deep, low-enthalpy geothermal resources and the potential for space heating and/or electricity generation based on geothermal energy to displace Ireland's significant reliance on carbon-based fuels. IRETHERM (www.iretherm.ie) is a four-and-a-half year, all-island, academic-government-industry collaborative project, initiated in 2011, with the overarching objective of developing a strategic and holistic understanding of Ireland's geothermal energy potential through integrated modelling of new and existing geophysical and geological data. One of the challenges in searching for deep geothermal resources in the relatively unexplored setting of Ireland lies in identifying those areas most likely to support significantly elevated temperatures at depth. Available borehole data, although sparse and clustered around areas of mineral and hydrocarbon interest, suggest a marked regional increase in surface heat-flow across Ireland, from ~40 mW/m2 in the south to >80 mW/m2 in the north. The origins of both the observed regional heat-flow trend and local temperature anomalies have not been investigated and are not currently understood. Although variations in the structure of the crust and lithosphere have been revealed by a number of active-source seismic and teleseismic experiments, their effects on surface heat-flow have not been modelled. Bulk 3-D variation in crustal heat-production across Ireland, which may contribute significantly to the observed regional and local temperature variations, has also not been determined. We investigate the origins of Ireland's regional heat-flow trend and regional and local temperature variations using the software package LitMod. This software combines petrological and geophysical modelling of the lithosphere and sub-lithospheric upper mantle within an internally consistent thermodynamic-geophysical framework, where all relevant properties are functions of temperature, pressure and chemical composition. The major regional controls on surface heat-flow and crustal temperatures are (a) crustal thickness, (b) crustal heat-production and (c) lithospheric thickness. These unknown geological variables are modelled in LitMod3D against geophysical observations at surface - heat-flow, topography, gravity and geoid data - to identify a crustal and lithospheric-mantle model that satisfies and accounts for all the observations at surface (most importantly in our context, heat-flow). We present a range of 3-D crustal and lithospheric-mantle models that satisfy all observable constraints and account for the regional sources of heat in Ireland. These models provide the basis for isolating local temperature anomalies and for assessing the extent to which local lithological variation in heat-production and thermal conductivity affects the distribution of temperatures in our target depth range of 2000 - 6000 m. Significant, well defined temperature anomalies that emerge from this work will be targeted for further assessment during IRETHERM's planned field program of magnetotelluric and controlled source electromagnetic surveys.
Communications technology satellite - A variable conductance heat pipe application
NASA Technical Reports Server (NTRS)
Mock, P. R.; Marcus, B. D.; Edelman, E. A.
1974-01-01
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.
Schwall, James R.; Karim, Naeem U.; Thakkar, Jivan G.; Taylor, Creed; Schulz, Terry; Wright, Richard F.
2006-07-01
The AP1000 is an 1100 MWe advanced nuclear power plant that uses passive safety features to enhance plant safety and to provide significant and measurable improvements in plant simplification, reliability, investment protection and plant costs. The AP1000 received final design approval from the US-NRC in 2004. The AP1000 design is based on the AP600 design that received final design approval in 1999. Wherever possible, the AP1000 plant configuration and layout was kept the same as AP600 to take advantage of the maturity of the design and to minimize new design efforts. As a result, the two-loop configuration was maintained for AP1000, and the containment vessel diameter was kept the same. It was determined that this significant power up-rate was well within the capability of the passive safety features, and that the safety margins for AP1000 were greater than those of operating PWRs. A key feature of the passive core cooling system is the passive residual heat removal heat exchanger (PRHR HX) that provides decay heat removal for postulated LOCA and non-LOCA events. The PRHR HX is a C-tube heat exchanger located in the in-containment refueling water storage tank (IRWST) above the core promoting natural circulation heat removal between the reactor cooling system and the tank. Component testing was performed for the AP600 PRHR HX to determine the heat transfer characteristics and to develop correlations to be used for the AP1000 safety analysis codes. The data from these tests were confirmed by subsequent integral tests at three separate facilities including the ROSA facility in Japan. Owing to the importance of this component, an independent analysis has been performed using the ATHOS-based computational fluid dynamics computer code PRHRCFD. Two separate models of the PRHR HX and IRWST have been developed representing the ROSA test geometry and the AP1000 plant geometry. Confirmation of the ROSA test results were used to validate PRHRCFD, and the AP1000 plant model was used to confirm the heat removal capacity for the full-sized heat exchanger. The results of these simulations show that the heat removal capacity of the PRHR HX is conservatively represented in the AP1000 safety analyses. (authors)
Comparative evaluation of fuel element heat conduction models
M. Panicker; E. T. Dugan; S. Anghaie
1986-01-01
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
Monte Carlo method of solving heat conduction problems
S. K. Fraley; T. J. Hoffman; P. N. Stevens
1977-01-01
An innovative approach in the use of Monte Carlo to solve heat conduction problems was developed using a transport equation approximation to the heat conduction equation. The method was shown to be applicable to the solution of multimedia problems in complex geometries with no inherent limitations as to the geometric complexity of problems which can be solved. Nuclear radiation transport
Sensitivity analysis of heat conduction for functionally graded materials
Biaosong Chen; Liyong Tong
2004-01-01
A sensitivity analysis is presented for the steady-state and transient heat conduction of functionally graded materials (FGMs). Based on the finite element method, the sensitivity equations of heat conduction are presented by using the direct method and the adjoint method. In the solution of transient problem, the precise time integration (PTI) is employed. The spatial volume fractions of materials of
Nonsteady heat conduction code with radiation boundary conditions
J. A. Fillo; R. Benenati; J. Powell
1975-01-01
A heat-transfer model for studying the temperature build-up in graphite ; blankets for fusion reactors is presented. In essence, the computer code ; developed is for two-dimensional, nonsteady heat conduction in heterogeneous, ; anisotropic solids with nonuniform internal heating. Thermal radiation as well ; as bremsstrahlung radiation boundary conditions are included. Numerical ; calculations are performed for two design options
Manufacture of high heat conductivity resistant clay bricks containing perlite
?lker Bekir Topçu; Burak I??kda?
2007-01-01
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.
Heat conduction errors and time lag in cryogenic thermometer installations
NASA Technical Reports Server (NTRS)
Warshawsky, I.
1973-01-01
Installation practices are recommended that will increase rate of heat exchange between the thermometric sensing element and the cryogenic fluid and that will reduce the rate of undesired heat transfer to higher-temperature objects. Formulas and numerical data are given that help to estimate the magnitude of heat-conduction errors and of time lag in response.
Author's personal copy Pyroelectric waste heat energy harvesting using heat conduction
Pilon, Laurent
refriger- ants and hydrocarbons to harvest waste heat up to 200e300 C [4,5]. However, their performanceAuthor's personal copy Pyroelectric waste heat energy harvesting using heat conduction Felix Y. Lee heat harvesting Olsen cycle a b s t r a c t Waste heat can be directly converted into electrical energy
NASA Astrophysics Data System (ADS)
Püthe, C.; Kuvshinov, A.
2013-11-01
Mapping the three-dimensional (3-D) electrical conductivity of Earth's mantle has been identified as one of the primary scientific objectives for the Swarm satellite mission. We present a 3-D frequency domain inversion scheme to recover mantle conductivity from satellite magnetic data. The scheme is based on an inversion of time spectra of internal (induced) spherical harmonic coefficients of the magnetic potential due to magnetospheric sources. Time series of internal and external (inducing) coefficients, whose determination is a prerequisite for this formulation, will be available as a Swarm Level-2 data product. An iterative gradient-type (quasi-Newton) optimization method is chosen to solve our 3-D non-linear inverse problem. In order to make the inversion tractable, we elaborate an adjoint approach for a fast and robust calculation of the data misfit gradient. We verify our approach with synthetic, but realistic time spectra of internal coefficients, obtained by simulating induction due to a realistic magnetospheric source in a 3-D conductivity model of the Earth. In these model studies, both shape and conductivity of a large-scale conductivity anomaly in the mid-mantle are recovered very well. The inversion scheme also shows to be robust with respect to noise and is therefore ready to process Swarm data.
Testing of a single graded groove variable conductance heat pipe
NASA Astrophysics Data System (ADS)
Kapolnek, Michael R.; Holmes, H. R.; Hager, Brian
1992-07-01
Variable conductance heat pipes (VCHPs) with transport capacities in the 50,000 to 100,000 Watt-inch range will be required to transport the large heat loads anticipated for advanced spacecraft. A high-reliability, nonarterial constant conductance heat pipe with this capacity, the Single Graded Groove (SGG) heat pipe, was developed for NASA's Space Station Freedom. The design and testing of a variable conductance SGG heat pipe are described. Response of the pipe to startup and heat load changes was excellent. After correcting for condenser temperature changes, the evaporator temperature varied by only +/- 4 F for large evaporator heat load changes. The surface tension difference between ends of the gas blocked region was found to measurably affect the performance of the pipe. Performance was negligibly affected by Marangoni flow in the gas blocked region.
Heat conductivity in relativistic systems investigated using a partonic cascade
NASA Astrophysics Data System (ADS)
Greif, M.; Reining, F.; Bouras, I.; Denicol, G. S.; Xu, Z.; Greiner, C.
2013-03-01
Motivated by the classical picture of heat flow, we construct a stationary temperature gradient in a relativistic microscopic transport model. Employing the relativistic Navier-Stokes ansatz, we extract the heat conductivity ? for a massless Boltzmann gas using only binary collisions with isotropic cross sections. We compare the numerical results to analytical expressions from different theories and discuss the final results. The directly extracted value for the heat conductivity can be referred to as a literature reference within the numerical uncertainties.
Enhanced quasiparticle heat conduction in the multigap superconductor Lu2Fe3Si5 .
Machida, Y; Sakai, S; Izawa, K; Okuyama, H; Watanabe, T
2011-03-11
Thermal transport measurements have been made on the Fe-based superconductor Lu2Fe3Si5 (T(c) ? 6??K) down to a very low temperature T(c)/120. The field and temperature dependences of the thermal conductivity confirm the multigap superconductivity with fully opened gaps on the whole Fermi surfaces. In comparison to MgB2, Lu2Fe3Si5 reveals a remarkably enhanced quasiparticle heat conduction in the mixed state. The results can be interpreted as a consequence of the unequal weight of the Fe 3d-electron character among the distinct bands. PMID:21469825
Efficient Reformulation of HOTFGM: Heat Conduction with Variable Thermal Conductivity
NASA Technical Reports Server (NTRS)
Zhong, Yi; Pindera, Marek-Jerzy; Arnold, Steven M. (Technical Monitor)
2002-01-01
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.
A quasi-3D analysis of the thermal performance of a flat heat pipe G. Carbajal a,*, C.B. Sobhan b
Wadley, Haydn
A quasi-3D analysis of the thermal performance of a flat heat pipe G. Carbajal a,*, C.B. Sobhan b form 29 January 2007 Available online 8 May 2007 Abstract The thermal performance of a flat heat pipe. Due to the effect of phase change at the evaporator and condenser sides, a significant amount
LavaSIM: the effect of heat transfer in 3D on lava flow characteristics (Invited)
NASA Astrophysics Data System (ADS)
Fujita, E.
2013-12-01
Characteristics of lava flow are governed by many parameters like lava viscosity, effusion rate, ground topography, etc. The accuracy and applicability of lava flow simulation code is evaluated whether the numerical simulation can reproduce these features quantitatively, which is important from both strategic and scientific points of views. Many lava flow simulation codes are so far proposed, and they are classified into two categories, i.e., the deterministic and the probabilistic models. LavaSIM is one of the former category models, and has a disadvantage of time consuming. But LavaSIM can solves the equations of continuity, motion, energy by step and has an advantage in the calculation of three-dimensional analysis with solid-liquid two phase flow, including the heat transfer between lava, solidified crust, air, water and ground, and three-dimensional convection in liquid lava. In other word, we can check the detailed structure of lava flow by LavaSIM. Therefore, this code can produce both channeled and fan-dispersive flows. The margin of the flow is solidified by cooling and these solidified crusts control the behavior of successive lava flow. In case of a channel flow, the solidified margin supports the stable central main flow and elongates the lava flow distance. The cross section of lava flow shows that the liquid lava flows between solidified crusts. As for the lava extrusion flow rate, LavaSIM can include the time function as well as the location of the vents. In some cases, some parts of the solidified wall may be broken by the pressure of successive flow and/or re-melting. These mechanisms could characterize complex features of the observed lava flows at many volcanoes in the world. To apply LavaSIM to the benchmark tests organized by V-hub is important to improve the lava flow evaluation technique.
Wang, G.L.; Chew, W.C.; Cui, T.J.; Aydiner, A.A.; Wright, D.L.; Smith, D.V.
2004-01-01
Three-dimensional (3D) subsurface imaging by using inversion of data obtained from the very early time electromagnetic system (VETEM) was discussed. The study was carried out by using the distorted Born iterative method to match the internal nonlinear property of the 3D inversion problem. The forward solver was based on the total-current formulation bi-conjugate gradient-fast Fourier transform (BCCG-FFT). It was found that the selection of regularization parameter follow a heuristic rule as used in the Levenberg-Marquardt algorithm so that the iteration is stable.
Analysis and application of variable conductance heat pipe air preheater
NASA Astrophysics Data System (ADS)
Shi, Chengming; Wang, Yang; Liao, Quan; Yang, Ying
2011-09-01
The heat transfer analysis of variable conductance heat pipe air preheater was carried out. The temperature transfer matrix was obtained for the air preheater that comprises several discrete heat transfer units with same or different heat transfer surface area in a parallel or counter flow mode. By using the temperature transfer matrix, the outlet fluid temperatures could be easily calculated for a given air preheater and inlet fluid temperatures. The active length of condenser in a variable conductance heat pipe is determined according to the flat interface model. With the same initial conditions, the comparisons between variable conductance heat-pipe air preheater and regular heat pipe air preheater has been analyzed and tested in terms of heat pipe wall temperature, heat transfer surface area and outlet fluid temperatures. Based on the real industrial applications, it has been confirmed that the variable conductance heat pipe air preheater has excellent performance of anti-corrosion and anti-ash-deposition especially at the variable working condition and the sulfur coal (5%-6% mass fraction of sulfur) condition.
Evolutionary topology optimization for temperature reduction of heat conducting fields
Qing Li; Grant P. Steven; Y. M. Xie; Osvaldo M. Querin
2004-01-01
This paper aims at developing an efficient finite element based computational procedure for the topology design of heat conducting fields. To evaluate the temperature change in a specific position, due to varying the conducting material distribution in other regions, a discrete temperature sensitivity is derived for an evolutionary topology optimization method. In the topology optimization of the conducting fields, the
Partially coherent phonon heat conduction in superlattices
B. Yang; G. Chen
2003-01-01
In this paper, the phonon thermal conductivity of semiconductor superlattices is calculated with the use of a modified lattice dynamics model, in which an imaginary wave vector is added. The mean free path caused by diffuse interface scattering is included in the imaginary wave vector. This model combines the effects of phonon confinement and diffuse interface scattering on the thermal
Heat conduction in relativistic neutral gases revisited
A. L. Garcia-Perciante; A. R. Mendez
2010-09-30
The kinetic theory of dilute gases to first order in the gradients yields linear relations between forces and fluxes. The heat flux for the relativistic gas has been shown to be related not only to the temperature gradient but also to the density gradient in the representation where number density, temperature and hydrodynamic velocity are the independent state variables. In this work we show the calculation of the corresponding transport coefficients from the full Boltzmann equation and compare the magnitude of the relativistic correction.
NASA Astrophysics Data System (ADS)
Gould, C. A.; Shammas, N. Y. A.; Grainger, S.; Taylor, I.; Simpson, K.
2012-06-01
This paper documents the 3D modeling and simulation of a three couple thermoelectric module using the Synopsys Technology Computer Aided Design (TCAD) semiconductor simulation software. Simulation results are presented for thermoelectric power generation, cooling and heating, and successfully demonstrate the basic thermoelectric principles. The 3D TCAD simulation model of a three couple thermoelectric module can be used in the future to evaluate different thermoelectric materials, device structures, and improve the efficiency and performance of thermoelectric modules.
NASA Astrophysics Data System (ADS)
Natale, Giovanni; Popescu, Cristina; Tuffs, Richard
2015-08-01
A major difficulty hampering the accuracy of UV/optical star formation rate tracers is the effect of interstellar dust, absorbing and scattering light produced by both young and old stellar populations (SPs). Although empirically calibrated corrections or energy balance SED fitting are often used for fast de-reddening of galaxy stellar emission, eventually only radiative transfer calculations can provide self-consistent predictions of galaxy model spectra, taking into account important factors such as galaxy inclination, different morphological components, non-local heating of the dust and scattered radiation. In addition, dust radiative transfer can be used to determine the fraction of monochromatic dust emission which is powered by either young or old SPs. This calculation needs to take into account the different response of the dust grains to the UV and optical radiation field, depending on the grain size and composition. We determined the dust heating fractions, on both global and local scales, for high-resolution galaxy models by using our 3D ray-tracing dust radiative transfer code "DART-Ray". We will show the results obtained using this method and discuss the consequences for star formation rate indicators.
NASA Astrophysics Data System (ADS)
Titarenko, S.; McCaig, A. M.
2014-12-01
A perennial problem in near-ridge hydrothermal circulation is that the only directly measurable data to test models is often vent fluid temperature. Surface heat flow measurements may be available but without the underlying thermal structure it is not known if they are transient and affected by local hydrothermal flow, or conductive. The Atlantis Massif oceanic core complex at 30 °N on the mid-Atlantic Ridge, offers a unique opportunity to better constrain hydrothermal circulation models. The temperature profile in gabbroic rocks of IODP Hole 1309D was measured in IODPExpedition 340T, and found to be near-conductive, but with a slight inflexion at ~750 mbsf indicating downward advection of fluid above that level. The lack of deep convection is especially remarkable given that the long-lived Lost City Hydrothermal Field (LCHF) is located only 5km to the south. We have modelled hydrothermal circulation in the Massif using Comsol Multiphysics, comparing 2-D and 3-D topographic models and using temperature-dependent conductivity to give the best estimate of heatflow into the Massif. We can constrain maximum permeability in gabbro below 750 mbsf to 5e-17 m2. The thermal gradient in the upper part of the borehole can be matched with a permeability of 3e-14 m2 in a 750 m thick layer parallel to the surface of the massif, with upflow occurring in areas of high topography and downflow at the location of the borehole. However in 3-D the precise flow pattern is quite model dependent, and the thermal structure can be matched either by downflow centred on the borehole at lower permeability or centred a few hundred metres from the borehole at higher permeability. The borehole gradient is compatible with the longevity (>120 kyr) and outflow temperature (40-90 °C) of the LCHF either with a deep more permeable (1e-14 m2 to 1e-15 m2) domain beneath the vent site in 2-D or a permeable fault slot 500 to 1000m wide and parallel to the transform fault in 3-D. In both cases topography exerts a strong control on vent location, and steep boundaries between permeable and impermeable domains stabilise long term steady venting. Work is in progress to model the thermal evolution of the massif during fault exhumation over the last 1.2 million years, comparing this with the present day heatflow estimated from measurements.
Guerin, Gilles
temperature anomalies affecting the entire mini-basin. We present a method to interpret such complex: Bottom Hole Temperatures (BHT) and 3D seismic interpretation. More than 600 BHT from 200 wells allowed us from the main seismic reflectors interpreted from 3D surveys, we perform a 3D numerical simulation
NASA Astrophysics Data System (ADS)
Dorfman, S. M.; Nabiei, F.; Cantoni, M.; Badro, J.; Gaal, R.; Gillet, P.
2014-12-01
The laser-heated diamond anvil cell is a unique tool for subjecting materials to pressures over few hundreds of GPa and temperatures of thousands of Kelvins which enables us to experimentally simulate the inaccessible interiors of planets. However, small sample size, laser profile and thermally conductive diamonds cause temperature gradients of 1000s K over a few microns which also affects chemical and structural distribution of phases in the sample. We have examined samples of San Carlos olivine (Mg,Fe)2SiO3 powder melted in the diamond anvil cell by double-sided and single-sided laser heating for 3-6 minutes to ~3000 K at 35-37 GPa. Moreover, MgO is used as an insulating media in one of the sample. Recovered samples were analyzed by a combination of focused ion beam (FIB) and scanning electron microscope (SEM) equipped with energy dispersive x-ray (EDX) detector. Images and chemical maps were acquired for ~300 slices with ~70 nm depth from each sample, comprising about half of the heated zone. Detailed chemical and structural analysis by transmission electron microscopy (TEM) of lamellas prepared from the remaining section of the samples will also be presented. In all samples the heated zone included (Mg,Fe)SiO3 perovskite-structured bridgmanite (PV) phase and two (Mg, Fe)O phases, one of which, magnesiowüstite (MW), is richer in iron than the other one, ferropericlase (FP). In double-side heated samples we observe a Fe-rich quenched melt core surrounded by MW phase. Our results show that with increasing heating time, Fe migrates to the molten center of the sample. In the single-side heated sample, the Fe-rich MW phase is concentrated in the center of heated zone. In all samples a FP crust was observed around the heated zone. This crust, however, is broken in the upper part (colder part) of the single-side heated sample due the high asymmetrical temperature gradient within the sample. The results confirm the importance of double-side heating and insulating media for generating homogenous central temperature and chemical distribution.
Kohlrausch Heat Conductivity Apparatus for Intermediate or Advanced Laboratory
ERIC Educational Resources Information Center
Jensen, H. G.
1970-01-01
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)
Experimental evidence of hyperbolic heat conduction in processed meat
Mitra, K.; Kumar, S.; Vedavarz, A.; Moallemi, M.K. [Polytechnic Univ., Brooklyn, NY (United States)
1995-08-01
The objective of this paper is to present experimental evidence of the wave nature of heat propagation in processed meat and to demonstrate that the hyperbolic heat conduction model is an accurate representation, on a macroscopic level, of the heat conduction process in such biological material. The value of the characteristic thermal time of a specific material, processed bologna meat, is determined experimentally. As a part of the work different thermophysical properties are also measured. The measured temperature distributions in the samples are compared with the Fourier results and significant deviation between the two is observed, especially during the initial stages of the transient conduction process. The measured values are found to match the theoretical non-Fourier hyperbolic predictions very well. The superposition of waves occurring inside the meat sample due to the hyperbolic nature of heat conduction is also proved experimentally. 14 refs., 7 figs., 2 tabs.
Ballistic heat conduction and mass disorder in one dimension
NASA Astrophysics Data System (ADS)
Ong, Zhun-Yong; Zhang, Gang
2014-08-01
It is well-known that in the disordered harmonic chain, heat conduction is subballistic and the thermal conductivity (?) scales asymptotically as \\lim_{L\\rightarrow\\infty}\\kappa\\propto L^{0.5} where L is the chain length. However, using the nonequilibrium Green's function (NEGF) method and analytical modelling, we show that there exists a critical crossover length scale (LC) below which ballistic heat conduction (\\kappa\\propto L) can coexist with mass disorder. This ballistic-to-subballistic heat conduction crossover is connected to the exponential attenuation of the phonon transmittance function ? i.e. ?(?, L) = exp[-L/?(?)], where ? is the frequency-dependent attenuation length. The crossover length can be determined from the minimum attenuation length, which depends on the maximum transmitted frequency. We numerically determine the dependence of the transmittance on frequency and mass composition as well as derive a closed form estimate, which agrees closely with the numerical results. For the length-dependent thermal conductance, we also derive a closed form expression which agrees closely with numerical results and reproduces the ballistic to subballistic thermal conduction crossover. This allows us to characterize the crossover in terms of changes in the length, mass composition and temperature dependence, and also to determine the conditions under which heat conduction enters the ballistic regime. We describe how the mass composition can be modified to increase ballistic heat conduction.
Ballistic heat conduction and mass disorder in one dimension.
Ong, Zhun-Yong; Zhang, Gang
2014-08-20
It is well-known that in the disordered harmonic chain, heat conduction is subballistic and the thermal conductivity (?) scales asymptotically as lim(L--> ?) ? ? L(0.5) where L is the chain length. However, using the nonequilibrium Green's function (NEGF) method and analytical modelling, we show that there exists a critical crossover length scale (LC) below which ballistic heat conduction (? ? L) can coexist with mass disorder. This ballistic-to-subballistic heat conduction crossover is connected to the exponential attenuation of the phonon transmittance function ? i.e. ?(?, L) = exp[-L/?(?)], where ? is the frequency-dependent attenuation length. The crossover length can be determined from the minimum attenuation length, which depends on the maximum transmitted frequency. We numerically determine the dependence of the transmittance on frequency and mass composition as well as derive a closed form estimate, which agrees closely with the numerical results. For the length-dependent thermal conductance, we also derive a closed form expression which agrees closely with numerical results and reproduces the ballistic to subballistic thermal conduction crossover. This allows us to characterize the crossover in terms of changes in the length, mass composition and temperature dependence, and also to determine the conditions under which heat conduction enters the ballistic regime. We describe how the mass composition can be modified to increase ballistic heat conduction. PMID:25077430
Finite element solution of transient heat conduction using iterative solvers
Mile R. Vuji?i?
2006-01-01
Purpose – To provide an analysis of transient heat conduction, which is solved using different iterative solvers for graduate and postgraduate students (researchers) which can help them develop their own research. Design\\/methodology\\/approach – Three-dimensional transient heat conduction in homogeneous materials using different time-stepping methods such as finite difference (? explicit, implicit and Crank-Nicolson) and finite element (weighted residual and least
The enthalpy method for heat conduction problems with moving boundaries
Hunter, L.W.; Kuttler, J.R. )
1989-05-01
The purpose of this paper is to demonstrate how an enthalpy method for heat conduction problems with moving boundaries associated with phase changes can be combined with Kirchoff and coordinate transformations to put these problems in a particularly simple form. All nonlinearities in density, conductivity, and specific heat can be concentrated in the functional relation between enthalpy and the generalized temperature. Convection in the fluid is neglected. A simple numerical example is included.
Heat conduction in relativistic systems: alternatives and perspectives
C. S. Lopez-Monsalvo
2010-11-30
The non-equilibrium thermodynamics of relativistic systems have a rich phenomenology. The simplest phenomenon in the class of dissipative processes is that of heat. This letter presents a brief summary of the efforts made to tackle the problem of relativistic heat conduction. In particular, we focus on the multi-fluid approach to relativistic dissipation.
Radiative heat conduction and the magnetorotational instability
NASA Astrophysics Data System (ADS)
Araya-Góchez, Rafael A.; Vishniac, Ethan T.
2004-12-01
A photon or a neutrino gas, semicontained by a non-diffusive particle species through scattering, comprises a rather peculiar magnetohydrodynamic fluid where the magnetic field is truly frozen only to the comoving volume associated with the mass density. Although radiative diffusion precludes a formal adiabatic treatment of compressive perturbations, we cast the energy equation in quasi-adiabatic form by assuming a negligible rate of energy exchange among species on the time-scale of the perturbation. This leads to a simplified dispersion relation for toroidal, non-axisymmetric magnetorotational modes when the accretion disc has comparable stress contributions from diffusive and non-diffusive components. The properties of the modes of fastest growth are shown to depend strongly on the compressibility of the mode, with a reduction in growth rate consistent with the results of Blaes & Socrates for axisymmetric modes. A clumpy disc structure is anticipated on the basis of the polarization properties of the fastest-growing modes. This analysis is accurate in the near-hole region of locally cooled, hyper-accreting flows if the electron gas becomes moderately degenerate such that non-conductive, thermalizing processes with associated electron-positron release (i.e. neutrino annihilation and neutrino absorption on to nuclei) are effectively blocked by high occupation of the Fermi levels.
Oldenburg, Douglas W.
Inversion of 3D time-domain EM data for high conductivity contrasts Greg A. Oldenborger1 Inversion of 3D time-domain electromagnetic data for high conductivity contrasts is a challenging endeavor. Convergence to acceptable solu- tions can be catalyzed with techniques of overly-conductive initialization
Single-photon heat conduction in electrical circuits
P. J. Jones; J. A. M. Huhtamäki; K. Y. Tan; M. Möttönen
2011-07-14
We study photonic heat conduction between two resistors coupled weakly to a single superconducting microwave cavity. At low enough temperature, the dominating part of the heat exchanged between the resistors is transmitted by single-photon excitations of the fundamental mode of the cavity. This manifestation of single-photon heat conduction should be experimentally observable with the current state of the art. Our scheme can possibly be utilized in remote interference-free temperature control of electric components and environment engineering for superconducting qubits coupled to cavities.
Heat Pipe Embedded AlSiC Plates for High Conductivity - Low CTE Heat Spreaders
Johnson, Matthew ); Weyant, J.; Garner, S. ); Occhionero, M. )
2010-01-07
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.
Fourier analysis of conductive heat transfer for glazed roofing materials
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah [Faculty of Computer and Mathematical Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia); Zakaria, Nor Zaini [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia)
2014-07-10
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
Heat Conduction in Fine Scale Mixtures With Interfacial Contact Resistance
Heat Conduction in Fine Scale Mixtures With Interfacial Contact Resistance Robert Lipton Department conduction ina #12;ne scale mixtureoftwo conductors is examinedinthe presence of a contact resistance between exhibits a size eect under rescaling. Key Words. composite medium, contact resistance, homogenization. AMS
Heat conductivity in linear mixing systems Baowen Li,1
aimed at answering this question. Indeed in Ref. 10 the thermal conductivity was studied for a LorentzHeat conductivity in linear mixing systems Baowen Li,1 Giulio Casati,1,2 and Jiao Wang1,3 1 Fisica della Materia, Unita´ di Como, Como, Italy; and Istituto Nazionale di Fisica Nucleare, Sezione di
An Experiment in Heat Conduction Using Hollow Cylinders
ERIC Educational Resources Information Center
Ortuno, M.; Marquez, A.; Gallego, S.; Neipp, C.; Belendez, A.
2011-01-01
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…
Development of downhole geothermal heat flux and thermal conductivity transducers
Poppendiek, H.F.; Connelly, D.J.; Sellers, A.J.
1982-10-01
Two new downhole geothermal transducers were developed for the Department of Energy for the purpose of measuring the geothermal heat flux and thermal conductivity in exploration holes without the necessity of taking core samples. One transducer system was based on the principle of quasi steady state two dimensional heat conduction; the transducers consisted of cylindrical rods having thermal conductivities different from the surrounding earth. A second cylindrical transducer system based on transient conduction generated a step function heat flux that was transferred into the earth. Both systems required that the annular space between the transducer and the hole wall be filled with water or a drilling fluid. This paper describes the new measurement techniques, the field tests and the results.
Kenneth L. Kipp
1987-01-01
The Heat- and Soil-Transport Program (HST3D) simulates groundwater flow and associated heat and solute transport in three dimensions. The three governing equations are coupled through the interstitial pore velocity, the dependence of the fluid density on pressure, temperature, the solute-mass fraction , and the dependence of the fluid viscosity on temperature and solute-mass fraction. The solute transport equation is for
NASA Astrophysics Data System (ADS)
Chen-Wiegart, Yu-Chen Karen; Figueroa-Santos, Miriam Aileen; Petrash, Stanislas; Garcia-Miralles, Jose; Wang, Jun
2014-12-01
Conductive adhesives are found favorable in a wide range of applications including a lead-free solder in micro-chips, flexible and printable electronics and enhancing the performance of energy storage devices. Composite materials comprised of metallic fillers and a polymer matrix are of great interest to be implemented as hybrid conductive adhesives. Here we investigated a cost-effective conductive adhesive material consisting of silver-coated copper as micro-fillers using synchrotron-based three-dimensional (3D) X-ray nano-tomography. The key factors affecting the quality and performance of the material were quantitatively studied in 3D on the nanometer scale for the first time. A critical characteristic parameter, defined as a shape-factor, was determined to yield a high-quality silver coating, leading to satisfactory performance. A `stack-and-screen' mechanism was proposed to elaborate such a phenomenon. The findings and the technique developed in this work will facilitate the future advancement of conductive adhesives to have a great impact in micro-electronics and other applications.Conductive adhesives are found favorable in a wide range of applications including a lead-free solder in micro-chips, flexible and printable electronics and enhancing the performance of energy storage devices. Composite materials comprised of metallic fillers and a polymer matrix are of great interest to be implemented as hybrid conductive adhesives. Here we investigated a cost-effective conductive adhesive material consisting of silver-coated copper as micro-fillers using synchrotron-based three-dimensional (3D) X-ray nano-tomography. The key factors affecting the quality and performance of the material were quantitatively studied in 3D on the nanometer scale for the first time. A critical characteristic parameter, defined as a shape-factor, was determined to yield a high-quality silver coating, leading to satisfactory performance. A `stack-and-screen' mechanism was proposed to elaborate such a phenomenon. The findings and the technique developed in this work will facilitate the future advancement of conductive adhesives to have a great impact in micro-electronics and other applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06068g
Heat Transfer Analysis for a Concentric Tube Heat Exchanger Including the Wall Axial Conduction
Mehmet Emin Arici
2010-01-01
The effect of wall axial conduction on the heat transfer in a concentric tube heat exchanger is examined for the inner flow laminar flow regime. The procedure used for the current analysis combines the analytical solution for the inner fluid with a numerical approximation for the wall conduction and has the capability of handling the temperature variation for the outer
On the solution of heat conduction problems involving heat sources via boundary-fitted grids
G. M. Grandi; J. C. Ferreri
1989-01-01
It is shown that codes employing boundary-fitted grids (BFG) in heat conduction problems involving heat sources must be implemented in strictly numerically conservative form if accurate results are to be obtained. It is demonstrated that, for one-dimensional problems, nonconservative form imply errors originated in grid nonuniformity that cause a spurious increase in the heat source. This in turn leads to
A new heat-conduction logging technique and its application
NASA Astrophysics Data System (ADS)
Li, Bin; Li, Zishun; Zhu, Guotong; Fu, Zhifang
2005-06-01
The results of a heat-conduction experiment with a central point source in a sand barrel shows that the temperature of the heat source increase much faster in sand saturated with oil and air (dry sand) than in water sand. During cooling the temperature of the central heat source goes down slower in oil- or air-saturated sands than in water sands. Based on the theory of heat-conduction in porous media and the experimental results, we developed a new heat-conduction logging technique which utilizes an artificial heat source (dynamite charge or electric heater) to heat up target formations in the borehole and then measure the change of temperature at a later time. Post-frac oil production is shown to be directly proportional to the size of the temperature anomaly when other reservoir parameters are fairly consistent. The method is used to evaluate potential oil production for marginal reservoirs in the FY formation in Song-Liao basin of China.
Heat conductance in nonlinear lattices at small temperature gradients
T. Yu. Astakhova; V. N. Likhachev; G. A. Vinogradov
2010-06-09
This paper proposes a new methodological framework within which the heat conductance in 1D lattices can be studied. The total process of heat conductance is separated into two parts where the first one is the equilibrium process at equal temperatures $T$ of both ends and the second one -- non-equilibrium with the temperature $\\Delta T$ of one end and zero temperature of the other. This approach allows significant decrease of computational time at $\\Delta T \\to 0$. The threshold temperature $T_{\\rm thr}$ is found which scales $T_{\\rm thr}(N) \\sim N^{-3}$ with the lattice size $N$ and by convention separates two mechanisms of heat conductance: phonon mechanism dominates at $T T_{\\rm thr}$. Solitons and breathers are directly visualized in numerical experiments. The problem of heat conductance in non-linear lattices in the limit $\\Delta T \\to 0$ can be reduced to the heat conductance of harmonic lattice with time-dependent stochastic rigidities determined by the equilibrium process at temperature $T$. The detailed analysis is done for the $\\beta$-FPU lattice though main results are valid for one-dimensional lattices with arbitrary potentials.
The Tonga-Vanuatu Subduction Complex -- a Self-Optimized 3D Slab-Slab-Mantle Heat Pump
NASA Astrophysics Data System (ADS)
McCreary, J. A.
2008-12-01
Recently published geophysical and geochemical data and increasingly actualistic free subduction models prompted a fresh look at 2 classics hinting, in combination, that a coupled 3D slab-slab-upper mantle interaction (Scholz and Campos, 1995; full citations at URL below) might power the prodigious surface heat dissipation (Lagabrielle et al., 1997) characterizing one of Earth's most remarkable tectonomagmatic systems, the Tonga-Vanuatu Subduction Complex (TVSC). The 3D TVSC includes (1) the kinematically, magmatically, and bathymetrically distinct North Tonga (NT, 14-26° S) and South Vanuatu (SV, 16-23° S) trenches and slabs, (2) the shared NT-SV backarc, and (3) entrained mobile upper mantle (MUM). That Earth's greatest convergence, rollback, and spreading rates; most disseminated spreading (the North Fiji Basin (NFB) ridge swarm); and greatest concentration of aggregate active ridge length coincide in a 1,500 km TVSC can't be accidental. To the north and south, the respective active NT and SV trenches swing abruptly 90° counterclockwise into continuity with the Vitiaz and Hunter fossil trenches, both active in the Late Miocene but now sinistral strike-slip loci standing over long exposed PA and AU slab edges. These 2 active-fossil trench pairs bracket a hot, shallow and geophysically and geochemically exceptional TVSC interior consisting of 2 rapidly spreading backarcs set back-to-back in free sublithospheric communication: The Lau-Havre NT backarc on the east and the ridge-infested SV backarc (NFB) on the west. The NFB and adjacent North Fiji Plateau make up the unplatelike New Hebrides-Fiji Orogen (Bird, 2003). As in the western Aleutians, the NT-Vitiaz and SV-Hunter subduction-to-strike-slip transitions (SSSTs) stand above toroidal fluxes of hot, dry PA and AU MUM driven along-trench and around the free NT and SV slab edges from subslab to supraslab regions by dynamic pressure gradients powered by slab free-fall and induced viscous couplings. These edge flows must converge and mix beneath the shared TVSC backarc, which must then shed a huge advected subslab heat load by maximizing ridge length in the area available. Found at both SSSTs are adakites indicative of a TVSC source laced with slab-edge melt and boninites consistent with flux- melting of hot, dry subslab MUM on entry to the supraslab wedge. Isotopics reveal widespread source mixing of Pacific and Indian MOR end-members. Diverging NT and VS trenches rotate clockwise at extremely high rates about pinning points at and Euler poles near trench-floater intercepts: Louisville Ridge on PA, and West Torres Plateau-D'Entrecasteaux Ridge on AU. In this configuration, the spinning, free-falling NT and SV slabs form a highly coupled self-organized gravity-powered pump pulling hot subslab MUM beneath the TVSC with enough left-over head to power severe transition zone buckling of an 80+ Ma NT (PA) slab also actively extending toward its free edge. Several nonlinear couplings (e.g., temperature-dependent viscosity and slab damage at tightening upper hinges) feedback positively to pump efficiency. The TVSC is but one possible slab-mantle pump partaking of the strong self-optimizing tendency characteristic of all natural flow systems (e.g., Bejan and Lorente, 2006). Slab-mantle pump natural history is now under investigation, as such pumps may have allowed a shrinking post-Pangean Pacific with an unrelenting sublithospheric room problem to relieve itself of excess MUM by making efficient use of available circum-Pacific slab curtain porosity -- a commodity that may have been in very short supply through most of the Cretaceous.
Thermally conductive cementitious grout for geothermal heat pump systems
Allan, Marita (Old Field, NY)
2001-01-01
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.
Mechanical control of heat conductivity in molecular chains.
Savin, A V; Gendelman, O V
2014-01-01
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
Neutrino Heat Conduction and Inhomogeneities in the Early Universe
NASA Technical Reports Server (NTRS)
Heckler, A.; Hogan, C. J.
1993-01-01
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).
Electronic heat capacity and conductivity of gapped graphene
NASA Astrophysics Data System (ADS)
Mousavi, Hamze; Khodadadi, Jabbar
2013-05-01
It investigated the effects of orderly substituted atoms on density of states, electronic heat capacity and electrical conductivity of graphene plane within tight-binding Hamiltonian model and Green's function method. The results reveal a band gap in the density of states, leading to an acceptor or donor semiconductor. In the presence of foreign atoms, the heat capacity decreases (increases) before (after) the Schottky anomaly. Moreover, the electrical conductivity of the gapped graphene reduces on all ranges of temperature compared to the pristine case. Deductively, all changes in the electronic properties depend on the difference between the on-site energies of the carbon and replaced atoms.
Application of Genetic Algorithms in Nonlinear Heat Conduction Problems
Khan, Waqar A.
2014-01-01
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
Chen-Wiegart, Yu-chen Karen; Figueroa-Santos, Miriam Aileen; Petrash, Stanislas; Garcia-Miralles, Jose; Wang, Jun
2015-01-21
Conductive adhesives are found favorable in a wide range of applications including a lead-free solder in micro-chips, flexible and printable electronics and enhancing the performance of energy storage devices. Composite materials comprised of metallic fillers and a polymer matrix are of great interest to be implemented as hybrid conductive adhesives. Here we investigated a cost-effective conductive adhesive material consisting of silver-coated copper as micro-fillers using synchrotron-based three-dimensional (3D) X-ray nano-tomography. The key factors affecting the quality and performance of the material were quantitatively studied in 3D on the nanometer scale for the first time. A critical characteristic parameter, defined as a shape-factor, was determined to yield a high-quality silver coating, leading to satisfactory performance. A 'stack-and-screen' mechanism was proposed to elaborate such a phenomenon. The findings and the technique developed in this work will facilitate the future advancement of conductive adhesives to have a great impact in micro-electronics and other applications. PMID:25474162
Wu, Xiaodong; Lu, Canhui; Xu, Haoyu; Zhang, Xinxing; Zhou, Zehang
2014-12-10
Development of novel and versatile strategies to construct conductive polymer composites with low percolation thresholds and high mechanical properties is of great importance. In this work, we report a facile and effective strategy to prepare polyaniline@cellulose nanowhiskers (PANI@CNs)/natural rubber (NR) nanocomposites with 3D hierarchical multiscale structure. Specifically, PANI was synthesized in situ on the surface of CNs biotemplate to form PANI@CNs nanohybrids with high aspect ratio and good dispersity. Then NR latex was introduced into PANI@CNs nanohybrids suspension to enable the self-assembly of PANI@CNs nanohybrids onto NR latex microspheres. During cocoagulation process, PANI@CNs nanohybrids selectively located in the interstitial space between NR microspheres and organized into a 3D hierarchical multiscale conductive network structure in NR matrix. The combination of the biotemplate synthesis of PANI and latex cocoagulation method significantly enhanced the electrical conductivity and mechanical properties of the NR-based nanocomposites simultaneously. The electrical conductivity of PANI@CNs/NR nanocomposites containing 5 phr PANI showed 11 orders of magnitude higher than that of the PANI/NR composites at the same loading fraction,; meanwhile, the percolation threshold was drastically decreased from 8.0 to 3.6 vol %. PMID:25384188
Tunable heat conduction through coupled Fermi-Pasta-Ulam chains
NASA Astrophysics Data System (ADS)
Su, Ruixia; Yuan, Zongqiang; Wang, Jun; Zheng, Zhigang
2015-01-01
We conduct a study on heat conduction through coupled Fermi-Pasta-Ulam (FPU) chains by using classical molecular dynamics simulations. Our attention is dedicated to showing how the phonon transport is affected by the interchain coupling. It has been well accepted that the heat conduction could be impeded by the interchain interaction due to the interface phonon scattering. However, recent theoretical and experimental studies suggest that the thermal conductivity of nanoscale materials can be counterintuitively enhanced by the interaction with the substrate. In the present paper, by consecutively varying the interchain coupling intensity, we observed both enhancement and suppression of thermal transport through the coupled FPU chains. For weak interchain couplings, it is found that the heat flux increases with the coupling intensity, whereas in the case of strong interchain couplings, the energy transport is found to be suppressed by the interchain interaction. Based on the phonon spectral energy density method, we attribute the enhancement of the energy transport to the excited phonon modes (in addition to the intrinsic phonon modes), while the upward shift of the high-frequency phonon branch and the interface phonon-phonon scattering account for the suppressed heat conduction.
Tunable heat conduction through coupled Fermi-Pasta-Ulam chains.
Su, Ruixia; Yuan, Zongqiang; Wang, Jun; Zheng, Zhigang
2015-01-01
We conduct a study on heat conduction through coupled Fermi-Pasta-Ulam (FPU) chains by using classical molecular dynamics simulations. Our attention is dedicated to showing how the phonon transport is affected by the interchain coupling. It has been well accepted that the heat conduction could be impeded by the interchain interaction due to the interface phonon scattering. However, recent theoretical and experimental studies suggest that the thermal conductivity of nanoscale materials can be counterintuitively enhanced by the interaction with the substrate. In the present paper, by consecutively varying the interchain coupling intensity, we observed both enhancement and suppression of thermal transport through the coupled FPU chains. For weak interchain couplings, it is found that the heat flux increases with the coupling intensity, whereas in the case of strong interchain couplings, the energy transport is found to be suppressed by the interchain interaction. Based on the phonon spectral energy density method, we attribute the enhancement of the energy transport to the excited phonon modes (in addition to the intrinsic phonon modes), while the upward shift of the high-frequency phonon branch and the interface phonon-phonon scattering account for the suppressed heat conduction. PMID:25679599
Nonlinear solution adaptive structured grids via heat-conduction analogies
H. M. Tsai
2001-01-01
This paper discusses an adaptive grid approach, developed using Fortran 77, on quadrilateral meshes for the Euler and Navier-Stokes solvers. Solution adaptation is through two nonlinear heat-conduction analogies applied directly on a two-dimensional surface using the finite volume method. Clustering of the grid generated is controlled by the conductivity in the computational domain, which is related arbitrarily to the geometrical
A heat conduction study at non-continuum scales
NASA Astrophysics Data System (ADS)
Guajardo Cuellar, Alejandro
An extensive and detailed description of heat conduction at the micro- and nano-scale is presented. During the last two decades this phenomenon has become very attractive to study because of the shrinking in size of thermoelectric technologies and electronic devices. These newer technologies are at the micro- and nano-scale. Due to the small size, a power dissipation problem has presented itself in these applications. The proper thermal performance is related with the performance of the technology. Because of these facts a description of the thermal transport in different materials at these scales is required. This problem is important because understanding the energy transport will allow engineers to design faster electronic devices and more efficient thermoelectric applications. For macro-scale it is known that diffusive behavior is presented in heat conduction; here models that show different behavior than diffusive such as wave-like are presented. One extra tool to understand heat conduction is to calculate the thermal conductivity. Equilibrium molecular dynamics combined with the Green-Kubo formula can be used to calculate the thermal conductivity of materials such as germanium and carbon. The foundation of this calculation is extracting the heat current from the results, and implementing it into the Green-Kubo formula. This work considers all formulations from the literature that calculate the heat current for the Tersoff potential, the interatomic potential most applicable to semiconductor materials. The formulations for the heat current are described, and results for germanium and carbon are presented. The formulations are compared with respect to how well they capture the physics of the Tersoff potential and how well the calculated value of the thermal conductivity reflects the experimentally-measured value. The second part of this work deals with heat transport in low dimensions at the nano-scale. The energy transport in a two dimensional graphene sheet is studied and compared to that in a one dimensional chain. The equations of motion for each individual atom of the sheet are solved numerically to generate the distribution of kinetic energy in the structure. The distribution of kinetic energy in the sheet shows two different characteristics of the transport. The components of frequency of the kinetic energy in the graphene structure are identified. The components allow the identification under which potential more low frequency carriers are expected. The presence of chaos in the graphene sheet using the anharmonic potential is identified. Finally, conclusions and recommendations for the study of heat conduction at the nano-scale are presented.
Cristian Roman; Virgiliu Fireteanu
2011-01-01
The paper presents a proposition of a DC electromagnetic pump of conduction type for molten salts and describes the process of finite element analysis of its multiphysics model. The subject of molten salts pumping has a technical interest due to the current studies and attempts from the energy industry. Thanks to their good thermal characteristics, molten salts are envisaged in
Modelling heat conduction in polycrystalline hexagonal boron-nitride films
Mortazavi, Bohayra; Pereira, Luiz Felipe C.; Jiang, Jin-Wu; Rabczuk, Timon
2015-01-01
We conducted extensive molecular dynamics simulations to investigate the thermal conductivity of polycrystalline hexagonal boron-nitride (h-BN) films. To this aim, we constructed large atomistic models of polycrystalline h-BN sheets with random and uniform grain configuration. By performing equilibrium molecular dynamics (EMD) simulations, we investigated the influence of the average grain size on the thermal conductivity of polycrystalline h-BN films at various temperatures. Using the EMD results, we constructed finite element models of polycrystalline h-BN sheets to probe the thermal conductivity of samples with larger grain sizes. Our multiscale investigations not only provide a general viewpoint regarding the heat conduction in h-BN films but also propose that polycrystalline h-BN sheets present high thermal conductivity comparable to monocrystalline sheets. PMID:26286820
Modelling heat conduction in polycrystalline hexagonal boron-nitride films
NASA Astrophysics Data System (ADS)
Mortazavi, Bohayra; Pereira, Luiz Felipe C.; Jiang, Jin-Wu; Rabczuk, Timon
2015-08-01
We conducted extensive molecular dynamics simulations to investigate the thermal conductivity of polycrystalline hexagonal boron-nitride (h-BN) films. To this aim, we constructed large atomistic models of polycrystalline h-BN sheets with random and uniform grain configuration. By performing equilibrium molecular dynamics (EMD) simulations, we investigated the influence of the average grain size on the thermal conductivity of polycrystalline h-BN films at various temperatures. Using the EMD results, we constructed finite element models of polycrystalline h-BN sheets to probe the thermal conductivity of samples with larger grain sizes. Our multiscale investigations not only provide a general viewpoint regarding the heat conduction in h-BN films but also propose that polycrystalline h-BN sheets present high thermal conductivity comparable to monocrystalline sheets.
Modelling heat conduction in polycrystalline hexagonal boron-nitride films.
Mortazavi, Bohayra; Pereira, Luiz Felipe C; Jiang, Jin-Wu; Rabczuk, Timon
2015-01-01
We conducted extensive molecular dynamics simulations to investigate the thermal conductivity of polycrystalline hexagonal boron-nitride (h-BN) films. To this aim, we constructed large atomistic models of polycrystalline h-BN sheets with random and uniform grain configuration. By performing equilibrium molecular dynamics (EMD) simulations, we investigated the influence of the average grain size on the thermal conductivity of polycrystalline h-BN films at various temperatures. Using the EMD results, we constructed finite element models of polycrystalline h-BN sheets to probe the thermal conductivity of samples with larger grain sizes. Our multiscale investigations not only provide a general viewpoint regarding the heat conduction in h-BN films but also propose that polycrystalline h-BN sheets present high thermal conductivity comparable to monocrystalline sheets. PMID:26286820
Systems analysis of the inverse heat conduction problem
David Bruce Manner
1987-01-01
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
Transient three-dimensional heat conduction computations using Brian's technique
John A. Watson
1988-01-01
A transient three dimensional heat conduction code was developed using finite differences. A stability restriction on the time step was avoided using a technique proposed by Brian. Computations from the code were validated using both the explicit technique and an available closed from solution for small times. The maximum error was found to be within 0.019 percent for an 11
ICARUS: A general one-dimensional heat conduction code
S. B. Sutton
1984-01-01
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 finite difference scheme for the heat conduction equation
E. Livne; A. Glasner
1985-01-01
A symmetrical semi-implicit (SSI) difference scheme is formulated for the heat conduction equation. The scheme is easy to code, fast and quite accurate. The advantage of the scheme appears mainly when used for large, complicated, multidimensional grids and for nonlinear problems.
Three-dimensional transient heat conduction in a multilayer medium
R. M. Clever; A. T. Wassel
1985-01-01
Transient three-dimensional heat conduction calculations are required in many aerospace applications. The computer codes available have several drawbacks. The explicit codes require a small time step to avoid numerical instability, while the implicit codes require an inversion of large matrices. If large numbers of nodes are used, both methods can become quite expensive. By using implicit finite difference techniques, such
Phonon heat conduction in a semiconductor nanowire and Alexander Balandin
October 2000; accepted for publication 4 December 2000 A model for phonon heat conduction in a semiconductor nanowire with dimensions comparable to the phonon mean free path is developed. It is based in a generic semiconductor nanowire with lateral dimensions comparable to the acoustic phonon mean free path
Coupled heat conduction and deformation in a viscoelastic composite cylinder
Shah, Sneha
2010-01-16
field due to unsteady heat conduction phenomenon is analyzed on the short term and long term material response in terms of stress, strain and displacement fields. The material properties of the two layers of the composite cylinder at any given location...
Validation of a heat conduction model for finite domain, non-uniformly heated, laminate bodies
NASA Astrophysics Data System (ADS)
Desgrosseilliers, Louis; Kabbara, Moe; Groulx, Dominic; White, Mary Anne
2015-08-01
Infrared thermographic validation is shown for a closed-form analytical heat conduction model for non-uniformly heated, laminate bodies with an insulated domain boundary. Experiments were conducted by applying power to rectangular electric heaters and cooled by natural convection in air, but also apply to constant-temperature heat sources and forced convection. The model accurately represents two-dimensional laminate heat conduction behaviour giving rise to heat spreading using one-dimensional equations for the temperature distributions and heat transfer rates under steady-state and pseudo-steady-state conditions. Validation of the model with an insulated boundary (complementing previous studies with an infinite boundary) provides useful predictions of heat spreading performance and simplified temperature uniformity calculations (useful in log-mean temperature difference style heat exchanger calculations) for real laminate systems such as found in electronics heat sinks, multi-ply stovetop cookware and interface materials for supercooled salt hydrates. Computational determinations of implicit insulated boundary condition locations in measured data, required to assess model equation validation, were also demonstrated. Excellent goodness of fit was observed (both root-mean-square error and R 2 values), in all cases except when the uncertainty of low temperatures measured via infrared thermography hindered the statistical significance of the model fit. The experimental validation in all other cases supports use of the model equations in design calculations and heat exchange simulations.
High temperature electrically conducting ceramic heating element and control system
NASA Technical Reports Server (NTRS)
Halbach, C. R.; Page, R. J.
1975-01-01
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.
Thermal conductivity, electrical conductivity and specific heat of copper-carbon fiber composite
NASA Technical Reports Server (NTRS)
Kuniya, Keiichi; Arakawa, Hideo; Kanai, Tsuneyuki; Chiba, Akio
1988-01-01
A new material of copper/carbon fiber composite is developed which retains the properties of copper, i.e., its excellent electrical and thermal conductivity, and the property of carbon, i.e., a small thermal expansion coefficient. These properties of the composite are adjustable within a certain range by changing the volume and/or the orientation of the carbon fibers. The effects of carbon fiber volume and arrangement changes on the thermal and electrical conductivity, and specific heat of the composite are studied. Results obtained are as follows: the thermal and electrical conductivity of the composite decrease as the volume of the carbon fiber increases, and were influenced by the fiber orientation. The results are predictable from a careful application of the rule of mixtures for composites. The specific heat of the composite was dependent, not on fiber orientation, but on fiber volume. In the thermal fatigue tests, no degradation in the electrical conductivity of this composite was observed.
Estimating interfacial thermal conductivity in metamaterials through heat flux mapping
NASA Astrophysics Data System (ADS)
Canbazoglu, Fatih M.; Vemuri, Krishna P.; Bandaru, Prabhakar R.
2015-04-01
The variability of the thickness as well as the thermal conductivity of interfaces in composites may significantly influence thermal transport characteristics and the notion of a metamaterial as an effective medium. The consequent modulations of the heat flux passage are analytically and experimentally examined through a non-contact methodology using radiative imaging, on a model anisotropic thermal metamaterial. It was indicated that a lower Al layer/silver interfacial epoxy ratio of ˜25 compared to that of a Al layer/alumina interfacial epoxy (of ˜39) contributes to a smaller deviation of the heat flux bending angle.
Development of a high capacity variable conductance heat pipe.
NASA Technical Reports Server (NTRS)
Kosson, R.; Hembach, R.; Edelstein, F.; Loose, J.
1973-01-01
The high-capacity, pressure-primed, tunnel-artery wick concept was used in a gas-controlled variable conductance heat pipe. A variety of techniques were employed to control the size of gas/vapor bubbles trapped within the artery. Successful operation was attained with a nominal 6-foot long, 1-inch diameter cold reservoir VCHP using ammonia working fluid and nitrogen control gas. The pipe contained a heat exchanger to subcool the liquid in the artery. Maximum transport capacity with a 46-inch effective length was 1200 watts level (more than 50,000 watt-inches) and 800 watts at 0.5-inch adverse tilt.
Heating rate controller for thermally stimulated conductivity and thermoluminescence measurements.
NASA Technical Reports Server (NTRS)
Manning, E. G.; Littlejohn, M. A.; Oakley, E. M.; Hutchby , J. A.
1972-01-01
A temperature controller is described which enables the temperature of a sample mounted on a cold finger to be varied linearly with time. Heating rates between 0.5 and 10 K/min can be achieved for temperatures between 90 and 300 K. Provision for terminating the sample heating at any temperature between these extremes is available. The temperature can be held at the terminating temperature or be reduced to the starting temperature in a matter of minutes. The controller has been used for thermally stimulated conductivity measurements and should be useful for thermoluminescence measurements as well.
Increasing Boiling Heat Transfer using Low Conductivity Materials.
Mahamudur Rahman, Md; Pollack, Jordan; McCarthy, Matthew
2015-01-01
We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches. PMID:26281890
Increasing Boiling Heat Transfer using Low Conductivity Materials
NASA Astrophysics Data System (ADS)
Mahamudur Rahman, Md; Pollack, Jordan; McCarthy, Matthew
2015-08-01
We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches.
Increasing Boiling Heat Transfer using Low Conductivity Materials
Mahamudur Rahman, Md; Pollack, Jordan; McCarthy, Matthew
2015-01-01
We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches. PMID:26281890
Heating of foods in space-vehicle environments. [by conductive heat transfer
NASA Technical Reports Server (NTRS)
Bannerot, R. B.; Cox, J. E.; Chen, C. K.; Heidelbaugh, N. D.
1973-01-01
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.
Revealing the complex conduction heat transfer mechanism of nanofluids
NASA Astrophysics Data System (ADS)
Sergis, A.; Hardalupas, Y.
2015-06-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects
Revealing the complex conduction heat transfer mechanism of nanofluids.
Sergis, A; Hardalupas, Y
2015-12-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects. PMID:26058515
Collins, Kimberlee C. (Kimberlee Chiyoko)
2015-01-01
Studies of non-diffusive heat conduction provide insight into the fundamentals of heat transport in condensed matter. The mean free paths (MFPs) of phonons that are most important for conducting heat are well represented ...
Kinematic Self-Similar Heat Conducting and Charge Solutions
M. Sharif; Wajiha Javed
2010-12-01
The objective of this paper is to study the plane symmetric kinematic self-similar heat conducting fluid and charge dust solutions of the Einstein field equations. These solutions are classified according to self-similarity of the first, second, zeroth and infinite kinds with different equations of state. We take the self-similar vector to be tilted, orthogonal and parallel to the fluid flow. For heat conducting fluid, it is found that there exist only \\emph{one} solution in parallel case. In all other possibilities, these solutions reduce to the perfect fluid kinematic self-similar solutions. For charge dust case, we also obtain only \\emph{one} kinematic self-similar solution.
An eigenvalue method for solving transient heat conduction problems
NASA Technical Reports Server (NTRS)
Shih, T. M.; Skladany, J. T.
1983-01-01
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.
Numerical solution of the imprecisely defined inverse heat conduction problem
NASA Astrophysics Data System (ADS)
Smita, Tapaswini; Chakraverty, S.; Diptiranjan, Behera
2015-05-01
This paper investigates the numerical solution of the uncertain inverse heat conduction problem. Uncertainties present in the system parameters are modelled through triangular convex normalized fuzzy sets. In the solution process, double parametric forms of fuzzy numbers are used with the variational iteration method (VIM). This problem first computes the uncertain temperature distribution in the domain. Next, when the uncertain temperature measurements in the domain are known, the functions describing the uncertain temperature and heat flux on the boundary are reconstructed. Related example problems are solved using the present procedure. We have also compared the present results with those in [Inf. Sci. (2008) 178 1917] along with homotopy perturbation method (HPM) and [Int. Commun. Heat Mass Transfer (2012) 39 30] in the special cases to demonstrate the validity and applicability.
Niu, Xufeng; Rouabhia, Mahmoud; Chiffot, Nicolas; King, Martin W; Zhang, Ze
2015-08-01
This study was to demonstrate that an extremely thin coating of poly(3,4-ethylenedioxythiophene) (PEDOT) on nonwoven microfibrous poly(l-lactic acid) (PLLA) web is of sufficient electrical conductivity and stability in aqueous environment to sustain electrical stimulation (ES) to cultured human skin fibroblasts. The PEDOT imparted the web a surface resistivity of approximately 0.1 K?/square without altering the web morphology. X-ray photoelectron spectroscopy demonstrated that the surface chemistry of the PLLA/PEDOT is characteristic of both PLLA and PEDOT. The PEDOT-coated web also showed higher hydrophilicity, lower glass transition temperature and unchanged fiber crystallinity and thermal stability compared with the PLLA web. The addition of PEDOT to the web marginally increased the web's tensile strength and lowered the elongation. An electrical stability test showed that the PLLA/PEDOT structure was more stable than a polypyrrole treated PLLA fabric, showing only a slow deterioration in conductivity when exposed to culture medium. The cytotoxicity test showed that the PLLA/PEDOT scaffold was not cytotoxic and supported human dermal fibroblast adhesion, migration, and proliferation. Preliminary ES experiments have demonstrated that this conductive web mediated effective ES to fibroblasts. Therefore, this new conductive biodegradable scaffold may be used to electrically modulate cellular activity and tissue regeneration. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 2635-2644, 2015. PMID:25630631
Dynamic adaptation method in gasdynamic simulations with nonlinear heat conduction
P. V. Breslavskii; V. I. Mazhukin
2008-01-01
A dynamic adaptation method is applied to gas dynamics problems with nonlinear heat conduction. The adaptation function is\\u000a determined by the condition that the energy equation is quasi-stationary and the grid point distribution is quasi-uniform.\\u000a The dynamic adaptation method with the adaptation function thus determined and a front-tracking technique are used to solve\\u000a the model problem of a piston moving
Traffic-and Thermal-Aware Run-Time Thermal Management Scheme for 3D NoC Systems
Wu, An-Yeu "Andy"
the majority of the switching activities close to the heat sink is a specialized technique. For the 3D consumption, and higher network bandwidth. However, the length of heat conduction path and power density per 3D NoC. As more dies stacked vertically, power density (in W/m2 ) increases, and the length of heat
Fuzzy and interval finite element method for heat conduction problem
Sarangam Majumdar; Sukanta Nayak; S. Chakraverty
2012-09-26
Traditional finite element method is a well-established method to solve various problems of science and engineering. Different authors have used various methods to solve governing differential equation of heat conduction problem. In this study, heat conduction in a circular rod has been considered which is made up of two different materials viz. aluminum and copper. In earlier studies parameters in the differential equation have been taken as fixed (crisp) numbers which actually may not. Those parameters are found in general by some measurements or experiments. So the material properties are actually uncertain and may be considered to vary in an interval or as fuzzy and in that case complex interval arithmetic or fuzzy arithmetic has to be considered in the analysis. As such the problem is discretized into finite number of elements which depend on interval/fuzzy parameters. Representation of interval/fuzzy numbers may give the clear picture of uncertainty. Hence interval/fuzzy arithmetic is applied in the finite element method to solve a steady state heat conduction problem. Application of fuzzy finite element method in the said problem gives fuzzy system of linear equations in general. Here new methods have also been proposed to handle such type of fuzzy system of linear equations. Corresponding results are computed and has been reported here.
Douglas W. Marshall; Changhu Xing; Charles Folsom; Colby Jensen; Heng Ban
2014-05-01
As an important factor affecting the accuracy of the thermal conductivity measurement, systematic (bias) error in the guarded comparative axial heat flow (cut-bar) method was mostly neglected by previous researches. This bias is due primarily to the thermal conductivity mismatch between sample and meter bars (reference), which is common for a sample of unknown thermal conductivity. A correction scheme, based on a finite element simulation of the measurement system, was proposed to reduce the magnitude of the overall measurement uncertainty. This scheme was experimentally validated by applying corrections on four types of sample measurements in which the specimen thermal conductivity is much smaller, slightly smaller, equal and much larger than that of the meter bar. As an alternative to the optimum guarding technique proposed before, the correction scheme can be used to minimize uncertainty contribution from the measurement system with non-optimal guarding conditions. It is especially necessary for large thermal conductivity mismatches between sample and meter bars.
Calibrated Heat Flow Model for Determining the Heat Conduction Losses in Laser Cutting of CFRP
NASA Astrophysics Data System (ADS)
Mucha, P.; Weber, R.; Speker, N.; Berger, P.; Sommer, B.; Graf, T.
Laser machining has great potential regarding automation in fabrication of CFRP (carbon-fiber-reinforced plastics) parts, due to the nearly force and tool-wear free processing at high process speeds. The high vaporization temperatures and the large heat conductivity of the carbon fibers lead to a large heat transport into the sample. This causes the formation of a heat-affected zone and a decrease of the process speed. In the present paper,an analytical heat flow model was adapted in order to understand and investigate the heat conduction losses. Thermal sensors were embedded in samples at different distances from the kerf to fit the calculated to the measured temperatures. Heat conduction losses of up to 30% of the laser power were determined. Furthermore, the energy not absorbed by the sample, the energy for sublimating the composite material in the kerf, the energy for the formation of the HAZ, and the residual heat in the sample are compared in an energy balance.
Thermal conductivity measurements of proton-heated warm dense matter
NASA Astrophysics Data System (ADS)
McKelvey, A.; Fernandez-Panella, A.; Hua, R.; Kim, J.; King, J.; Sio, H.; McGuffey, C.; Kemp, G. E.; Freeman, R. R.; Beg, F. N.; Shepherd, R.; Ping, Y.
2015-06-01
Accurate knowledge of conductivity characteristics in the strongly coupled plasma regime is extremely important for ICF processes such as the onset of hydrodynamic instabilities, thermonuclear burn propagation waves, shell mixing, and efficient x-ray conversion of indirect drive schemes. Recently, an experiment was performed on the Titan laser platform at the Jupiter Laser Facility to measure the thermal conductivity of proton-heated warm dense matter. In the experiment, proton beams generated via target normal sheath acceleration were used to heat bi-layer targets with high-Z front layers and lower-Z back layers. The stopping power of a material is approximately proportional to Z2 so a sharp temperature gradient is established between the two materials. The subsequent thermal conduction from the higher-Z material to the lower-Z was measured with time resolved streaked optical pyrometry (SOP) and Fourier domain interferometry (FDI) of the rear surface. Results will be used to compare predictions from the thermal conduction equation and the Wiedemann-Franz Law in the warm dense matter regime. Data from the time resolved diagnostics for Au/Al and Au/C Targets of 20-200 nm thickness will be presented.
NASA Astrophysics Data System (ADS)
Erlekampf, J.; Seebeck, J.; Savva, P.; Meissner, E.; Friedrich, J.; Alt, N. S. A.; Schlücker, E.; Frey, L.
2014-10-01
A numerical analysis of an ammonothermal synthesis process for the bulk growth of nitride crystals was performed. The analysis includes the development of a thermal model for a lab-scale ammonothermal autoclave, which was validated by in situ temperature measurements and applied to tailor the temperature field inside the autoclave. Based on the results of the global thermal 2D simulations, a local 3D model was used to include convective phenomena in the analysis. Moreover, the influence of the baffle and different baffle shapes on the flow velocity was investigated. Fluctuations of the temperature as well as the flow velocities occur, indicating that 3D considerations are essential to accurately investigate the heat and mass transport in ammonothermal systems.
NASA Technical Reports Server (NTRS)
Kachanov, Mark
1998-01-01
Analysis of the effective thermal conductivity of ceramic coatings and its relation to the microstructure continued. Results (obtained in Task 1) for the three-dimensional problem of heat conduction in a solid containing an inclusion (or, in particular, cavity - thermal insulator) of the ellipsoidal shape, were further advanced in the following two directions: (1) closed form expressions of H tensor have been derived for special cases of ellipsoidal cavity geometry: spheroid, crack-like spheroidal cavity and needle shaped spheroidal cavity; (2) these results for one cavity have been incorporated to construct heat energy potential for a solid with many spheroidal cavities (in the approximation of non-interacting defects). This problem constitutes a basic building block for further analyses.
Jin Wen
2011-01-01
In this article, we use the method of fundamental solutions to reconstruct the heat source and part of the initial temperature simultaneously in one-dimensional heat conduction problem. This problem is ill-posed, thus a Tikhonov regularization method with generalized cross-validation criterion is applied to obtain a stable numerical solution. Numerical experiments for several examples show that the proposed method is reasonable
Sodium Variable Conductance Heat Pipe for Radioisotope Stirling Systems
NASA Technical Reports Server (NTRS)
Tarau, Calin; Anderson, William G.; Walker, Kara
2009-01-01
In a Stirling radioisotope system, heat must continually be removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the converter stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, and also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) has been designed to allow multiple stops and restarts of the Stirling convertor in an Advanced Stirling Radioisotope Generator (ASRG). When the Stirling convertor is turned off, the VCHP will activate when the temperatures rises 30 C above the setpoint temperature. A prototype VCHP with sodium as the working fluid was fabricated and tested in both gravity aided and against gravity conditions for a nominal heater head temperature of 790 C. The results show very good agreement with the predictions and validate the model. The gas front was located at the exit of the reservoir when heater head temperature was 790 C while cooling was ON, simulating an operating Advanced Stirling Converter (ASC). When cooling stopped, the temperature increased by 30 C, allowing the gas front to move past the radiator, which transferred the heat to the case. After resuming the cooling flow, the front returned at the initial location turning OFF the VCHP. The against gravity working conditions showed a colder reservoir and faster transients.
Fabrication and test of a variable conductance heat pipe
NASA Technical Reports Server (NTRS)
Lehtinen, A. M.
1978-01-01
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.
Variable Conductance Heat Pipes for Radioisotope Stirling Systems
NASA Technical Reports Server (NTRS)
Anderson, William G.; Tarau, Calin
2008-01-01
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.
Hierarchical Parallelism in Finite Difference Analysis of Heat Conduction
NASA Technical Reports Server (NTRS)
Padovan, Joseph; Krishna, Lala; Gute, Douglas
1997-01-01
Based on the concept of hierarchical parallelism, this research effort resulted in highly efficient parallel solution strategies for very large scale heat conduction problems. Overall, the method of hierarchical parallelism involves the partitioning of thermal models into several substructured levels wherein an optimal balance into various associated bandwidths is achieved. The details are described in this report. Overall, the report is organized into two parts. Part 1 describes the parallel modelling methodology and associated multilevel direct, iterative and mixed solution schemes. Part 2 establishes both the formal and computational properties of the scheme.
Tunable single-photon heat conduction in electrical circuits
NASA Astrophysics Data System (ADS)
Jones, P. J.; Huhtamäki, J. A. M.; Partanen, M.; Tan, K. Y.; Möttönen, M.
2012-07-01
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.
Specific heat and thermal conductivity of solid fullerenes
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
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.
THERM: A three-dimensional transient heat conduction computer program
NASA Astrophysics Data System (ADS)
Cook, W. A.
1991-10-01
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.
Combined conduction and radiation heat transfer in concentric cylindrical media
NASA Technical Reports Server (NTRS)
Pandey, D. K.
1987-01-01
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.
A simple optical probe of transient heat conduction
NASA Astrophysics Data System (ADS)
Brody, Jed; Andreae, Phillip; Robinson, C. Andrew
2010-05-01
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.
Tunable single-photon heat conduction in electrical circuits
P. J. Jones; J. A. M. Huhtamäki; M. Partanen; K. Y. Tan; M. Möttönen
2012-05-21
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.
Pseudo-updated constrained solution algorithm for nonlinear heat conduction
NASA Technical Reports Server (NTRS)
Tovichakchaikul, S.; Padovan, J.
1983-01-01
This paper develops efficiency and stability improvements in the incremental successive substitution (ISS) procedure commonly used to generate the solution to nonlinear heat conduction problems. This is achieved by employing the pseudo-update scheme of Broyden, Fletcher, Goldfarb and Shanno in conjunction with the constrained version of the ISS. The resulting algorithm retains the formulational simplicity associated with ISS schemes while incorporating the enhanced convergence properties of slope driven procedures as well as the stability of constrained approaches. To illustrate the enhanced operating characteristics of the new scheme, the results of several benchmark comparisons are presented.
AdS/CFT correspondence with heat conduction
NASA Astrophysics Data System (ADS)
Alsup, James; Siopsis, George; Middleton, Chad
2007-10-01
We study an extension of the gravity dual to a perfect fluid model found by Janik and Peschanski. By relaxing one of the constraints, namely invariance under reflection in the longitudinal direction, we introduce a metric ansatz which includes off-diagonal terms. We also include an R-charge following Bak and Janik. We solve the Maxwell-Einstein equations and through holographic renormalization, we show that the off-diagonal components of the bulk metric give rise to heat conduction in the corresponding CFT on the boundary.
NASA Astrophysics Data System (ADS)
von Hebel, Christian; Rudolph, Sebastian; Huisman, Johan A.; van der Kruk, Jan; Vereecken, Harry
2013-04-01
Electromagnetic induction (EMI) systems enable the non-invasive spatial characterization of soil structural and hydrogeological variations, since the measured apparent electrical conductivity (ECa) can be related to changes in soil moisture, soil water, clay content and/or salinity. Due to the contactless operation, ECa maps of relatively large areas, i.e. field to (small) catchment scale, can be measured in reasonably short times. A multi-configuration EMI system with one electromagnetic field transmitter and various receivers with different offsets provide simultaneous ECa measurements that are representative of different sensing depths. Unfortunately, measured ECa values can only be considered as qualitative values due to external influences like the operator, cables or other metal objects. Of course, a better vertical characterization of the subsurface is possible when quantitative measurement values could be obtained. To obtain such quantitative ECa values, the measured EMI apparent conductivities are calibrated using a linear regression approach with predicted apparent conductivities obtained from a Maxwell-based full-solution forward model using inverted electrical resistivity tomography (ERT) data as input. These calibrated apparent conductivities enable a quantitative multi-layer-inversion to resolve for the electrical conductivity of certain layers. To invert for a large scale three-layer model, a one-dimensional (1D) shuffled-complex-evolution inversion scheme was parallelized and run on JUROPA - one of the supercomputers of the Forschungszentrum Jülich. This novel inversion routine was applied to calibrated electromagnetic induction data acquired at the Selhausen test site (Germany), which has a size of about 190 x 70 m. The test site is weakly inclined and a distinct gradient in soil texture is present with considerably higher gravel content at the upper part of the field. Parallel profiles with approximately three meter distance were measured using three different coil offsets in HCP and VCP measurement modes. This resulted in six high spatial resolution data sets of approximately 60000 measurements with different sensing depths. A 5 m block-kriging was applied to all six data sets to re-grid the sampling points on the same regular grid. For each grid node, the six measured apparent conductivities were used in a three-layer inversion. The three-layer inversion results of electrical conductivity thus obtained were used to derive a three-dimensional (3D) model of subsurface heterogeneity, which clearly indicated lateral and vertical conductivity changes of the subsurface that are related to changes in soil texture and soil water content.
Homogeneous Thermal Cloak with Constant Conductivity and Tunable Heat Localization
Han, Tiancheng; Yuan, Tao; Li, Baowen; Qiu, Cheng-Wei
2013-01-01
Invisible cloak has long captivated the popular conjecture and attracted intensive research in various communities of wave dynamics, e.g., optics, electromagnetics, acoustics, etc. However, their inhomogeneous and extreme parameters imposed by transformation-optic method will usually require challenging realization with metamaterials, resulting in narrow bandwidth, loss, polarization-dependence, etc. In this paper, we demonstrate that thermodynamic cloak can be achieved with homogeneous and finite conductivity only employing naturally available materials. It is demonstrated that the thermal localization inside the coating layer can be tuned and controlled robustly by anisotropy, which enables an incomplete cloak to function perfectly. Practical realization of such homogeneous thermal cloak has been suggested by using two naturally occurring conductive materials, which provides an unprecedentedly plausible way to flexibly realize thermal cloak and manipulate heat flow with phonons. PMID:23549139
Homogeneous thermal cloak with constant conductivity and tunable heat localization.
Han, Tiancheng; Yuan, Tao; Li, Baowen; Qiu, Cheng-Wei
2013-01-01
Invisible cloak has long captivated the popular conjecture and attracted intensive research in various communities of wave dynamics, e.g., optics, electromagnetics, acoustics, etc. However, their inhomogeneous and extreme parameters imposed by transformation-optic method will usually require challenging realization with metamaterials, resulting in narrow bandwidth, loss, polarization-dependence, etc. In this paper, we demonstrate that thermodynamic cloak can be achieved with homogeneous and finite conductivity only employing naturally available materials. It is demonstrated that the thermal localization inside the coating layer can be tuned and controlled robustly by anisotropy, which enables an incomplete cloak to function perfectly. Practical realization of such homogeneous thermal cloak has been suggested by using two naturally occurring conductive materials, which provides an unprecedentedly plausible way to flexibly realize thermal cloak and manipulate heat flow with phonons. PMID:23549139
Zhang, Xian; Wang, Qiuran; Ma, Zhimin; He, Jianqiao; Wang, Zhe; Zheng, Chong; Lin, Jianhua; Huang, Fuqiang
2015-06-01
Two compounds with the formulas of Na4Cu32Sn12S48·4H2O and K11Cu32Sn12S48·4H2O were synthesized via flux (with thiourea as reactive flux) and hydrothermal method, respectively. The black crystals of Na4Cu32Sn12S48·4H2O and K11Cu32Sn12S48·4H2O both crystallize in the cubic space group of Fm3?c with the cell constants a = 17.921(2) Å and a = 18.0559(6) Å, respectively. The crystal structures feature a 3D open-framework with the unique [Cu8Sn6S24](z-) (z = 13 for Na4Cu32Sn12S48·4H2O; z = 14.75 for K11Cu32Sn12S48·4H2O) clusters acting as building blocks. The [Cu8Sn6S24](z-) cluster of the Th symmetry is built up by eight [CuS3] triangles and six [SnS4] tetrahedra. The powder samples were investigated by X-ray diffraction and optical absorption measurements. Both phase-pure compounds show multiabsorption character with a main absorption edge (2.0 eV for Na4Cu32Sn12S48·4H2O and 1.9 eV for K11Cu32Sn12S48·4H2O) and an additional absorption peak (1.61 eV for Na4Cu32Sn12S48·4H2O and 1.52 eV for K11Cu32Sn12S48·4H2O), which are perfectly consistent with the first-principle calculation results. The analyses of the density of states further reveal that the two optical absorption bands in each compound are attributed to the two transitions of Cu-3d-S-3p ? Sn-5s. The multiband nature of two compounds also enhances photocatalytic activity under visible light irradiation, with which the degradation of methyl blue over Na4Cu32Sn12S48·4H2O reached 100% in 3 h. The 3D open-framework features also facilitate the ionic conductivity nature of the Na4Cu32Sn12S48·4H2O compound, which achieved ?10(-5) S/cm at room temperature. PMID:25955506
Zhou, Huan-Ping; Zhang, Ya-Wen; Mai, Hao-Xin; Sun, Xiao; Liu, Qiang; Song, Wei-Guo; Yan, Chun-Hua
2008-01-01
Uniform CeO(2) nanoflowers were synthesized by rapid thermolysis of (NH(4))(2)Ce(NO(3))(6) in oleic acid (OA)/oleylamine (OM), by a unique 3D oriented-attachment mechanism. CeO(2) nanoflowers with controlled shape (cubic, four-petaled, and starlike) and tunable size (10-40 nm) were obtained by adjusting the reaction conditions including solvent composition, precursor concentration, reaction temperature, and reaction time. The nanoflower growth mechanism was investigated by in situ electrical conductance measurements, transmission electron microscopy, and UV/Vis spectroscopy. The CeO(2) nanoflowers are likely formed in two major steps, that is, initial formation of ceria cluster particles capped with various ligands (e.g., OA, OM, and NO(3) (-)) via hydrolysis of (NH(4))(2)Ce(NO(3))(6) at temperatures in the range 140-220 degrees C, and subsequent spontaneous organization of the primary particles into nanoflowers by 3D oriented attachment, due to a rapid decrease in surface ligand coverage caused by sudden decomposition of the precursor at temperatures above 220 degrees C in a strong redox reaction. After calcination at 400 degrees C for 4 h the 33.8 nm CeO(2) nanoflowers have a specific surface area as large as 156 m(2) g(-1) with high porosity, and they are highly active for conversion of CO to CO(2) in the low temperature range of 200-400 degrees C. The present approach has also been extended to the preparation of other transition metal oxide (CoO, NiO, and CuO(x)) nanoflowers. PMID:18260069
Time-dependent simulations of point explosions with heat conduction
Shestakov, A.I. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
1999-05-01
A hydrodynamic-diffusion code is used to simulate a point explosion. The gas motion is governed by both hydrodynamics and nonlinear heat conduction and is a combination of the well-known, self-similar Taylor{endash}Sedov spherically expanding shock wave and the spherically expanding thermal wave. Two problems are discussed. In the first problem, a similarity solution exists if the diffusion coefficient is given in terms of powers of density and temperature which also define the ambient spatial density profile. If the initial explosion energy is small, the diffusive effect is limited to a region behind the shock. However, if the explosion energy is large, the thermal front precedes the hydrodynamic front, which is then an isothermal shock. In the second problem, the initial density is constant and the diffusion coefficient depends on only a power of the temperature. In this case, the solution is not self-similar; in early times, heat conduction dominates; in late times{emdash}hydrodynamics. The problems were previously analyzed by Reinicke and Meyer-ter-Vehn in terms of similarity variables. {copyright} {ital 1999 American Institute of Physics.}
High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems
NASA Technical Reports Server (NTRS)
Tarau, Calin; Walker, Kara L.; Anderson, William G.
2009-01-01
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.
High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems
NASA Astrophysics Data System (ADS)
Tarau, Calin; Walker, Kara L.; Anderson, William G.
2009-03-01
In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling converter provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) is under development to allow multiple stops and restarts of the Stirling engine. The status of the ongoing effort in developing this technology is presented in this paper. An earlier, preliminary design had a radiator outside the Advanced Stirling Radioisotope Generator (ASRG) casing, used NaK as the working fluid, and had the reservoir located on the cold side adapter flange. The revised design has an internal radiator inside the casing, with the reservoir embedded inside the insulation. A large set of advantages are offered by this new design. In addition to reducing the overall size and mass of the VCHP, simplicity, compactness and easiness in assembling the VCHP with the ASRG are significantly enhanced. Also, the permanently elevated temperatures of the entire VCHP allows the change of the working fluid from a binary compound (NaK) to single compound (Na). The latter, by its properties, allows higher performance and further mass reduction of the system. Preliminary design and analysis shows an acceptable peak temperature of the ASRG case of 140° C while the heat losses caused by the addition of the VCHP are 1.8 W.
Tzanova, S; Avenas, Y; Schaeffer, Ch
2008-01-01
The reported research work presents numerical studies validated by experimental results of a flat micro heat pipe with sintered copper wick structure. The objectives of this project are to produce and demonstrate the efficiency of the passive cooling technology (heat pipe) integrated in a very thin electronic substrate that is a part of a multifunctional 3-D electronic package. The enhanced technology is dedicated to the thermal management of high dissipative microsystems having heat densities of more than 10W/cm2. Future applications are envisaged in the avionics sector. In this research 2D numerical hydraulic model has been developed to investigate the performance of a very thin flat micro heat pipe with sintered copper wick structure, using water as a refrigerant. Finite difference method has been used to develop the model. The model has been used to determine the mass transfer and fluid flow in order to evaluate the limits of heat transport capacity as functions of the dimensions of the wick and the vapou...
Variable Conductance Heat Pipes for Radioisotope Stirling Systems
NASA Astrophysics Data System (ADS)
Anderson, William G.; Tarau, Calin
2008-01-01
In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) was designed to allow multiple stops and restarts of the Stirling engine. A VCHP was designed for the Advanced Stirling Radioisotope Generator, with a 850 °C heater head temperature. The VCHP turns on with a ?T of 30 °C, which is high enough to not risk standard ASRG operation but low enough to save most heater head life. This VCHP has a low mass, and low thermal losses for normal operation. In addition to the design, a proof-of-concept NaK VCHP was fabricated and tested. While NaK is normally not used in heat pipes, it has an advantage in that it is liquid at the reservoir operating temperature, while Na or K alone would freeze. The VCHP had two condensers, one simulating the heater head, and the other simulating the radiator. The experiments successfully demonstrated operation with the simulated heater head condenser off and on, while allowing the reservoir temperature to vary over 40 to 120 °C, the maximum range expected. In agreement with previous NaK heat pipe tests, the evaporator ?T was roughly 70 °C, due to distillation of the NaK in the evaporator.
Jeong, J.Y.; Ryou, H.S.
1997-03-01
Heat transfer characteristics and flow structure in turbulent flows through a flat plate three-dimensional turbulent boundary layer containing built-in vortex generators have been analyzed by means of the space marching Crank-Nicolson finite difference method. The method solves the slender flow approximation of the steady three-dimensional Navier-Stokes and energy equations. This study used the eddy diffusivity model and standard {kappa}-{epsilon} model to predict heat transfer and flow field in the turbulent flow with imbedded longitudinal vortex. The results show boundary layer distortion due to vortices, such as strong spanwise flow divergence and boundary layer thinning. The heat transfer and skin friction show relatively good results in comparison with experimental data. The vortex core moves slightly away from the wall and grows slowly; consequently, the vortex influences the flow over a very long distance downstream. The enhancement of the heat transfer in the vicinity of the wall is due to the increasing spanwise separation of the vortices as they develop in the streamwise direction.
Federal Register 2010, 2011, 2012, 2013, 2014
2012-12-12
...TRADE COMMISSION [Investigation No. 337-TA-851...with Multiple Heat- Conducting Paths and Products...Termination of the Investigation Based on Withdrawal...with multiple heat-conducting paths and products...moved to terminate the investigation in its entirety...
Heat conduction through a trapped solid: effect of structural changes on thermal conductance
Debasish Chaudhuri; Abhishek Chaudhuri; Surajit Sengupta
2007-03-20
We study the conduction of heat across a narrow solid strip trapped by an external potential and in contact with its own liquid. Structural changes, consisting of addition and deletion of crystal layers in the trapped solid, are produced by altering the depth of the confining potential. Nonequilibrium molecular dynamics simulations and, wherever possible, simple analytical calculations are used to obtain the thermal resistance in the liquid, solid and interfacial regions (Kapitza or contact resistance). We show that these layering transitions are accompanied by sharp jumps in the contact thermal resistance. Dislocations, if present, are shown to increase the thermal resistance of the strip drastically.
Wei, Meilin, E-mail: weimeilinhd@163.com [School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007 (China); Wang, Xiaoxiang; Sun, Jingjing [School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007 (China); Duan, Xianying, E-mail: dxynumber@163.com [Institute of Chemistry, Henan Academy of Sciences, Zhengzhou 450002 (China)
2013-06-01
We have succeeded in constructing a 3D POM–MOF, (H[Ni(Hbpdc)(H?O)?]?[PW??O??]·8H?O)_{n} (H?bpdc=2,2´-bipyridyl-3,3´-dicarboxylic acid), by the controllable self-assembly of H?bpdc, Keggin-anions and Ni²? ions based on the electrostatic and coordination interactions. Interestingly, Hbpdc? as polydentate organic ligands and Keggin-anion as polydentate inorganic ligands are covalently linked transition-metal nickel at the same time. The title complex represents a new example of introducing the metal N-heterocyclic multi-carboxylic acid frameworks into POMs chemistry. Based on Keggin-anions being immobilized as part of the metal N-heterocyclic multi-carboxylic acid framework, the title complex realizes four approaches in the 1D hydrophilic channel used to engender proton conductivity in MOFs. Its water adsorption isotherm at room temperature and pressure shows that the water content in it was 31 cm³ g?¹ at the maximum allowable humidity, corresponding to 3.7 water molecules per unit formula. It exhibits good proton conductivities (10??–10?³ S cm?¹) at 100 °C in the relative humidity range 35–98%. The corresponding activation energy (E{sub a}) of conductivity was estimated to be 1.01 eV. - Graphical abstract: A POM–MOF composite constructed by Keggin-type polyanion, Ni²? and H?bpdc shows good proton conductivities of 10??–10?³ S cm?¹ at 100 °C under 35–98% RH. - Highlights: • A POM–MOF was constructed by combining metal N-heterocyclic multi-carboxylic acid framework and Keggin anion. • It opens a pathway for design and synthesis of multifunctional hybrid materials based on two building units. • Three types of potential proton-carriers have been assembled in the 1D hydrophilic channels of the POM–MOF. • It achieved such proton conductivities as 10??–10?³ S cm?¹ at 100 °C in the RH range 35–98%.
Heat conduction in nanoscale materials: A statistical-mechanics derivation of the local heat flux
NASA Astrophysics Data System (ADS)
Li, Xiantao
2014-09-01
We derive a coarse-grained model for heat conduction in nanoscale mechanical systems. Starting with an all-atom description, this approach yields a reduced model, in the form of conservation laws of momentum and energy. The model closure is accomplished by introducing a quasilocal thermodynamic equilibrium, followed by a linear response approximation. Of particular interest is the constitutive relation for the heat flux, which is expressed nonlocally in terms of the spatial and temporal variation of the temperature. Nanowires made of copper and silicon are presented as examples.
Heat conduction in nanoscale materials: a statistical-mechanics derivation of the local heat flux.
Li, Xiantao
2014-09-01
We derive a coarse-grained model for heat conduction in nanoscale mechanical systems. Starting with an all-atom description, this approach yields a reduced model, in the form of conservation laws of momentum and energy. The model closure is accomplished by introducing a quasilocal thermodynamic equilibrium, followed by a linear response approximation. Of particular interest is the constitutive relation for the heat flux, which is expressed nonlocally in terms of the spatial and temporal variation of the temperature. Nanowires made of copper and silicon are presented as examples. PMID:25314400
Finite-element analysis of quasi-steady coupled nonlinear heat and electric conduction problems
S. R. Robertson
1986-01-01
The finite-element equations for coupled nonlinear heat conduction with phase change and steady current flow in the case where the electric field moves with constant speed are derived. The resulting matrix equations for quasi-static problems are nonsymmetric for the heat conduction part and symmetric for the electric field. The formulation is applied to several classical problems in heat conduction and
Efficient linear and nonlinear heat conduction with a quadrilateral element
NASA Technical Reports Server (NTRS)
Liu, W. K.; Belytschko, T.
1983-01-01
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.
Current fluctuations in a two dimensional model of heat conduction
NASA Astrophysics Data System (ADS)
Pérez-Espigares, Carlos; Garrido, Pedro L.; Hurtado, Pablo I.
2011-03-01
In this work we study numerically and analytically current fluctuations in the two-dimensional Kipnis-Marchioro-Presutti (KMP) model of heat conduction. For that purpose, we use a recently introduced algorithm which allows the direct evaluation of large deviations functions. We compare our results with predictions based on the Hydrodynamic Fluctuation Theory (HFT) of Bertini and coworkers, finding very good agreement in a wide interval of current fluctuations. We also verify the existence of a well-defined temperature profile associated to a given current fluctuation which depends exclusively on the magnitude of the current vector, not on its orientation. This confirms the recently introduced Isometric Fluctuation Relation (IFR), which results from the time-reversibility of the dynamics, and includes as a particular instance the Gallavotti-Cohen fluctuation theorem in this context but adds a completely new perspective on the high level of symmetry imposed by timereversibility on the statistics of nonequilibrium fluctuations.
THERM: A three-dimensional transient heat conduction computer program
Cook, W.A.
1991-10-01
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.
High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems
Tarau, Calin; Walker, Kara L.; Anderson, William G. [Advanced Cooling Technologies, Inc. 1046 New Holland Ave. Lancaster, PA 17601 (United States)
2009-03-16
In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling converter provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) is under development to allow multiple stops and restarts of the Stirling engine. The status of the ongoing effort in developing this technology is presented in this paper. An earlier, preliminary design had a radiator outside the Advanced Stirling Radioisotope Generator (ASRG) casing, used NaK as the working fluid, and had the reservoir located on the cold side adapter flange. The revised design has an internal radiator inside the casing, with the reservoir embedded inside the insulation. A large set of advantages are offered by this new design. In addition to reducing the overall size and mass of the VCHP, simplicity, compactness and easiness in assembling the VCHP with the ASRG are significantly enhanced. Also, the permanently elevated temperatures of the entire VCHP allows the change of the working fluid from a binary compound (NaK) to single compound (Na). The latter, by its properties, allows higher performance and further mass reduction of the system. Preliminary design and analysis shows an acceptable peak temperature of the ASRG case of 140 deg. C while the heat losses caused by the addition of the VCHP are 1.8 W.
Manipulating Steady Heat Conduction by Sensu-shaped Thermal Metamaterials.
Han, Tiancheng; Bai, Xue; Liu, Dan; Gao, Dongliang; Li, Baowen; Thong, John T L; Qiu, Cheng-Wei
2015-01-01
The ability to design the control of heat flow has innumerable benefits in the design of electronic systems such as thermoelectric energy harvesters, solid-state lighting, and thermal imagers, where the thermal design plays a key role in performance and device reliability. In this work, we employ one identical sensu-unit with facile natural composition to experimentally realize a new class of thermal metamaterials for controlling thermal conduction (e.g., thermal concentrator, focusing/resolving, uniform heating), only resorting to positioning and locating the same unit element of sensu-shape structure. The thermal metamaterial unit and the proper arrangement of multiple identical units are capable of transferring, redistributing and managing thermal energy in a versatile fashion. It is also shown that our sensu-shape unit elements can be used in manipulating dc currents without any change in the layout for the thermal counterpart. These could markedly enhance the capabilities in thermal sensing, thermal imaging, thermal-energy storage, thermal packaging, thermal therapy, and more domains beyond. PMID:25974383
Manipulating Steady Heat Conduction by Sensu-shaped Thermal Metamaterials
Han, Tiancheng; Bai, Xue; Liu, Dan; Gao, Dongliang; Li, Baowen; Thong, John T. L.; Qiu, Cheng-Wei
2015-01-01
The ability to design the control of heat flow has innumerable benefits in the design of electronic systems such as thermoelectric energy harvesters, solid-state lighting, and thermal imagers, where the thermal design plays a key role in performance and device reliability. In this work, we employ one identical sensu-unit with facile natural composition to experimentally realize a new class of thermal metamaterials for controlling thermal conduction (e.g., thermal concentrator, focusing/resolving, uniform heating), only resorting to positioning and locating the same unit element of sensu-shape structure. The thermal metamaterial unit and the proper arrangement of multiple identical units are capable of transferring, redistributing and managing thermal energy in a versatile fashion. It is also shown that our sensu-shape unit elements can be used in manipulating dc currents without any change in the layout for the thermal counterpart. These could markedly enhance the capabilities in thermal sensing, thermal imaging, thermal-energy storage, thermal packaging, thermal therapy, and more domains beyond. PMID:25974383
Manipulating Steady Heat Conduction by Sensu-shaped Thermal Metamaterials
NASA Astrophysics Data System (ADS)
Han, Tiancheng; Bai, Xue; Liu, Dan; Gao, Dongliang; Li, Baowen; Thong, John T. L.; Qiu, Cheng-Wei
2015-05-01
The ability to design the control of heat flow has innumerable benefits in the design of electronic systems such as thermoelectric energy harvesters, solid-state lighting, and thermal imagers, where the thermal design plays a key role in performance and device reliability. In this work, we employ one identical sensu-unit with facile natural composition to experimentally realize a new class of thermal metamaterials for controlling thermal conduction (e.g., thermal concentrator, focusing/resolving, uniform heating), only resorting to positioning and locating the same unit element of sensu-shape structure. The thermal metamaterial unit and the proper arrangement of multiple identical units are capable of transferring, redistributing and managing thermal energy in a versatile fashion. It is also shown that our sensu-shape unit elements can be used in manipulating dc currents without any change in the layout for the thermal counterpart. These could markedly enhance the capabilities in thermal sensing, thermal imaging, thermal-energy storage, thermal packaging, thermal therapy, and more domains beyond.
NASA Astrophysics Data System (ADS)
Rodrigues, Dario B.; Maccarini, Paolo F.; Salahi, Sara; Colebeck, Erin; Topsakal, Erdem; Pereira, Pedro J. S.; Limão-Vieira, Paulo; Stauffer, Paul R.
2013-02-01
Background: Brown adipose tissue (BAT) plays an important role in whole body metabolism and could potentially mediate weight gain and insulin sensitivity. Although some imaging techniques allow BAT detection, there are currently no viable methods for continuous acquisition of BAT energy expenditure. We present a non-invasive technique for long term monitoring of BAT metabolism using microwave radiometry. Methods: A multilayer 3D computational model was created in HFSSTM with 1.5 mm skin, 3-10 mm subcutaneous fat, 200 mm muscle and a BAT region (2-6 cm3) located between fat and muscle. Based on this model, a log-spiral antenna was designed and optimized to maximize reception of thermal emissions from the target (BAT). The power absorption patterns calculated in HFSSTM were combined with simulated thermal distributions computed in COMSOL® to predict radiometric signal measured from an ultra-low-noise microwave radiometer. The power received by the antenna was characterized as a function of different levels of BAT metabolism under cold and noradrenergic stimulation. Results: The optimized frequency band was 1.5-2.2 GHz, with averaged antenna efficiency of 19%. The simulated power received by the radiometric antenna increased 2-9 mdBm (noradrenergic stimulus) and 4-15 mdBm (cold stimulus) corresponding to increased 15-fold BAT metabolism. Conclusions: Results demonstrated the ability to detect thermal radiation from small volumes (2-6 cm3) of BAT located up to 12 mm deep and to monitor small changes (0.5 °C) in BAT metabolism. As such, the developed miniature radiometric antenna sensor appears suitable for non-invasive long term monitoring of BAT metabolism.
Rodrigues, Dario B.; Maccarini, Paolo F.; Salahi, Sara; Colebeck, Erin; Topsakal, Erdem; Pereira, Pedro J. S.; Limão-Vieira, Paulo; Stauffer, Paul R.
2013-01-01
Background Brown adipose tissue (BAT) plays an important role in whole body metabolism and could potentially mediate weight gain and insulin sensitivity. Although some imaging techniques allow BAT detection, there are currently no viable methods for continuous acquisition of BAT energy expenditure. We present a non-invasive technique for long term monitoring of BAT metabolism using microwave radiometry. Methods A multilayer 3D computational model was created in HFSS™ with 1.5 mm skin, 3–10 mm subcutaneous fat, 200 mm muscle and a BAT region (2–6 cm3) located between fat and muscle. Based on this model, a log-spiral antenna was designed and optimized to maximize reception of thermal emissions from the target (BAT). The power absorption patterns calculated in HFSS™ were combined with simulated thermal distributions computed in COMSOL® to predict radiometric signal measured from an ultra-low-noise microwave radiometer. The power received by the antenna was characterized as a function of different levels of BAT metabolism under cold and noradrenergic stimulation. Results The optimized frequency band was 1.5–2.2 GHz, with averaged antenna efficiency of 19%. The simulated power received by the radiometric antenna increased 2–9 mdBm (noradrenergic stimulus) and 4–15 mdBm (cold stimulus) corresponding to increased 15-fold BAT metabolism. Conclusions Results demonstrated the ability to detect thermal radiation from small volumes (2–6 cm3) of BAT located up to 12 mm deep and to monitor small changes (0.5 °C) in BAT metabolism. As such, the developed miniature radiometric antenna sensor appears suitable for non-invasive long term monitoring of BAT metabolism. PMID:24244831
NASA Astrophysics Data System (ADS)
Enssle, Carl Philipp; Croisé, Jean; Poller, Andreas; Mayer, Gerhard; Wendling, Jacques
An important question related to the long-term safety performance of a repository for long-lived medium and high-level radioactive waste in the Callovo-Oxfordian clay unit is the impact of heat and gas generated in the waste emplacement areas on the gas and water pressure and on the water saturation in the backfilled repository and in the host rock. The current design of such a repository consists of a multitude of different underground structures, such as emplacement drifts for waste canisters and other types of waste packages, access and ventilation drifts, and access shafts in the central part of the repository. The individual underground structures exhibit different thermo-hydraulic and geometrical properties yielding a large and complex system for the flow and transport of gas, water and heat. A detailed 3D modelling of the entire repository would require a tremendous computational effort, even when using high performance simulator codes. A newly developed method ( Poller et al., 2011) allows for the 3D modelling of the two-phase gas-water flow and thermal evolution in the entire repository/host-rock system in a simplified manner. Besides accounting for both the detailed structures at local scale and the global geometry of the drift network, it also allows for an assessment of the gas phase pressure as well as the hydrogen and heat fluxes developing over the complete lifetime of the repository system. In this paper, the results of a reference scenario are presented. The assessment focuses on the two dominant processes, i.e. the dissolution and diffusion of the generated hydrogen, and the advective migration of the forming hydrogen gas phase in space and time (up to 1 million years). Further, the main findings of a sensitivity analysis on different features, physical processes and parameter uncertainty are presented.
Tzanos, C. P.; Dionne, B. (Nuclear Engineering Division)
2011-05-23
To support the analyses related to the conversion of the BR2 core from highly-enriched (HEU) to low-enriched (LEU) fuel, the thermal-hydraulics codes PLTEMP and RELAP-3D are used to evaluate the safety margins during steady-state operation (PLTEMP), as well as after a loss-of-flow, loss-of-pressure, or a loss of coolant event (RELAP). In the 1-D PLTEMP and RELAP simulations, conduction in the azimuthal and axial directions is not accounted. The very good thermal conductivity of the cladding and the fuel meat and significant temperature gradients in the lateral directions (axial and azimuthal directions) could lead to a heat flux distribution that is significantly different than the power distribution. To evaluate the significance of the lateral heat conduction, 3-D computational fluid dynamics (CFD) simulations, using the CFD code STAR-CD, were performed. Safety margin calculations are typically performed for a hot stripe, i.e., an azimuthal region of the fuel plates/coolant channel containing the power peak. In a RELAP model, for example, a channel between two plates could be divided into a number of RELAP channels (stripes) in the azimuthal direction. In a PLTEMP model, the effect of azimuthal power peaking could be taken into account by using engineering factors. However, if the thermal mixing in the azimuthal direction of a coolant channel is significant, a stripping approach could be overly conservative by not taking into account this mixing. STAR-CD simulations were also performed to study the thermal mixing in the coolant. Section II of this document presents the results of the analyses of the lateral heat conduction and azimuthal thermal mixing in a coolant channel. Finally, PLTEMP and RELAP simulations rely on the use of correlations to determine heat transfer coefficients. Previous analyses showed that the Dittus-Boelter correlation gives significantly more conservative (lower) predictions than the correlations of Sieder-Tate and Petukhov. STAR-CD 3-D simulations were performed to compare heat transfer predictions from CFD and the correlations. Section III of this document presents the results of this analysis.
Numerical heat conduction in hydrodynamical models of colliding hypersonic flows
Parkin, E R
2010-01-01
Hydrodynamical models of colliding hypersonic flows are presented which explore the dependence of the resulting dynamics and the characteristics of the derived X-ray emission on numerical conduction and viscosity. For the purpose of our investigation we present models of colliding flow with plane-parallel and cylindrical divergence. Numerical conduction causes erroneous heating of gas across the contact discontinuity which has implications for the rate at which the gas cools. We find that the dynamics of the shocked gas and the resulting X-ray emission are strongly dependent on the contrast in the density and temperature either side of the contact discontinuity, these effects being strongest where the postshock gas of one flow behaves quasi-adiabatically while the postshock gas of the other flow is strongly radiative. Introducing additional numerical viscosity into the simulations has the effect of damping the growth of instabilities, which in some cases act to increase the volume of shocked gas and can re-he...
The Dance of Heating and Cooling in Galaxy Clusters: 3D Simulations of Self-Regulated AGN Outflows
Gaspari, M; Brighenti, F; D'Ercole, A
2010-01-01
It is now widely accepted that heating processes play a fundamental role in galaxy clusters, struggling in an intricate but fascinating `dance' with its antagonist, radiative cooling. Last generation observations, especially X-ray, are giving us tiny hints about the notes of this endless ballet. Cavities, shocks, turbulence and wide absorption-lines indicate the central active nucleus is injecting huge amount of energy in the intracluster medium. However, which is the real dominant engine of self-regulated heating? One of the model we propose are massive subrelativistic outflows, probably generated by a wind disc or just the result of the entrainment on kpc scale by the fast radio jet. Using a modified version of AMR code FLASH 3.2, we explored several feedback mechanisms which self-regulate the mechanical power. Two are the best schemes that answer our primary question, id est quenching cooling flow and at the same time preserving a cool core appearance for a long term evolution (7 Gyr): one more explosive (...
Waluyo, I.; Nordlund, D.; Naslund, L.-A.; Ogasawara, H.; Pettersson, L.G.M.; Nilsson, A.
2009-05-26
The formation of crystalline ice through isothermal heating of 80 layers amorphous ice on Pt(111) at 150 K is studied using X-ray photoelectron spectroscopy and infrared reflection absorption spectroscopy. An early indicator for inhomogeneous crystallization is provided by the uncharacteristically high Pt 4f photoelectron peak for crystalline ice compared with the corresponding uniformly thick amorphous case. O 1s photoelectron spectra unambiguously show that the first monolayer is exposed after crystallization at multilayer total coverage. Using the relative intensities between the first monolayer and multilayer contributions to the O 1s photoelectron spectra, we estimated that -46% and -80% of the first monolayer is exposed to vacuum with an average crystallite height of -41 and -31 layers for an equivalent total coverage of -23 and -7 layers, respectively.
Underground heat conduction near a spherical inhomogeneity: theory and applications
NASA Astrophysics Data System (ADS)
Rabinovich, A.; Dagan, G.; Miloh, T.
2012-06-01
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.
NASA Astrophysics Data System (ADS)
Ping, Y.; Fernandez-Panella, A.; Sio, H.; Correa, A.; Shepherd, R.; Landen, O.; London, R. A.; Sterne, P. A.; Whitley, H. D.; Fratanduono, D.; Boehly, T. R.; Collins, G. W.
2015-09-01
We propose a method for thermal conductivity measurements of high energy density matter based on differential heating. A temperature gradient is created either by surface heating of one material or at an interface between two materials by different energy deposition. The subsequent heat conduction across the temperature gradient is observed by various time-resolved probing techniques. Conceptual designs of such measurements using laser heating, proton heating, and x-ray heating are presented. The sensitivity of the measurements to thermal conductivity is confirmed by simulations.
Transient three-dimensional heat conduction computations using Brian's technique
NASA Astrophysics Data System (ADS)
Watson, John A.
1988-09-01
A transient three dimensional heat conduction code was developed using finite differences. A stability restriction on the time step was avoided using a technique proposed by Brian. Computations from the code were validated using both the explicit technique and an available closed from solution for small times. The maximum error was found to be within 0.019 percent for an 11 x 11 x 11 grid and time step of 17.117 seconds. The total CPU time to carry out the computations up to 3,600 seconds using Brian's techniques was six times that required for the explicit technique with the same time step of 17.117 seconds. However, as the time step was increased without altering the heometry, the CPU time using Brian's technique decreased and was less than that used in the explicit technique for time steps larger than 110 seconds. The validated code was also used in the analysis of the transient thermal response of a component on an orbiting spacecraft.
INCAP: A finite element program for one-dimensional nonlinear inverse heat conduction analysis
B. R. Bass
1979-01-01
The calculation of the surface temperature and surface heat flux from a measured temperature history at an interior point of a body, identified in literature as the inverse heat conduction problem, is examined. An inverse solution technique that utilizes a finite element heat conduction model and a nonlinear estimation procedure is presented. The technique is applicable to the one dimensional
Correlations and scaling in one-dimensional heat conduction J. M. Deutsch and Onuttom Narayan
Deutsch, Josh
of the heat current, through the Kubo formula, gives a thermal conductivity exponent of 1/3 in agreementCorrelations and scaling in one-dimensional heat conduction J. M. Deutsch and Onuttom Narayan of boundary conditions: for periodic boundary conditions as opposed to open boundary conditions with heat
Heat conduction in simple networks: The effect of interchain coupling Zonghua Liu1,2
Li, Baowen
Heat conduction in simple networks: The effect of interchain coupling Zonghua Liu1,2 and Baowen Li2; published 16 November 2007 Heat conduction in simple networks consisting of different one dimensional nonlinear chains is studied. We find that the coupling between chains has a different function in heat
Solution of the Heat Equation for transient conduction by LaPlace
McCready, Mark J.
Solution of the Heat Equation for transient conduction by LaPlace Transform This notebook has been for copying and dissemination Version: 3/17/98 #12;This notebook shows how to solve transient heat conduction in Mathematica. This problem is the heat transfer analog to the "Rayleigh" problem that starts on page 91
Thermographic validation of a novel, laminate body, analytical heat conduction model
NASA Astrophysics Data System (ADS)
Desgrosseilliers, Louis; Groulx, Dominic; White, Mary Anne
2014-07-01
The two-region fin model captures the heat spreading behaviour in multilayered composite bodies (i.e., laminates), heated only over a small part of their domains (finite heat source), where there is an inner layer that has a substantial capacity for heat conduction parallel to the heat exchange surface (convection cooling). This resulting heat conduction behaviour improves the overall heat transfer process when compared to heat conduction in homogeneous bodies. Long-term heat storage using supercooling salt hydrate phase change materials, stovetop cookware, and electronics cooling applications could all benefit from this kind of heat-spreading in laminates. Experiments using laminate films reclaimed from post-consumer Tetra Brik cartons were conducted with thin rectangular and circular heaters to confirm the laminate body, steady-state, heat conduction behaviour predicted by the two-region fin model. Medium to high accuracy experimental validation of the two-region fin model was achieved in Cartesian and cylindrical coordinates for forced external convection and natural convection, the latter for Cartesian only. These were conducted using constant heat flux finite heat source temperature profiles that were measured by infrared thermography. This validation is also deemed valid for constant temperature heat sources.
Thermal Conductivity of Composites Under Di erent Heating Scenarios
composite sample, and (iii) a continuous heat source. 1 Introduction Adhesives such as epoxies, gels, a ux due to the heat source at one end, and Newton cooling at the other end. Let u(t; z) represent): Here T1 denotes the ambient temperature, h is the Newton cooling constant (or heat transfer coe
SEP BIMOD variable conductance heat pipes acceptance and characterization tests
NASA Technical Reports Server (NTRS)
Hemminger, J. A.
1981-01-01
A series of six heat pipes, similar in design to those flown on the Comunications Technology Satellite Hermes, for use in a prototype Solar Electric Propulsion BIMOD thrust module are evaluated. The results of acceptance and characterization tests performed on the heat pipe subassemble are reported. The performance of all the heat pipes met, or exceeded, design specifications.
NASA Astrophysics Data System (ADS)
Yao, C.; Deschamps, F.; Lowman, J. P.; Sanchez-Valle, C.; Tackley, P. J.
2014-08-01
Because the viscosity of ice is strongly temperature dependent, convection in the ice layers of icy moons and dwarf planets likely operates in the stagnant lid regime, in which a rigid lid forms at the top of the fluid and reduces the heat transfer. A detailed modeling of the thermal history and radial structure of icy moons and dwarf planets thus requires an accurate description of stagnant lid convection. We performed numerical experiments of stagnant lid convection in 3-D spherical geometries for various ice shell curvatures f (measured as the ratio between the inner and outer radii), effective Rayleigh number Ram, and viscosity contrast ??. From our results, we derived scaling laws for the average temperature of the well-mixed interior, ?m, and the heat flux transported through the shell. The nondimensional temperature difference across the bottom thermal boundary layer is well described by (1-?m)=1.23?/f1.5, where ? is a parameter that controls the magnitude of the viscosity contrast. The nondimensional heat flux at the bottom of the shell, Fbot, scales as Fbot=1.46Ram0.27?1.21/f1.78. Our models also show that the development of the stagnant lid regime depends on f. For given values of Ram and ??, the stagnant lid is less developed as the shell's curvature increases (i.e., as f decreases), leading to improved heat transfer. Therefore, as the outer ice shells of icy moons and dwarf planets grow, the effects of a stagnant lid are less pronounced.
Microbeam Beam Heating Analysis of Thin Foils Using Heat Conduction Theory
Lovelace, B.; Haberl, A. W. [Ion Beam Laboratory, University at Albany, 1400 Washington Ave., Albany NY 12222 (United States); Bakhru, H. [College of Nanoscale Science and Engineering, University at Albany, 1400 Washington Ave., Albany NY 12203 (United States); Kimball, J. C.; Benenson, R. E. [Physics Department, University at Albany, 1400 Washington Ave., Albany NY 12222 (United States)
2009-03-10
The temperature distribution in and near the scan region of an ion microbeam is estimated using heat conduction theory. In the calculation, the energy deposited by a beam spot on a thin foil is treated as a point energy source. The spatial and time dependent temperature contributions from energy deposited by the ion beam rastering in a square scan pattern were then computed. The results showed that for poor conductors, the temperature of the material under the scan region can rise rapidly by up to two orders of magnitude, while that of good conductors remains virtually unchanged. The calculated results were consistent with experimental data where Mylar foils were scanned using an He microbeam and the time for melt through was measured. Radiational cooling effects were also investigated and found to contribute little to the heat losses at typical microbeam beam powers.
Yin Chou; Ruey-Jen Yang
2008-01-01
This study employs the space–time conservation element and solution element (CESE) method to simulate the temperature and heat flux distributions in a finite medium subject to various non-Fourier heat conduction models. The simulations consider three specific cases, namely a single phase lag (SPL) thermal wave model with a pulsed temperature condition, a SPL model with a surface heat flux input,
Jin Wen; Masahiro Yamamoto; Ting Wei
2012-01-01
In this article, we consider an inverse heat conduction problem of determining a time-dependent unknown heat source and unknown initial temperature by means of observations of the temperature at the final time and temperature profile at one fixed point over the time interval. We prove that the heat source and initial temperature can be determined uniquely from two kinds of
NASA Astrophysics Data System (ADS)
Rainey, E. S.; Kavner, A.; Hernlund, J. W.; Pilon, L.; Veitch, M.
2012-12-01
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.
Li, Baowen; Wang, Jiao; Wang, Lei; Zhang, Gang
2005-03-01
We study anomalous heat conduction and anomalous diffusion in low-dimensional systems ranging from nonlinear lattices, single walled carbon nanotubes, to billiard gas channels. We find that in all discussed systems, the anomalous heat conductivity can be connected with the anomalous diffusion, namely, if energy diffusion is sigma(2)(t)=2Dt(alpha) (0
Chen, Lin; Li, Zhen; Guo, Zeng-Yuan
2009-07-15
In this paper, two modified types of polypropylene (PP) with high thermal conductivity up to 2.3 W/m K and 16.5 W/m K are used to manufacture the finned-tube heat exchangers, which are prospected to be used in liquid desiccant air conditioning, heat recovery, water source heat pump, sea water desalination, etc. A third plastic heat exchanger is also manufactured with ordinary PP for validation and comparison. Experiments are carried out to determine the thermal performance of the plastic heat exchangers. It is found that the plastic finned-tube heat exchanger with thermal conductivity of 16.5 W/m K can achieve overall heat transfer coefficient of 34 W/m{sup 2} K. The experimental results are compared with calculation and they agree well with each other. Finally, the effect of material thermal conductivity on heat exchanger thermal performance is studied in detail. The results show that there is a threshold value of material thermal conductivity. Below this value improving thermal conductivity can considerably improve the heat exchanger performance while over this value improving thermal conductivity contributes very little to performance enhancement. For the finned-tube heat exchanger designed in this paper, when the plastic thermal conductivity can reach over 15 W/m K, it can achieve more than 95% of the titanium heat exchanger performance and 84% of the aluminum or copper heat exchanger performance with the same dimension. (author)
HEAT CONDUCTION OF SINGLE-WALLED CARBON NANOTUBE IN VARIOUS ENVIRONMENTS
Maruyama, Shigeo
-ku, Tokyo 113-8656, Japan ABSTRACT Some of our recent studies on the heat conduction of single-walled carbon simulations by Maruyama [1, 2] showed the power-law length dependence of SWNT thermal conductivity up to sub. The heat conduction can be altered by local thermal resistance due to defects, hetero-junctions and isotope
NASA Astrophysics Data System (ADS)
Gómez-Muñoz, José Luis; Bravo-Castillero, Julián
2008-08-01
The study of the effective properties of composite materials with anisotropic constituents and different inclusion shapes has motivated the development of the Mathematica 6.0 package "CompositeMaterials". This package can be used to calculate the effective anisotropic conductivity tensor of two-phase composites. Any fiber cross section, even percolating ones, can be studied in the 2D composites. "Rectangular Prism" and "Ellipsoidal" inclusion shapes with arbitrary orientations can be investigated in the 3D composites. This package combines the Asymptotic Homogenization Method and the Finite Element Method in order to obtain the effective conductivity tensor. The commands and options of the package are illustrated with two sample applications for two- and three-dimensional composites. Program summaryProgram title:CompositeMaterials Catalogue identifier:AEAU_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAU_v1_0.html Program obtainable from:CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions:Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.:132 183 No. of bytes in distributed program, including test data, etc.:1 334 908 Distribution format:tar.gz Programming language:Mathematica 6.0 Computer:Any that can run Mathematica 6.0 and where the open-source free C-programs Triangle ( http://www.cs.cmu.edu/ quake/triangle.html) and TetGen ( http://tetgen.berlios.de/) can be compiled and executed. Tested in Intel Pentium computers. Operating system:Any that can run Mathematica 6.0 and where the open-source free C-programs Triangle ( http://www.cs.cmu.edu/ quake/triangle.html) and TetGen ( http://tetgen.berlios.de/) can be compiled and executed. Tested in Windows XP. RAM:Small two-dimensional calculations require less than 100 MB. Large three-dimensional calculations require 500 MB or more. Classification:7.9 External routines:One Mathematica Add-on and two external programs: The free Mathematica Add-On IMS ( http://www.imtek.uni-freiburg.de/simulation/Mathematica/IMSweb/), The open-source free C-program Triangle ( http://www.cs.cmu.edu/ quake/triangle.html). The open-source free C-program TetGen ( http://tetgen.berlios.de/). The distribution file contains Windows executables for Triangle and TetGen. Nature of problem:The calculation of effective thermal conductivity tensor for two-dimensional and three-dimensional composite materials with anisotropic constituents and different inclusion shapes. Solution method:Asymptotic Homogenization Method, with the Cell Problems solved with Finite Element Method. Unusual features:Different inclusion shapes can be easily created. The constituents can be anisotropic. The intermediate stages and the final results can be graphed and analyzed with all the power of Mathematica 6.0. The use of the external meshing programs Triangle and TetGen is totally transparent for the end user. A typical calculation requires the use of only four special commands that follow standard Mathematica syntax. Additional comments:The executable binary files for Triangle and TetGen must be accessible from the directory specified by Mathematica's variable HomeDirectory. The IMS add-on and the CompositeMaterials package, which is the package presented in this work, must be installed in the directory specified by Mathematica's variable BaseDirectory or in the variable $UserBaseDirectory. The 2D calculations of Composite Materials will run successfully in Mathematica 5.2 and 6.0 but for the 3D calculations it is necessary to use Mathematica 6.0 or higher. Running time:Simple two-dimensional calculations can be done in less than a minute. Complex three-dimensional calculations can take an hour or more.
Conjugate conduction-convection heat transfer model for four-stroke heat-barrier-piston engines
Blank, D.A.; Shih, T.M.
1989-01-01
A numerical model for conjugate conduction-convection heat transfer in a four-stroke heat-barrier-piston engine has been developed. The system boundaries were extended beyond the flow to fixed distances within the piston and cylinder linings. The model was used to simulate the compression stroke and fuel injection portion of the power stroke of a four-stroke engine cycle. Final runs involved a 20 X 26 mesh to solve the conjugate heat transfer problem in the large region made up of the flow field and a thin portion of the adjacent cylinder linings. A smaller mesh was used for other flow field calculations inside the interior boundary of the cylinder linings and piston. The engine was modeled with the fuel injector co-located with a single valve, making possible an axisymmetric solution. The effects of swirl were not considered. It was found to be convenient to divide the flow field into three regions: one fixed in space with time, one utilizing a stretching and compressing computational mesh, and one moving with time without stretching and compressing.
Effective heat conductivity of fuel element bundles and steam generator tube bundles
NASA Astrophysics Data System (ADS)
Fedotovsky, V.; Orlov, A.
2008-06-01
Effective heat conductivity of rod and tube bundles is one of thermophysical properties necessary for calculation of thermo hydraulic characteristics of heat producing devices, heat exchange devices and steam generators. This report introduces results of mathematical modeling of effective heat conductivity of transversally anisotropic rod bundles in solid conductive medium. The considered bundles represented cylindrical rods fitted in corners of stretched and compressed in direction of heat transfer rectangular and triangular grids. The calculated results were compared to analytical solutions and previous numerical results.
Torres-Verdín, Carlos
in arbitrary 3D inhomogeneous anisotropic media can be expressed as -=× sE 0µi sH , (1) sss JEH +=× ' , (2 frequency of EM fields. The scattered electric and magnetic fields are denoted by sE and sH , respectively
NASA Astrophysics Data System (ADS)
Yvonne, Cherubini; Mauro, Cacace; Scheck-Wenderoth, Magdalena
2013-04-01
Faults can provide permeable pathways for fluids at a variety of scales, from great depth in the crust to flow through fractured aquifers, geothermal fields, and hydrocarbon reservoirs (Barton et al. 1995). In terms of geothermal energy exploration, it is essential to understand the role of faults and their impact on the thermal field and fluid system. 3D numerical simulations provide a useful tool for investigating the active physical processes in the subsurface. To assess the influence of major fault zones on the thermal field and fluid system, 3D coupled fluid and heat transport simulations are carried out. The study is based on a recently published structural model of the Brandenburg area, which is located in the south-eastern part of the Northeast German Basin (NEGB) (Noack et al. 2010). Two major fault zones of the Elbe Fault System (Gardelegen and Lausitz Escarpments) vertically offset the pre-Permian basement against the Permian to Cenozoic basin fill at the southern margin by several km (Scheck et al. 2002). Within the numerical models, these two major fault zones are represented as equivalent porous media and vertical discrete elements. The coupled system of equations describing fluid flow and heat transport in saturated porous media are numerically solved by the Finite Element software FEFLOW® (Diersch, 2002). Different possible geological scenarios are modelled and compared to a simulation in which no faults are considered. In one scenario the fault zones are set as impermeable. In this case, the thermal field is similar to the no fault model. Fluid flow is redirected because the fault zones act as hydraulic barriers that prevent a lateral fluid advection into the fault zones. By contrast, modelled permeable fault zones induce a pronounced thermal signature with distinctly cooler temperatures than in the no fault model. Fluid motion within the fault is initially triggered by advection due to hydraulic head gradients, but may be even enhanced by buoyancy forces caused by density gradients mainly occurring due to differences in the temperature. References: Barton, C.A., Zoback, M.D., Moos, D., 1995. Fluid flow along potentially active faults in crystalline rock. Geology 23 (8), 683-686.
NASA Astrophysics Data System (ADS)
Hamamatsu, Teruhide
A theoretical approach to heat conduction in phase changing solid with convective surface heat transfer has been tried to disclose the effect of the heat transfer, and to get the governing equation for the phase-changing front movement and the transient temperature field. As a result of the analytical work in the rectangular heat conduction field, the quasi-theoretical solutions containing the Stefan's problem for the phase change front movement and the transient temperature distribution have been obtained, and in addition one of the key parameters newly introduced is a non-dimensional heat transfer factor. HTF (convective heat tranferrability vs. latent heat capacity) which can indicate the acceleration of phase change and the difference from the Stefan's solution.
A two-parameter nondiffusive heat conduction model for data analysis in pump-probe experiments
NASA Astrophysics Data System (ADS)
Ma, Yanbao
2014-12-01
Nondiffusive heat transfer has attracted intensive research interests in last 50 years because of its importance in fundamental physics and engineering applications. It has unique features that cannot be described by the Fourier law. However, current studies of nondiffusive heat transfer still focus on studying the effective thermal conductivity within the framework of the Fourier law due to a lack of a well-accepted replacement. Here, we show that nondiffusive heat conduction can be characterized by two inherent material properties: a diffusive thermal conductivity and a ballistic transport length. We also present a two-parameter heat conduction model and demonstrate its validity in different pump-probe experiments. This model not only offers new insights of nondiffusive heat conduction but also opens up new avenues for the studies of nondiffusive heat transfer outside the framework of the Fourier law.
Two-dimensional heat conducting simulation of plasma armatures
Huerta, M.A.; Boynton, G. . Dept. of Physics)
1991-01-01
This paper reports on our development of a two-dimensional MHD code to simulate internal motions in a railgun plasma armature. The authors use the equations of resistive MHD, with Ohmic heating, and radiation heat transport. The authors use a Flux Corrected Transport code to advance all quantities in time. Our runs show the development of complex flows, subsequent shedding of secondary arcs, and a drop in the acceleration of the armature.
Examples of the 3D anatomical features extracted with 3D OOA
cloud data. In the first phase of this research synthetic 3D geophysical data will be used. The research will focus on the automation of the extraction of the 3D objects and how to conduct. Examples of geophysical data as depth slices or 3D cubes that will be used as input for the 3D OOA Islam
Shrestha, R.; Lee, K. M.; Chang, W. S.; Kim, D. S.; Rhee, G. H.; Choi, T. Y.
2013-01-01
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
NASA Astrophysics Data System (ADS)
Zou, Ling
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.
Solving Heat Conduction Problems by the Direct Meshless Local Petrov-Galerkin (DMLPG) method
Wardetzky, Max
Solving Heat Conduction Problems by the Direct Meshless Local Petrov-Galerkin (DMLPG) method Davoud¨ottingen, Germany. SUMMARY As an improvement of the Meshless Local PetrovGalerkin (MLPG), the Direct Meshless Local; Meshless methods; MLPG methods; DMLPG methods; Heat conduction problem. 1. INTRODUCTION Meshless methods
B. F. Blackwell
1981-01-01
A very efficient numerical technique has been developed to solve the one-dimensional Inverse problem of heat conduction. The Gauss elimination algorithm for solving the tridiagonal system of linear algebraic equations associated with most implicit heat conduction codes is specialized to the inverse problem. When compared to the corresponding direct problem, the upper limit in additional computation time generally does not
Interface integral BEM for solving multi-medium heat conduction problems
Xiao-Wei Gao; Jing Wang
2009-01-01
In this paper, a new and simple boundary element method, called interface integral boundary element method (IIBEM), is presented for solving heat conduction problems consisting of multiple media. In the method, the boundary integral equation is derived by a degeneration technique from domain integrals involved in varying heat conductivity problems into interface integrals in multi-medium problems. The main feature of
Robert L. McMasters; Kevin J. Dowding; James V. Beck; David H. Y. Yen
2002-01-01
This article describes the development of accurate solutions for transient three-dimensional conductive heat transfer in Cartesian coordinates for a parallelepiped which is homogeneous and has constant thermal properties. The intended use of these solutions is for verification of numerical computer programs which are used for solving transient heat conduction problems. Verification is a process to ensure that a computer code
B. F. Blackwell
1981-01-01
A very efficient numerical technique has been developed to solve the one-dimensional inverse problem of heat conduction. The Gauss elimination algorithm for solving the tridiagonal system of linear algebraic equations associated with most implicit heat conduction codes is specialized to the inverse problem. When compared to the corresponding direct problem, the upper limit in additional computation time generally does not
Melnik, Roderick
Phase transitions in shape memory alloys with hyperbolic heat conduction and differential are given. Keywords Phase transitions, Shape memory alloys, Hyperbolic heat conduction 1 Introduction One-called solidsolid phase transformations, in ``smart'' materials known as shape memory alloys (SMAs
K. C. Masiulaniec; T. G. Keith Jr.; K. J. Dewitt
1984-01-01
A numerical procedure is presented for analyzing a wide variety of heat conduction problems in multilayered bodies having complex geometry. The method is based on a finite difference solution of the heat conduction equation using a body fitted coordinate system transformation. Solution techniques are described for steady and transient problems with and without internal energy generation. Results are found to
A. AZIMI; S. KAZEMZADEH HANNANI; B. FARHANIEH
In this study a multi block procedure is implemented to solve accurately two-dimensional transient Inverse Heat Conduction Problems (IHCPs). The multi block method is implemented for geometric decomposition of physical domain into regions with blocked-interface structured grids. The Finite Element Method (FEM) with Galerkin weighting function is employed for direct solution of transient heat conduction equation. Inverse algorithms used in
Li, Baowen
Nonballistic heat conduction in an integrable random-exchange Ising chain studied with quantum numerically investigate the heat conduction in a random-exchange Ising spin chain by using the quantum master equation. The chain is subject to a uniform transverse field h, while the exchange couplings Qn between
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2012-06-06
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A Simple Rate Law Experiment Using a Custom-Built Isothermal Heat Conduction Calorimeter
ERIC Educational Resources Information Center
Wadso, Lars; Li, Xi.
2008-01-01
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…
A. Tadeu; J. António; L. Godinho; N. Simões
2004-01-01
The boundary element method (BEM) is used to compute the three-dimensional transient heat conduction through an unbounded solid layer that may contain heterogeneities, when a pointwise heat source placed at some point in the media is excited. Analytical solutions for the steady-state response of this solid layer when subjected to a spatially sinusoidal harmonic heat line source are presented when
Rish
1985-01-01
Heat transfer results are presented for fibrous insulations (fiberglass) undergoing coupled transient conduction and radiation heat transfer under the influence of a temporally varying incident radiative flux and with temporally varying temperature boundaries. The heat transfer analysis was performed by solving the one-dimensional radiative transport equation for an absorbing, emitting, and scattering medium simultaneously with the one-dimensional energy equation. An
Numerical model for combined conductive and radiative heat transfer in annular packed beds
Kamiuto, K.; Saito, S.; Ito, K. . Dept. of Production Systems Engineering)
1993-06-01
A numerical model is developed for quantitatively analyzing combined conductive and radiative heat transfer in concentric annular packed beds. A packed bed is considered to be a continuous medium for heat transfer, but the porosity distribution within a packed bed is taken into account. To examine the validity of the proposed model, combined conductive and radiative heat transfer through annular packed beds of cordierite or porcelain beads is analyzed numerically using finite differences under conditions corresponding to heat transfer experiments of these packed beds. The resultant temperature profiles and heat transfer characteristics are compared with the experimental results.
Variable Conductance Heat Pipe Cooling of Stirling Convertor and General Purpose Heat Source
NASA Technical Reports Server (NTRS)
Tarau, Calin; Schwendeman, Carl; Anderson, William G.; Cornell, Peggy A.; Schifer, Nicholas A.
2013-01-01
In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental results from integrating the VCHP with an operating Stirling convertor and describes the methodology used to achieve their successful combined operation.
Spring 2005 Test #1 1. Steady state heat conduction in a slab with heat generation. (40 points)
McCready, Mark J.
ChEg 356 Spring 2005 Test #1 2/17/05 1. Steady state heat conduction in a slab with heat generation. (40 points) Consider a slab that has a thickness B in the x direction. The y and z directions are infinite and completely uniform. There is a heat generation rate of S W/m3 -s. The wall at x=0 is insulated
Analysis of transient nonlinear heat conduction in wood using finite-difference solutions
A. Khattabi; P. Steinhagen
1993-01-01
This paper describes three-dimensional, transient heat conduction in a rectangular piece of wood with crossgrain, and in an\\u000a orthotropic wooden cylinder. Computerized solutions of a generalized, nonlinear heat equation are derived by discretizing\\u000a the space and the time domains, using explicit and implicit finite-difference techniques. A simplified example of linear heat\\u000a conduction in cylindrical coordinates illustrates how to apply the
Investigation of Heat Conductivity in Relativistic Systems using a Partonic Cascade
M. Greif; F. Reining; I. Bouras; G. S. Denicol; Z. Xu; C. Greiner
2013-01-07
Motivated by the classical picture of heat flow we construct a stationary temperature gradient in a relativistic microscopic transport model. Employing the relativistic Navier-Stokes ansatz we extract the heat conductivity {\\kappa} for a massless Boltzmann gas using only binary collisions with isotropic cross sections. We compare the numerical results to analytical expressions from different theories and discuss the final results. The directly extracted value for the heat conductivity can be referred to as a literature reference within the numerical uncertainties.
Hyperbolic Heat Conduction in a Cracked Thermoelastic Half-Plane Bonded to a Coating
NASA Astrophysics Data System (ADS)
Chen, Z. T.; Hu, K. Q.
2012-05-01
In this paper, the transient temperature field around a thermally insulated crack in a substrate bonded to a coating is obtained using the hyperbolic heat conduction model. Fourier and Laplace transforms are applied, and the thermal conduction problem is reduced to solving a singular integral equation. Numerical results show that the hyperbolic heat conduction parameters, the heat conductivity of the substrate and coating, and the geometric size of the composite have significant influence on the transient temperature field. In the case of very small time scales, the results predicted by the hyperbolic model are more conservative than that by the parabolic model.
NASA Technical Reports Server (NTRS)
Brandon, S.; Derby, J. J.
1992-01-01
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.
A two-fluid model for relativistic heat conduction
López-Monsalvo, César S.
2014-01-14
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.
Inverse modeling for heat conduction problem in human abdominal phantom
Ming Huang; Wenxi Chen
2011-01-01
Noninvasive methods for deep body temperature measurement are based on the principle of heat equilibrium between the thermal sensor and the target location theoretically. However, the measurement position is not able to be definitely determined. In this study, a 2-dimensional mathematical model was built based upon some assumptions for the physiological condition of the human abdomen phantom. We evaluated the
Glass-Like Heat Conduction in Crystalline Semiconductors
Nolas, G.S.; Cohn, J.L.; Chakoumakos, B.C.; Slack, G.A.
1999-06-13
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.
Ground thermal response to heat conduction in a power transmission tower foundation
Xili Duan; Greg F. Naterer
2008-01-01
An analytical formulation is developed to predict transient heat conduction in a semi-infinite medium with a vertical finite\\u000a line heat source, which represents a buried tower of a power transmission line foundation. Unlike past studies with a constant\\u000a line heat source, the current model develops a time-dependent variable heating strength, as well as a time varying surface\\u000a temperature of the
Jinbo Hou; Xinwei Wang; Jiaqi Guo
2006-01-01
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,
The evolution of interstellar clouds in a streaming hot plasma including heat conduction
NASA Astrophysics Data System (ADS)
Vieser, W.; Hensler, G.
2007-09-01
Context: The interstellar medium contains warm clouds that are embedded in a hot dilute gas produced by supernovae. Because both gas phases are in contact, an interface forms where mass and energy are exchanged. Whether heat conduction leads to evaporation of these clouds or whether condensation dominates has been analytically derived. Both phases behave differently dynamically so that their relative motion has to be taken into account. Aims: Real clouds in static conditions that experience saturated heat conduction are stabilized against evaporation if self-gravity and cooling play a role. Here, we investigte to what extent heat conduction can hamper the dynamical disruption of clouds embedded in a streaming hot plasma. Methods: To examine the evolution of giant molecular clouds in the stream of a hot plasma we performed two-dimensional hydrodynamical simulations that take full account of self-gravity, heating and cooling effects and heat conduction by electrons. We use the thermal conductivity of a fully ionized hydrogen plasma proposed by Spitzer and a saturated heat flux according to Cowie & McKee in regions where the mean free path of the electrons is large compared to the temperature scaleheight. Results: Significant structural and evolutionary differences occur between simulations with and without heat conduction. Dense clouds in pure dynamical models experience dynamical destruction by Kelvin-Helmholtz (KH) instability. In static models heat conduction leads to evaporation of such clouds. Heat conduction acting on clouds in a gas stream smooths out steep temperature and density gradients at the edge of the cloud because the conduction timescale is shorter than the cooling timescale. This diminishes the velocity gradient between the streaming plasma and the cloud, so that the timescale for the onset of KH instabilities increases, and the surface of the cloud becomes less susceptible to KH instabilities. The stabilisation effect of heat conduction against KH instability is more pronounced for smaller and less massive clouds. As in the static case more realistic cloud conditions allow heat conduction to transfer hot material onto the cloud's surface and to mix the accreted gas deeper into the cloud. Conclusions: In contrast to pure dynamical models of clouds in a plasma and to analytical considerations of heat conduction that can evaporate such clouds embedded in a hot plasma, our realistic numerical simulations demonstrate that this destructive effect of KH instability is significantly slowed by heat conduction so that clouds can survive their passage through hot gas. Appendices A and B are only available in electronic form at http://www.aanda.org
TOPAZ. 2D Finite Element Heat Conduction Code
1985-01-01
TOPAZ and TOPAZ2D are two-dimensional implicit finite element computer codes for heat transfer analysis. TOPAZ2D can also be used to solve electrostatic and magnetostatic problems. The programs solve for the steady-state or transient temperature or electrostatic and magnetostatic potential field on two-dimensional planar or axisymmetric geometries. Material properties may be temperature or potential-dependent and either isotropic or orthotropic. A variety
Hybrid Spline Difference Method (HSDM) for Transient Heat Conduction
Chi-Chang Wang; Lu-Ping Chao; Wu-Jung Liao
2012-01-01
This study develops a high-accuracy numerical method named the hybrid spline difference method (HSDM), to replace the finite-difference method. Verification by transient heat transfer finds that the concept of the spline finite-difference method can greatly simplify the complexity of the traditional spline calculation, while having a solution procedure as in the finite-difference method. In addition, the hybrid spline technique can
Heat conduction in caricature models of the Lorentz gas
Kramli, A.; Simanyi, N.; Szasz, D.
1987-01-01
Heat transport coefficients are calculated for various random walks with internal states (the Markov partition of the Sinai billiard connects these walks with the Lorentz gas among a periodic configuration of scatterers). Models with reflecting or absorbing barriers and also those without or with local thermal equilibrium are investigated. The method is unified and is based on the Keldysh expansion of the resolvent of a matrix polynomial.
Pokorny, Richard; Rice, Jarrett A.; Schweiger, Michael J.; Hrma, Pavel R.
2013-06-01
The cold cap is a layer of reacting glass batch floating on the surface of melt in an all-electric continuous glass melter. The heat needed for the conversion of the melter feed to molten glass must be transferred to and through the cold cap. Since the heat flux into the cold cap determines the rate of melting, the heat conductivity is a key property of the reacting feed. We designed an experimental setup consisting of a large cylindrical crucible with an assembly of thermocouples that monitors the evolution of the temperature field while the crucible is heated at a constant rate. Then we used two methods to calculate the heat conductivity and thermal diffusivity of the reacting feed: the approximation of the temperature field by polynomial functions and the finite-volume method coupled with least-squares analysis. Up to 680°C, the heat conductivity of the reacting melter feed was represented by a linear function of temperature.
Heat conductivity in the beta-FPU lattice. Solitons and breathers as energy carriers
T. Yu. Astakhova; V. N. Likhachev; G. A. Vinogradov
2011-03-18
This paper consists of two parts. The first part proposes a new methodological framework within which the heat conductivity in 1D lattices can be studied. The total process of heat conductivity is decomposed into two contributions where the first one is the equilibrium process at equal temperatures T of both lattice ends and the second -- non-equilibrium process with the temperature \\Delta T of one end and zero temperature of the other. The heat conductivity in the limit \\Delta T \\to 0 is reduced to the heat conductivity of harmonic lattice. A threshold temperature T_{thr} scales T_{thr}(N) \\sim N^{-3} with the lattice size N. Some unusual properties of heat conductivity can be exhibited on nanoscales at low temperatures. The thermodynamics of the \\beta-FPU lattice can be adequately approximated by the harmonic lattice. The second part testifies in the favor of the soliton and breather contribution to the heat conductivity in contrast to [N. Li, B. Li, S. Flach, PRL 105 (2010) 054102]. In the continuum limit the \\beta-FPU lattice is reduced to the modified Korteweg - de Vries equation with soliton and breather solutions. Numerical simulations demonstrate their high stability. New method for the visualization of moving solitons and breathers is suggested. An accurate expression for the dependence of the sound velocity on temperature is also obtained. Our results support the conjecture on the solitons and breathers contribution to the heat conductivity.
NASA Astrophysics Data System (ADS)
Pletinckx, D.
2011-09-01
The current 3D hype creates a lot of interest in 3D. People go to 3D movies, but are we ready to use 3D in our homes, in our offices, in our communication? Are we ready to deliver real 3D to a general public and use interactive 3D in a meaningful way to enjoy, learn, communicate? The CARARE project is realising this for the moment in the domain of monuments and archaeology, so that real 3D of archaeological sites and European monuments will be available to the general public by 2012. There are several aspects to this endeavour. First of all is the technical aspect of flawlessly delivering 3D content over all platforms and operating systems, without installing software. We have currently a working solution in PDF, but HTML5 will probably be the future. Secondly, there is still little knowledge on how to create 3D learning objects, 3D tourist information or 3D scholarly communication. We are still in a prototype phase when it comes to integrate 3D objects in physical or virtual museums. Nevertheless, Europeana has a tremendous potential as a multi-facetted virtual museum. Finally, 3D has a large potential to act as a hub of information, linking to related 2D imagery, texts, video, sound. We describe how to create such rich, explorable 3D objects that can be used intuitively by the generic Europeana user and what metadata is needed to support the semantic linking.
Low heat conduction in white dwarf boundary layers?
F. K. Liu; F. Meyer; E. Meyer-Hofmeister; V. Burwitz
2008-01-01
Context: X-ray spectra of dwarf novae in quiescence observed by Chandra and XMM-Newton provide new information on the boundary layers of their accreting white dwarfs. Aims: Comparison of observations and models allows us to extract estimates for the thermal conductivity in the accretion layer and reach conclusions on the relevant physical processes. Methods: We calculate the structure of the dense
Tables for solution of the heat-conduction equation with a time-dependent heating rate
Bergles A. E.
1962-01-01
Tables are presented for the solution of the transient onedimensional heat flow in a solid body of constant material properties with the heating rate at one boundary dependent on time. These tables allow convenient and ...
Phonon Transport in Graphene: Umklapp Quenching and Heat Conduction
NASA Astrophysics Data System (ADS)
Balandin, Alexander
2009-11-01
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)
Heat conduction in a chain of dissociating particles: Effect of dimensionality
NASA Astrophysics Data System (ADS)
Zolotarevskiy, V.; Savin, A. V.; Gendelman, O. V.
2015-03-01
The paper considers heat conduction in a model chain of composite particles with hard core and elastic external shell. Such model mimics three main features of realistic interatomic potentials—hard repulsive core, quasilinear behavior in a ground state, and possibility of dissociation. It has become clear recently that this latter feature has crucial effect on convergence of the heat conduction coefficient in thermodynamic limit. We demonstrate that in one-dimensional chain of elastic particles with hard core the heat conduction coefficient also converges, as one could expect. Then we explore effect of dimensionality on the heat transport in this model. For this sake, longitudinal and transversal motions of the particles are allowed in a long narrow channel. With varying width of the channel, we observe sharp transition from "one-dimensional" to "two-dimensional" behavior. Namely, the heat conduction coefficient drops by about order of magnitude for relatively small widening of the channel. This transition is not unique for the considered system. Similar phenomenon of transition to quasi-1D behavior with growth of aspect ratio of the channel is observed also in a gas of densely packed hard (billiard) particles, both for two- and three-dimensional cases. It is the case despite the fact that the character of transition in these two systems is not similar, due to different convergence properties of the heat conductivity. In the billiard model, the divergence pattern of the heat conduction coefficient smoothly changes from logarithmic to power-like law with increase of the length.
Abu Saleem, R. A.; Rizwan-Uddin [Dept. of Nuclear, Plasma and Radiological Engineering, Univ. of Illinois at Urbana-Champaign, 216 Talbot Lab., 104 S. Wright St, Urbana, IL 61801 (United States)
2012-07-01
An empirical approach to determine the effective thermal conductivity of a binary mixed material with heat generation is developed and reported. The approach is developed for a steady state problem with spherical geometry. The approach is based on two main ideas: a structural approximation and an empirical formulation. As for the structural approximation, the binary mixed material was assumed to be equivalent to a binary layered system of adjacent fuel and moderator layers oriented perpendicular to the heat flux. An empirical approach was then used to conduct a general correlation for the effective thermal conductivity of a binary layered system with heat generation. This empirical approach was conducted systematically by considering the parametric and operational condition effects of the system on the overall effective thermal conductivity. Results are then compared to some experimental data as well as with thermal conductivity values predicted by an empirical correlation that is based on experimental data. (authors)
Heat Exchangers for Heavy Vehicles Utilizing High Thermal Conductivity Graphite Foams
James Klett, Ron Ott; April McMillan
2000-06-19
Approximately two thirds of the world's energy consumption is wasted as heat. In an attempt to reduce heat losses, heat exchangers are utilized to recover some of the energy. A unique graphite foam developed at the Oak Ridge National Laboratory (ORNL) and licensed to Poco Graphite, Inc., promises to allow for novel, more efficient heat exchanger designs. This graphite foam, Figure 1, has a density between 0.2 and 0.6 g/cm 3 and a bulk thermal conductivity between 40 and 187 W/m{center_dot}K. Because the foam has a very accessible surface area (> 4 m 2 /g) and is open celled, the overall heat transfer coefficients of foam-based heat exchangers can be up to two orders of magnitude greater than conventional heat exchangers. As a result, foam-based heat exchangers could be dramatically smaller and lighter.
Molecular dynamics analysis of spectral characteristics of phonon heat conduction in silicon
Henry, Asegun Sekou Famake
2006-01-01
Due to the technological significance of silicon, its heat conduction mechanisms have been studied extensively. However, there have been some lingering questions surrounding the phonon mean free path and importance of ...
Effect of viscosity and wall heat conduction on shock attenuation in narrow channels
NASA Astrophysics Data System (ADS)
Deshpande, A.; Puranik, B.
2015-02-01
In the present work, the effects due to viscosity and wall heat conduction on shock propagation and attenuation in narrow channels are numerically investigated. A two-dimensional viscous shock tube configuration is simulated, and heat conduction in the channel walls is explicitly included. The simulation results indicate that the shock attenuation is significantly less in case of an adiabatic wall, and the use of an isothermal wall model is adequate to take into account the wall heat conduction. A parametric study is performed to characterize the effects of viscous forces and wall heat conduction on shock attenuation, and the behaviour is explained on the basis of boundary layer formation in the post-shock region. A dimensionless parameter that describes the shock attenuation is correlated with the diaphragm pressure ratio and a dimensionless parameter which is expressed using the characteristic Reynolds number and the dimensionless shock travel.
Transition from near-field thermal radiation to phonon heat conduction at sub-nanometre gaps.
Chiloyan, Vazrik; Garg, Jivtesh; Esfarjani, Keivan; Chen, Gang
2015-01-01
When the separation of two surfaces approaches sub-nanometre scale, the boundary between the two most fundamental heat transfer modes, heat conduction by phonons and radiation by photons, is blurred. Here we develop an atomistic framework based on microscopic Maxwell's equations and lattice dynamics to describe the convergence of these heat transfer modes and the transition from one to the other. For gaps >1?nm, the predicted conductance values are in excellent agreement with the continuum theory of fluctuating electrodynamics. However, for sub-nanometre gaps we find the conductance is enhanced up to four times compared with the continuum approach, while avoiding its prediction of divergent conductance at contact. Furthermore, low-frequency acoustic phonons tunnel through the vacuum gap by coupling to evanescent electric fields, providing additional channels for energy transfer and leading to the observed enhancement. When the two surfaces are in or near contact, acoustic phonons become dominant heat carriers. PMID:25849305
Stryk, Oskar von
Login Register Home Videos Jobs Games 3D Printing Electronics Design Software Designer Edge is the connectivity. Here in the US everyone assumes high ... Boeing Utilizing Sigma Labs (SGLB) "PrintRite3D" System for 3D Printing · -- B6 Sigma Labs (ticker SGLB) is not the same company as Sigma Technologies
NASA Astrophysics Data System (ADS)
Rushmer, T.; Beier, C.; Turner, S.
2007-12-01
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.
NASA Technical Reports Server (NTRS)
Huerre, P.; Karamcheti, K.
1976-01-01
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.
NASA Technical Reports Server (NTRS)
Masiulaniec, K. C.; Keith, T. G., Jr.; Dewitt, K. J.
1984-01-01
A numerical procedure is presented for analyzing a wide variety of heat conduction problems in multilayered bodies having complex geometry. The method is based on a finite difference solution of the heat conduction equation using a body fitted coordinate system transformation. Solution techniques are described for steady and transient problems with and without internal energy generation. Results are found to compare favorably with several well known solutions.
Identification of a moving boundary for a heat conduction problem in a multilayer medium
Y. S. LiT; T. Wei
2010-01-01
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
Zabaras, Nicholas J.
, metallurgy, chemical, aerospace and nuclear engineering, food science, medical diagnostics, etc. The main Engineering, 188 Frank H.T. Rhodes Hall, Cornell University, Ithaca, NY 14853-3801, USA Abstract A Bayesian distribution of the unknown heat flux. 1 Introduction In the inverse heat conduction problem (IHCP), one
Convection under a lid of finite conductivity: Heat flux scaling and application to continents
C. Grigné; S. Labrosse; P. J. Tackley
2007-01-01
A scaling law for the heat flux out of a convective fluid covered totally or partially by a finitely conducting lid is proposed. This scaling is constructed in order to quantify the heat transfer out of the Earth's mantle, taking into account the effect of the dichotomy between oceans and continents, which imposes heterogeneous thermal boundary conditions at the surface
MOLECULAR DYNAMICS SIMULATION OF QUASI-BALLISTIC HEAT CONDUCTION IN CARBON NANOTUBES
Maruyama, Shigeo
-8656, Japan In device applications of carbon nanotubes, characterization of the heat transfer is essential in practical applications. For example, as SWNTs form a bundle in many cases, the influence of the inter-tube interaction on the heat conduction is of an interest. In addition, we consider an SWNT confining an ice-tube
One-velocity model of a multicomponent heat-conducting medium
NASA Astrophysics Data System (ADS)
Surov, V. S.
2010-03-01
A model of a one-velocity heat-conducting heterogeneous medium with the Fourier relaxation law of heat transfer has been constructed. It is shown that the model’s equations are of hyperbolic type. The results of numerical experiments for a three-component mixture of ideal gases carried out with the use of the Courant-Isaacson-Rees scheme are presented.
Majed M. Al-Hazmy
2006-01-01
In the present study, the coupled convective and conduction heat transport mode in a common hollow building brick is studied. Heat transfer rate through building bricks is examined in order to asses the suitable brick insulation configuration. Three different configurations for building bricks are considered. The first is a typical brick of three identical hollow cells (air cavities), the second
J. M. Zhao; L. H. Liu
2007-01-01
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
A MECHANICAL MODEL FOR FOURIER'S LAW OF HEAT CONDUCTION. by David Ruelle+.
Ruelle, David
A MECHANICAL MODEL FOR FOURIER'S LAW OF HEAT CONDUCTION. by David Ruelle+. Abstract. Nonequilibrium response formula of GreenÂKubo. This formula results from a formal first order perturbation calculation without rigorous jusÂ tification. A rigorous derivation of Fourier's law for heat conducÂ tion from
Heat conduction in anisotropic media: Nonlinear self-adjointness and conservation laws
Nail H. Ibragimov; Elena D. Avdonina
2012-02-27
Nonlinear self-adjointness of the anisotropic nonlinear heat equation is investigated. Mathematical models of heat conduction in anisotropic media with a source are considered and a class of self-adjoint models is identified. Conservation laws corresponding to the symmetries of the equations in question are computed.
On the examination of the heat conduction phenomena of low-pressure gases
G. Lakatos; J. Bitó
1966-01-01
The authors determine the energy trasferred by heat condution from the cathode of low-pressure gas discharge. They indicate\\u000a for various gases under given discharge conditions the quantity of energy transmitted from the unit surface area of the cathode\\u000a by heat conduction of the gas.
J. Sladek; V. Sladek; Ch. Zhang
2003-01-01
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
Current methods to handle wall conduction and room internal heat transfer
1999-01-01
This paper reviews methods of handling wall conduction and room internal heat exchange adopted by ASHRAE (1993 Handbook of Fundamentals and later developments), CIBSE (1986 Guide and current proposals), and the CEN\\/TC89\\/WG6 proposals to calculate heating and cooling loads and related topics.
Effects of anisotropic conduction and heat pipe interaction on minimum mass space radiators
NASA Technical Reports Server (NTRS)
Baker, Karl W.; Lund, Kurt O.
1991-01-01
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.
NASA Astrophysics Data System (ADS)
Zhang, Haihui; Wang, Wanlin; Zhou, Lejun
2015-07-01
A novel method for the estimation of the mold hot surface heat flux based on the measured responding temperatures from two columns of thermocouples that embedded inside the mold during continuous casting has been developed. The method includes a Two-Dimensional Inverse transient Heat Conduction Problem (2D-IHCP) model that was solved by the conjugate gradient method with Adjoint Equation. The model was validated by comparing the results with those calculated by a robust One-Dimensional Inverse transient Heat Conduction Problem (1D-IHCP). The solution of a test problem indicated that the Mean Absolute Percentage Error of the estimated heat flux calculated by the new method is about 9 to 40 pct of those calculated by the 1D-IHCP. Then, the method is applied to compute the heat flux for a mold simulator experiment. The results indicated that the heat fluxes and temperatures across mold hot surface calculated by 2D-IHCP show the same variation tendency as those calculated by 1D-IHCP. However, the heat fluxes calculated by 2D-IHCP are about 1.2 to 2 times larger than those calculated by 1D-IHCP for the locations below the liquid mold flux surface and are about 50 to 90 pct of those calculated by 1D-IHCP for the locations above the liquid mold flux surface.
Du Pei; Ke Ye
2015-03-16
We test the 3d-3d correspondence for theories that are labelled by Lens spaces. We find a full agreement between the index of the 3d N=2 "Lens space theory" $T[L(p,1)]$ and the partition function of complex Chern-Simons theory on $L(p,1)$. In particular, for $p=1$, we show how the familiar $S^3$ partition function of Chern-Simons theory arises from the index of a free theory. For large $p$, we find that the index of $T[L(p,1)]$ becomes a constant independent of $p$. In addition, we study $T[L(p,1)]$ on the squashed three-sphere $S^3_b$. This enables us to see clearly, at the level of partition function, to what extent $G_\\mathbb{C}$ complex Chern-Simons theory can be thought of as two copies of Chern-Simons theory with compact gauge group $G$.
On Thermo-viscoelasticity with Variable Thermal Conductivity and Fractional-Order Heat Transfer
NASA Astrophysics Data System (ADS)
Ezzat, M. A.; El-Karamany, A. S.; El-Bary, A. A.
2015-07-01
The equations of generalized thermo-viscoelasticity for an isotropic medium with variable thermal conductivity and fractional-order heat transfer are given. The resulting formulation is applied to a half-space subjected to arbitrary heating which is taken as a function of time and is traction free. The Laplace transform technique is used. A numerical method is employed for the inversion of the Laplace transforms. Numerical results for temperature, displacement, and stress distributions are given and illustrated graphically for the problem. The effects of the fractional order and the variable thermal conductivity for heat transfer on a viscoelastic material such as poly(methyl methacrylate) (Perspex) are discussed.
Thermoelasticity of thin shells based on the time-fractional heat conduction equation
NASA Astrophysics Data System (ADS)
Povstenko, Yuriy
2013-06-01
The time-nonlocal generalizations of Fourier's law are analyzed and the equations of the generalized thermoelasticity based on the time-fractional heat conduction equation with the Caputo fractional derivative of order 0 < ? ? 2 are presented. The equations of thermoelasticity of thin shells are obtained under the assumption of linear dependence of temperature on the coordinate normal to the median surface of a shell. The conditions of Newton's convective heat exchange between a shell and the environment have been assumed. In the particular case of classical heat conduction ( ? = 1) the obtained equations coincide with those known in the literature.
Thermoelasticity of thin shells based on the time-fractional heat conduction equation
NASA Astrophysics Data System (ADS)
Povstenko, Yuriy
2013-06-01
The time-nonlocal generalizations of Fourier's law are analyzed and the equations of the generalized thermoelasticity based on the time-fractional heat conduction equation with the Caputo fractional derivative of order 0 < ? ? 2 are presented. The equations of thermoelasticity of thin shells are obtained under the assumption of linear dependence of temperature on the coordinate normal to the median surface of a shell. The conditions of Newton's convective heat exchange between a shell and the environment have been assumed. In the particular case of classical heat conduction (? = 1) the obtained equations coincide with those known in the literature.
About influence of gravity on heat conductivity process of the Planets
S. O. Gladkov; Anil Yadav; Saibal Ray; F. Rahaman
2014-07-30
In the present study it is shown that the interaction of a quasi-static gravitational wave through density fluctuations gives rise to a heat conductivity coefficient and hence temperature. This fact is a very important characteristics to establish a heat equilibrium process of such massive body as the Earth and other Planets. To carry out this exercise general mechanism has been provided, which makes a bridge between classical physics and quantum theory, and specific dependence of heat conductivity coefficient in wide region is also calculated.
Chandy, John A.
-dependent electrical resistivity, q(T), and thermal conductivity, k(T), of nanocrystalline silicon microwires self-heated of the electrical resistivity and thermal conductivity up to very high temperatures from self-heated microstructures such as electrical resistivity q(T), thermal conductivity k(T), Seebeck coefficient S(T), and heat capacity C
Object-Oriented Development of Inverse Heat Conduction Code Adaptable to Various Configurations
Sun Kyoung Kim
2006-01-01
This article suggests a method for developing computer code that can solve inverse heat conduction problems (IHCPs). The concept of object-oriented development is employed to implement the computer code in an efficient and flexible fashion. The software design is conducted based on the unified modeling language. Furthermore, this article also explains how to implement the deliverable computer code using existing
Analysis of the statistical error in a heat conduction code calculation
D. I. Herborn
1974-01-01
Statistical errors were determined for a heat conduction computer program resulting from uncertainties in fuel rod power level and fuel thermal conductivities in a nuclear fuel rod. To determine the error bands for the computed best estimate temperature values a linear propagation technique was used. A Monte Carlo statistical analysis was performed. The temperature distribution in the nuclear fuel rod
Micheal W. Glass; Hogan Roy E. Jr; David K. Gartling
2010-01-01
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
Thermal Conductivity of Argillaceous Rocks: Determination Methodology Using In Situ Heating Tests
NASA Astrophysics Data System (ADS)
Garitte, Benoit; Gens, Antonio; Vaunat, Jean; Armand, Gilles
2014-01-01
This study focuses on the characterisation of thermal conductivity for three potential host rocks for radioactive waste disposal. First, the heat conduction process is reviewed on the basis of an analytical solution and key aspects related to anisotropic conduction are discussed. Then the existing information on the three rocks is summarised and a broad uncertainty range of thermal conductivity is estimated based on the mineralogical composition. Procedures to backanalyse the thermal conductivity on the basis of in situ heating tests are assessed and a methodology is put forward. Finally, this methodology is used to estimate the impact of experimental uncertainties and applied to the four in situ heating tests. In the three potential host rocks, a clear influence of the bedding planes was identified and anisotropic heat conduction was shown to be necessary to interpret the observed temperature field. Experimental uncertainties were also shown to induce a larger uncertainty on the anisotropy ratio than on the equivalent thermal conductivity defined as the geometric mean of the thermal conductivity in the three principal directions.
ERIC Educational Resources Information Center
Chiou, Guo-Li; Anderson, O. Roger
2010-01-01
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…
Convection under a lid of finite conductivity: Heat flux scaling and application to continents
Tackley, Paul J.
Convection under a lid of finite conductivity: Heat flux scaling and application to continents C of the dichotomy between oceans and continents, which imposes heterogeneous thermal boundary conditions and continents represented by nondeformable lids of finite thermal conductivity set above the surface
Kumar, Suhas; Pickett, Matthew D; Strachan, John Paul; Gibson, Gary; Nishi, Yoshio; Williams, R Stanley
2013-11-13
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
Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997
Allan, M.L.
1997-11-01
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.
Fourier Heat Conduction as a phenomenon described within the scope of the Second Law
Christopher G. Jesudason
2014-07-29
The historical development of the Carnot cycle necessitated the construction of isothermal and adiabatic pathways within the cycle that were also mechanically "reversible" which lead eventually to the Kelvin-Clausius development of the entropy function where the heat absorption is for the diathermal (isothermal) paths of the cycle only. It is deduced from traditional arguments that Fourier heat conduction involves mechanically "reversible" heat transfer with irreversible entropy increase. Here we model heat conduction as a thermodynamically reversible but mechanically irreversible process. The MD simulations conducted shows excellent agreement with the theory. Such views and results as these, if developed to a successful conclusion could imply that the Carnot cycle be viewed as describing a local process of energy-work conversion and that irreversible local processes might be brought within the scope of this cycle, implying a unified treatment of thermodynamically (i) irreversible, (ii) reversible, (iii) isothermal and (iv) adiabatic processes.
NASA Astrophysics Data System (ADS)
Gururaja Rao, C.; Santhosh, D.; Vijay Chandra, P.
2009-08-01
Prominent results pertaining to the problem of multi-mode heat transfer from an L-corner equipped with three identical flush-mounted discrete heat sources in its left leg are given here. The heat generated in the heat sources is conducted along the two legs of the device before being dissipated by combined convection and radiation into air that is considered to be the cooling agent. The governing equations for temperature distribution along the L-corner are obtained by making appropriate energy balance between the heat generated, conducted, convected and radiated. The non-linear partial differential equations thus obtained are converted into algebraic form using a finite-difference formulation. The resulting equations are solved simultaneously by Gauss-Seidel iterative solver. A computer code is specifically written to solve the problem. The computational domain is discretised using 101 grids along the left leg, with 15 grids taken per heat source, and 21 grids along the bottom leg. The effects of surface emissivity, convection heat transfer coefficient, thermal conductivity and aspect ratio on local temperature distribution, peak device temperature and relative contributions of convection and radiation to heat dissipation from the L-corner are studied in detail. The point that one cannot overlook radiation in problems of this class has been clearly elucidated.
Two-phase numerical model for thermal conductivity and convective heat transfer in nanofluids
2011-01-01
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
Heat conduction: hyperbolic self-similar shock-waves in solids
Imre Ferenc Barna; Robert Kersner
2012-04-19
Analytic solutions for cylindrical thermal waves in solid medium is given based on the nonlinear hyperbolic system of heat flux relaxation and energy conservation equations. The Fourier-Cattaneo phenomenological law is generalized where the relaxation time and heat propagation coefficient have a general power law temperature dependence. From such laws one cannot form a second order parabolic or telegraph-type equation. We consider the original non-linear hyperbolic system itself with the self-similar Ansatz for the temperature distribution and for the heat flux. As results continuous and shock-wave solutions are presented. For physical establishment numerous materials with various temperature dependent heat conduction coefficients are mentioned.
NASA Astrophysics Data System (ADS)
Meulien Ohlmann, Odile
2013-02-01
Today the industry offers a chain of 3D products. Learning to "read" and to "create in 3D" becomes an issue of education of primary importance. 25 years professional experience in France, the United States and Germany, Odile Meulien set up a personal method of initiation to 3D creation that entails the spatial/temporal experience of the holographic visual. She will present some different tools and techniques used for this learning, their advantages and disadvantages, programs and issues of educational policies, constraints and expectations related to the development of new techniques for 3D imaging. Although the creation of display holograms is very much reduced compared to the creation of the 90ies, the holographic concept is spreading in all scientific, social, and artistic activities of our present time. She will also raise many questions: What means 3D? Is it communication? Is it perception? How the seeing and none seeing is interferes? What else has to be taken in consideration to communicate in 3D? How to handle the non visible relations of moving objects with subjects? Does this transform our model of exchange with others? What kind of interaction this has with our everyday life? Then come more practical questions: How to learn creating 3D visualization, to learn 3D grammar, 3D language, 3D thinking? What for? At what level? In which matter? for whom?
Dimant, Y S
2011-01-01
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 two. At these times, strong DC electric fields penetrate to the E region and drive plasma instabilities that create turbulence. This plasma density turbulence induces non-linear currents, while associated electrostatic field fluctuations result in strong anomalous electron heating. These two effects will increase the global ionospheric conductance. Based on the theory of non-linear currents developed in the companion paper, 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 heati...
NASA Astrophysics Data System (ADS)
Dhar, Purbarun; Sen Gupta, Soujit; Chakraborty, Saikat; Pattamatta, Arvind; Das, Sarit K.
2013-04-01
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.
Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties
Hansen, B.J.; White, M.J.; Klebaner, A.; /Fermilab
2011-06-10
Future superconducting radio frequency (SRF) cavities, as part of Project X at Fermilab, will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule-Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchangers will be utilized. Due to their compact size and ease of fabrication, plate-fin heat exchangers are an effective option. However, the design of compact and high-effectiveness cryogenic heat exchangers operating at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger. The model is used to guide design decisions on heat exchanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger to analyze the effect of heat load and cryogenic supply parameters. A numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger was developed and the effect of various design parameters on overall heat exchanger size was investigated. It was found that highly conductive metals should be avoided in the design of compact JT heat exchangers. For the geometry considered, the optimal conductivity is around 3.5 W/m-K and can range from 0.3-10 W/m-K without a large loss in performance. The model was implemented with an isenthalpic expansion process. Increasing the cold side inlet temperature from 2K to 2.2 K decreased the liquid fraction from 0.856 to 0.839 which corresponds to a 0.12 g/s increase in supercritical helium supply needed to maintain liquid level in the cooling bath. Lastly, it was found that the effectiveness increased when the heat load was below the design value. Therefore, the heat exchanger should be sized on the high end of the required heat load.
NASA Astrophysics Data System (ADS)
Liu, D.; Medley, S. S.; Gorelenkova, M. V.; Heidbrink, W. W.; Stagner, L.
2014-10-01
A cloud of halo neutrals is created in the vicinity of beam footprint during the neutral beam injection and the halo neutral density can be comparable with beam neutral density. Proper modeling of halo neutrals is critical to correctly interpret neutral particle analyzers (NPA) and fast ion D-alpha (FIDA) signals since these signals strongly depend on local beam and halo neutral density. A 3D halo neutral model has been recently developed and implemented inside TRANSP code. The 3D halo neutral code uses a ``beam-in-a-box'' model that encompasses both injected beam neutrals and resulting halo neutrals. Upon deposition by charge exchange, a subset of the full, one-half and one-third beam energy components produce thermal halo neutrals that are tracked through successive halo neutral generations until an ionization event occurs or a descendant halo exits the box. A benchmark between 3D halo neural model in TRANSP and in FIDA/NPA synthetic diagnostic code FIDASIM is carried out. Detailed comparison of halo neutral density profiles from two codes will be shown. The NPA and FIDA simulations with and without 3D halos are applied to projections of plasma performance for the National Spherical Tours eXperiment-Upgrade (NSTX-U) and the effects of halo neutral density on NPA and FIDA signal amplitude and profile will be presented. Work supported by US DOE.
Joern Ostermann
2010-01-01
There are several technologies available for the transmission and presentation of 3D information to the human user. The appropriate selection of technology depends to a large extent on the application as well as on the maturity of the required technology. 3D video was established in niche markets, including professional applications (e.g., scientific visualization) and entertainment (IMAX cinemas, 3D gaming) some
NASA Astrophysics Data System (ADS)
Mutabazi, Innocent; Yoshikawa, Harunori; Peixinho, Jorge; Kahouadji, Lyes
2013-11-01
Görtler vortices appear in a flow over a concave wall as a result of centrifugal instability [Saric, Annu. Rev. Fluid Mech. 26, 379 (1994)]. They may have a strong influence on heat transfer [Momayez et al., Int. J. heat Mass transfer 47, 3783 (2004)]. The purpose of this work is to model heat transfer by Görtler vortices using a weakly nonlinear analysis of Smith &-Haj- Hariri [Phys. Fluids A 5, 2815 (1993)]. We have investigated the coupling of the convective heat transfer by the stationary vortices with the heat conduction inside the solid wall. The finite thickness and thermal conductivity of the wall enter into the boundary conditions of the problem through the ratio ? of the wall thickness to the boundary layer thickness and through the ratio K of the thermal conductivities of the fluid and the wall. The parametric dependence Nu (? , K) of the Nusselt number is performed and it is shown that found the heat transfer is quite well modified by these two parameters. The local thermal stress can be estimated in order to analyze the effects on ageing of the wall material. Görtler vortices appear in a flow over a concave wall as a result of centrifugal instability [Saric, Annu. Rev. Fluid Mech. 26, 379 (1994)]. They may have a strong influence on heat transfer [Momayez et al., Int. J. heat Mass transfer 47, 3783 (2004)]. The purpose of this work is to model heat transfer by Görtler vortices using a weakly nonlinear analysis of Smith &-Haj- Hariri [Phys. Fluids A 5, 2815 (1993)]. We have investigated the coupling of the convective heat transfer by the stationary vortices with the heat conduction inside the solid wall. The finite thickness and thermal conductivity of the wall enter into the boundary conditions of the problem through the ratio ? of the wall thickness to the boundary layer thickness and through the ratio K of the thermal conductivities of the fluid and the wall. The parametric dependence Nu (? , K) of the Nusselt number is performed and it is shown that found the heat transfer is quite well modified by these two parameters. The local thermal stress can be estimated in order to analyze the effects on ageing of the wall material. The authors acknowledge the financial support of the french Agence Nationale de la Recherche (ANR), through the program ``Investissements d'Avenir'' (ANR-10-LABX-09-01), LabEx EMC3.
Heat conduction in a chain of dissociating particles: Effect of dimensionality.
Zolotarevskiy, V; Savin, A V; Gendelman, O V
2015-03-01
The paper considers heat conduction in a model chain of composite particles with hard core and elastic external shell. Such model mimics three main features of realistic interatomic potentials--hard repulsive core, quasilinear behavior in a ground state, and possibility of dissociation. It has become clear recently that this latter feature has crucial effect on convergence of the heat conduction coefficient in thermodynamic limit. We demonstrate that in one-dimensional chain of elastic particles with hard core the heat conduction coefficient also converges, as one could expect. Then we explore effect of dimensionality on the heat transport in this model. For this sake, longitudinal and transversal motions of the particles are allowed in a long narrow channel. With varying width of the channel, we observe sharp transition from "one-dimensional" to "two-dimensional" behavior. Namely, the heat conduction coefficient drops by about order of magnitude for relatively small widening of the channel. This transition is not unique for the considered system. Similar phenomenon of transition to quasi-1D behavior with growth of aspect ratio of the channel is observed also in a gas of densely packed hard (billiard) particles, both for two- and three-dimensional cases. It is the case despite the fact that the character of transition in these two systems is not similar, due to different convergence properties of the heat conductivity. In the billiard model, the divergence pattern of the heat conduction coefficient smoothly changes from logarithmic to power-like law with increase of the length. PMID:25871074
Thermoelastic damping in thin microrings with two-dimensional heat conduction
NASA Astrophysics Data System (ADS)
Fang, Yuming; Li, Pu
2015-05-01
Accurate determination of thermoelastic damping (TED) is very challenging in the design of micro-resonators. Microrings are widely used in many micro-resonators. In the past, to model the TED effect on the microrings, some analytical models have been developed. However, in the previous works, the heat conduction within the microring is modeled by using the one-dimensional approach. The governing equation for heat conduction is solved only for the one-dimensional heat conduction along the radial thickness of the microring. This paper presents a simple analytical model for TED in microrings. The two-dimensional heat conduction over the thermoelastic temperature gradients along the radial thickness and the circumferential direction are considered in the present model. A two-dimensional heat conduction equation is developed. The solution of the equation is represented by the product of an assumed sine series along the radial thickness and an assumed trigonometric series along the circumferential direction. The analytical results obtained by the present 2-D model show a good agreement with the numerical (FEM) results. The limitations of the previous 1-D model are assessed.
The program FANS-3D (finite analytic numerical simulation 3-dimensional) and its applications
NASA Technical Reports Server (NTRS)
Bravo, Ramiro H.; Chen, Ching-Jen
1992-01-01
In this study, the program named FANS-3D (Finite Analytic Numerical Simulation-3 Dimensional) is presented. FANS-3D was designed to solve problems of incompressible fluid flow and combined modes of heat transfer. It solves problems with conduction and convection modes of heat transfer in laminar flow, with provisions for radiation and turbulent flows. It can solve singular or conjugate modes of heat transfer. It also solves problems in natural convection, using the Boussinesq approximation. FANS-3D was designed to solve heat transfer problems inside one, two and three dimensional geometries that can be represented by orthogonal planes in a Cartesian coordinate system. It can solve internal and external flows using appropriate boundary conditions such as symmetric, periodic and user specified.
Wang, Hsin; Porter, Wallace D; Bottner, Harold; Konig, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolett, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Partricia; Sharp, J; Lo, Jason; Keinke, Holger; Kiss, Laszlo I.
2013-01-01
For bulk thermoelectrics, figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In recent years, the most significant improvements in ZT were mainly due to successful reduction of thermal conductivity. However, thermal conductivity cannot be measured directly at high temperatures. The combined measurements of thermal diffusivity and specific heat and density are required. It has been shown that thermal conductivity is the property with the greatest uncertainty and has a direct influence on the accuracy of the figure of merit. The International Energy Agency (IEA) group under the implementing agreement for Advanced Materials for Transportation (AMT) has conducted two international round-robins since 2009. This paper is Part II of the international round-robin testing of transport properties of bulk bismuth telluride. The main focuses in Part II are on thermal diffusivity, specific heat and thermal conductivity.
High heat flux Kapitza conductance of technical copper with several different surface preparations
NASA Astrophysics Data System (ADS)
Kashani, A.; Van Sciver, S. W.
1985-05-01
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.
NASA Astrophysics Data System (ADS)
Hartung, M.; Köhler, W.
2005-06-01
We present a two-dimensional model to account for the role of heat-conducting walls in the measurement of heat transport and Soret-effect-driven mass transport in transient holographic grating experiments. Heat diffusion into the walls leads to non-exponential decay of the temperature grating. Under certain experimental conditions it can be approximated by an exponential function and assigned an apparent thermal diffusivity Dth, app < Dth, s, where Dth,s is the true thermal diffusivity of the sample. The ratio Dth, app/Dth, s depends on only three dimensionless parameters, d /ls, ?s/?w, and Dth, s/Dth, w. d is the grating period, ls the sample thickness, ?s and ?w the thermal conductivities of sample and wall, respectively, and Dth,w the thermal diffusivity of the wall. If at least two measurements are performed at different d /ls, both Dth,s and ?s can be determined. Instead of costly solving PDEs, Dth,s can be obtained by finding the zero of an analytic function. For thin samples and large grating periods, heat conduction into the walls plays a predominant role and the concentration grating in binary mixtures is no longer one-dimensional. Nevertheless, the normalized heterodyne diffraction efficiency of the concentration grating remains unaffected and the true thermal and collective diffusion coefficient and the correct Soret coefficient are still obtained from a simple one-dimensional model.
ERIC Educational Resources Information Center
Hastings, S. K.
2002-01-01
Discusses 3 D imaging as it relates to digital representations in virtual library collections. Highlights include X-ray computed tomography (X-ray CT); the National Science Foundation (NSF) Digital Library Initiatives; output peripherals; image retrieval systems, including metadata; and applications of 3 D imaging for libraries and museums. (LRW)
Development and implementation of sensitivity coefficient equations for heat conduction problems
Blackwell, B.F.; Cochran, R.J.; Dowding, K.J.
1997-12-15
Three different methods are discussed for computing the sensitivity of the temperature field to changes in material properties and initial-boundary condition parameters for heat conduction problems. The most general method is to derive sensitivity equations by differentiating the energy equation with respect to the parameter of interest and numerically solving the resulting sensitivity equations. An example problem in which there are twelve parameters of interest is presented and the resulting sensitivity equations are derived. Numerical results are presented for thermal conductivity and volumetric heat capacity sensitivity coefficients for heat conduction in a 2-D orthotropic body. The numerical results are compared with the analytical solution to demonstrate that the numerical method is second order accurate as the mesh is refined spatially.
Combined conduction and correlated-radiation heat transfer in packed beds
Kamiuto, K.; Iwamoto, M.; Nagumo, Y. )
1993-09-01
A quasi-homogeneous model for heat transfer in a plane-parallel packed bed of opaque spheres is presented. The proposed model takes into account the variable porosity distribution within a packed bed and the correlated radiative properties of packed spheres having gray diffuse surfaces. On the basis of the proposed model, combined conductive and radiative heat transfer through comparatively thin packed layers of cordierite spheres or oxidized steel spheres are analyzed numerically and the obtained results are compared with the experimental ones. Additionally, the adequacy of a simplified analytical formula for the total effective thermal conductivities of a packed bed is discussed. It is found that the detailed theoretical model accurately predicts the heat transfer characteristics and the temperature profiles of the plane-parallel packed beds, and the predictions derived from the approximate formula well-correlate with the present experimental data for the total effective thermal conductivities. 22 refs.
Thermal conductivity, heat capacity, and thermal diffusivity of selected commercial AlN substrates
Dinwiddie, R.B.; Whittaker, A.J.; Onn, D.G. (Univ. of Delaware, Newark (USA))
1989-09-01
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.
J. Donea; S. Giuliani
1980-01-01
The present report is the user's manual for the computer code CONDIF-01 developed at the JRC-Ispra for use in Post-Accident Heat Removal (PAHR) studies following a hypothetical fast-reactor core meltdown. CONDIF-01 makes use of the finite element method to solve transient convective-conductive heat transfer problems in a fluid and its enclosing structures. Plane and axisymmetric situations may be analyzed. The
R. G. Keanini; Xianwu Ling; H. P. Cherukuri
2005-01-01
A method for enhancing the stability of parabolic inverse heat conduction problems (IHCP) is presented. The investigation extends recent work on non-iterative finite element-based IHCP algorithms which, following Beck’s two-step approach, first derives a discretized standard form equation relating the instantaneous global temperature and surface heat flux vectors, and then formulates a least squares-based linear matrix normal equation in the
Naoki Asai; Naoya Fukuda; Ryoji Matsumoto
2004-04-07
Recent Chandra observations of clusters of galaxies revealed the existence of a sharp ridge in the X-ray surface brightness where the temperature drops across the front. This front is called the cold front. We present the results of two-dimensional magnetohydrodynamic simulations of the time evolution of a dense subcluster plasma moving in a cluster of galaxies. Anisotropic heat conduction along the magnetic field lines is included. In the models without magnetic fields, the numerical results indicate that the heat conduction from the hot ambient plasma heats the cold dense plasma of the subcluster and diffuses out the cold front. When magnetic fields exist in a cluster of galaxies, however, cold fronts can be maintained because the heat conduction across the magnetic field lines is suppressed. We found that, even when the magnetic fields in a cluster of galaxies are disordered, heat conduction across the front is restricted because the magnetic field lines are stretched along the front. Numerical results reproduced the X-ray intensity distribution observed in the A3667 cluster of galaxies.
Are X-ray Clusters Cooled by Heat Conduction to the Surrounding Intergalactic Medium?
Abraham Loeb
2002-04-29
We show that X-ray clusters would have cooled substantially over a Hubble time by transport of heat from their hot interior to the their envelope, if the heat conductivity had not been heavily suppressed relative to the Spitzer value due to magnetic fields. The suppression is required in order for the observed abundance of hot X-ray clusters to be consistent with predictions from popular cosmological models. If a similar or stronger suppression factor applies to cluster cores, then thermal conduction can not be the mechanism that prevents cooling flows there.
Collisionless conductivity and stochastic heating of the plasma sheet in the geomagnetic tail
Horton, W.; Tajima, T. (Univ. of Texas, Austin (United States))
1991-09-01
The chaotic single particle orbits in the geomagnetic tail are used to calculate the collisionless conductivity. It is shown that the stochasticity from inhomogeneous magnetic fields leads to a power law decay of the single particle correlation function similar to an elastic collisional process. The height-integrated dissipative part of the collisionless conductivity governs the irreversible stochastic heating of the plasma sheet. Both exponentially growing reconnection type magnetic perturbations and a sinusoidal pulse with a half period up to 1 hour in duration are used to analyze the plasma sheet heating.
NASA Astrophysics Data System (ADS)
Xu, K. Q.; Zeng, H. R.; Yu, H. Z.; Zhao, K. Y.; Li, G. R.; Song, J. Q.; Shi, X.; Chen, L. D.
2015-01-01
An ultrahigh resolution probe technique for charactering nanoscale Seebeck coefficient was developed based on a modified conductive AFM probe with local heating function. The heated AFM conductive tip realizes nanoscale thermal contact between the AFM tip and the thermoelectric samples and successfully excites nanoscale thermoelectric signal. Excellent agreement was found between nanoscale Seebeck coefficient values and their corresponding macroscopy measurements in thermoelectric bulk and thin films. Such AFM-based thermoelectric probe technique provides a very convenient and promising tool for measuring nanoscale thermoelectric parameters with ultrahigh resolution up to 15 nm.
Equilibration and Universal Heat Conduction in Fermi-Pasta-Ulam Chains
NASA Astrophysics Data System (ADS)
Mai, Trieu; Dhar, Abhishek; Narayan, Onuttom
2007-05-01
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.
A new finite-difference method for the nonlinear inverse heat conduction problem
NASA Astrophysics Data System (ADS)
Raynaud, M.; Bransier, J.
A new space-marching finite-difference algorithm is developed to solve the nonlinear inverse heat conduction problem. This algorithm uses interior temperature measurements at future times to estimate the surface heat flux. The results of this method are compared on a test case with four other numerical schemes. The method is as accurate as the method developed by Beck (1982) and uses a smaller computational time. This scheme is also employed to estimate the effects of different types of experimental errors on the estimation of the surface heat flux. Errors due to temperature measurements, thermocouple locations, and material properties are each investigated.
Heat conductivity in small quantum systems: Kubo formula in Liouville space
Mathias Michel; Jochen Gemmer; Guenter Mahler
2005-03-22
We consider chains consisting of several identical subsystems weakly coupled by various types of next neighbor interactions. At both ends the chain is coupled to a respective heat bath with different temperature modeled by a Lindblad formalism. The temperature gradient introduced by this environment is then treated as an external perturbation. We propose a method to evaluate the heat current and the local temperature profile of the resulting stationary state as well as the heat conductivity in such systems. This method is similar to Kubo techniques used e.g. for electrical transport but extended here to the Liouville space.
Non-Realistic 3D Object Stylization Julian Kratt1
Sharf, Andrei
or might be printed using a 3D printer. We conducted a user study to verify the proposed stylizationsNon-Realistic 3D Object Stylization Julian Kratt1 Ferdinand Eisenkeil1 S¨oren Pirk1 Andrei Sharf2 paradigm of non-realistic 3D stylization, where the expressiveness of a given 3D model is man- ifested
Estimating thermal diffusivity and specific heat from needle probe thermal conductivity data
Waite, W.F.; Gilbert, L.Y.; Winters, W.J.; Mason, D.H.
2006-01-01
Thermal diffusivity and specific heat can be estimated from thermal conductivity measurements made using a standard needle probe and a suitably high data acquisition rate. Thermal properties are calculated from the measured temperature change in a sample subjected to heating by a needle probe. Accurate thermal conductivity measurements are obtained from a linear fit to many tens or hundreds of temperature change data points. In contrast, thermal diffusivity calculations require a nonlinear fit to the measured temperature change occurring in the first few tenths of a second of the measurement, resulting in a lower accuracy than that obtained for thermal conductivity. Specific heat is calculated from the ratio of thermal conductivity to diffusivity, and thus can have an uncertainty no better than that of the diffusivity estimate. Our thermal conductivity measurements of ice Ih and of tetrahydrofuran (THF) hydrate, made using a 1.6 mm outer diameter needle probe and a data acquisition rate of 18.2 pointss, agree with published results. Our thermal diffusivity and specific heat results reproduce published results within 25% for ice Ih and 3% for THF hydrate. ?? 2006 American Institute of Physics.
Bass
1979-01-01
The calculation of the surface temperature and surface heat flux from a measured temperature history at an interior point of a body is identified in the literature as the inverse heat conduction problem. This report presents apparently the first application of an inverse solution technique that utilizes a finite element heat conduction model and Beck's nonlinear estimation procedure. The technique
Michal Beneš
2011-08-08
We study an initial-boundary-value problem for time-dependent flows of heat-conducting viscous incompressible fluids in channel-like domains on a time interval $(0,T)$. For the parabolic system with strong nonlinearities and including the artificial (the so called "do nothing") boundary conditions, we prove the local in time existence, global uniqueness and smoothness of the solution on a time interval $(0,T^*)$, where $0< T^* \\leq T$.
NASA Astrophysics Data System (ADS)
Zhang, Liqiang; Reilly, Carl; Li, Luoxing; Cockcroft, Steve; Yao, Lu
2014-07-01
The interfacial heat transfer coefficient (IHTC) is required for the accurate simulation of heat transfer in castings especially for near net-shape processes. The large number of factors influencing heat transfer renders quantification by theoretical means a challenge. Likewise experimental methods applied directly to temperature data collected from castings are also a challenge to interpret because of the transient nature of many casting processes. Inverse methods offer a solution and have been applied successfully to predict the IHTC in many cases. However, most inverse approaches thus far focus on use of in-mold temperature data, which may be a challenge to obtain in cases where the molds are water-cooled. Methods based on temperature data from the casting have the potential to be used however; the latent heat released during the solidification of the molten metal complicates the associated IHTC calculations. Furthermore, there are limits on the maximum distance the thermocouples can be placed from the interface under analysis. An inverse conduction based method have been developed, verified and applied successfully to temperature data collected from within an aluminum casting in proximity to the mold. A modified specific heat method was used to account for latent heat evolution in which the rate of change of fraction solid with temperature was held constant. An analysis conducted with the inverse model suggests that the thermocouples must be placed no more than 2 mm from the interface. The IHTC values calculated for an aluminum alloy casting were shown to vary from 1,200 to 6,200 Wm-2 K-1. Additionally, the characteristics of the time-varying IHTC have also been discussed.
A meshless model for transient heat conduction in functionally graded materials
H. Wang; Q. H. Qin; Y. L. Kang
2006-01-01
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
A peridynamic formulation for transient heat conduction in bodies with evolving discontinuities
NASA Astrophysics Data System (ADS)
Bobaru, Florin; Duangpanya, Monchai
2012-04-01
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.
Rice, Jarrett A.; Pokorny, Richard; Schweiger, Michael J.; Hrma, Pavel R.
2014-06-01
The heat conductivity ({lambda}) and the thermal diffusivity (a) of reacting glass batch, or melter feed, control the heat flux into and within the cold cap, a layer of reacting material floating on the pool of molten glass in an all-electric continuous waste glass melter. After previously estimating {lambda} of melter feed at temperatures up to 680 deg C, we focus in this work on the {lambda}(T) function at T > 680 deg C, at which the feed material becomes foamy. We used a customized experimental setup consisting of a large cylindrical crucible with an assembly of thermocouples, which monitored the evolution of the temperature field while the crucible with feed was heated at a constant rate from room temperature up to 1100°C. Approximating measured temperature profiles by polynomial functions, we used the heat transfer equation to estimate the {lambda}(T) approximation function, which we subsequently optimized using the finite-volume method combined with least-squares analysis. The heat conductivity increased as the temperature increased until the feed began to expand into foam, at which point the conductivity dropped. It began to increase again as the foam turned into a bubble-free glass melt. We discuss the implications of this behavior for the mathematical modeling of the cold cap.
Heat Transfer Investigation of Air Flow in Microtubes-Part II: Scale and Axial Conduction Effects.
Lin, Ting-Yu; Kandlikar, Satish G
2013-03-01
In this paper, the scale effects are specifically addressed by conducting experiments with air flow in different microtubes. Three stainless steel tubes of 962, 308, and 83??m inner diameter (ID) are investigated for friction factor, and the first two are investigated for heat transfer. Viscous heating effects are studied in the laminar as well as turbulent flow regimes by varying the air flow rate. The axial conduction effects in microtubes are experimentally explored for the first time by comparing the heat transfer in SS304 tube with a 910??m ID/2005??m outer diameter nickel tube specifically fabricated using an electrodeposition technique. After carefully accounting for the variable heat losses along the tube length, it is seen that the viscous heating and the axial conduction effects become more important at microscale and the present models are able to predict these effects accurately. It is concluded that neglecting these effects is the main source of discrepancies in the data reported in the earlier literature. PMID:23918039
Ultrafine particle emissions from desktop 3D printers
NASA Astrophysics Data System (ADS)
Stephens, Brent; Azimi, Parham; El Orch, Zeineb; Ramos, Tiffanie
2013-11-01
The development of low-cost desktop versions of three-dimensional (3D) printers has made these devices widely accessible for rapid prototyping and small-scale manufacturing in home and office settings. Many desktop 3D printers rely on heated thermoplastic extrusion and deposition, which is a process that has been shown to have significant aerosol emissions in industrial environments. However, we are not aware of any data on particle emissions from commercially available desktop 3D printers. Therefore, we report on measurements of size-resolved and total ultrafine particle (UFP) concentrations resulting from the operation of two types of commercially available desktop 3D printers inside a commercial office space. We also estimate size-resolved (11.5 nm-116 nm) and total UFP (<100 nm) emission rates and compare them to emission rates from other desktop devices and indoor activities known to emit fine and ultrafine particles. Estimates of emission rates of total UFPs were large, ranging from ˜2.0 × 1010 # min-1 for a 3D printer utilizing a polylactic acid (PLA) feedstock to ˜1.9 × 1011 # min-1 for the same type of 3D printer utilizing a higher temperature acrylonitrile butadiene styrene (ABS) thermoplastic feedstock. Because most of these devices are currently sold as standalone devices without any exhaust ventilation or filtration accessories, results herein suggest caution should be used when operating in inadequately ventilated or unfiltered indoor environments. Additionally, these results suggest that more controlled experiments should be conducted to more fundamentally evaluate particle emissions from a wider arrange of desktop 3D printers.
NASA Astrophysics Data System (ADS)
Li, Chongxiang; Asundi, Anand K.; Fang, Zhong P.
2001-10-01
With the increasing demand for micro-products and bioengineering research, resolutions of profiles with micrometer or even nanometer scale are becoming commonplace. In addition development of large integrated manufacturing systems and the real time life science growth and adaptation need high-speed display and real-time inspection. Single point measurement is time consuming method with large area profile and micrometer resolution. Thus there is a need for a fast 3-D measurement system with high resolution. This paper presents a short overview among optical 3-D shape measurement techniques, and concentrates on the confocal method. Based on the properties analysis, a novel multi-channel 3-D topography measurement system was proposed. The feasibility and the construction of system were described A unique new structure of fiber coupled confocal system is put forth to solve present problems confronted in confocal system. This system can meet the current demand of high resolution and fast 3-D measurement.
Level Set-based Topological Shape Optimization of Nonlinear Heat Conduction Problems
Seung-Hyun Ha; Seonho Cho
2008-01-01
A level set-based topological shape optimization method is developed for nonlinear heat conduction problems. While minimizing the objective function of instantaneous thermal compliance and satisfying the constraint of allowable volume, solution of the Hamilton-Jacobi equation leads the initial boundary to an optimal one according to the normal velocity field determined from the descent direction of the Lagrangian. To overcome the
On the numerical solution of phase change problems in transient non-linear heat conduction
K. Mastanaiah
1976-01-01
A finite difference solution for the transient nonlinear heat conduction with phase change in a finite slab is proposed. A two-time level implicit method is used while Taylor's forward projection method is employed for taking into account the nonlinearities. The stability due to the boundary conditions at the moving front is verified. The numerical solution is compared with the analytical
Topological Shape Optimization of Heat Conduction Problems using Level Set Approach
Seung-Hyun Ha; Seonho Cho
2005-01-01
A topological shape optimization method for heat conduction problems is developed using a level set method. The level set function obtained from the “Hamilton-Jacobi type” equation is embedded into a fixed initial domain to implicitly represent thermal boundaries and obtain the finite-element response and adjoint sensitivity. The developed method minimizes the thermal compliance, satisfying the constraint of allowable volume by
COYOTE: a finite-element computer program for nonlinear heat-conduction problems
Gartling, D.K.
1982-10-01
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.
D. K. Gartling; R. E. Hogan
1994-01-01
The theoretical and numerical background for the finite element computer program, COYOTE II, is presented in detail. COYOTE II is designed for the multi-dimensional analysis of nonlinear heat conduction problems and other types of diffusion 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
Development and Implementation of Sensitivity Coefficient Equations for Heat Conduction Problems
Bennie F. Blackwell; Kevin J. Dowding; R. J. Cochran
1999-01-01
Methods are discussed for computing the sensitivity of the temperature field to changes in material properties and initial\\/boundary condition parameters for heat conduction problems. The most general method is to derive sensitivity equations by differentiating the energy equation with respect to the parameter of interest and solving the resulting sensitivity equations numerically. An example problem in which there are 12
Arima statistical models of transient heat conduction errors for Aitken's confidence region
I. P. Schisler
1979-01-01
An iterative Aitken's least squares estimator was implemented within an existing standard least squares computer program for the heat conduction problem. The accuracy of this modified computer code was verified in a simulation study. It was found that the effects of correlated errors for the available dynamic measurements and associated models can be treated without great difficulty. The parameter estimates
COYOTE: a finite element computer program for nonlinear heat conduction problems
Gartling
1978-01-01
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.
COYOTE: A finite-element computer program for nonlinear heat-conduction problems
D. K. Gartling
1983-01-01
A finite element computer program COYOTE was 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.
TOPAZ: A finite element heat conduction code for analyzing 2-D solids
A. B. Shapiro
1984-01-01
The TOPAZ is a two dimensional implicit finite element computer code for heat conduction analysis. A user's manual for TOPAZ and a description of the numerical algorithms used is presented. Sample problems with analytical solutions are created. The TOPAZ has been implemented on the CRAY and VAX computers.
A time-stepping DRBEM for transient heat conduction in anisotropic solids
Masataka Tanaka; Koutarou Kurokawa; Toshiro Matsumoto
2008-01-01
This paper is concerned with a dual reciprocity boundary element method (DRBEM) applied to transient heat conduction problems for time-dependent, anisotropic materials. The integral equation formulation employs the fundamental solution of the Laplace equation for linear isotropic materials. As a result, from the nonlinear and also from the anisotropic parts of the governing differential equation, domain integrals arise in the
Karl R. Heinz
1988-01-01
A FORTRAN 77 computer code employing an adaptation of the finite differencing algorithm proposed by Brian was developed for the solution of transient heat conduction problems in cylindrical geometries. Validation of code was accomplished by comparison with an analytic solution derived for a model with symmetric, linear boundary conditions. Accuracy of results for asymmetric and non-linear boundary conditions was determined
Finite element modeling of the transient heat conduction between colliding particles
J. H. Zhou; A. B. Yu; M. Horio
2008-01-01
Finite element method (FEM) is employed to simulate the transient heat conduction during the collision between spherical particles. The total collision time is divided into many small time steps. At each time step, the contact area is evaluated by the Hertz's theory of elastic collision and based on this information, a grid system is generated for FEM computation to determine
DRM APPLIED TO THE TIME-STEPPING BEM FOR TRANSIENT HEAT CONDUCTION
Masataka Tanaka; Toshiro Matsumoto
This paper presents application of dual reciprocity method (DRM) to time-stepping BEM for the transient heat conduction problem in homogeneous media. The integral equation fomulation uses the fundamental solution of Laplace equation, and time derivative is approximated by the time-stepping method. Hence the domain integral arises in the boundary integral equation. This domain integral is transformed into bound- ary integrals
R. V. N. Melnik; A. J. Roberts; K. A. Thomas
2002-01-01
The dynamics of phase transitions and hysteresis phenomena in materials with memory are described by a strongly nonlinear coupled system of partial differential equations which, in its generality, can be solved only numerically. Following principles of extended thermodynamics, in this paper we construct a new model for the description of this dynamics based on the Cattaneo-Vernotte law for heat conduction.
COYOTE: a finite-element computer program for nonlinear heat-conduction problems
Gartling
1982-01-01
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.
Implementation of heat conduction in 2D hydrodynamic code CAVEAT-TR
M. M. Basko; J. A. Maruhn; K. Witte
2007-01-01
Combination of intense laser and ion beams at GSI of- fers a unique possibility to study matter at high energy den- sities. The PHELIX laser beam will be used to create hot plasmas by direct target irradiation or using indirect-dri ve schemes based on radiative hohlraums. A two-dimensional hydrodynamic code including heat conduction and spec- tral radiation transport is required
Chang-New Chen
1999-01-01
A new numerical approach for solving steady-state heat conduction problems by using the irregular elements of the differential quadrature element method (DQEM) is proposed. The mapping technique is used to transform the governing partial differential equation, the natural transition condition of two adjacent elements and the Newmann boundary condition defined on the irregular physical element into the parent space. The
Numerical study of conductive heat losses from a magmatic source at Phlegraean Fields
NASA Astrophysics Data System (ADS)
Di Maio, Rosa; Piegari, Ester; Mancini, Cecilia; Scandone, R.
2015-01-01
The thermal evolution of the Phlegraean magmatic system (southern Italy) is studied by analyzing the influence of the thermal property variations on the solution of the heat conduction equation. The aim of this paper is to verify if appropriate choices of thermal parameters can reproduce, at least to greater depths, the high temperatures measured in the geothermal wells, drilled inside the caldera, under the assumption of heat loss from a magma chamber by conduction. Since the main purpose is to verify the plausibility of such an assumption, rather simple models of the magmatic system are adopted and only major volcanic events (i.e., the Campanian Ignimbrite and the Neapolitan Yellow Tuff eruptions) are considered. The results of the simulated two-dimensional model scenarios show that by assuming an extended source region, whose emplacement time is longer than 40 ka, heat conduction mechanisms can provide temperatures as high as those measured at depths deeper than about 2000 m. On the other hand, the 1D simulations show that appropriate choices for the thermal conductivity depth profiles can reproduce the observed temperatures at depths deeper than about 1000 m. These findings question the apparent consensus that convection is the only dominant form of heat transfer at Phlegraean Fields and might motivate new research for reconstructing the thermal evolution of the Phlegraean magmatic system.
Kostic, Milivoje M.
size. For example, a 1 cm copper sphere centered in a cube with a solid material of TC as water, or 10 mixtures if exposed to "over-all unidirectional" boundary conditions. This approach has been used to model conductivity, unidirectional heat transfer, heterogeneous mixtures, nanofluids, cubic model, Maxwell model 1
Heat Flow, Thermal Conductivity, and the Plausibility of the White Mars Hypothesis
NASA Technical Reports Server (NTRS)
Urquhart, M. L.; Gulick, V. C.
2002-01-01
Due to the low thermal conductivity of CO2 ice and clathrate vs. water ice, we find that liquid water reservoirs would not be confined to the deep subsurface as predicted by the controversial White Mars model, even assuming low global heat flow. Additional information is contained in the original extended abstract.
Heat conduction in one-dimensional nonintegrable systems Bambi Hu,1,2
the existence of scattering. However, the different heat conduction behaviors in the two categories into three categories. The first one consists of integrable sys- tems such as the harmonic chain. It was rigorously shown 12 that, in this category, no temperature gradient can be formed, and the thermal
An analytical solution to the one-dimensional heat conduction-convection equation in soil
Technology Transfer Automated Retrieval System (TEKTRAN)
Heat transfer in soil occurs by conduction and convection. Infiltrating water affects soil temperature distributions, and measuring soil temperature distributions below infiltrating water can provide a signal for the flux of water. In earlier work a sine wave function (hereinafter referred to as the...
Martin, Timothy
Summary Weusedthreemethodstomeasureboundarylayer conductance to heat transfer (gbH) and water vapor, water vapor transfer. Introduction Water loss from plant leaves is controlled by boundary layer of the density, size and degree of opening of stomata. Boundary layer conduc- tance to water vapor (gbV) depends
Jiann-Quo Tarn; Yung-Ming Wang
2004-01-01
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.
NASA Astrophysics Data System (ADS)
Wang, Tao
2015-09-01
We establish an initial-boundary value problem for the compressible magnetohydrodynamic equations in one space dimension with large initial data when the heat conductivity is some positive power of the temperature. We prove that as the shear viscosity vanishes, global weak solutions convergence to a solution of the original equations with zero shear viscosity.
R. Alsan Meric
1998-01-01
In this article, the shape optimization for the Joule heating of solid bodies is investigated. The conductivity coefficients are permitted to vary with temperature. The shape design sensitivity analysis is performed for a general objective function using Ike adjoint variable method and the material derivative technique. The Kirchhoffs transformation or the Newton-Ralpson method is utilized during the Galerkin finite-element discretizations.
Specific heat and thermal conductivity of UCu4+ x Al8- x compounds
NASA Astrophysics Data System (ADS)
Nasreen, F.; Torikachvili, M. S.; Kothapalli, K.; Kohama, Y.; Zapf, V. S.; Nakotte, H.
2013-05-01
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.
Li, Baowen
, and billiard gas channels Baowen Li Department of Physics, National University of Singapore, 117542 Singapore nanotubes, to billiard gas channels. We find that in all discussed systems, the anomalous heat conductivity the Fourier law. Unlike the billiard gas channel, we still do not have a clear answer to this question
Lattice thermal conductivity of lower mantle minerals and heat flux from Earth's core.
Manthilake, Geeth M; de Koker, Nico; Frost, Dan J; McCammon, Catherine A
2011-11-01
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 MgSiO(3) perovskite at 26 GPa up to 1,073 K, and of ferropericlase containing 0, 5, and 20% Fe, at 8 and 14 GPa up to 1,273 K. We find the incorporation of these elements in silicate perovskite and ferropericlase to result in a ?50% decrease of lattice thermal conductivity relative to the end member compositions. A model of thermal conductivity constrained from our results indicates that a peridotitic mantle would have k = 9.1 ± 1.2 W/m K at the top of the thermal boundary layer and k = 8.4 ± 1.2 W/m K at its base. These values translate into a heat flux of 11.0 ± 1.4 terawatts (TW) from Earth's core, a range of values consistent with a variety of geophysical estimates. PMID:22021444
Maria del Puy Carretero; Amalia Ortiz; David Oyarzun; Isabel Torre; Maria Linaza; Alejandro Garcia-Alonso
2010-01-01
The focus of our research is enabling the users to interact with three-dimensional (3-D) graphics and interactive applications with the same content, appearance, and interaction paradigm on different platforms [Internet, television (TV), and mobile devices]. The main contribution of this article is the design and implementation of a platform-dependent architecture for 3-D graphics and content, validated in the entertainment and
NASA Astrophysics Data System (ADS)
Stern, Jonathan M.; Ozguz, Volkan H.
2006-05-01
The ever increasing demand for more electronic functionality integrated in silicon chips requires new approaches. One solution is to explore several technology fronts such as nanometer lithography or advanced materials. A better (but complementary) solution is to use the third dimension by stacking multiple layers of integrated circuits that overcomes the limitations of planar approaches. A general overview of 3D packaging and integration approaches is presented in relation to system architectures that will benefit from 3D implementation.
NSDL National Science Digital Library
2012-07-20
Several major companies, including Google, are working on getting elaborate 3D maps online. This latest iteration of Google maps for Android-powered devices allows users to browse select cities in a 3D fashion. Utilizing aerial imagery, the buildings appear in a three-dimensional format, which can aid people navigating their way around an unfamiliar urban environment. Visitors can customize their own views with the "tilt" and "compass" mode features, which makes things a bit more fun.
Thermal conductivity and diffusivity of biomaterials measured with self-heated thermistors
NASA Astrophysics Data System (ADS)
Valvano, J. W.; Cochran, J. R.; Diller, K. R.
1985-05-01
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.
Soliton mechanism of the uranium nitride microdynamics and heat conductivity at high temperatures
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
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).
NASA Astrophysics Data System (ADS)
Fredman, T. P.
2004-12-01
A boundary identification problem in inverse heat conduction is studied, based on data from internal measurement of temperature and heat flux. Formulated as a sideways heat conduction equation, a spatial continuation technique is applied to extend the solution to a known boundary condition at the desired boundary position. Recording the positions traversed in the continuation for each time instant yields the boundary position trajectory and hence the solution of the identification problem. A prospective application of the method can be found in the ironmaking blast furnace, where it is desired to monitor the thickness of the accreted refractory wall based on measurement of its internal state. Simulations featuring noisy measurement data demonstrate the feasibility of the identification method for blast furnace wall thickness estimation.
NASA Technical Reports Server (NTRS)
Tamma, Kumar K.; Railkar, Sudhir B.
1988-01-01
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.
Heat conduction in systems with Kolmogorov-Arnold-Moser phase space structure
I. F. Herrera-González; H. I. Pérez-Aguilar; A. Mendoza-Suárez; E. S Tututi
2012-09-28
We study heat conduction in a billiard channel formed by two sinusoidal walls and the diffusion of particles in the corresponding channel of infinite length; the latter system has an infinite horizon, i.e., a particle can travel an arbitrary distance without colliding with the rippled walls. For small ripple amplitudes, the dynamics of the heat carriers is regular and analytical results for the temperature profile and heat flux are obtained using an effective potential. The study also proposes a formula for the temperature profile that is valid for any ripple amplitude. When the dynamics is regular, ballistic conductance and ballistic diffusion are present. The Poincar\\'e plots of the associated dynamical system (the infinitely long channel) exhibit the generic transition to chaos as ripple amplitude is increased.When no Kolmogorov-Arnold-Moser (KAM) curves are present to forbid the connection of all chaotic regions, the mean square displacement grows asymptotically with time t as tln(t).
NASA Astrophysics Data System (ADS)
Canavan, E. R.; Tuttle, J. G.
2006-03-01
The James Webb Space Telescope will include an optical bench known as the integrated science instrument module (ISIM). Candidate structural materials for the ISIM must have low density, high stiffness, and low thermal expansion coefficient at the operating temperature of 30 Kelvin. The thermal conductivity and specific heat are important in modeling the on-orbit cooldown. We built two different systems for measuring the thermal conductivity and specific heat of samples between 4 Kelvin and 290 Kelvin. Both experiments were carefully designed to minimize potential errors due to radiative heat transfer. We chose the cooling system and instrumentation to allow long-term unattended operation. Software was developed to automate each experiment. It used an algorithm designed to ensure that each system was in steady state before a measurement was taken. We describe the two experiments and present the data.
Effect of heat treatment time on microstructure and electrical conductivity in LATP glass ceramics
Sonigra, Dhiren, E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in; Soman, Swati, E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in; Kulkarni, Ajit R., E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in [Dept. of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai-400076 (India)
2014-04-24
Glass-ceramic is prepared by heat treatment of melt quenched 14Li{sub 2}O?9Al{sub 2}O{sub 3}?38TiO{sub 2}?39P{sub 2}O{sub 5} glass in the vicinity of crystallization temperature. Growth of ceramic phase is controlled by tuning heat treatment time at fixed temperature. Ceramic phase was identified to be LiTi{sub 2}(PO{sub 4}){sub 3} from X Ray Diffraction analysis. Microstructural evolution of this phase with hold time was observed under high resolution Scanning Electron Microscope. DC conductivity is observed to increase by 4-5 orders of magnitude in this glass-ceramic compared to parent glass. However, formation of pores and cracks with very large heat treatment time seem to hinder further increase of conductivity.
Heat conduction in systems with Kolmogorov-Arnold-Moser phase space structure.
Herrera-González, I F; Pérez-Aguilar, H I; Mendoza-Suárez, A; Tututi, E S
2012-09-01
We study heat conduction in a billiard channel formed by two sinusoidal walls and the diffusion of particles in the corresponding channel of infinite length; the latter system has an infinite horizon, i.e., a particle can travel an arbitrary distance without colliding with the rippled walls. For small ripple amplitudes, the dynamics of the heat carriers is regular and analytical results for the temperature profile and heat flux are obtained using an effective potential. The study also proposes a formula for the temperature profile that is valid for any ripple amplitude. When the dynamics is regular, ballistic conductance and ballistic diffusion are present. The Poincaré plots of the associated dynamical system (the infinitely long channel) exhibit the generic transition to chaos as ripple amplitude is increased. When no Kolmogorov-Arnold-Moser (KAM) curves are present to forbid the connection of all chaotic regions, the mean square displacement grows asymptotically with time t as tln(t). PMID:23030897
Heat conduction in systems with Kolmogorov-Arnold-Moser phase space structure
NASA Astrophysics Data System (ADS)
Herrera-González, I. F.; Pérez-Aguilar, H. I.; Mendoza-Suárez, A.; Tututi, E. S.
2012-09-01
We study heat conduction in a billiard channel formed by two sinusoidal walls and the diffusion of particles in the corresponding channel of infinite length; the latter system has an infinite horizon, i.e., a particle can travel an arbitrary distance without colliding with the rippled walls. For small ripple amplitudes, the dynamics of the heat carriers is regular and analytical results for the temperature profile and heat flux are obtained using an effective potential. The study also proposes a formula for the temperature profile that is valid for any ripple amplitude. When the dynamics is regular, ballistic conductance and ballistic diffusion are present. The Poincaré plots of the associated dynamical system (the infinitely long channel) exhibit the generic transition to chaos as ripple amplitude is increased. When no Kolmogorov-Arnold-Moser (KAM) curves are present to forbid the connection of all chaotic regions, the mean square displacement grows asymptotically with time t as tln(t).
Heat Conduction of Walls with a Monotone Temperature Change. Asymptotics and Quasi-Stationarity
NASA Astrophysics Data System (ADS)
Korshunov, O. V.
2014-07-01
Systematizing the partial solutions of the nonstationarity heat conduction problem of a flat wall in comparison with the general asymptotic solution of this problem, we have found the transverse temperature distributions with any monotone change in the ambient conditions and elucidated the heat conduction properties of the wall under these conditions. The asymptotic solution is given by semiconvergent series and definite integrals and has been investigated for power time dependences with an exponent of 0-2, which has enabled us to justify the concept of quasi-stationarity of the thermal parameters of the wall and obtain asymptotic errors and corrections defining the deviations of these parameters from their stationary values. The features of the average heat flows most resistant to thermal disturbances as to both time and amplitude have been considered.
Solution of non-linear inverse heat conduction problems using the method of lines
NASA Astrophysics Data System (ADS)
Taler, J.; Duda, P.
Two space marching methods for solving the one-dimensional nonlinear inverse heat conduction problems are presented. The temperature-dependent thermal properties and the boundary condition on the accessible part of the boundary of the body are known. Additional temperature measurements in time are taken with a sensor located in an arbitrary position within the solid, and the objective is to determine the surface temperature and heat flux on the remaining part of the unspecified boundary. The methods have the advantage that time derivatives are not replaced by finite differences and the good accuracy of the method results from an appropriate approximation of the first time derivative using smoothing polynomials. The extension of the first method presented in this study to higher dimensions inverse heat conduction problems is straightforward.
NASA Astrophysics Data System (ADS)
Kshirsagar, Jagdeep M.; Shrivastava, Ramakant
2015-03-01
Nanofluids, the fluid suspensions of nonmaterials, have shown many interesting properties and the unique features offer unprecedented potential for many applications. Research on nanofluids has progressed rapidly since its enhanced thermal conductivity was first noted, about a decade ago, though much debate and inconsistency have been reported. Insufficient understanding of the formulation, mechanism of nanofluids further limits their applications [1-34]. Inconsistent data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers [35-43] have noted an enhancement in the critical heat flux during nanofluid boiling. Some researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux augmentation. In the review, the future developments of these technologies are discussed. In order to be able to put the nanofluid heat transfer technologies into practice, fundamental of these studies are greatly needed to comprehend the physical mechanisms.
A Review on the Finite Element Methods for Heat Conduction in Functionally Graded Materials
NASA Astrophysics Data System (ADS)
Sharma, R.; Jadon, V. K.; Singh, B.
2015-01-01
The review presented in this paper focuses mainly on the application of finite element methods for investigating the effect of heat transfer, variation of temperature and other parameters in the functionally graded materials. Different methods have been investigated for thermal conduction in functionally graded materials. The use of FEM for steady state heat transfer has been addressed in this work. The authors have also discussed the utilization of FEM based shear deformation theories and FEM in combination with other methods for the problems involving complexity of the shape and geometry of functionally graded materials. Finite element methods proved to be effective for the solution of heat transfer problem in functionally graded materials. These methods can be used for steady state heat transfer and as well as for transient state.
On the role of surface shape in a micro-scale heat conduction problem
NASA Astrophysics Data System (ADS)
Dinler, A.; Graur, I. A.; Barber, R. W.; Emerson, D. R.; Perrier, P.
2012-05-01
The present study investigates the importance of the surface shape in a micro-scale heat conduction problem. A heated infinitely-thin cylindrical shell is positioned in the middle of two concentric cylinders, and the heat transfer through a rarefied gas between the shell and the confining inner (or outer) cylinder is investigated. The study initially considers the solution of the first- and second-order temperature-jump models (i.e. the conventional heat equation with temperature-jump boundary conditions). The study then examines the numerical solution of the nonlinear Shakhov model kinetic equation subject to the Maxwell boundary condition using the discrete velocity method (DVM). The variable-hard-sphere molecular interaction model is taken into account in the temperature-jump models allowing the presence of significant temperature differences between surfaces to be considered. Anomalous temperature profiles near the convex (or concave) side of the shell are attributed to the effects of surface shape.
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Anderson, Betty Lise
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Armstrong, Jeff; Bresme, Fernando
2014-06-28
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
Naya, Daniel E.; Spangenberg, Lucía; Naya, Hugo; Bozinovic, Francisco
2013-01-01
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
Experimental and Theoretical Study of Heat Conduction for Air up to 5000 K
NASA Technical Reports Server (NTRS)
Peng, Tzy-Cheng; Ahtye, Warren F.
1961-01-01
The theoretical value of the integral of thermal conductivity is compared with the experimental values from shock-tube measurements. The particular case considered is the one-dimensional nonsteady flow of heat through air at constant pressure. This approach has been previously described in NASA TR R-27. experiment was uncertain because of the large scatter in the experimental data. In this paper, an attempt is made to improve the correlation by use of a more refined calculation of the integral of thermal conductivity, and by use of improved experimental techniques and instrumentation. As a result of these changes, a much closer correlation is shown between the experimental and theoretical heat-flux potentials. This indicates that the predicted values of the coefficient of thermal conductivity for high-temperature air may be suitably accurate for many engineering needs, up to the limits of the test (4600 K).
Fourier heat conduction as a phenomenon described within the scope of the second law
NASA Astrophysics Data System (ADS)
Jesudason, Christopher G.
2014-12-01
The historical development of the Carnot cycle necessitated the construction of isothermal and adiabatic pathways within the cycle that were also mechanically "reversible" which lead eventually to the Kelvin-Clausius development of the entropy function S where for any reversible closed path C, ?C dS = 0 based on an infinite number of concatenated Carnot engines that approximated the said path and where for each engine ?Q1/T1+?Q2/T2 = 0 where the Q's and T's are the heat absorption increments and temperature respectively with the subscripts indicating the isothermal paths (1;2) where for the Carnot engine, the heat absorption is for the diathermal (isothermal) paths of the cycle only. Since 'heat' has been defined as that form of energy that is transferred as a result of a temperature difference and a corollary of the Clausius statement of the Second law is that it is impossible for heat to be transferred from a cold to a hot reservoir with no other effect on the environment, these statements suggested that the local mode of transfer of 'heat' in the isothermal segments of the pathway does imply a Fourier heat conduction mechanism (to conform to the definition of 'heat') albeit of a "reversible" kind, but on the other hand, the Fourier mechanism is apparently irreversible, leading to an increase in entropy of the combined reservoirs at either end of the material involved in the conveyance of the heat energy. These and several other considerations lead Benofy and Quay (BQ) to postulate the Fourier heat conduction phenomenon to be an ancillary principle in thermodynamics, with this principle being strictly local in nature, where the global Second law statements could not be applied to this local process. Here we present equations that model heat conduction as a thermodynamically reversible but mechanically irreversible process where due to the belief in mechanical time reversible symmetry, thermodynamical reversibility has been unfortunately linked to mechanical reversibility, that has discouraged such an association. The modeling is based on an application of a "recoverable transition", defined and developed earlier on ideas derived from thermal desorption of particles from a surface where the Fourier heat conduction process is approximated as a series of such desorption processes. We recall that the original Carnot engine required both adiabatic and isothermal steps to complete the zero entropy cycle, and this construct lead to the consequent deduction that any Second law statement that refers to heat-work conversion processes are only globally relevant. Here, on the other hand, we examine Fourier heat conduction from MD simulation and model this process as a zero-entropy forward scattering process relative to each of the atoms in the lattice chain being treated as a system where the Carnot cycle can be applied individually. The equations developed predicts the "work" done to be equal to the energy transfer rate. The MD simulations conducted shows excellent agreement with the theory. Such views and results as these, if developed to a successful conclusion could imply that the Carnot cycle be viewed as describing a local process of energy-work conversion and that irreversible local processes might be brought within the scope of this cycle, implying a unified treatment of thermodynamically (i) irreversible, (ii) reversible, (iii) isothermal and (iv) adiabatic processes.
NASA Astrophysics Data System (ADS)
Gr?dziel, s?awomir
2011-12-01
The following paper presents the method for solving one-dimensional inverse boundary heat conduction problems. The method is used to estimate the unknown thermal boundary condition on inner surface of a thick-walled Y-branch. Solution is based on measured temperature transients at two points inside the element's wall thickness. Y-branch is installed in a fresh steam pipeline in a power plant in Poland. Determination of an unknown boundary condition allows for the calculation of transient temperature distribution in the whole element. Next, stresses caused by non-uniform transient temperature distribution and by steam pressure inside a Y-branch are calculated using the finite element method. The proposed algorithm can be used for thermal-strength state monitoring in similar elements, when it is not possible to determine a 3-D thermal boundary condition. The calculated temperature and stress transients can be used for the calculation of element durability. More accurate temperature and stress monitoring will contribute to a substantial decrease of maximal stresses that occur during transient start-up and shut-down processes.
Evaluation of heat transfer in acupuncture needles: convection and conduction approaches.
Tzou, Chieh-Han John; Yang, Tzyy-Yih; Chung, Ya-Chien
2015-04-01
Originating in ancient China, acupuncture using needles has been developed for thousands of years and has received attention for its reported medical remedies, such as pain relief and chronic disease treatment. Heat transfer through the needles, which might have effects on the biomechanism of acupuncture, providing a stimulus and regulating homeostasis, has never been studied. This article analyzes the significance of heat transfer through needles via convection and conduction, approached by means of computational analysis. The needle is a cylindrical body, and an axis symmetrical steady-state heat-transfer model that viscosity and static pressure was not applied. This article evaluates heat transfer via acupuncture needles by using five metal materials: silver, copper, brass, iron, and stainless steel. A silver needle of the type extensively applied in acupuncture can dissipate more than seven times as much heat as a stainless steel needle of the same type. Heat transfer through such a needle is significant, compared to natural body-energy consumption over a range of ambient temperatures. The mechanism by which heat flows in or out of the body through the needles may be crucial in the remedial efficacy of acupuncture. PMID:25952124
Feng, Yaya; Liu, Xiangyu; Duan, Linqiang; Yang, Qi; Wei, Qing; Xie, Gang; Chen, Sanping; Yang, Xuwu; Gao, Shengli
2015-02-01
A reticular 3D heterometallic metal-organic framework (MOF), [Cu4Na(Mtta)5(CH3CN)]n () (N% = 40.08%), has been synthesized, using a 5-methyl tetrazole (Mtta) ligand formed from acetonitrile and azide, through in situ synthesis and structurally characterized by X-ray single crystal diffraction. The fluorescence spectra demonstrate that undergoes an interesting structural transformation in aqueous solution, yielding the compound [Cu4Na(Mtta)5H2O]n () as confirmed by (1)H NMR, IR and PXRD. Thermoanalysis showed that possesses excellent thermostability up to 335 °C. The calculated detonation properties and the sensitivity test illustrate that compound could be used as a potential explosive. In addition, the non-isothermal kinetics for were studied using the Kissinger and Ozawa-Doyle methods. The enthalpy of formation was obtained from the determination of the constant-volume combustion energy. PMID:25534462
Thermal Characterization for a Modular 3-D Multichip Module
NASA Technical Reports Server (NTRS)
Fan, Mark S.; Plante, Jeannette; Shaw, Harry
2000-01-01
NASA Goddard Space Flight Center has designed a high-density modular 3-D multichip module (MCM) for future spaceflight use. This MCM features a complete modular structure, i.e., each stack can be removed from the package without damaging the structure. The interconnection to the PCB is through the Column Grid Array (CGA) technology. Because of its high-density nature, large power dissipation from multiple layers of circuitry is anticipated and CVD diamond films are used in the assembly for heat conduction enhancement. Since each stacked layer dissipates certain amount of heat, designing effective heat conduction paths through each stack and balancing the heat dissipation within each stack for optimal thermal performance become a challenging task. To effectively remove the dissipated heat from the package, extensive thermal analysis has been performed with finite element methods. Through these analyses, we are able to improve the thermal design and increase the total wattage of the package for maximum electrical performance. This paper provides details on the design-oriented thermal analysis and performance enhancement. It also addresses issues relating to contact thermal resistance between the diamond film and the metallic heat conduction paths.
Heat Conduction Analysis in a Tissue Phantom Calculated by FDTD and HCE Method
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
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.
NASA Astrophysics Data System (ADS)
Wang, Zhi-Hua; Bou-Zeid, Elie; Smith, James A.
2011-02-01
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.
Khine, Soe Minn; Houra, Tomoya; Tagawa, Masato
2013-04-01
In temperature measurement of non-isothermal fluid flows by a contact-type temperature sensor, heat conduction along the sensor body can cause significant measurement error which is called "heat-conduction error." The conventional formula for estimating the heat-conduction error was derived under the condition that the fluid temperature to be measured is uniform. Thus, if we apply the conventional formula to a thermal field with temperature gradient, the heat-conduction error will be underestimated. In the present study, we have newly introduced a universal physical model of a temperature-measurement system to estimate accurately the heat-conduction error even if a temperature gradient exists in non-isothermal fluid flows. Accordingly, we have been able to successfully derive a widely applicable estimation and/or evaluation formula of the heat-conduction error. Then, we have verified experimentally the effectiveness of the proposed formula using the two non-isothermal fields-a wake flow formed behind a heated cylinder and a candle flame-whose fluid-dynamical characteristics should be quite different. As a result, it is confirmed that the proposed formula can represent accurately the experimental behaviors of the heat-conduction error which cannot be explained appropriately by the existing formula. In addition, we have analyzed theoretically the effects of the heat-conduction error on the fluctuating temperature measurement of a non-isothermal unsteady fluid flow to derive the frequency response of the temperature sensor to be used. The analysis result shows that the heat-conduction error in temperature-fluctuation measurement appears only in a low-frequency range. Therefore, if the power-spectrum distribution of temperature fluctuations to be measured is sufficiently away from the low-frequency range, the heat-conduction error has virtually no effect on the temperature-fluctuation measurements even by the temperature sensor accompanying the heat-conduction error in the mean-temperature measurements. PMID:23635222
Hartenstine, J.R.
1991-08-01
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 eclipses, 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 I 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.
Thermal conductance of and heat generation in tire-pavement interface and effect on aircraft braking
NASA Technical Reports Server (NTRS)
Miller, C. D.
1976-01-01
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.
Ritchie, R.H.; Sakakura, A.Y.
1956-01-01
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.
NASA Astrophysics Data System (ADS)
Oldham, Mark
2015-01-01
Radiochromic materials exhibit a colour change when exposed to ionising radiation. Radiochromic film has been used for clinical dosimetry for many years and increasingly so recently, as films of higher sensitivities have become available. The two principle advantages of radiochromic dosimetry include greater tissue equivalence (radiologically) and the lack of requirement for development of the colour change. In a radiochromic material, the colour change arises direct from ionising interactions affecting dye molecules, without requiring any latent chemical, optical or thermal development, with important implications for increased accuracy and convenience. It is only relatively recently however, that 3D radiochromic dosimetry has become possible. In this article we review recent developments and the current state-of-the-art of 3D radiochromic dosimetry, and the potential for a more comprehensive solution for the verification of complex radiation therapy treatments, and 3D dose measurement in general.
NASA Astrophysics Data System (ADS)
de Caritat, Patrice
1993-05-01
A simple, accurate, numerical approximation of the one-dimensional equation of heat transport by conduction and advection is presented. The method is based on the iterative solution of an implicit, finite difference, Crank-Nicolson algorithm, featuring alternating differencing direction as a function of the thermal Peclet number, and is implemented in a documented FORTRAN code. The program allows users to evaluate how porewater flow may affect the thermal profile of permeable rock formations, under steady-state or unsteady-state boundary conditions, and with linear or nonlinear initial conditions. Several possible applications illustrate the potential usefulness of the program in first order, evaluative investigations.
Self-gravitational instability of rotating anisotropic heat-conducting plasma
Prajapati, R. P.; Parihar, A. K.; Chhajlani, R. K. [School of Studies in Physics, Vikram University, Ujjain-456010 (India)
2008-01-15
The self-gravitational instability of rotating anisotropic heat-conducting plasma with modified Chew-Goldberger-Low equations is investigated. The general dispersion relation is obtained using normal mode analysis by constructing the linearized set of equations. This dispersion relation is further reduced for propagation parallel and perpendicular to the direction of magnetic field. These conditions are discussed for axis of rotation along and perpendicular to the magnetic field. It is found that the heat flux vector does not influence the transverse mode of propagation for both cases of rotation and Jeans condition remains unchanged. In case of propagation parallel to the magnetic field with axis of rotation perpendicular to the magnetic field, we get the dispersion relation, which shows the joint effect of rotation and heat flux vector. The two separate modes of propagation are obtained in terms of rotation and heat flux vector for rotation parallel to the magnetic field. It is demonstrated that the Alfven wave and the associated firehose instability are not affected by the presence of heat flux corrections and rotation also. The numerical analysis is performed to show the effect of rotation, pressure anisotropy, and heat flux parameter on the condition of instability in the spiral arms of galaxy. The Jeans condition of gravitational instability is obtained for both the cases of propagation.
NASA Astrophysics Data System (ADS)
Xuan, Yimin; Huang, Yong; Li, Qiang
2009-09-01
We develop a novel type of functional fluid-magnetic microencapsulated phase change material (MMPCM) suspension which incorporates the advantages of microencapsulated phase change material (MPCM) suspension and magnetic fluid (MF) for controllable and efficient energy transport processes. The specific heat capacity and thermal conductivity of this type of functional fluid are experimentally investigated, respectively. The effects of the mass fraction of components in the MMPCM on the thermal properties of the fluid are discussed. In addition, the effect of an eternal magnetic field on the thermal conductivity of the fluid is discussed.
Two-Gradient Convection in a Vertical Slot with Maxwell-Cattaneo Heat Conduction
Papanicolaou, N. C. [Department of Computer Science, University of Nicosia, P.O. Box 24005, 1700 Nicosia (Cyprus); Christov, C. I. [Department of Mathematics, University of Louisiana at Lafayette, LA 70504-1010 (United States); Jordan, P. M. [Entropy Reversal Consultants (L.L.C), P. O. Box 691, Abita Springs, LA 70420 (United States); Code 7181, Naval Research Lab., Stennis Space Ctr., MS 39529 (United States)
2009-10-29
We study the effect of the Maxwell-Cattaneo law of heat conduction (MCHC) on the 1D flow in a vertical slot subject to both vertical and horizontal temperature gradients. The gravitational acceleration is allowed to oscillate, which provides an opportunity to investigate the quantitative contribution of thermal inertia as epitomized by MCHC. The addition of the time derivative in MCHC increases the order of the system. We use a spectral expansion with Rayleigh's beam functions as the basis set, which is especially suited to fourth order boundary value problems (BVP). We show that the time derivative (relaxation of the thermal flux) has a dissipative nature and leads to the appearance of purely real negative eigenvalues. Yet it also increases the absolute value of the imaginary part and decreases the absolute value of the real part of the complex eigenvalues. Thus, the system has a somewhat more oscillatory behavior than the one based on Fourier's heat conduction law (FHC)
The role of heat conduction to the formation of [WC]-type planetary nebulae
NASA Astrophysics Data System (ADS)
Sandin, Christer; Steffen, Matthias; Jacob, Ralf; Schönberner, Detlef; Rühling, Ute; Hamann, Wolf-Rainer; Todt, Helge
2012-08-01
X-ray observations of young Planetary Nebulæ (PNe) have revealed diffuse emission in extended regions around both H-rich and H-deficient central stars. In order to also reproduce physical properties of H-deficient objects, we have, at first, extended our time-dependent radiation-hydrodynamic models with heat conduction for such conditions. Here we present some of the important physical concepts, which determine how and when a hot wind-blown bubble forms. In this study we have had to consider the, largely unknown, evolution of the CSPN, the slow (AGB) wind, the fast hot-CSPN wind, and the chemical composition. The main conclusion of our work is that heat conduction is needed to explain X-ray properties of wind-blown bubbles also in H-deficient objects.
NASA Technical Reports Server (NTRS)
Winget, J. M.; Hughes, T. J. R.
1985-01-01
The particular problems investigated in the present study arise from nonlinear transient heat conduction. One of two types of nonlinearities considered is related to a material temperature dependence which is frequently needed to accurately model behavior over the range of temperature of engineering interest. The second nonlinearity is introduced by radiation boundary conditions. The finite element equations arising from the solution of nonlinear transient heat conduction problems are formulated. The finite element matrix equations are temporally discretized, and a nonlinear iterative solution algorithm is proposed. Algorithms for solving the linear problem are discussed, taking into account the form of the matrix equations, Gaussian elimination, cost, and iterative techniques. Attention is also given to approximate factorization, implementational aspects, and numerical results.
CTS-type variable conductance heat pipes for SEP FM/PPU
NASA Technical Reports Server (NTRS)
Antoniuk, D.; Luedke, E. E.
1978-01-01
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.
Hamiltonian dynamics of thermostated systems: two-temperature heat-conducting phi4 chains.
Hoover, Wm G; Hoover, Carol G
2007-04-28
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
Heat transfer enhancement study of a LHTS unit containing dispersed high conductivity particles
Seeniraj, R.V.; Velraj, R.; Narasimhan, N.L.
1999-07-01
A theoretical analysis is presented for the performance study of a Latent Heat Thermal Storage (LHTS) system which contains a phase change material (PCM) dispersed with high conductivity solid particles. The effect of fraction of dispersed particles in the PCM on energy storage time and heat flux is presented for laminar and turbulent flows, and also analytical expressions for various quantities of interest to study the energy storage capabilities. The combined effect of thermal and flow properties of both the heat transfer fluid (HTF) and the PCM-mixture is also included in the study. It is observed that there exists an optimum fraction of particles to be dispersed in the PCM for maximum energy storage/extraction.
Numerical solution of the non-isothermal moving boundary problem in heat conduction
R. Áik; R. Erný
1991-01-01
A computational method has been developed for treating the heat-conduction equation in one dimension with moving boundary. An important feature of the model is the capability of allowing non-equilibrium melting and solidification to occur at temperatures other than the thermodynamical phase-change temperature. As a result, interfacial overheating and undercooling is introduced and the position of the free boundary is not
Min-Geun Kim; Seung-Hyun Ha; Seonho Cho
2009-01-01
A level set-based topological shape-optimization method is developed to relieve the well-known convergence difficulty in nonlinear heat-conduction problems. While minimizing the objective function of instantaneous thermal compliance and satisfying the constraint of allowable volume, the solution of the Hamilton–Jacobi equation leads the initial implicit boundary to an optimal one according to the normal velocity determined from the descent direction of
Yong Liu; R. D. Reitz
1998-01-01
A two-dimensional (axisymmetric) transient heat conduction in components computer program (HCC) was successfully developed for predicting engine combustion chamber wall temperatures. The alternating direction explicit (ADE) Saul'yev method, an explicit, unconditionally stable finite difference method, was used in the code. Special treatments for the head gasket and the piston-liner air gap, the piston movement, and a grid transformation for describing
COYOTE 2: A Finite Element Computer Program for noonlinear heat conduction problems
D. K. Gartling; R. E. Hogan
1994-01-01
User instructions are given for the finite element computer program, COYOTE 2. COYOTE 2 is designed for the multi-dimensional analysis of nonlinear heat conduction problems including the effects of enclosure radiation and chemical reaction. The theoretical background and numerical methods used in the program are documented in SAND94-1173. Examples of the use of the code are presented in SAND94-1180.
COYOTE 2: A Finite Element Computer Program for noonlinear heat conduction problems
NASA Astrophysics Data System (ADS)
Gartling, D. K.; Hogan, R. E.
1994-10-01
User instructions are given for the finite element computer program, COYOTE 2. COYOTE 2 is designed for the multi-dimensional analysis of nonlinear heat conduction problems including the effects of enclosure radiation and chemical reaction. The theoretical background and numerical methods used in the program are documented in SAND94-1173. Examples of the use of the code are presented in SAND94-1180.
R. V. N. Melnik; A. J. Roberts; K. A. Thomas
2002-01-01
The dynamics of phase transitions and hysteresis phenomena in materials with memory are described by a strongly nonlinear\\u000a coupled system of partial differential equations which, in its generality, can be solved only numerically. Following principles\\u000a of extended thermodynamics, in this paper we construct a new model for the description of this dynamics based on the Cattaneo–Vernotte\\u000a law for heat conduction.
M. H. Hojjati; H. Tari
2010-01-01
Purpose – The purpose of this paper is to show how a system of differential equations of one-dimensional transient cooling heat conduction of different multi-layer slabs has been solved numerically. A simple deterministic filtering matrix has been developed to remove errors involved in the experimental temperature measurements. Design\\/methodology\\/approach – The system of differential equations is solved through Crank-Nicolson method using
TOODEE: A two-dimensional, time-dependent heat conduction program
Brent J. Sackett; Richard G. Ambrosek; John A. McClure
1990-01-01
TOODEE is a two-dimensional, time-dependent heat conduction computer program written in FORTRAN. This program is suitable for investigating general transient and\\/or steady-state problems. Typical of (but not limited to) the type of problems for which the program has been used are the calculation of temperature distributions in reactor fuel elements during power excursions. The mesh for the program is formed
In-Situ Thermal Conductivity Testing Using a Portable Heat Flow Meter
Harr, K. S.; Hutto, F. B., Jr.
1979-01-01
using the Heat Flow Meter technique. Tests have been conducted in power plants, chemical plants and refineries from all parts of the country. Emphasis has been on high temperature insulations in four categories; calcium silicate, perlite, mineral wool... fibrous materials and minerals such as perlite, which depend on organic binders to provide their physical strength, were found to degrade at high temperatues over extended periods of time. The amount of degradation depends upon the specific material...
Transient conductive, radiative heat transfer coupled with moisture transport in attic insulations
R. Gorthala; K. T. Harris; J. A. Roux; T. A. McCarty
1994-01-01
A transient, one-dimensional thermal model that incorporates combined conduction, radiation heat transfer, and moisture transport for residential attic insulations has been developed. The governing equations are the energy equation, the radiative transport equation for volumetric radiation within the insulation batt, and the species equations for bound H2O and vapor H2O. A simultaneous solution procedure with a Eulerian control volume-based finite
Uniform-Parameter Spline Method for Solving Non-Fourier Heat Conduction Problems
Chi-Chang Wang; Zong-Yi Lee
2009-01-01
From the theoretical basis of the parameter spline method, this study establishes a simple computing procedure to solve multidimensional non-Fourier heat conduction problems. Compared with the ordinary finite-difference method and the traditional cubic spline method, this method is similar in computing process, but the numerical results increase by two-order accuracy without adding computer load. It also can solve for numeric
Implicitly balanced solution of the two-phase flow equations coupled to nonlinear heat conduction
V. A. Mousseau
2004-01-01
This paper presents the solution of the two-phase flow equations coupled to nonlinear heat conduction using the Jacobian-free Newton–Krylov (JFNK) method which employs a physics-based preconditioner. Computer simulations will demonstrate that the implicitly balanced solution obtained from the JFNK method is more accurate than traditional approaches that employ operator splitting and linearizing. Results will also indicate that by employing a
Shock tube determination of the heat conductivity of non-ionized and partially ionized argon
A. Hirschberg
1981-01-01
A procedure to determine the heat conductivity of a monatomic gas, from measurements of the structure of the unsteady thermal boundary layer at the end-wall of a shock tube, is proposed. In the non-ionized case the structure of the boundary layer determined by means of laser schlieren measurements appears to be self-similar. Improved analysis of the schlieren data and accurate
On heat conduction in multicomponent, non-Maxwellian spherically symmetric solar wind plasmas
NASA Technical Reports Server (NTRS)
Cuperman, S.; Dryer, M.
1985-01-01
A generalized expression for the steady-state heat flux in multicomponent, moderately non-Maxwellian spherically symmetric plasmas is presented and discussed. The work was motivated by the inability of the simple, Fourier-type formula for the thermal conductivity to explain the observed correlations in the solar wind. The results hold for situations not far from local thermodynamic equilibrium. The generalized expression includes not only correlations that have been observed but also correlations not sought for previously.
The initial value problem for motion of micropolar fluids with heat conduction in Banach spaces
Ryôhei Kakizawa
2010-06-04
We consider the abstract initial value problem for the system of evolution equations which describe motion of micropolar fluids with heat conduction in a bounded domain. This problem has uniquely a mild solution locally in time for general initial data, and globally in time for small initial data. Moreover, a mild solution of this problem can be a strong or classical solution under appropriate assumptions for initial data. We prove the above properties by the theory of analytic semigroups on Banach spaces.
Specific Heat and Electrical Conductivity of Low temperature Phase of Magnetite
Masaaki Matsui; Sakae Todo; Soshin Chikazumi
1977-01-01
It was observed for Fe3O4 that the presence of residual stresses lowers the so-called Verwey temperature, Tv, considerably, broadens the temperature-width of the anomalous specific heat at Tv, produces another additional peak and decreases the discontinuous conductivity change at Tv. The entropy change at the phase transition was determined to be 5.4 J\\/mole\\\\cdotdeg but when the effect of short range
Ohmic heating behaviour and electrical conductivity of two-phase food systems
M. R Zareifard; H. S Ramaswamy; M Trigui; M Marcotte
2003-01-01
Ohmic heating behaviour and electrical conductivity (EC) of two-phase food systems were studied. Food systems were comprised of a liquid phase using 4% w\\/w starch solution with 0.5% w\\/w salt, and a solid phase containing carrot puree and cubes of different sizes (6 and 13 mm) in different concentrations (30 and 50% w\\/w). A set of experiments was carried out
A variable conductance heat pipe/radiator for the lunar surface magnetometer.
NASA Technical Reports Server (NTRS)
Kirkpatrick, J. P.; Marcus, B. D.
1972-01-01
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.
Towards a Thermodynamic 3D MHD Model of Coronal Jets
NASA Astrophysics Data System (ADS)
Lionello, R.; Torok, T.; Linker, J.; Mikic, Z.
2014-12-01
Transient collimated plasma eruptions in the corona, so-called "standard" and "blowout" coronal jets, are among the most intriguing manifestations of solar activity. We have begun to use the PSI "thermodynamic" 3D MHD model to improve our understanding of the origin, dynamics, and plasma properties of coronal jets. Our code models the corona by taking into account thermal conduction, radiative cooling, empirical coronal heating, and the solar wind, and it is capable of using observed magnetograms as boundary condition for the magnetic field. Furthermore, the model is coupled with 3D MHD flux emergence simulations, i.e it can use boundary conditions provided by such simulations to drive a time-dependent coronal evolution. These properties enable us to simulate the energy transfer in coronal jetsin a more realistic manner. We will present preliminary results.
Zhijie Xu
2012-07-01
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.
Conditions for Aeronomic Applicability of the Classical Electron Heat Conduction Formula
NASA Technical Reports Server (NTRS)
Cole, K. D.; Hoegy, W. R.
1998-01-01
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.
The effect of heat conduction on the realization of the primary standard for sound pressure
NASA Astrophysics Data System (ADS)
Jackett, Richard J.
2014-10-01
Pressure reciprocity calibration of microphones provides the basis for primary measurement standards for sound pressure in air. At low frequencies, reciprocity calibration requires that a heat conduction correction be employed to account for energy transfer to and from the bounding surfaces of the close-coupled microphone arrangement. The standard governing reciprocity calibration, IEC 61094-2?:?2009, provides two models for the heat conduction correction: the Low Frequency Solution, and the Broadband Solution. Analysis has revealed significant and unexplained differences in behaviour between the models at very low frequencies, leading to inconsistency in calibration results, which has been quantified. Additionally, both heat conduction solutions given in IEC 61094-2 are simplifications that strictly apply only above their respective lower limiting frequencies. An international comparison on microphone calibration is currently underway that includes measurements below the lower limiting frequencies of the models. In this paper, the origin and nature of the Broadband simplifications have been identified, and estimates of the error given. A flaw in the Broadband theory is identified and its effect quantified. Simplification error for the Low Frequency solution is evaluated, and the full spectrum solution is given. This paper urges caution in the application of the models at low frequency and provides data useful for assessing the contribution to the measurement uncertainty.
Francisco Alhama; Antonio Campo; Joaquín Zueco
2005-01-01
The central objective of this paper is to provide numerical analysts with a new procedure named the network simulation method (NSM) for solving the heat conduction equation in bodies of regular shape. In principle, NSM rests on the electro-thermal analogy (loosely called the resistance–capacitance analogy or the RC analogy) that exists between the unsteady, unidirectional conduction of heat and the
Aziz Azimi; Siamak Kazemzadeh Hannani; Bijan Farhanieh
2005-01-01
In this study a structured multiblock grid is used to solve two-dimensional transient inverse heat conduction problems. The multiblock method is implemented for geometric decomposition of the physical domain into regions with blocked interfaces. The finite-element method is employed for direct solution of the transient heat conduction equation in a Cartesian coordinate system. Inverse algorithms used in this research are
Gordon N. Ellison
1995-01-01
This paper provides an overview of the solution and application of the three-dimensional heat conduction equation for a rectangular-shaped, multilayer structure with discrete surface heat sources. A Fourier series expansion is used to represent both the heat source function and temperature solution. Trigonometric terms are used for the two planar coordinates whereas the Fourier coefficient for the temperature expansion provides
Parallelization of ICF3D, a Diffusion and Hydrodynamics Code
NASA Astrophysics Data System (ADS)
Shestakov, A. I.; Milovich, J. L.
1997-11-01
We describe the parallelization of the unstructured grid ICF3D code. The strategy divides physical space into a collection of disjoint subdomains, one per processing element (PE). The subdomains may be of arbitrary shape but, for efficiency, should have small surface-to-volume ratios. The strategy is ideally suited for distributed memory computers, but also works on shared memory architectures. The hydrodynamic module, which uses a cell-based algorithm using discontinuous finite elements, is parallelized by assigning cells to different PEs. This assignment is done by a separate program and constitutes input data for ICF3D. The diffusion module, a kernel of the heat conduction and radiation diffusion packages, advances continuous fields which are discretized using a nodal finite element method. This module is parallelized by assigning points to individual PEs. The assignment is done within ICF3D. The code is in C++. Special message passing objects (MPO) determine the connectivity of the subdomains and transfer data between them by calling MPI functions. Results are presented on a variety of computers: CRAY T3D and IBM SP2 at Livermore, and Intel's ASCI RED at Sandia, Albuquerque.
NASA Astrophysics Data System (ADS)
Tsuzuki, Yutaka
2015-09-01
This paper is concerned with a system of heat equations with hysteresis and Navier-Stokes equations. In Tsuzuki (J Math Anal Appl 423:877-897, 2015) an existence result is obtained for the problem in a 2-dimensional domain with the Navier-Stokes equation in a weak sense. However the result does not include uniqueness for the problem due to the low regularity for solutions. This paper establishes existence and uniqueness in 2- and 3-dimensional domains with the Navier-Stokes equation in a stronger sense. Moreover this work decides required height of regularity for the initial data by introducing the fractional power of the Stokes operator.
NASA Astrophysics Data System (ADS)
Tsuzuki, Yutaka
2015-07-01
This paper is concerned with a system of heat equations with hysteresis and Navier-Stokes equations. In Tsuzuki (J Math Anal Appl 423:877-897, 2015) an existence result is obtained for the problem in a 2-dimensional domain with the Navier-Stokes equation in a weak sense. However the result does not include uniqueness for the problem due to the low regularity for solutions. This paper establishes existence and uniqueness in 2- and 3-dimensional domains with the Navier-Stokes equation in a stronger sense. Moreover this work decides required height of regularity for the initial data by introducing the fractional power of the Stokes operator.