Quantum-limited heat conduction over macroscopic distances

NASA Astrophysics Data System (ADS)

Partanen, Matti; Tan, Kuan Yen; Govenius, Joonas; Lake, Russell E.; Mäkelä, Miika K.; Tanttu, Tuomo; Möttönen, Mikko

2016-05-01

The emerging quantum technological apparatuses, such as the quantum computer, call for extreme performance in thermal engineering. Cold distant heat sinks are needed for the quantized electric degrees of freedom owing to the increasing packaging density and heat dissipation. Importantly, quantum mechanics sets a fundamental upper limit for the flow of information and heat, which is quantified by the quantum of thermal conductance. However, the short distance between the heat-exchanging bodies in the previous experiments hinders their applicability in quantum technology. Here, we present experimental observations of quantum-limited heat conduction over macroscopic distances extending to a metre. We achieved this improvement of four orders of magnitude in the distance by utilizing microwave photons travelling in superconducting transmission lines. Thus, it seems that quantum-limited heat conduction has no fundamental distance cutoff. This work establishes the integration of normal-metal components into the framework of circuit quantum electrodynamics, which provides a basis for the superconducting quantum computer. Especially, our results facilitate remote cooling of nanoelectronic devices using faraway in situ-tunable heat sinks. Furthermore, quantum-limited heat conduction is important in contemporary thermodynamics. Here, the long distance may lead to ultimately efficient mesoscopic heat engines with promising practical applications.

Azimuthally and radially excited charge transfer plasmon and Fano lineshapes in conductive sublayer-mediated nanoassemblies.

PubMed

Ahmadivand, Arash; Gerislioglu, Burak; Pala, Nezih

2017-11-01

Here, the plasmon responses of both symmetric and antisymmetric oligomers on a conductive substrate under linear, azimuthal, and radial polarization excitations are analyzed numerically. By observing charge transfer plasmons under cylindrical vector beam (CVB) illumination for what we believe is the first time, we show that our studies open new horizons to induce significant charge transfer plasmons and antisymmetric Fano resonance lineshapes in metallic substrate-mediated plasmonic nanoclusters under both azimuthal and radial excitation as CVBs.

Quantum-limited heat conduction over macroscopic distances

PubMed Central

Partanen, Matti; Tan, Kuan Yen; Govenius, Joonas; Lake, Russell E.; Mäkelä, Miika K.; Tanttu, Tuomo; Möttönen, Mikko

2016-01-01

The emerging quantum technological apparatuses1, 2, such as the quantum computer3–6, call for extreme performance in thermal engineering7. Cold distant heat sinks are needed for the quantized electric degrees of freedom due to the increasing packaging density and heat dissipation. Importantly, quantum mechanics sets a fundamental upper limit for the flow of information and heat, which is quantified by the quantum of thermal conductance8–10. However, the short distance between the heat-exchanging bodies in the previous experiments11–14 hinders their applicability in quantum technology. Here, we present experimental observations of quantum-limited heat conduction over macroscopic distances extending to a metre. We achieved this improvement of four orders of magnitude in the distance by utilizing microwave photons travelling in superconducting transmission lines. Thus, it seems that quantum-limited heat conduction has no fundamental distance cutoff. This work establishes the integration of normal-metal components into the framework of circuit quantum electrodynamics15–17 which provides a basis for the superconducting quantum computer18–21. Especially, our results facilitate remote cooling of nanoelectronic devices using far-away in-situ-tunable heat sinks22, 23. Furthermore, quantum-limited heat conduction is important in contemporary thermodynamics24, 25. Here, the long distance may lead to ultimately efficient mesoscopic heat engines with promising practical applications26. PMID:27239219

Nanoscale Heat Conduction in Crystalline Solids

NASA Astrophysics Data System (ADS)

Christenson, Joel; Phillips, Ronald

Heat conduction in crystalline solids occurs through the motion of molecular-scale vibrations, or phonons. In continuum scale problems, there are sufficient phonon-phonon interactions for local equilibrium to be established, and heat conduction is accurately described by Fourier's law. However, at length scales comparable to the phonon mean free path, Fourier's law becomes inaccurate, and more fundamental descriptions of heat transfer are required. We are investigating the viability of the phonon Boltzmann Transport Equation (BTE) to describe heat conduction in nanoscale simulations of the high-explosive material β-HMX. By using a combination of numerical and analytic solutions of the BTE, we demonstrate the existence of physical behavior that is not qualitatively captured by the classical Fourier's law in the nanoscale regime. The results are interpreted in terms of continuum-scale simulations of shock-induced collapse of air-filled pores in β-HMX, which is believed to be a precursory step towards complete detonation of the material.

Evolution of the radial electric field in high-Te ECH heated plasmas on LHD

NASA Astrophysics Data System (ADS)

Pablant, Novimir; Bitter, Manfred; Delgado Aparicio, Luis F.; Dinklage, Andreas; Gates, David; Goto, Motoshi; Ido, Takeshi; Hill, Kenneth H.; Kubo, Shin; Morita, Shigeru; Nagaoka, Kenichi; Oishi, Tetsutarou; Satake, Shinsuke; Takahashi, Hiromi; Yokoyama, Masayuki; LHD Experiment Group Team

2014-10-01

A detailed study is presented on the evolution of the radial electric field (Er) under a range of densities and injected ECH powers on the Large Helical Device (LHD). These plasmas focused on high-electron temperature ECH heated plasmas which exhibit a transition of Er from the ion-root to the electron-root when either the density is reduced or the ECH power is increased. Measurements of poloidal rotation were achieved using the X-Ray Imaging Crystal Spectrometer (XICS) and are compared with neo-classical predictions of the radial electric field using the GSRAKE and FORTEC-3D codes. This study is based on a series of experiments on LHD which used fast modulation of the gyrotrons on LHD to produce a detailed power scan with a constant power deposition profile. This is a novel application of this technique to LHD, and has provided the most detailed study to date on dependence of the radial electric field on the injected power. Detailed scans of the density at constant injected power were also made, allowing a separation of the power and density dependence.

Fourth order discretization of anisotropic heat conduction operator

NASA Astrophysics Data System (ADS)

Krasheninnikova, Natalia; Chacon, Luis

2008-11-01

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 of magnitude. The computational difficulties in treating such heat conduction anisotropies are significant, as perpendicular dynamics numerically is polluted by the parallel one. In this work, we report on progress of the implementation of a fourth order, conservative finite volume discretization scheme for the anisotropic heat conduction operator into the extended MHD code PIXIE3D [1]. We will demonstrate its spatial discretization accuracy and its effectiveness with two physical applications of interest, both of which feature a strong sensitivity to the heat conduction anisotropy: the thermal instability and the neoclassical tearing mode. [1] L. Chacon Phys. Plasmas 15, 056103 (2008)

Transient Heat Conduction Simulation around Microprocessor Die

NASA Astrophysics Data System (ADS)

Nishi, Koji

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

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.

Two-dimensional finite element heat transfer model of softwood. Part I, Effective thermal conductivity

Treesearch

John F. Hunt; Hongmei Gu

2006-01-01

The anisotropy of wood complicates solution of heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models use average thermal properties across either the radial or tangential direction and do not differentiate the effects of cellular alignment, earlywood/latewood differences, or...

Interface Shape Control Using Localized Heating during Bridgman Growth

NASA Technical Reports Server (NTRS)

Volz, M. P.; Mazuruk, K.; Aggarwal, M. D.; Croll, A.

2008-01-01

Numerical calculations were performed to assess the effect of localized radial heating on the melt-crystal interface shape during vertical Bridgman growth. System parameters examined include the ampoule, melt and crystal thermal conductivities, the magnitude and width of localized heating, and the latent heat of crystallization. Concave interface shapes, typical of semiconductor systems, could be flattened or made convex with localized heating. Although localized heating caused shallower thermal gradients ahead of the interface, the magnitude of the localized heating required for convexity was less than that which resulted in a thermal inversion ahead of the interface. A convex interface shape was most readily achieved with ampoules of lower thermal conductivity. Increasing melt convection tended to flatten the interface, but the amount of radial heating required to achieve a convex interface was essentially independent of the convection intensity.

Radiofrequency Electric Field Heating of Conductive Media: Understanding Aqueous and Nanoparticle Heating Mechanisms and a Method for Heating Optimization

NASA Astrophysics Data System (ADS)

Lara, Nadia Chantal

Use of radiofrequency (RF) electric fields coupled with nanoparticles to enhance non-invasive hyperthermia in cancer cells and tumors sparked debate over the RF heating mechanisms of nanoparticles and the role of salts in heating. Under RF field exposure at 13.56 MHz, aqueous systems including electrolyte solutions, buffers, and blood, were shown to heat according to bulk material properties, regardless of composition. This universal aqueous heating behavior extended to suspensions of nanoparticles such as gold nanoparticles, full-length and ultra-short single-walled carbon nanotubes, and water-soluble fullerene derivatives. These suspensions displayed the same RF heating properties as saline solutions of the same conductivity, indicating that these nanoparticles themselves do not contribute to RF heating by any unique mechanism; rather, they modulate bulk conductivity, which in turn affects bulk RF heating. At 13.56 MHz, peak heating for an aqueous system occurs at a conductivity of 0.06 S/m, beyond which increases in conductivity result in reduced heating rates. Biologically relevant materials, such as blood, intra- and extracellular fluids, and most human tissues, exceed this peak heating conductivity, precluding the use of conductive materials for RF heating rate enhancement. Instead, kosmotropic or water-structuring materials, including sugars, glycols, zwitterionic molecules, and a water-soluble fullerene derivative, when added to blood or phosphate buffered saline reduced the bulk conductivity of these materials and enhanced their heating rates accordingly. A dielectric heating rate model taking into account the geometry of the sample under RF exposure was used to explain the experimental RF heating behavior of aqueous solutions and semi-aqueous materials, which generated distinct RF heating curves due to differences in bulk dielectric and physical properties.

Measurement of heat conduction through stacked screens

NASA Technical Reports Server (NTRS)

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

1998-01-01

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

Measurement of heat conduction through stacked screens.

PubMed

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

1998-01-01

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

Radial turbine cooling

NASA Technical Reports Server (NTRS)

Roelke, Richard J.

1992-01-01

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

Effect of the radial buoyancy on a circular Couette flow

NASA Astrophysics Data System (ADS)

Meyer, Antoine; Yoshikawa, Harunori N.; Mutabazi, Innocent

2015-11-01

The effect of a radial temperature gradient on the stability of a circular Couette flow is investigated when the gravitational acceleration is neglected. The induced radial stratification of the fluid density coupled with the centrifugal acceleration generates radial buoyancy which is centrifugal for inward heating and centripetal for outward heating. This radial buoyancy modifies the Rayleigh discriminant and induces the asymmetry between inward heating and outward heating in flow behavior. The critical modes are axisymmetric and stationary for inward heating while for outward heating, they can be oscillatory axisymmetric or nonaxisymmetric depending on fluid diffusion properties, i.e., on the Prandtl number Pr. The dependence of the critical modes on Pr is explored for different values of the radius ratio of the annulus. The power input of the radial buoyancy is compared with other power terms. The critical frequency of the oscillatory axisymmetric modes is linked to the Brunt-Väisälä frequency due to the density stratification in the radial gravity field induced by the rotation. These modes are associated with inertial waves. The dispersion relation of the oscillatory axisymmetric modes is derived in the vicinity of the critical conditions. A weakly nonlinear amplitude equation with a forcing term is proposed to explain the domination of these axisymmetric oscillatory modes over the stationary centrifugal mode.

Development of a thermal and structural analysis procedure for cooled radial turbines

NASA Technical Reports Server (NTRS)

Kumar, Ganesh N.; Deanna, Russell G.

1988-01-01

A procedure for computing the rotor temperature and stress distributions in a cooled radial turbine is considered. Existing codes for modeling the external mainstream flow and the internal cooling flow are used to compute boundary conditions for the heat transfer and stress analyses. An inviscid, quasi three-dimensional code computes the external free stream velocity. The external velocity is then used in a boundary layer analysis to compute the external heat transfer coefficients. Coolant temperatures are computed by a viscous one-dimensional internal flow code for the momentum and energy equation. These boundary conditions are input to a three-dimensional heat conduction code for calculation of rotor temperatures. The rotor stress distribution may be determined for the given thermal, pressure and centrifugal loading. The procedure is applied to a cooled radial turbine which will be tested at the NASA Lewis Research Center. Representative results from this case are included.

Development of a thermal and structural analysis procedure for cooled radial turbines

NASA Technical Reports Server (NTRS)

Kumar, Ganesh N.; Deanna, Russell G.

1988-01-01

A procedure for computing the rotor temperature and stress distributions in a cooled radial turbine are considered. Existing codes for modeling the external mainstream flow and the internal cooling flow are used to compute boundary conditions for the heat transfer and stress analysis. The inviscid, quasi three dimensional code computes the external free stream velocity. The external velocity is then used in a boundary layer analysis to compute the external heat transfer coefficients. Coolant temperatures are computed by a viscous three dimensional internal flow cade for the momentum and energy equation. These boundary conditions are input to a three dimensional heat conduction code for the calculation of rotor temperatures. The rotor stress distribution may be determined for the given thermal, pressure and centrifugal loading. The procedure is applied to a cooled radial turbine which will be tested at the NASA Lewis Research Center. Representative results are given.

One-dimensional nonlinear instability study of a slightly viscoelastic, perfectly conducting liquid jet under a radial electric field

NASA Astrophysics Data System (ADS)

Li, Fang; Yin, Xie-Yuan; Yin, Xie-Zhen

2016-05-01

A one-dimensional electrified viscoelastic model is built to study the nonlinear behavior of a slightly viscoelastic, perfectly conducting liquid jet under a radial electric field. The equations are solved numerically using an implicit finite difference scheme together with a boundary element method. The electrified viscoelastic jet is found to evolve into a beads-on-string structure in the presence of the radial electric field. Although the radial electric field greatly enhances the linear instability of the jet, its influence on the decay of the filament thickness is limited during the nonlinear evolution of the jet. On the other hand, the radial electric field induces axial non-uniformity of the first normal stress difference within the filament. The first normal stress difference in the center region of the filament may be greatly decreased by the radial electric field. The regions with/without satellite droplets are illuminated on the χ (the electrical Bond number)-k (the dimensionless wave number) plane. Satellite droplets may be formed for larger wave numbers at larger radial electric fields.

Specific heat and thermal conductivity of nanomaterials

NASA Astrophysics Data System (ADS)

Bhatt, Sandhya; Kumar, Raghuvesh; Kumar, Munish

2017-01-01

A model is proposed to study the size and shape effects on specific heat and thermal conductivity of nanomaterials. The formulation developed for specific heat is based on the basic concept of cohesive energy and melting temperature. The specific heat of Ag and Au nanoparticles is reported and the effect of size and shape has been studied. We observed that specific heat increases with the reduction of particle size having maximum shape effect for spherical nanoparticle. To provide a more critical test, we extended our model to study the thermal conductivity and used it for the study of Si, diamond, Cu, Ni, Ar, ZrO2, BaTiO3 and SrTiO3 nanomaterials. A significant reduction is found in the thermal conductivity for nanomaterials by decreasing the size. The model predictions are consistent with the available experimental and simulation results. This demonstrates the suitability of the model proposed in this paper.

A Plasma Model of Missile Exhaust Plumes. (Axial and Radial Conductivity Distributions for the Redeye Missile).

DTIC Science & Technology

1977-04-01

Conductivity ...... . .i 6 Relief Map of Conductivity ......... i9 7a conductivity versus Axial Position with Radial Position a a Parater...concentrations ii. pressure iii. temperature iv. velocity v. snie, number and velocity distribuions of the liquid particlas (if any are to be considered) I vi...Number = 1 vi. J• velocity = 8644 fps; Edge velocity = 10 fps vii. Jet temperature = 21160 K; Edge temperature = 278*K Also, at the exit piane, the

A Global Assessment of Oceanic Heat Loss: Conductive Cooling and Hydrothermal Redistribution of Heat

NASA Astrophysics Data System (ADS)

Hasterok, D. P.; Chapman, D. S.; Davis, E. E.

2011-12-01

A new dataset of ~15000 oceanic heat flow measurements is analyzed to determine the conductive heat loss through the seafloor. Many heat flow values in seafloor younger than 60 Ma are lower than predicted by models of conductively cooled lithosphere. This heat flow deficit is caused by ventilated hydrothermal circulation discharging at crustal outcrops or through thin sedimentary cover. Globally filtering of heat flow data to retain sites with sediment cover >400 m thick and located >60 km from the nearest seamount minimizes the effect of hydrothermal ventilation. Filtered heat flow exhibit a much higher correlation coefficient with seafloor age (up to 0.95 for filtered data in contrast to 0.5 for unfiltered data) and lower variability (reduction by 30%) within an age bin. A small heat flow deficit still persists at ages <25 Ma, possibly as a result of global filtering limitations and incomplete thermal rebound following sediment burial. Detailed heat flow surveys co-located with seismic data can identify environments favoring conductive heat flow; heat flow collected in these environments is higher than that determined by the global dataset, and is more consistent with conductive cooling of the lithosphere. The new filtered data analysis and a growing number of site specific surveys both support estimates of global heat loss in the range 40-47 TW. The estimated hydrothermal deficit is consistent with estimates from geochemical studies ~7 TW, but is a few TW lower than previous estimates derived from heat flow determinations.

Ohmic Heating of an Electrically Conductive Food Package.

PubMed

Kanogchaipramot, Kanyawee; Tongkhao, Kullanart; Sajjaanantakul, Tanaboon; Kamonpatana, Pitiya

2016-12-01

Ohmic heating through an electrically conductive food package is a new approach to heat the food and its package as a whole after packing to avoid post-process contamination and to serve consumer needs for convenience. This process has been successfully completed using polymer film integrated with an electrically conductive film to form a conductive package. Orange juice packed in the conductive package surrounded with a conductive medium was pasteurized in an ohmic heater. A mathematical model was developed to simulate the temperature distribution within the package and its surroundings. A 3-D thermal-electric model showed heating uniformity inside the food package while the hot zone appeared in the orange juice adjacent to the conductive film. The accuracy of the model was determined by comparing the experimental results with the simulated temperature and current drawn; the model showed good agreement between the actual and simulated results. An inoculated pack study using Escherichia coli O157:H7 indicated negative growth of viable microorganisms at the target and over target lethal process temperatures, whereas the microorganism was present in the under target temperature treatment. Consequently, our developed ohmic heating system with conductive packaging offers potential for producing safe food. © 2016 Institute of Food Technologists®.

Effects of clinical infrared laser on superficial radial nerve conduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greathouse, D.G.; Currier, D.P.; Gilmore, R.L.

The purposes of this study were to demonstrate the effects of infrared laser radiation on the sensory nerve conduction of a specified peripheral nerve in man and determine temperature changes in the tissue surrounding the treated nerve. Twenty healthy adults were divided into three groups: control (n = 5); experimental (n = 10), infrared laser radiation at 20 sec/cm2; and experimental (n = 5), infrared laser radiation treatment at 120 sec/cm2. Antidromic sensory nerve conduction studies were performed on the superficial radial nerve of each subject's right forearm. The infrared laser radiation was applied at a fixed intensity for fivemore » 1-cm2 segments. Latency, amplitude, and temperature measurements were recorded pretest; posttest; and posttest intervals of 1, 3, 5, 10, and 15 minutes. An analysis of variance with repeated measures was used to examine the data. No significant change was noted in the distal sensory latency or amplitude of the evoked sensory potential in either experimental or control groups as a result of the applications of the infrared laser radiation treatment. This study demonstrates that infrared laser used at clinically applied intensities does not alter conduction of sensory nerves nor does it elevate the subcutaneous temperature.« less

Characterization of Single Phase and Two Phase Heat and Momentum Transport in a Spiraling Radial Inow Microchannel Heat Sink

NASA Astrophysics Data System (ADS)

Ruiz, Maritza

Thermal management of systems under high heat fluxes on the order of hundreds of W/cm2 is important for the safety, performance and lifetime of devices, with innovative cooling technologies leading to improved performance of electronics or concentrating solar photovoltaics. A novel, spiraling radial inflow microchannel heat sink for high flux cooling applications, using a single phase or vaporizing coolant, has demonstrated enhanced heat transfer capabilities. The design of the heat sink provides an inward swirl flow between parallel, coaxial disks that form a microchannel of 1 cm radius and 300 micron channel height with a single inlet and a single outlet. The channel is heated on one side through a conducting copper surface, and is essentially adiabatic on the opposite side to simulate a heat sink scenario for electronics or concentrated photovoltaics cooling. Experimental results on the heat transfer and pressure drop characteristics in the heat sink, using single phase water as a working fluid, revealed heat transfer enhancements due to flow acceleration and induced secondary flows when compared to unidirectional laminar fully developed flow between parallel plates. Additionally, thermal gradients on the surface are small relative to the bulk fluid temperature gain, a beneficial feature for high heat flux cooling applications. Heat flux levels of 113 W/cm2 at a surface temperature of 77 deg C were reached with a ratio of pumping power to heat rate of 0.03%. Analytical models on single phase flow are used to explore the parametric trends of the flow rate and passage geometry on the streamlines and pressure drop through the device. Flow boiling heat transfer and pressure drop characteristics were obtained for this heat sink using water at near atmospheric pressure as the working fluid for inlet subcooling levels ranging from 20 to 80 deg C and mean mass flux levels ranging from 184-716 kg/m. 2s. Flow enhancements similar to singlephase flow were expected, as well

Ballistic heat conduction and mass disorder in one dimension.

PubMed

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 (κ) scales asymptotically as lim(L--> ∞) κ ∝ 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 (κ ∝ L) can coexist with mass disorder. This ballistic-to-subballistic heat conduction crossover is connected to the exponential attenuation of the phonon transmittance function Ξ i.e. Ξ(ω, L) = exp[-L/λ(ω)], where λ 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.

Cryogenic regenerator including sarancarbon heat conduction matrix

NASA Technical Reports Server (NTRS)

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

1989-01-01

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

Transient heat conduction in a heat fin

NASA Astrophysics Data System (ADS)

Brody, Jed; Brown, Max

2017-08-01

We immerse the bottom of a rod in ice water and record the time-dependent temperatures at positions along the length of the rod. Though the experiment is simple, a surprisingly difficult problem in heat conduction must be solved to obtain a theoretical fit to the measured data. The required equipment is very inexpensive and could be assigned as a homework exercise or a hands-on component of an online course.

Heat Rejection from a Variable Conductance Heat Pipe Radiator Panel

NASA Technical Reports Server (NTRS)

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

2012-01-01

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

Characterization of heat transfer in nutrient materials, part 2

NASA Technical Reports Server (NTRS)

Cox, J. E.; Bannerot, R. B.; Chen, C. K.; Witte, L. C.

1973-01-01

A thermal model is analyzed that takes into account phase changes in the nutrient material. The behavior of fluids in low gravity environments is discussed along with low gravity heat transfer. Thermal contact resistance in the Skylab food heater is analyzed. The original model is modified to include: equivalent conductance due to radiation, radial equivalent conductance, wall equivalent conductance, and equivalent heat capacity. A constant wall-temperature model is presented.

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.

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.

SEAWAT-based simulation of axisymmetric heat transport.

PubMed

Vandenbohede, Alexander; Louwyck, Andy; Vlamynck, Nele

2014-01-01

Simulation of heat transport has its applications in geothermal exploitation of aquifers and the analysis of temperature dependent chemical reactions. Under homogeneous conditions and in the absence of a regional hydraulic gradient, groundwater flow and heat transport from or to a well exhibit radial symmetry, and governing equations are reduced by one dimension (1D) which increases computational efficiency importantly. Solute transport codes can simulate heat transport and input parameters may be modified such that the Cartesian geometry can handle radial flow. In this article, SEAWAT is evaluated as simulator for heat transport under radial flow conditions. The 1971, 1D analytical solution of Gelhar and Collins is used to compare axisymmetric transport with retardation (i.e., as a result of thermal equilibrium between fluid and solid) and a large diffusion (conduction). It is shown that an axisymmetric simulation compares well with a fully three dimensional (3D) simulation of an aquifer thermal energy storage systems. The influence of grid discretization, solver parameters, and advection solution is illustrated. Because of the high diffusion to simulate conduction, convergence criterion for heat transport must be set much smaller (10(-10) ) than for solute transport (10(-6) ). Grid discretization should be considered carefully, in particular the subdivision of the screen interval. On the other hand, different methods to calculate the pumping or injection rate distribution over different nodes of a multilayer well lead to small differences only. © 2013, National Ground Water Association.

Heat conduction in one-dimensional aperiodic quantum Ising chains.

PubMed

Li, Wenjuan; Tong, Peiqing

2011-03-01

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

Geometric model for softwood transverse thermal conductivity. Part I

Treesearch

Hong-mei Gu; Audrey Zink-Sharp

2005-01-01

Thermal conductivity is a very important parameter in determining heat transfer rate and is required for developing of drying models and in industrial operations such as adhesive cure rate. Geometric models for predicting softwood thermal conductivity in the radial and tangential directions were generated in this study based on obervation and measurements of wood...

Size effects in non-linear heat conduction with flux-limited behaviors

NASA Astrophysics Data System (ADS)

Li, Shu-Nan; Cao, Bing-Yang

2017-11-01

Size effects are discussed for several non-linear heat conduction models with flux-limited behaviors, including the phonon hydrodynamic, Lagrange multiplier, hierarchy moment, nonlinear phonon hydrodynamic, tempered diffusion, thermon gas and generalized nonlinear models. For the phonon hydrodynamic, Lagrange multiplier and tempered diffusion models, heat flux will not exist in problems with sufficiently small scale. The existence of heat flux needs the sizes of heat conduction larger than their corresponding critical sizes, which are determined by the physical properties and boundary temperatures. The critical sizes can be regarded as the theoretical limits of the applicable ranges for these non-linear heat conduction models with flux-limited behaviors. For sufficiently small scale heat conduction, the phonon hydrodynamic and Lagrange multiplier models can also predict the theoretical possibility of violating the second law and multiplicity. Comparisons are also made between these non-Fourier models and non-linear Fourier heat conduction in the type of fast diffusion, which can also predict flux-limited behaviors.

Measurement of Apparent Thermal Conductivity of JSC-1A Under Ambient Pressure

NASA Technical Reports Server (NTRS)

Yuan, Zeng-Guang; Kleinhenz, Julie E.

2011-01-01

The apparent thermal conductivity of JSC-1A lunar regolith simulant was measured experimentally using a cylindrical apparatus. Eleven thermocouples were embedded in the simulant bed to obtain the steady state temperature distribution at various radial, axial, and azimuthal locations. The high aspect ratio of a cylindrical geometry was proven to provide a one-dimensional, axisymmetric temperature field. A test series was performed at atmospheric pressure with varying heat fluxes. The radial temperature distribution in each test fit a logarithmic function, indicating a constant thermal conductivity throughout the soil bed. However, thermal conductivity was not constant between tests at different heat fluxes. This variation is attributed to stresses created by thermal expansion of the simulant particles against the rigid chamber wall. Under stress-free conditions (20 deg C), the data suggest a temperature independent apparent conductivity of 0.1961 +/- 0.0070 W/m/ deg C

Hyperbolic heat conduction, effective temperature, and third law for nonequilibrium systems with heat flux

NASA Astrophysics Data System (ADS)

Sobolev, S. L.

2018-02-01

Some analogies between different nonequilibrium heat conduction models, particularly random walk, the discrete variable model, and the Boltzmann transport equation with the single relaxation time approximation, have been discussed. We show that, under an assumption of a finite value of the heat carrier velocity, these models lead to the hyperbolic heat conduction equation and the modified Fourier law with relaxation term. Corresponding effective temperature and entropy have been introduced and analyzed. It has been demonstrated that the effective temperature, defined as a geometric mean of the kinetic temperatures of the heat carriers moving in opposite directions, acts as a criterion for thermalization and is a nonlinear function of the kinetic temperature and heat flux. It is shown that, under highly nonequilibrium conditions when the heat flux tends to its maximum possible value, the effective temperature, heat capacity, and local entropy go to zero even at a nonzero equilibrium temperature. This provides a possible generalization of the third law to nonequilibrium situations. Analogies and differences between the proposed effective temperature and some other definitions of a temperature in nonequilibrium state, particularly for active systems, disordered semiconductors under electric field, and adiabatic gas flow, have been shown and discussed. Illustrative examples of the behavior of the effective temperature and entropy during nonequilibrium heat conduction in a monatomic gas and a strong shockwave have been analyzed.

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

PubMed

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

2015-01-01

To date, heat conduction from heat sources to tissue has been estimated by complex mathematical modeling. In the present study, we developed an intuitive in vitro skin burn model that illustrates heat conduction patterns inside the skin. This was composed of tightly compressed thermal papers with compression frames. Heat flow through the model left a trace by changing the color of thermal papers. These were digitized and three-dimensionally reconstituted to reproduce the heat conduction patterns in the skin. For standardization, we validated K91HG-CE thermal paper using a printout test and bivariate correlation analysis. We measured the papers' physical properties and calculated the estimated depth of heat conduction using Fourier's equation. Through contact burns of 5, 10, 15, 20, and 30 seconds on porcine skin and our burn model using a heated brass comb, and comparing the burn wound and heat conduction trace, we validated our model. The heat conduction pattern correlation analysis (intraclass correlation coefficient: 0.846, p < 0.001) and the heat conduction depth correlation analysis (intraclass correlation coefficient: 0.93, p < 0.001) showed statistically significant high correlations between the porcine burn wound and our model. Our model showed good correlation with porcine skin burn injury and replicated its heat conduction patterns. © 2014 by the Wound Healing Society.

The Radial Temperature Gradient in the Gleeble® Hot-Torsion Test and Its Effect on the Interpretation of Plastic-Flow Behavior

NASA Astrophysics Data System (ADS)

Semiatin, S. L.; Mahaffey, D. W.; Levkulich, N. C.; Senkov, O. N.

2017-11-01

The radial temperature gradient developed via direct-resistance heating of round-bar hot-torsion specimens in a Gleeble® machine and its effect on the interpretation of plastic-flow behavior were established using a suite of experimental, analytical, and numerical-simulation tools. Observations of the microstructure variation developed within a γ'-strengthened nickel-base superalloy were used to infer the temperature gradient as well as differences between the temperature at the outer diameter and that indicated by thermocouples welded to the surface. At temperatures of the order of 1375 K (1102 °C), the radial variation of temperature was typically 20 K ( 20 °C). Such variations were in agreement with an analytical heat-conduction model based on the balance of input thermal energy and radiation heat loss at the free surface. Using a constitutive model for LSHR, the effect of the radial temperature gradient on plastic flow during hot torsion was assessed via numerical integration of the torque as a function of radial position for such cases as well as that corresponding to a uniformly-heated sample. These calculations revealed that the torque generated in the non-uniform case is almost identical to that developed in a sample uniformly preheated to a temperature corresponding to that experienced at a fractional radial location of 0.8 in the former case.

Heat-Conducting Anchors for Thermocouples

NASA Technical Reports Server (NTRS)

Macdavid, Kenton S.

1987-01-01

Metal particles in adhesive aid heat transfer. Aluminum caps containing silver-filled epoxy used as high-thermal-conductance anchors for thermocouples, epoxy providing thermal path between mounting surfaces and thermocouple measuring junctions. Normally, epoxy-filled aluminum caps used when measuring steady-state temperatures. Silver-filled epoxy used when thermocouple not isolated electrically from surface measured.

A numerical analysis of the effects of conjugate heat transfer, vapor compressibility, and viscous dissipation in heat pipes

NASA Astrophysics Data System (ADS)

Faghri, Amir; Chen, Ming-Ming

1989-10-01

The effects of conjugate heat transfer, vapor compressibility, and viscous dissipation in heat pipes are discussed. The accuracy of the partially parabolic versus the elliptic presentation of the governing equations is also examined. The results show that the axial wall conduction has a tendency to make the temperature distribution more uniform for heat pipes with large ratios of pipe wall to effective liquid-wick thermal conductivity. The compressible and incompressible models show very close agreement for the total pressure drop, while the local pressure variations along the heat pipe are quite different for these two models when the radial Reynolds number at the interface is high.

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.

Two-dimensional finite element heat transfer model of softwood. Part III, Effect of moisture content on thermal conductivity

Treesearch

Hongmei Gu; John F. Hunt

2007-01-01

The anisotropy of wood creates a complex problem for solving heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models for softwood use average thermal properties across either the radial or tangential direction and do not differentiate the effects of cellular alignment or...

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

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.

Thermally conductive cementitious grout for geothermal heat pump systems

DOEpatents

Allan, Marita

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.

Magnetohydrodynamic flow and heat transfer around a heated cylinder of arbitrary conductivity

NASA Astrophysics Data System (ADS)

Tassone, A.; Nobili, M.; Caruso, G.

2017-11-01

The interaction of the liquid metal with the plasma confinement magnetic field constitutes a challenge for the design of fusion reactor blankets, due to the arise of MHD effects: increased pressure drops, heat transfer suppression, etc. To overcome these issues, a dielectric fluid can be employed as coolant for the breeding zone. A typical configuration involves pipes transverse to the liquid metal flow direction. This numerical study is conducted to assess the influence of pipe conductivity on the MHD flow and heat transfer. The CFD code ANSYS CFX was employed for this purpose. The fluid is assumed to be bounded by rectangular walls with non-uniform thickness and subject to a skewed magnetic field with the main component aligned with the cylinder axis. The simulations were restricted to Re = (20; 40) and M = (10; 50). Three different scenarios for the obstacle were considered: perfectly insulating, finite conductivity and perfectly conducting. The electrical conductivity was found to affect the channel pressure penalty due to the obstacle insertion only for M = 10 and just for the two limiting cases. A general increment of the heat transfer with M was found due to the tendency of the magnetic field to equalize the flow rate between the sub-channels individuated by the pipe. The best results were obtained with the insulating pipe, due to the reduced electromagnetic drag. The generation of counter-rotating vortices close to the lateral duct walls was observed for M = 50 and perfectly conducting pipe as a result of the modified currents distribution.

Increasing Boiling Heat Transfer using Low Conductivity Materials

PubMed Central

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

Thermal conductivity measurements of proton-heated warm dense aluminum

DOE PAGES

McKelvey, A.; Kemp, G. E.; Sterne, P. A.; ...

2017-08-01

Thermal conductivity is one of the most crucial physical properties of matter when it comes to understanding heat transport, hydrodynamic evolution, and energy balance in systems ranging from astrophysical objects to fusion plasmas. In the warm dense matter regime, experimental data are very scarce so that many theoretical models remain untested. Here we present the first thermal conductivity measurements of aluminum at 0.5–2.7 g/cc and 2–10 eV, using a recently developed platform of differential heating. A temperature gradient is induced in a Au/Al dual-layer target by proton heating, and subsequent heat flow from the hotter Au to the Al rearmore » surface is detected by two simultaneous time-resolved diagnostics. A systematic data set allows for constraining both thermal conductivity and equation-of-state models. Simulations using Purgatorio model or Sesame S27314 for Al thermal conductivity and LEOS for Au/Al release equation-of-state show good agreement with data after 15 ps. Discrepancy still exists at early time 0–15 ps, likely due to non-equilibrium conditions.« less

Thermal conductivity measurements of proton-heated warm dense aluminum

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKelvey, A.; Kemp, G. E.; Sterne, P. A.

Thermal conductivity is one of the most crucial physical properties of matter when it comes to understanding heat transport, hydrodynamic evolution, and energy balance in systems ranging from astrophysical objects to fusion plasmas. In the warm dense matter regime, experimental data are very scarce so that many theoretical models remain untested. Here we present the first thermal conductivity measurements of aluminum at 0.5–2.7 g/cc and 2–10 eV, using a recently developed platform of differential heating. A temperature gradient is induced in a Au/Al dual-layer target by proton heating, and subsequent heat flow from the hotter Au to the Al rearmore » surface is detected by two simultaneous time-resolved diagnostics. A systematic data set allows for constraining both thermal conductivity and equation-of-state models. Simulations using Purgatorio model or Sesame S27314 for Al thermal conductivity and LEOS for Au/Al release equation-of-state show good agreement with data after 15 ps. Discrepancy still exists at early time 0–15 ps, likely due to non-equilibrium conditions.« less

Heat exchange apparatus

DOEpatents

Degtiarenko, Pavel V.

2003-08-12

A heat exchange apparatus comprising a coolant conduit or heat sink having attached to its surface a first radial array of spaced-apart parallel plate fins or needles and a second radial array of spaced-apart parallel plate fins or needles thermally coupled to a body to be cooled and meshed with, but not contacting the first radial array of spaced-apart parallel plate fins or needles.

Optical sensor for heat conduction measurement in biological tissue

NASA Astrophysics Data System (ADS)

Gutierrez-Arroyo, A.; Sanchez-Perez, C.; Aleman-Garcia, N.

2013-06-01

This paper presents the design of a heat flux sensor using an optical fiber system to measure heat conduction in biological tissues. This optoelectronic device is based on the photothermal beam deflection of a laser beam travelling in an acrylic slab this deflection is measured with a fiber optic angle sensor. We measure heat conduction in biological samples with high repeatability and sensitivity enough to detect differences in tissues from three chicken organs. This technique could provide important information of vital organ function as well as the detect modifications due to degenerative diseases or physical damage caused by medications or therapies.

Cooling apparatus with a resilient heat conducting member

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chainer, Timothy J.; Parida, Pritish R.; Schultz, Mark D.

2016-06-14

A cooling structure including a thermally conducting central element having a channel formed therein, the channel being configured for flow of cooling fluid there through, a first pressure plate, and a first thermally conductive resilient member disposed between the thermally conducting central element and the first pressure plate, wherein the first pressure plate, the first thermally conductive resilient member, and the thermally conducting central element form a first heat transfer path.

Conductive heat exchange with a gel-coated circulating water mattress.

PubMed

Bräuer, Anselm; Pacholik, Larissa; Perl, Thorsten; English, Michael John Murray; Weyland, Wolfgang; Braun, Ulrich

2004-12-01

The use of forced-air warming is associated with costs for the disposable blankets. As an alternative method, we studied heat transfer with a reusable gel-coated circulating water mattress placed under the back in eight healthy volunteers. Heat flux was measured with six calibrated heat flux transducers. Additionally, mattress temperature, skin temperature, and core temperature were measured. Water temperature was set to 25 degrees C, 30 degrees C, 35 degrees C, and 41 degrees C. Heat transfer was calculated by multiplying heat flux by contact area. Mattress temperature, skin temperature, and heat flux were used to determine the heat exchange coefficient for conduction. Heat flux and water temperature were related by the following equation: heat flux = 10.3 x water temperature - 374 (r(2) = 0.98). The heat exchange coefficient for conduction was 121 W . m(-2) . degrees C(-1). The maximal heat transfer with the gel-coated circulating water mattress was 18.4 +/- 3.3 W. Because of the small effect on the heat balance of the body, a gel-coated circulating water mattress placed only on the back cannot replace a forced-air warming system.

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

PubMed

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

2013-02-28

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

Cooled variable nozzle radial turbine for rotor craft applications

NASA Technical Reports Server (NTRS)

Rogo, C.

1981-01-01

An advanced, small 2.27 kb/sec (5 lbs/sec), high temperature, variable area radial turbine was studied for a rotor craft application. Variable capacity cycles including single-shaft and free-turbine engine configurations were analyzed to define an optimum engine design configuration. Parametric optimizations were made on cooled and uncooled rotor configurations. A detailed structural and heat transfer analysis was conducted to provide a 4000-hour life HP turbine with material properties of the 1988 time frame. A pivoted vane and a moveable sidewall geometry were analyzed. Cooling and variable geometry penalties were included in the cycle analysis. A variable geometry free-turbine engine configuration with a design 1477K (2200 F) inlet temperature and a compressor pressure ratio of 16:1 was selected. An uncooled HP radial turbine rotor with a moveable sidewall nozzle showed the highest performance potential for a time weighted duty cycle.

Fourier analysis of conductive heat transfer for glazed roofing materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja

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 heatmore » 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.« less

Thermal conductive properties of wood, green or dry, from -40° to +100° C: a literature review

Treesearch

H. Peter Steinhagen

1977-01-01

This literature review was conducted in connection with a study on heat transfer in frozen logs. A combination of data by two researchers on specific heat and thermal conductivity and diffusivity in the radial direction of wood, at various temperatures and moisture contents, is discussed and compared with data from other sources. Limited information found for the...

Experimental feasibility study of radial injection cooling of three-pad radial air foil bearings

NASA Astrophysics Data System (ADS)

Shrestha, Suman K.

Air foil bearings use ambient air as a lubricant allowing environment-friendly operation. When they are designed, installed, and operated properly, air foil bearings are very cost effective and reliable solution to oil-free turbomachinery. Because air is used as a lubricant, there are no mechanical contacts between the rotor and bearings and when the rotor is lifted off the bearing, near frictionless quiet operation is possible. However, due to the high speed operation, thermal management is one of the very important design factors to consider. Most widely accepted practice of the cooling method is axial cooling, which uses cooling air passing through heat exchange channels formed underneath the bearing pad. Advantage is no hardware modification to implement the axial cooling because elastic foundation structure of foil bearing serves as a heat exchange channels. Disadvantage is axial temperature gradient on the journal shaft and bearing. This work presents the experimental feasibility study of alternative cooling method using radial injection of cooling air directly on the rotor shaft. The injection speeds, number of nozzles, location of nozzles, total air flow rate are important factors determining the effectiveness of the radial injection cooling method. Effectiveness of the radial injection cooling was compared with traditional axial cooling method. A previously constructed test rig was modified to accommodate a new motor with higher torque and radial injection cooling. The radial injection cooling utilizes the direct air injection to the inlet region of air film from three locations at 120° from one another with each location having three axially separated holes. In axial cooling, a certain axial pressure gradient is applied across the bearing to induce axial cooling air through bump foil channels. For the comparison of the two methods, the same amount of cooling air flow rate was used for both axial cooling and radial injection. Cooling air flow rate was

Double-Sided Laser Heating in Radial Diffraction Geometry for Diamond Anvil Cell Deformation Experiments at Simultaneous High Pressures and Temperatures

NASA Astrophysics Data System (ADS)

Miyagi, L. M.; Kunz, M.; Couper, S.; Lin, F.; Yan, J.; Doran, A.; MacDowell, A. A.

2017-12-01

The rheology of rocks and minerals in the Earth's deep interior plays a primary role in controlling large scale geodynamic processes such as mantle convection and slab subduction. Plastic deformation resulting from these processes can lead to texture development and associated seismic anisotropy. If a detailed understanding of the link between deformation and seismic anisotropy is established, observations of seismic anisotropy can be used to understand the dynamic state in the deep Earth. However, performing deformation experiments at lower mantle pressure and temperature conditions are extremely challenging. Thus most deformation studies have been performed either at room temperature and high pressure or at reduced pressures and high temperature. Only a few extraordinary efforts have attained pressures and temperatures relevant to lower mantle. Therefore our ability to interpret observations of lower mantle seismic anisotropy in terms of mantle flow models remains limited. In order to expand the pressure and temperature range available for deformation of deep Earth relevant mineral phases, we have developed a laser heating system for in-situ double-sided heating in radial diffraction geometry at beamline 12.2.2 of the Advanced Light Source of Lawrence Berkeley National Laboratory. This allows texture and lattice strain measurements to be recorded at simultaneous high pressures and temperatures in the diamond anvil cell. This new system is integrated into the newly built axial laser heating system to allow for rapid and reliable transitioning between double-sided laser heating in axial and radial geometries. Transitioning to radial geometry is accomplished by redirecting the laser and imaging paths from 0° and 180° to 90° and 270°. To redirect the 90° path, a motorized periscope mirror pair with an objective lens can be inserted into the downstream axial beam path. The 270° redirection is accomplished by removing the upstream axial objective lens and

Finite element method formulation in polar coordinates for transient heat conduction problems

NASA Astrophysics Data System (ADS)

Duda, Piotr

2016-04-01

The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method (FEM) in polar or cylindrical coordinates for the solution of heat transfer problems. This document shows how to apply the most often used boundary conditions. The global equation system is solved by the Crank-Nicolson method. The proposed algorithm is verified in three numerical tests. In the first example, the obtained transient temperature distribution is compared with the temperature obtained from the presented analytical solution. In the second numerical example, the variable boundary condition is assumed. In the last numerical example the component with the shape different than cylindrical is used. All examples show that the introduction of the polar coordinate system gives better results than in the Cartesian coordinate system. The finite element method formulation in polar coordinates is valuable since it provides a higher accuracy of the calculations without compacting the mesh in cylindrical or similar to tubular components. The proposed method can be applied for circular elements such as boiler drums, outlet headers, flux tubes. This algorithm can be useful during the solution of inverse problems, which do not allow for high density grid. This method can calculate the temperature distribution in the bodies of different properties in the circumferential and the radial direction. The presented algorithm can be developed for other coordinate systems. The examples demonstrate a good accuracy and stability of the proposed method.

A semi-analytical model of disk evaporation by thermal conduction

NASA Astrophysics Data System (ADS)

Dullemond, C. P.

1999-01-01

The conditions for disk evaporation by electron thermal conduction are examined, using a simplified semi-analytical 1-D model. The model is based on the mechanism proposed by Meyer & Meyer-Hofmeister ( te{meyermeyhof:1994}) in which an advection dominated accretion flow evaporates the top layers from the underlying disk by thermal conduction. The evaporation rate is calculated as a function of the density of the advective flow, and an analysis is made of the time scales and length scales of the dynamics of the advective flow. It is shown that evaporation can only completely destroy the disk if the conductive length scale is of the order of the radius. This implies that radial conduction is an essential factor in the evaporation process. The heat required for evaporation is in fact produced at small radii and transported radially towards the evaporation region.

Heating and Cooling of Coronal Loops with Turbulent Suppression of Parallel Heat Conduction.

PubMed

Bian, Nicolas; Emslie, A Gordon; Horne, Duncan; Kontar, Eduard P

2018-01-10

Using the "enthalpy-based thermal evolution of loops" (EBTEL) model, we investigate the hydrodynamics of the plasma in a flaring coronal loop in which heat conduction is limited by turbulent scattering of the electrons that transport the thermal heat flux. The EBTEL equations are solved analytically in each of the two (conduction-dominated and radiation-dominated) cooling phases. Comparison of the results with typical observed cooling times in solar flares shows that the turbulent mean free path λ T lies in a range corresponding to a regime in which classical (collision-dominated) conduction plays at most a limited role. We also consider the magnitude and duration of the heat input that is necessary to account for the enhanced values of temperature and density at the beginning of the cooling phase and for the observed cooling times. We find through numerical modeling that in order to produce a peak temperature ≃1.5 × 10 7 K and a 200 s cooling time consistent with observations, the flare-heating profile must extend over a significant period of time; in particular, its lingering role must be taken into consideration in any description of the cooling phase. Comparison with observationally inferred values of post-flare loop temperatures, densities, and cooling times thus leads to useful constraints on both the magnitude and duration of the magnetic energy release in the loop, as well as on the value of the turbulent mean free path λ T .

Generalized thermoelastic diffusive waves in heat conducting materials

NASA Astrophysics Data System (ADS)

Sharma, J. N.

2007-04-01

Keeping in view the applications of diffusion processes in geophysics and electronics industry, the aim of the present paper is to give a detail account of the plane harmonic generalized thermoelastic diffusive waves in heat conducting solids. According to the characteristic equation, three longitudinal waves namely, elastodiffusive (ED), mass diffusion (MD-mode) and thermodiffusive (TD-mode), can propagate in such solids in addition to transverse waves. The transverse waves get decoupled from rest of the fields and hence remain unaffected due to temperature change and mass diffusion effects. These waves travel without attenuation and dispersion. The other generalized thermoelastic diffusive waves are significantly influenced by the interacting fields and hence suffer both attenuation and dispersion. At low frequency mass diffusion and thermal waves do not exist but at high-frequency limits these waves propagate with infinite velocity being diffusive in character. Moreover, in the low-frequency regions, the disturbance is mainly dominant by mechanical process of transportation of energy and at high-frequency regions it is significantly dominated by a close to diffusive process (heat conduction or mass diffusion). Therefore, at low-frequency limits the waves like modes are identifiable with small amplitude waves in elastic materials that do not conduct heat. The general complex characteristic equation is solved by using irreducible case of Cardano's method with the help of DeMoivre's theorem in order to obtain phase speeds, attenuation coefficients and specific loss factor of energy dissipation of various modes. The propagation of waves in case of non-heat conducting solids is also discussed. Finally, the numerical solution is carried out for copper (solvent) and zinc (solute) materials and the obtained phase velocities, attenuation coefficients and specific loss factor of various thermoelastic diffusive waves are presented graphically.

Temperature dependency of the thermal conductivity of porous heat storage media

NASA Astrophysics Data System (ADS)

Hailemariam, Henok; Wuttke, Frank

2018-04-01

Analyzing the variation of thermal conductivity with temperature is vital in the design and assessment of the efficiency of sensible heat storage systems. In this study, the temperature variation of the thermal conductivity of a commercial cement-based porous heat storage material named - Füllbinder L is analyzed in saturated condition in the temperature range between 20 to 70°C (water based storage) with a steady state thermal conductivity and diffusivity meter. A considerable decrease in the thermal conductivity of the saturated sensible heat storage material upon increase in temperature is obtained, resulting in a significant loss of system efficiency and slower loading/un-loading rates, which when unaccounted for can lead to the under-designing of such systems. Furthermore, a new empirical prediction model for the estimation of thermal conductivity of cement-based porous sensible heat storage materials and naturally occurring crystalline rock formations as a function of temperature is proposed. The results of the model prediction are compared with the experimental results with satisfactory results.

An experimental and numerical study of endwall heat transfer in a turbine blade cascade including tangential heat conduction analysis

NASA Astrophysics Data System (ADS)

Ratto, Luca; Satta, Francesca; Tanda, Giovanni

2018-06-01

This paper presents an experimental and numerical investigation of heat transfer in the endwall region of a large scale turbine cascade. The steady-state liquid crystal technique has been used to obtain the map of the heat transfer coefficient for a constant heat flux boundary condition. In the presence of two- and three-dimensional flows with significant spatial variations of the heat transfer coefficient, tangential heat conduction could lead to error in the heat transfer coefficient determination, since local heat fluxes at the wall-to-fluid interface tend to differ from point to point and surface temperatures to be smoothed out, thus making the uniform-heat-flux boundary condition difficult to be perfectly achieved. For this reason, numerical simulations of flow and heat transfer in the cascade including the effect of tangential heat conduction inside the endwall have been performed. The major objective of numerical simulations was to investigate the influence of wall heat conduction on the convective heat transfer coefficient determined during a nominal iso-flux heat transfer experiment and to interpret possible differences between numerical and experimental heat transfer results. Results were presented and discussed in terms of local Nusselt number and a convenient wall heat flux function for two values of the Reynolds number (270,000 and 960,000).

Application of genetic algorithms in nonlinear heat conduction problems.

PubMed

Kadri, Muhammad Bilal; 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.

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…

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

NASA Astrophysics Data System (ADS)

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

2002-11-01

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

Detection of small-size solder ball defects through heat conduction analysis

NASA Astrophysics Data System (ADS)

Zhou, Xiuyun; Chen, Yaqiu; Lu, Xiaochuan

2018-02-01

Aiming to solve the defect detection problem of a small-size solder ball in the high density chip, heat conduction analysis based on eddy current pulsed thermography is put forward to differentiate various defects. With establishing the 3D finite element model about induction heating, defects such as cracks and void can be distinguished by temperature difference resulting from heat conduction. Furthermore, the experiment of 0.4 mm-diameter solder balls with different defects is carried out to prove that crack and void solder can be distinguished. Three kinds of crack length on a gull-wing pin are selected, including 0.24 mm, 1.2 mm, and 2.16 mm, to verify that the small defect can be discriminated. Both the simulation study and experiment result show that the heat conduction analysis method is reliable and convenient.

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.

Differential heating: A versatile method for thermal conductivity measurements in high-energy-density matter

DOE PAGES

Ping, Y.; Fernandez-Panella, A.; Sio, H.; ...

2015-09-04

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. As a result, the sensitivity of the measurements to thermal conductivity is confirmed by simulations.

Radial-radial single rotor turbine

DOEpatents

Platts, David A [Los Alamos, NM

2006-05-16

A rotor for use in turbine applications has a radial compressor/pump having radially disposed spaced apart fins forming passages and a radial turbine having hollow turbine blades interleaved with the fins and through which fluid from the radial compressor/pump flows. The rotor can, in some applications, be used to produce electrical power.

Large variable conductance heat pipe. Transverse header

NASA Technical Reports Server (NTRS)

Edelstein, F.

1975-01-01

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

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, in addition to bringing about a reduction in 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.

Firearm suppressor having enhanced thermal management for rapid heat dissipation

DOEpatents

Moss, William C.; Anderson, Andrew T.

2014-08-19

A suppressor is disclosed for use with a weapon having a barrel through which a bullet is fired. The suppressor has an inner portion having a bore extending coaxially therethrough. The inner portion is adapted to be secured to a distal end of the barrel. A plurality of axial flow segments project radially from the inner portion and form axial flow paths through which expanding propellant gasses discharged from the barrel flow through. The axial flow segments have radially extending wall portions that define sections which may be filled with thermally conductive material, which in one example is a thermally conductive foam. The conductive foam helps to dissipate heat deposited within the suppressor during firing of the weapon.

The three-dimensional steady radial expansion of a viscous gas from a sonic source into a vacuum.

NASA Technical Reports Server (NTRS)

Bush, W. B.; Rosen, R.

1971-01-01

The three-dimensional steady radial expansion of a viscous, heat-conducting, compressible fluid from a spherical sonic source into a vacuum is analyzed using the Navier-Stokes equations as a basis. It is assumed that the model fluid is a perfect gas having constant specific heats, a constant Prandtl number of order unity, and viscosity coefficients varying as a power of the absolute temperature. Limiting forms for the flow variable solutions are studied for the Reynolds number based on the sonic source conditions, going to infinity and the Newtonian parameter both fixed and going to zero. For the case of the viscosity-temperature exponent between .5 and 1, it is shown that the velocity as well as the pressure approach zero as the radial distance goes to infinity. The formulations of the distinct regions that span the domain extending from the sonic source to the vacuum are presented.

Corrections of Heat Flux Measurements on Launch Vehicles

NASA Technical Reports Server (NTRS)

Reinarts, Thomas R.; Matson, Monique L.; Walls, Laurie K.

2002-01-01

Knowledge of aerothermally induced convective heat transfer is important in the design of thermal protection systems for launch vehicles. Aerothermal models are typically calibrated via the data from circular, in-flight, flush-mounted surface heat flux gauges exposed to the thermal and velocity boundary layers of the external flow. Typically, copper or aluminum Schmidt- Boelter gauges, which take advantage of the one-dimensional Fourier's law of heat conduction, are used to measure the incident heat flux. This instrumentation, when surrounded by low-conductivity insulation, has a wall temperature significantly lower than the insulation. As a result of this substantial disturbance to the thermal boundary layer, the heat flux incident on the gauge tends to be considerably higher than it would have been on the insulation had the calorimeter not been there. In addition, radial conductive heat transfer from the hotter insulation can cause the calorimeter to indicate heat fluxes higher than actual. An overview of an effort to develop and calibrate gauge correction techniques for both of these effects will be presented.

Transient behavior of a flare-associated solar wind. I - Gas dynamics in a radial open field region

NASA Technical Reports Server (NTRS)

Nagai, F.

1984-01-01

A numerical investigation is conducted into the way in which a solar wind model initially satisfying both steady state and energy balance conditions is disturbed and deformed, under the assumption of heating that correspoonds to the energy release of solar flares of an importance value of approximately 1 which occur in radial open field regions. Flare-associated solar wind transient behavior is modeled for 1-8 solar radii. The coronal temperature around the heat source region rises, and a large thermal conductive flux flows inward to the chromosphere and outward to interplanetary space along field lines. The speed of the front of expanding chromospheric material generated by the impingement of the conduction front on the upper chromosphere exceeds the local sound velocity in a few minutes and eventually exceeds 100 million cm/sec.

Thermal conductivity measurements of proton-heated warm dense aluminum

NASA Astrophysics Data System (ADS)

McKelvey, A.; Kemp, G.; Sterne, P.; Fernandez, A.; Shepherd, R.; Marinak, M.; Link, A.; Collins, G.; Sio, H.; King, J.; Freeman, R.; Hua, R.; McGuffey, C.; Kim, J.; Beg, F.; Ping, Y.

2017-10-01

We present the first thermal conductivity measurements of warm dense aluminum at 0.5-2.7 g/cc and 2-10 eV, using a recently developed platform of differential heating. A temperature gradient is induced in a Au/Al dual-layer target by proton heating, and subsequent heat flow from the hotter Au to the Al rear surface is detected by two simultaneous time-resolved diagnostics. A systematic data set allows for constraining both thermal conductivity and equation-of-state models. Simulations using Purgatorio model or Sesame S27314 for Al thermal conductivity and LEOS for Au/Al release equation-of-state show good agreement with data after 15 ps. Predictions by other models, such Lee-More, Sesame 27311 and 29373, are outside of experimental error bars. Discrepancy still exists at early time 0-15 ps, likely due to non-equilibrium conditions. (Y. Ping et al. Phys. Plasmas, 2015, A. Mckelvey, et al. Sci. Reports 2017). This work was performed under the auspices of the DOE by LLNL under contract DE-AC52-07NA27344 with support from DOE OFES Early Career program and LLNL LDRD program.

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

PubMed

Savin, A V; Gendelman, O V

2003-04-01

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

Heat conduction tuning by hyperbranched nanophononic metamaterials

NASA Astrophysics Data System (ADS)

Li, Bing; Tan, K. T.; Christensen, Johan

2018-05-01

Phonon dispersion and thermal conduction properties of hyperbranched nanostructures with unique topological complexity are theoretically and numerically investigated in this research. We present analytical cantilever-in-mass models to analyze and control the inherent resonance hybridization in hyperbranched nanomembranes containing different configurations and cross sections. We show that these local resonances hosted by hyperbranched nanopillars can generate numerous flat bands in the phonon dispersion relation and dramatically lower the group velocities, consequently resulting in a significant reduction of the thermal conductivity. The applicability of the proposed analytical models in thermal conductivity tuning is demonstrated, and a superior performance in reducing the heat flux in nano-structured membranes is exhibited, which can potentially lead to improved thermoelectric energy conversion devices.

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.

Implicit continuum mechanics approach to heat conduction in granular materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Massoudi, M.; Mehrabadi, M.

In this paper, we derive a properly frame-invariant implicit constitutive relationship for the heat flux vector for a granular medium (or a density-gradient-type fluid). The heat flux vector is commonly modeled by Fourier’s law of heat conduction, and for complex materials such as nonlinear fluids, porous media, or granular materials, the coefficient of thermal conductivity is generalized by assuming that it would depend on a host of material and kinematic parameters such as temperature, shear rate, porosity, concentration, etc. In this paper, we extend the approach of Massoudi [Massoudi, M. Math. Methods Appl. Sci. 2006, 29, 1585; Massoudi, M. Math.more » Methods Appl. Sci. 2006, 29, 1599], who provided explicit constitutive relations for the heat flux vector for flowing granular materials; in order to do so, we use the implicit scheme suggested by Fox [Fox, N. Int. J. Eng. Sci. 1969, 7, 437], who obtained implicit relations in thermoelasticity.« less

Thermal conductivity from hierarchical heat sinks using carbon nanotubes and graphene nanosheets.

PubMed

Hsieh, Chien-Te; Lee, Cheng-En; Chen, Yu-Fu; Chang, Jeng-Kuei; Teng, Hsi-sheng

2015-11-28

The in-plane (kip) and through-plane (ktp) thermal conductivities of heat sinks using carbon nanotubes (CNTs), graphene nanosheets (GNs), and CNT/GN composites are extracted from two experimental setups within the 323-373 K temperature range. Hierarchical three-dimensional CNT/GN frameworks display higher kip and ktp values, as compared to the CNT- and GN-based heat sinks. The kip and ktp values of the CNT/GN-based heat sink reach as high as 1991 and 76 W m(-1) K(-1) at 323 K, respectively. This improved thermal conductivity is attributed to the fact that the hierarchical heat sink offers a stereo thermal conductive network that combines point, line, and plane contact, leading to better heat transport. Furthermore, the compression treatment provided an efficient route to increase both kip and ktp values. This result reveals that the hierarchical carbon structures become denser, inducing more thermal conductive area and less thermal resistivity, i.e., a reduced possibility of phonon-boundary scattering. The correlation between thermal and electrical conductivity (ε) can be well described by two empirical equations: kip = 567 ln(ε) + 1120 and ktp = 20.6 ln(ε) + 36.1. The experimental results are obtained within the temperature range of 323-373 K, suitably complementing the thermal management of chips for consumer electronics.

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

USGS Publications Warehouse

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.

Core radial electric field and transport in Wendelstein 7-X plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pablant, N. A.; Langenberg, A.; Alonso, A.

The results from the investigation of neoclassical core transport and the role of the radial electric field profile (E r) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the E r profile are expected to have a strong effect on both the particle and heat fluxes. Investigation of the radial electric field is important in understanding neoclassical transport and in validation of neoclassical calculations. The radial electric field is closely related to the perpendicular plasma flow (u ⊥) through the force balance equation. This allows the radial electric fieldmore » to be inferred from measurements of the perpendicular flow velocity, which can be measured using the x-ray imaging crystal spectrometer and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu ⊥~ 5 km/s (ΔE r ~12 kV/m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW. These experiments are examined in detail to explore the relationship between heating power temperature, and density profiles and the radial electric field. Finally, the inferred E r profiles are compared to initial neoclassical calculations based on measured plasma profiles. The results from several neoclassical codes, sfincs, fortec-3d, and dkes, are compared both with each other and the measurements. Finally, these comparisons show good agreement, giving confidence in the applicability of the neoclassical calculations to the W7-X configuration.« less

Core radial electric field and transport in Wendelstein 7-X plasmas

NASA Astrophysics Data System (ADS)

Pablant, N. A.; Langenberg, A.; Alonso, A.; Beidler, C. D.; Bitter, M.; Bozhenkov, S.; Burhenn, R.; Beurskens, M.; Delgado-Aparicio, L.; Dinklage, A.; Fuchert, G.; Gates, D.; Geiger, J.; Hill, K. W.; Höfel, U.; Hirsch, M.; Knauer, J.; Krämer-Flecken, A.; Landreman, M.; Lazerson, S.; Maaßberg, H.; Marchuk, O.; Massidda, S.; Neilson, G. H.; Pasch, E.; Satake, S.; Svennson, J.; Traverso, P.; Turkin, Y.; Valson, P.; Velasco, J. L.; Weir, G.; Windisch, T.; Wolf, R. C.; Yokoyama, M.; Zhang, D.; W7-X Team

2018-02-01

The results from the investigation of neoclassical core transport and the role of the radial electric field profile (Er) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the Er profile are expected to have a strong effect on both the particle and heat fluxes. Investigation of the radial electric field is important in understanding neoclassical transport and in validation of neoclassical calculations. The radial electric field is closely related to the perpendicular plasma flow (u⊥) through the force balance equation. This allows the radial electric field to be inferred from measurements of the perpendicular flow velocity, which can be measured using the x-ray imaging crystal spectrometer and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu⊥˜ 5 km/s (ΔEr ˜ 12 kV/m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW. These experiments are examined in detail to explore the relationship between heating power temperature, and density profiles and the radial electric field. Finally, the inferred Er profiles are compared to initial neoclassical calculations based on measured plasma profiles. The results from several neoclassical codes, sfincs, fortec-3d, and dkes, are compared both with each other and the measurements. These comparisons show good agreement, giving confidence in the applicability of the neoclassical calculations to the W7-X configuration.

Core radial electric field and transport in Wendelstein 7-X plasmas

DOE PAGES

Pablant, N. A.; Langenberg, A.; Alonso, A.; ...

2018-02-12

The results from the investigation of neoclassical core transport and the role of the radial electric field profile (E r) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the E r profile are expected to have a strong effect on both the particle and heat fluxes. Investigation of the radial electric field is important in understanding neoclassical transport and in validation of neoclassical calculations. The radial electric field is closely related to the perpendicular plasma flow (u ⊥) through the force balance equation. This allows the radial electric fieldmore » to be inferred from measurements of the perpendicular flow velocity, which can be measured using the x-ray imaging crystal spectrometer and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu ⊥~ 5 km/s (ΔE r ~12 kV/m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW. These experiments are examined in detail to explore the relationship between heating power temperature, and density profiles and the radial electric field. Finally, the inferred E r profiles are compared to initial neoclassical calculations based on measured plasma profiles. The results from several neoclassical codes, sfincs, fortec-3d, and dkes, are compared both with each other and the measurements. Finally, these comparisons show good agreement, giving confidence in the applicability of the neoclassical calculations to the W7-X configuration.« less

Mathematical and information-geometrical entropy for phenomenological Fourier and non-Fourier heat conduction

NASA Astrophysics Data System (ADS)

Li, Shu-Nan; Cao, Bing-Yang

2017-09-01

The second law of thermodynamics governs the direction of heat transport, which provides the foundational definition of thermodynamic Clausius entropy. The definitions of entropy are further generalized for the phenomenological heat transport models in the frameworks of classical irreversible thermodynamics and extended irreversible thermodynamics (EIT). In this work, entropic functions from mathematics are combined with phenomenological heat conduction models and connected to several information-geometrical conceptions. The long-time behaviors of these mathematical entropies exhibit a wide diversity and physical pictures in phenomenological heat conductions, including the tendency to thermal equilibrium, and exponential decay of nonequilibrium and asymptotics, which build a bridge between the macroscopic and microscopic modelings. In contrast with the EIT entropies, the mathematical entropies expressed in terms of the internal energy function can avoid singularity paired with nonpositive local absolute temperature caused by non-Fourier heat conduction models.

Trajectories of charged particles in radial electric and uniform axial magnetic fields

NASA Technical Reports Server (NTRS)

Englert, G. W.

1979-01-01

Trajectories of charged particles were determined over a wide range of parameters characterizing motion in cylindrical low-pressure gas discharges and plasma heating devices which have steady radial electric fields perpendicular to uniform steady magnetic fields. Consideration was given to radial distributions characteristic of fields measured in a modified Penning discharge, in two NASA Lewis burnout-type plasma heating devices, and that estimated for the Ixion device. Numerical calculations of trajectories for such devices showed that differences between cyclotron frequency and qB/m and between azimuthal drift and a guiding center approximation are appreciable.

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.

Influence of crucible support and radial heating on the interface shape during vertical Bridgman GaAs growth

NASA Astrophysics Data System (ADS)

Koai, K.; Sonnenberg, K.; Wenzl, H.

1994-03-01

Crucible assembly in a vertical Bridgman furnace is investigated by a numerical finite element model with the aim to obtain convex interfaces during the growth of GaAs crystals. During the growth stage of the conic section, a new funnel shaped crucible support has been found more effective than the concentric cylinders design similar to that patented by AT & T in promoting interface convexity. For the growth stages of the constant diameter section, the furnace profile can be effectively modulated by localized radial heating at the gradient zone. With these two features being introduced into a new furnace design, it is shown numerically that enhancement of interface convexity can be achieved using the presently available crucible materials.

Endoscopic versus open radial artery harvest and mammario-radial versus aorto-radial grafting in patients undergoing coronary artery bypass surgery: protocol for the 2 × 2 factorial designed randomised NEO trial

PubMed Central

2014-01-01

Background Coronary artery bypass grafting using the radial artery has, since the 1990s, gone through a revival. Observational studies have indicated better long-term patency when using radial arteries. Therefore, radial artery might be preferred especially in younger patients where long time patency is important. During the last 10 years different endoscopic techniques to harvest the radial artery have evolved. Endoscopic radial artery harvest only requires a small incision near the wrist in contrast to open harvest, which requires an incision from the elbow to the wrist. However, it is unknown whether the endoscopic technique results in fewer complications or a graft patency comparable to open harvest. When the radial artery has been harvested, there are two ways to use the radial artery as a graft. One way is sewing it onto the aorta and another is sewing it onto the mammary artery. It is unknown which technique is the superior revascularisation technique. Methods/Design The NEO Trial is a randomised clinical trial with a 2 × 2 factorial design. We plan to randomise 300 participants into four intervention groups: (1) mammario-radial endoscopic group; (2) aorto-radial endoscopic group; (3) mammario-radial open surgery group; and (4) aorto-radial open surgery group. The hand function will be assessed by a questionnaire, a clinical examination, the change in cutaneous sensibility, and the measurement of both sensory and motor nerve conduction velocity at 3 months postoperatively. All the postoperative complications will be registered, and we will evaluate muscular function, scar appearance, vascular supply to the hand, and the graft patency including the patency of the central radial artery anastomosis. A patency evaluation by multi-slice computer tomography will be done at one year postoperatively. We expect the nerve conduction studies and the standardised neurological examinations to be able to discriminate differences in hand function comparing

Identification of the Thermal Conductivity Coefficient for Quasi-Stationary Two-Dimensional Heat Conduction Equations

NASA Astrophysics Data System (ADS)

Matsevityi, Yu. M.; Alekhina, S. V.; Borukhov, V. T.; Zayats, G. M.; Kostikov, A. O.

2017-11-01

The problem of identifying the time-dependent thermal conductivity coefficient in the initial-boundary-value problem for the quasi-stationary two-dimensional heat conduction equation in a bounded cylinder is considered. It is assumed that the temperature field in the cylinder is independent of the angular coordinate. To solve the given problem, which is related to a class of inverse problems, a mathematical approach based on the method of conjugate gradients in a functional form is being developed.

Core Radial Electric Field and Transport in Wendelstein 7-X Plasmas

NASA Astrophysics Data System (ADS)

Pablant, Novimir

2016-10-01

Results from the investigation of core transport and the role of the radial electric field profile (Er) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the Er profile are expected to have a strong effect on both the particle and heat fluxes. Neoclassical particle fluxes are not intrinsically ambipolar, which leads to the formation of a radial electric field that enforces ambipolarity. The radial electric field is closely related to the perpendicular plasma flow (u⊥) through the force balance equation. This allows the radial electric field to be inferred from measurements of the perpendicular flow velocity from the x-ray imaging crystal spectrometer (XICS) and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu⊥ 5km /s (ΔEr 12kV / m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW . These experiments are examined in detail to explore the relationship between, heating power, response of the temperature and density profiles and the response of the radial electric field. Estimations of the core transport are based on power balance and utilize electron temperature (Te) profiles from the ECE and Thomson scattering, electron density profiles (ne) from interferometry and Thomson scattering, ion temperature (Ti) profiles from XICS, along with measurements of the total stored energy and radiated power. Also described are a set core impurity confinement experiments and results. Impurity confinement has been investigated through the injection of trace amount of argon impurity gas at the plasma edge in conjunction with measurements of the density of various ionization states of argon from the XICS and High Efficiency eXtreme-UV Overview Spectrometer (HEXOS) diagnostics. Finally the inferred Er and heat flux profiles are compared to initial neoclassical calculations using measured

Control and design heat flux bending in thermal devices with transformation optics.

PubMed

Xu, Guoqiang; Zhang, Haochun; Jin, Yan; Li, Sen; Li, Yao

2017-04-17

We propose a fundamental latent function of control heat transfer and heat flux density vectors at random positions on thermal materials by applying transformation optics. The expressions for heat flux bending are obtained, and the factors influencing them are investigated in both 2D and 3D cloaking schemes. Under certain conditions, more than one degree of freedom of heat flux bending exists corresponding to the temperature gradients of the 3D domain. The heat flux path can be controlled in random space based on the geometrical azimuths, radial positions, and thermal conductivity ratios of the selected materials.

Electron heating within interaction zones of simple high-speed solar wind streams

NASA Technical Reports Server (NTRS)

Feldman, W. C.; Asbridge, J. R.; Bame, S. J.; Gosling, J. T.; Lemons, D. S.

1978-01-01

In the present paper, electron heating within the high-speed portions of three simple stream-stream interaction zones is studied to further our understanding of the physics of heat flux regulation in interplanetary space. To this end, the thermal signals present in the compressions at the leading edges of the simple high-speed streams are analyzed, showing that the data are inconsistent with the Spitzer conductivity. Instead, a polynomial law is found to apply. Its implication concerning the mechanism of interplanetary heat conduction is discussed, and the results of applying this conductivity law to high-speed flows inside of 1 AU are studied. A self-consistent model of the radial evolution of electrons in the high-speed solar wind is proposed.

Reduction in thermal conductivity and tunable heat capacity of inorganic/organic hybrid superlattices

NASA Astrophysics Data System (ADS)

Giri, Ashutosh; Niemelä, Janne-Petteri; Szwejkowski, Chester J.; Karppinen, Maarit; Hopkins, Patrick E.

2016-01-01

We study the influence of molecular monolayers on the thermal conductivities and heat capacities of hybrid inorganic/organic superlattice thin films fabricated via atomic/molecular layer deposition. We measure the cross plane thermal conductivities and volumetric heat capacities of TiO2- and ZnO-based superlattices with periodic inclusion of hydroquinone layers via time domain thermoreflectance. In comparison to their homogeneous counterparts, the thermal conductivities in these superlattice films are considerably reduced. We attribute this reduction in the thermal conductivity mainly due to incoherent phonon boundary scattering at the inorganic/organic interface. Increasing the inorganic/organic interface density reduces the thermal conductivity and heat capacity of these films. High-temperature annealing treatment of the superlattices results in a change in the orientation of the hydroquinone molecules to a 2D graphitic layer along with a change in the overall density of the hybrid superlattice. The thermal conductivity of the hybrid superlattice increases after annealing, which we attribute to an increase in crystallinity.

Wave propagation model of heat conduction and group speed

NASA Astrophysics Data System (ADS)

Zhang, Long; Zhang, Xiaomin; Peng, Song

2018-03-01

In view of the finite relaxation model of non-Fourier's law, the Cattaneo and Vernotte (CV) model and Fourier's law are presented in this work for comparing wave propagation modes. Independent variable translation is applied to solve the partial differential equation. Results show that the general form of the time spatial distribution of temperature for the three media comprises two solutions: those corresponding to the positive and negative logarithmic heating rates. The former shows that a group of heat waves whose spatial distribution follows the exponential function law propagates at a group speed; the speed of propagation is related to the logarithmic heating rate. The total speed of all the possible heat waves can be combined to form the group speed of the wave propagation. The latter indicates that the spatial distribution of temperature, which follows the exponential function law, decays with time. These features show that propagation accelerates when heated and decelerates when cooled. For the model media that follow Fourier's law and correspond to the positive heat rate of heat conduction, the propagation mode is also considered the propagation of a group of heat waves because the group speed has no upper bound. For the finite relaxation model with non-Fourier media, the interval of group speed is bounded and the maximum speed can be obtained when the logarithmic heating rate is exactly the reciprocal of relaxation time. And for the CV model with a non-Fourier medium, the interval of group speed is also bounded and the maximum value can be obtained when the logarithmic heating rate is infinite.

Computer modeling of the combined effects of perfusion, electrical conductivity, and thermal conductivity on tissue heating patterns in radiofrequency tumor ablation.

PubMed

Ahmed, Muneeb; Liu, Zhengjun; Humphries, Stanley; Goldberg, S Nahum

2008-11-01

To use an established computer simulation model of radiofrequency (RF) ablation to characterize the combined effects of varying perfusion, and electrical and thermal conductivity on RF heating. Two-compartment computer simulation of RF heating using 2-D and 3-D finite element analysis (ETherm) was performed in three phases (n = 88 matrices, 144 data points each). In each phase, RF application was systematically modeled on a clinically relevant template of application parameters (i.e., varying tumor and surrounding tissue perfusion: 0-5 kg/m(3)-s) for internally cooled 3 cm single and 2.5 cm cluster electrodes for tumor diameters ranging from 2-5 cm, and RF application times (6-20 min). In the first phase, outer thermal conductivity was changed to reflect three common clinical scenarios: soft tissue, fat, and ascites (0.5, 0.23, and 0.7 W/m- degrees C, respectively). In the second phase, electrical conductivity was changed to reflect different tumor electrical conductivities (0.5 and 4.0 S/m, representing soft tissue and adjuvant saline injection, respectively) and background electrical conductivity representing soft tissue, lung, and kidney (0.5, 0.1, and 3.3 S/m, respectively). In the third phase, the best and worst combinations of electrical and thermal conductivity characteristics were modeled in combination. Tissue heating patterns and the time required to heat the entire tumor +/-a 5 mm margin to >50 degrees C were assessed. Increasing background tissue thermal conductivity increases the time required to achieve a 50 degrees C isotherm for all tumor sizes and electrode types, but enabled ablation of a given tumor size at higher tissue perfusions. An inner thermal conductivity equivalent to soft tissue (0.5 W/m- degrees C) surrounded by fat (0.23 W/m- degrees C) permitted the greatest degree of tumor heating in the shortest time, while soft tissue surrounded by ascites (0.7 W/m- degrees C) took longer to achieve the 50 degrees C isotherm, and complete ablation

Modelling heat conduction in polycrystalline hexagonal boron-nitride films

PubMed Central

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

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

PubMed

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) (0conductivity can be expressed in terms of the system size L as kappa=cL(beta) with beta=2-2/alpha. This result predicts that a normal diffusion (alpha=1) implies a normal heat conduction obeying the Fourier law (beta=0), a superdiffusion (alpha>1) implies an anomalous heat conduction with a divergent thermal conductivity (beta>0), and more interestingly, a subdiffusion (alpha<1) implies an anomalous heat conduction with a convergent thermal conductivity (beta<0), consequently, the system is a thermal insulator in the thermodynamic limit. Existing numerical data support our theoretical prediction.

The combined effects of longitudinal heat conduction, flow nonuniformity and temperature nonuniformity in crossflow plate-fin heat exchangers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ranganayakulu, C.; Seetharamu, K.N.

An analysis of a crossflow plate-fin compact heat exchanger, accounting for the combined effects of two-dimensional longitudinal heat conduction through the exchanger wall and nonuniform inlet fluid flow and temperature distribution is carried out using a finite element method. A mathematical equation is developed to generate different types of fluid flow/temperature maldistribution models considering the possible deviations in fluid flow. Using these models, the exchanger effectiveness and its deterioration due to the combined effects of longitudinal heat conduction, flow nonuniformity and temperature nonuniformity are calculated for various design and operating conditions of the exchanger. It was found that the performancemore » variations are quite significant in some typical applications.« less

Characterization of Molten CZT Using Thermal Conductivity and Heat Capacity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nero, Franco; Jackson, Maxx; Stowe, Ashley

To compare thermal conductivity of a polycrystalline semiconductor to the single crystal semiconductor using thermo-physical data acquired from Simultaneous Thermal Analysis and Transient Plane Source heating.

Radial forces in a misaligned radial face seal

NASA Technical Reports Server (NTRS)

Etsion, I.

1978-01-01

Radial forces on the primary seal ring of a flat misaligned seal are analyzed, taking into account the radial variation in seal clearance. An analytical solution for both hydrostatic and hydrodynamic effects is presented that covers the whole range from zero to full angular misalignment. The net radial force on the primary seal ring is always directed so as to produce a radial eccentricity which generates inward pumping. Although the radial force is usually very small, in some cases it may be one of the reasons for excessive leakage through both the primary and secondary seals of a radial face seal.

Radial forces in a misaligned radial face seal

NASA Technical Reports Server (NTRS)

Etsion, I.

1977-01-01

Radial forces on the primary seal ring of a flat misaligned seal are analyzed, taking into account the radial variation in seal clearance. An analytical solution for both hydrostatic and hydrodynamic effects is presented that covers the whole range from zero to full angular misalignment. The net radial force on the primary seal ring is always directed so as to produce a radial eccentricity which generates inward pumping. Although the radial force is usually very small, in some cases it may be one of the reasons for excessive leakage through both the primary and secondary seals of a radial face seal.

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.

Self-sustained flow oscillations and heat transfer in radial flow through co-rotating parallel disks

NASA Astrophysics Data System (ADS)

Mochizuki, S.; Inoue, T.

1990-03-01

An experimental study was conducted to determine the fluid flow and heat transfer characteristics in a passage formed by two parallel rotating disks. The local heat transfer coefficients along the disk radius were measured in detail and the flow patterns between the two rotating disks were visualized by using paraffin mist and a laser-light sheet. It was disclosed that: (1) the self-sustained laminar flow separation which is characteristic of the stationary disks still exists even when the disks are set in motion, giving significant influence to the heat transfer; (2) for small source flow Reynolds number, Re, and large rotational Reynolds number, Re(omega), rotating stall dominates the heat transfer; and (3) heat transfer for steady laminar flow occurs only when Re is less than 1200 and Re(omega) is less than 20.

An Assessment of the Axial and Radial Dilation of a DPIMS Tantalum Cartridge for Space Shuttle Flight Experiments

NASA Technical Reports Server (NTRS)

Raj, S.V.; Ghosn, L. J.

1998-01-01

Ground-based heat treatment tests are planned on an argon gas-filled tantalum cartridge developed as pan of a Diffusion Processes in Molten Semiconductors (DPIMS) experiment conducted on NASA's Space Shuttle. The possibility that the cartridge may creep during testing and touch the furnace walls is of real concern in this program. The present paper discusses the results of calculations performed to evaluate this possibility. Deformation mechanism maps were constructed using literature data in order to identify the creep mechanism dominant under the appropriate stresses and temperatures corresponding to the test conditions. These results showed that power-law creep was dominant when the grain size of the material exceeded 55 gm but Coble creep was the important mechanism below this value of grain size. Finite element analysis was used to analyze the heat treatment tWs assuming a furnace run away condition (which is a worst case scenario) using the appropriate creep parameters corresponding to grain sizes of 1 and 100 gm. Calculations were also conducted to simulate the effect of an initial 3 tilt of the cartridge assembly, the maximum possible tilt angle. The von Mises stress and su-ain distributions were calculated assuming that the cartridge was fixed at one end as it was heated from ambient temperature to 1823 K in 1.42 h, maintained at 1823 K for 9.5 h and then further heated to an over temperature condition of 2028 K in 0.3 h. The inelastic axial and radial displacements of the cartridge walls were evaluated by resolving the von Mises strain along the corresponding directions. These calculations reveal that the maximum axial and radial displacements are expected to be about 2.9 and 0.25 mm, respectively, for both fine and coarse-grained materials at 2028 K. It was determined that these displacements occur during heat-up to temperature and creep of the cartridge is likely to be relatively insignificant irrespective of grain size. Furthermore, with a 3' tilt of

Thermal Conductivity of Single-Walled Carbon Nanotube with Internal Heat Source Studied by Molecular Dynamics Simulation

NASA Astrophysics Data System (ADS)

Li, Yuan-Wei; Cao, Bing-Yang

2013-12-01

The thermal conductivity of (5, 5) single-walled carbon nanotubes (SWNTs) with an internal heat source is investigated by using nonequilibrium molecular dynamics (NEMD) simulation incorporating uniform heat source and heat source-and-sink schemes. Compared with SWNTs without an internal heat source, i.e., by a fixed-temperature difference scheme, the thermal conductivity of SWNTs with an internal heat source is much lower, by as much as half in some cases, though it still increases with an increase of the tube length. Based on the theory of phonon dynamics, a function called the phonon free path distribution is defined to develop a simple one-dimensional heat conduction model considering an internal heat source, which can explain diffusive-ballistic heat transport in carbon nanotubes well.

Microscale Heat Conduction Models and Doppler Feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hawari, Ayman I.; Ougouag, Abderrafi

2015-01-22

The objective of this project is to establish an approach for providing the fundamental input that is needed to estimate the magnitude and time-dependence of the Doppler feedback mechanism in Very High Temperature reactors. This mechanism is the foremost contributor to the passive safety of gas-cooled, graphite-moderated high temperature reactors that use fuel based on Tristructural-Isotropic (TRISO) coated particles. Therefore, its correct prediction is essential to the conduct of safety analyses for these reactors. Since the effect is directly dependent on the actual temperature reached by the fuel during transients, the underlying phenomena of heat deposition, heat transfer and temperaturemore » rise must be correctly predicted. To achieve the above objective, this project will explore an approach that accounts for lattice effects as well as local temperature variations and the correct definition of temperature and related local effects.« less

Fast gas heating and radial distribution of active species in nanosecond capillary discharge in pure nitrogen and N2:O2 mixtures

NASA Astrophysics Data System (ADS)

Lepikhin, N. D.; Popov, N. A.; Starikovskaia, S. M.

2018-05-01

Fast gas heating is studied experimentally and numerically using pulsed nanosecond capillary discharge in pure nitrogen and N2:O2 mixtures under the conditions of high specific deposited energy (up to 1 eV/molecule) and high reduced electric fields (100–300 Td). Deposited energy, electric field and gas temperature are measured as functions of time. The radial distribution of active species is analyzed experimentally. The roles of processes involving {{{N}}}2({{B}}) ={{{N}}}2({{{B}}}3{{{\\Pi }}}{{g}},{{{W}}}3{{{Δ }}}{{u}},{{B}}{{\\prime} }3{{{Σ }}}{{u}}-), {{{N}}}2({{{A}}}3{{{Σ }}}{{u}}+) and N(2D) excited nitrogen species leading to heat release are analyzed using numerical modeling in the framework of 1D axial approximation.

Thermal conduction study of warm dense aluminum by proton differential heating

NASA Astrophysics Data System (ADS)

Ping, Y.; Kemp, G.; McKelvey, A.; Fernandez-Panella, A.; Shepherd, R.; Collins, G.; Sio, H.; King, J.; Freeman, R.; Hua, R.; McGuffey, C.; Kim, J.; Beg, F.

2016-10-01

A differential heating platform has been developed for thermal conduction study (Ping et al. PoP 2015), where a temperature gradient is induced and subsequent heat flow is probed by time-resolved diagnostics. An experiment using proton differential heating has been carried out at Titan laser for Au/Al targets. Two single-shot time-resolved diagnostics are employed, SOP (streaked optical pyrometry) for surface temperature and FDI (Fourier Domain Interferometry) for surface expansion. Hydrodynamic simulations show that after 15ps, absorption in underdense plasma needs to be taken into account to correctly interpret SOP data. Comparison between simulations with different thermal conductivity models and a set of data with varying target thickness will be presented. This work was performed under DOE contract DE-AC52-07NA27344 with support from OFES Early Career program and LLNL LDRD program.

Laser ablation under different electron heat conduction models in inertial confinement fusion

NASA Astrophysics Data System (ADS)

Li, Shuanggui; Ren, Guoli; Huo, Wen Yi

2018-06-01

In this paper, we study the influence of three different electron heat conduction models on the laser ablation of gold plane target. Different from previous studies, we concentrate on the plasma conditions, the conversion efficiency from laser into soft x rays and the scaling relation of mass ablation, which are relevant to hohlraum physics study in indirect drive inertial confinement fusion. We find that the simulated electron temperature in corona region is sensitive to the electron heat conduction models. For different electron heat conduction models, there are obvious differences in magnitude and spatial profile of electron temperature. For the flux limit model, the calculated conversion efficiency is sensitive to flux limiters. In the laser ablation of gold, most of the laser energies are converted into x rays. So the scaling relation of mass ablation rate is quite different from that of low Z materials.

Performance evaluation of cryogenic counter-flow heat exchangers with longitudinal conduction, heat in-leak and property variations

NASA Astrophysics Data System (ADS)

Jiang, Q. F.; Zhuang, M.; Zhu, Z. G.; Y Zhang, Q.; Sheng, L. H.

2017-12-01

Counter-flow plate-fin heat exchangers are commonly utilized in cryogenic applications due to their high effectiveness and compact size. For cryogenic heat exchangers in helium liquefaction/refrigeration systems, conventional design theory is no longer applicable and they are usually sensitive to longitudinal heat conduction, heat in-leak from surroundings and variable fluid properties. Governing equations based on distributed parameter method are developed to evaluate performance deterioration caused by these effects. The numerical model could also be applied in many other recuperators with different structures and, hence, available experimental data are used to validate it. For a specific case of the multi-stream heat exchanger in the EAST helium refrigerator, quantitative effects of these heat losses are further discussed, in comparison with design results obtained by the common commercial software. The numerical model could be useful to evaluate and rate the heat exchanger performance under the actual cryogenic environment.

Modeling studies for a Mars penetrator heat flow measurement

NASA Technical Reports Server (NTRS)

Keihm, S. J.; Langseth, M. G.

1976-01-01

There were, two different design concepts considered for the purpose of measuring heat flow as part of a Mars penetrator mission. The first of the tentative designs utilizes temperature sensors emplaced along the trailing umbilicus at regularly spaced intervals, no greater than 1m, which is thermally coupled to the adjacent regolith radiatively and possibly convectively or conductively. The second of the heat flow designs considered requires the radial deployment of two or more low thermal mass temperature sensors outward from the penetrator body over a vertical (depth) range on the order of 1m.

Modeling of heat conduction via fractional derivatives

NASA Astrophysics Data System (ADS)

Fabrizio, Mauro; Giorgi, Claudio; Morro, Angelo

2017-09-01

The modeling of heat conduction is considered by letting the time derivative, in the Cattaneo-Maxwell equation, be replaced by a derivative of fractional order. The purpose of this new approach is to overcome some drawbacks of the Cattaneo-Maxwell equation, for instance possible fluctuations which violate the non-negativity of the absolute temperature. Consistency with thermodynamics is shown to hold for a suitable free energy potential, that is in fact a functional of the summed history of the heat flux, subject to a suitable restriction on the set of admissible histories. Compatibility with wave propagation at a finite speed is investigated in connection with temperature-rate waves. It follows that though, as expected, this is the case for the Cattaneo-Maxwell equation, the model involving the fractional derivative does not allow the propagation at a finite speed. Nevertheless, this new model provides a good description of wave-like profiles in thermal propagation phenomena, whereas Fourier's law does not.

Analytical and numerical solutions for heat transfer and effective thermal conductivity of cracked media

NASA Astrophysics Data System (ADS)

Tran, A. B.; Vu, M. N.; Nguyen, S. T.; Dong, T. Q.; Le-Nguyen, K.

2018-02-01

This paper presents analytical solutions to heat transfer problems around a crack and derive an adaptive model for effective thermal conductivity of cracked materials based on singular integral equation approach. Potential solution of heat diffusion through two-dimensional cracked media, where crack filled by air behaves as insulator to heat flow, is obtained in a singular integral equation form. It is demonstrated that the temperature field can be described as a function of temperature and rate of heat flow on the boundary and the temperature jump across the cracks. Numerical resolution of this boundary integral equation allows determining heat conduction and effective thermal conductivity of cracked media. Moreover, writing this boundary integral equation for an infinite medium embedding a single crack under a far-field condition allows deriving the closed-form solution of temperature discontinuity on the crack and particularly the closed-form solution of temperature field around the crack. These formulas are then used to establish analytical effective medium estimates. Finally, the comparison between the developed numerical and analytical solutions allows developing an adaptive model for effective thermal conductivity of cracked media. This model takes into account both the interaction between cracks and the percolation threshold.

Heat conduction in double-walled carbon nanotubes with intertube additional carbon atoms.

PubMed

Cui, Liu; Feng, Yanhui; Tan, Peng; Zhang, Xinxin

2015-07-07

Heat conduction of double-walled carbon nanotubes (DWCNTs) with intertube additional carbon atoms was investigated for the first time using a molecular dynamics method. By analyzing the phonon vibrational density of states (VDOS), we revealed that the intertube additional atoms weak the heat conduction along the tube axis. Moreover, the phonon participation ratio (PR) demonstrates that the heat transfer in DWCNTs is dominated by low frequency modes. The added atoms cause the mode weight factor (MWF) of the outer tube to decrease and that of the inner tube to increase, which implies a lower thermal conductivity. The effects of temperature, tube length, and the number and distribution of added atoms were studied. Furthermore, an orthogonal array testing strategy was designed to identify the most important structural factor. It is indicated that the tendencies of thermal conductivity of DWCNTs with added atoms change with temperature and length are similar to bare ones. In addition, thermal conductivity decreases with the increasing number of added atoms, more evidently for atom addition concentrated at some cross-sections rather than uniform addition along the tube length. Simultaneously, the number of added atoms at each cross-section has a considerably more remarkable impact, compared to the tube length and the density of chosen cross-sections to add atoms.

Effect of recent popularity on heat-conduction based recommendation models

NASA Astrophysics Data System (ADS)

Li, Wen-Jun; Dong, Qiang; Shi, Yang-Bo; Fu, Yan; He, Jia-Lin

2017-05-01

Accuracy and diversity are two important measures in evaluating the performance of recommender systems. It has been demonstrated that the recommendation model inspired by the heat conduction process has high diversity yet low accuracy. Many variants have been introduced to improve the accuracy while keeping high diversity, most of which regard the current node-degree of an item as its popularity. However in this way, a few outdated items of large degree may be recommended to an enormous number of users. In this paper, we take the recent popularity (recently increased item degrees) into account in the heat-conduction based methods, and propose accordingly the improved recommendation models. Experimental results on two benchmark data sets show that the accuracy can be largely improved while keeping the high diversity compared with the original models.

Advective and Conductive Heat Flow Budget Across the Wagner Basin, Northern Gulf of California

NASA Astrophysics Data System (ADS)

Neumann, F.; Negrete-Aranda, R.; Contreras, J.; Müller, C.; Hutnak, M.; Gonzalez-Fernandez, A.; Harris, R. N.; Sclater, J. G.

2015-12-01

In May 2015, we conducted a cruise across the northern Gulf of California, an area of continental rift basin formation and rapid deposition of sediments. The cruise was undertaken aboard the R/V Alpha Helix; our goal was to study variation in superficial conductive heat flow, lateral changes in the shallow thermal conductivity structure, and advective transport of heat across the Wagner basin. We used a Fielax heat flow probe with 22 thermistors that can penetrate up to 6 m into the sediment cover. The resulting data set includes 53 new heat flow measurements collected along three profiles. The longest profile (42 km) contains 30 measurements spaced 1-2 km apart. The western part of the Wagner basin (hanging wall block) exhibit low to normal conductive heat flow whereas the eastern part of the basin (foot wall block) heat flow is high to very high (up to 2500 mWm-2). Two other short profiles (12 km long each) focused on resolving an extremely high heat flow anomaly up to 15 Wm-2 located near the intersection between the Wagner bounding fault system and the Cerro Prieto fault. We hypothesize that the contrasting heat flow values observed across the Wagner basin are due to horizontal water circulation through sand layers and fault pathways of high permeability. Circulation appears to be from west (recharge zone) to east (discharge zone). Additionally, our results reveal strong vertical advection of heat due to dehydration reactions and compaction of fine grained sediments.

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…

Exact solution of conductive heat transfer in cylindrical composite laminate

NASA Astrophysics Data System (ADS)

Kayhani, M. H.; Shariati, M.; Nourozi, M.; Karimi Demneh, M.

2009-11-01

This paper presents an exact solution for steady-state conduction heat transfer in cylindrical composite laminates. This laminate is cylindrical shape and in each lamina, fibers have been wound around the cylinder. In this article heat transfer in composite laminates is being investigated, by using separation of variables method and an analytical relation for temperature distribution in these laminates has been obtained under specific boundary conditions. Also Fourier coefficients in each layer obtain by solving set of equations that related to thermal boundary layer conditions at inside and outside of the cylinder also thermal continuity and heat flux continuity between each layer is considered. In this research LU factorization method has been used to solve the set of equations.

The role of anisotropic thermal conduction in a collisionless magnetized hot accretion flow

NASA Astrophysics Data System (ADS)

Ghasemnezhad, Maryam

2018-06-01

We study the importance and the effects of anisotropic thermal conduction in a collisionless magnetized advection dominated accretion flow in the presence of discontinuity of mass, angular momentum and energy between inflow and outflow. In this paper, we have considered that the thermal conduction is a heating mechanism like viscosity and leads to an increase in the temperature of the gas. A set of self similar solutions are used for steady state and axisymmetric structure of such hot accretion disc to solve the MHD equations in our model. Based on these solutions, we have found that increasing the level of two parts of anisotropic thermal conduction (parallel & transverse) results in increasing the mass accretion rate or radial velocity but decreasing the rotational velocity. Also both radial and rotational velocities are sub-Keplerian. Also we have shown that the anisotropic thermal conduction can be effective in the parameter space of specific energy of outflow, toroidal and vertical components of magnetic field according to a physical constraint tinfall ≥ t⊥, conduction.

Extended foil capacitor with radially spoked electrodes

DOEpatents

Foster, James C.

1990-01-01

An extended foil capacitor has a conductive disk electrically connected in oncrushing contact to the extended foil. A conductive paste is placed through spaces between radial spokes on the disk to electrically and mechanically connect the extended foil to the disk.

Aircraft radial-belted tire evaluation

NASA Technical Reports Server (NTRS)

Yager, Thomas J.; Stubbs, Sandy M.; Davis, Pamela A.

1990-01-01

An overview is given of the ongoing joint NASA/FAA/Industry Surface Traction And Radial Tire (START) Program being conducted at NASA Langley's Aircraft Landing Dynamics Facility (ALDF). The START Program involves tests using three different tire sizes to evaluate tire rolling resistance, braking, and cornering performance throughout the aircraft ground operational speed range for both dry and wet runway surfaces. Preliminary results from recent 40 x 14 size bias-ply, radial-belted, and H-type aircraft tire tests are discussed. The paper concludes with a summary of the current program status and planned ALDF test schedule.

Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu, Hao; Zhang, Tao; Han, Xiang

2015-08-15

An X-mode polarized V band (50 GHz–75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz–19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured bymore » the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from −1 km/s to −3 km/s.« less

Heat conduction in diatomic chains with correlated disorder

NASA Astrophysics Data System (ADS)

Savin, Alexander V.; Zolotarevskiy, Vadim; Gendelman, Oleg V.

2017-01-01

The paper considers heat transport in diatomic one-dimensional lattices, containing equal amounts of particles with different masses. Ordering of the particles in the chain is governed by single correlation parameter - the probability for two neighboring particles to have the same mass. As this parameter grows from zero to unity, the structure of the chain varies from regular staggering chain to completely random configuration, and then - to very long clusters of particles with equal masses. Therefore, this correlation parameter allows a control of typical cluster size in the chain. In order to explore different regimes of the heat transport, two interatomic potentials are considered. The first one is an infinite potential wall, corresponding to instantaneous elastic collisions between the neighboring particles. In homogeneous chains such interaction leads to an anomalous heat transport. The other one is classical Lennard-Jones interatomic potential, which leads to a normal heat transport. The simulations demonstrate that the correlated disorder of the particle arrangement does not change the convergence properties of the heat conduction coefficient, but essentially modifies its value. For the collision potential, one observes essential growth of the coefficient for fixed chain length as the limit of large homogeneous clusters is approached. The thermal transport in these models remains superdiffusive. In the Lennard-Jones chain the effect of correlation appears to be not monotonous in the limit of low temperatures. This behavior stems from the competition between formation of long clusters mentioned above, and Anderson localization close to the staggering ordered state.

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

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-12

... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-851] Certain Integrated Circuit Packages Provided with Multiple Heat- Conducting Paths and Products Containing Same; Commission Determination Not To... provided with multiple heat-conducting paths and products containing same by reason of infringement of...

Turbulent resistive heating of solar coronal arches

NASA Technical Reports Server (NTRS)

Benford, G.

1983-01-01

The possibility that coronal heating occurs by means of anomalous Joule heating by electrostatic ion cyclotron waves is examined, with consideration given to currents running from foot of a loop to the other. It is assumed that self-fields generated by the currents are absent and currents follow the direction of the magnetic field, allowing the plasma cylinder to expand radially. Ion and electron heating rates are defined within the cylinder, together with longitudinal conduction and convection, radiation and cross-field transport, all in terms of Coulomb and turbulent effects. The dominant force is identified as electrostatic ion cyclotron instability, while ion acoustic modes remain stable. Rapid heating from an initial temperature of 10 eV to 100-1000 eV levels is calculated, with plasma reaching and maintaining a temperature in the 100 eV range. Strong heating is also possible according to the turbulent Ohm's law and by resistive heating.

Nonlinear Thermal Instability in Compressible Viscous Flows Without Heat Conductivity

NASA Astrophysics Data System (ADS)

Jiang, Fei

2018-04-01

We investigate the thermal instability of a smooth equilibrium state, in which the density function satisfies Schwarzschild's (instability) condition, to a compressible heat-conducting viscous flow without heat conductivity in the presence of a uniform gravitational field in a three-dimensional bounded domain. We show that the equilibrium state is linearly unstable by a modified variational method. Then, based on the constructed linearly unstable solutions and a local well-posedness result of classical solutions to the original nonlinear problem, we further construct the initial data of linearly unstable solutions to be the one of the original nonlinear problem, and establish an appropriate energy estimate of Gronwall-type. With the help of the established energy estimate, we finally show that the equilibrium state is nonlinearly unstable in the sense of Hadamard by a careful bootstrap instability argument.

Scaling Relations for the Efficiency of Radial Migration in Disk Galaxies

NASA Astrophysics Data System (ADS)

Daniel, Kathryne J.

2018-01-01

Radial migration is frequently recognized as an internal, secular process that could play an important role in disk galaxy evolution. The driving mechanism for radial migration is transient spiral patterns, which rearrange the orbital angular momentum distribution of disk stars around corotation without causing kinematic heating. Should radial migration be an efficient process, it could cause a substantial fraction of disk stars to move large radial distances over the lifetime of the disk, thus having a significant impact on the disk’s kinematic, structural and chemical evolution. Observational and simulated data are consistent with radial migration being important for kinematically cold stellar populations and less so for populations with hot kinematics. I will present an analytic criterion that determines which stars are in orbits that could lead to radial migration. I will then show some scaling relations for the efficacy of radial migration that result from applying this analytic criterion to a series of models that have a variety of distribution functions and spiral patterns in systems with an assumed flat rotation curve. Most importantly, I will argue that these scaling relations can be used to place constraints on the efficiency of radial migration, where stronger spiral patterns and kinematically cold populations will lead to a higher fraction of stars in orbits that can lead to radial migration.

Radial evolution of ion distribution functions

NASA Technical Reports Server (NTRS)

Marsch, E.

1983-01-01

A survey of solar wind ion velocity distributions and derived parameters (temperature, ion differential speed, heat flux, adiabatic invariants) is presented with emphasis on the heliocentric distance range between 0.3 and 1 AU traversed by the Helios solar probe. The radial evolution of nonthermal features are discussed which are observed to be most pronounced at perihelion. Within the framework of quasilinear plasma theory, wave particle interactions that may shape the ion distributions are considered. Some results of a self consistent model calculation are presented accounting for ion acceleration and heating by resonant momentum and energy exchange with ion cyclotron and magnetosonic waves propagating away from the Sun along the interplanetary magnetic field. Another tentative explanation for the occurrence of large perpendicular proton temperatures is offered in terms of heating by Landau damping of lower hybrid waves.

Single-side conduction modeling for high heat flux coolant channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyd, R.D. Sr.

In the development of plasma-facing components (PFCs), most investigators have erroneously postulated negligible water critical heat flux dependence on the coolant channel length-to-diameter (L/D) ratio above a constant value of L/D. Although encouraging results have been obtained in characterizing peaking factors for local two-dimensional boiling curves and critical heat flux, additional experimental data and theoretical model development are needed to validate the applicability to PFCs. Both these and related issues will affect the flow boiling correlation and data reduction associated with the development of PFCs for fusion reactors and other physical problems that are dependent on conduction modeling in themore » heat flux spectrum of applications. Both exact solutions and numerical conjugate analyses are presented for a one-side heated (OSH) geometry. The results show (a) the coexistence of three flow regimes inside an OSH circular geometry, (b) the correlational dependence of the inside wall heat flux and temperature, and (c) inaccuracies that could arise in some data reduction procedures.« less

B2.5-Eirene modeling of radial transport in the MAGPIE linear plasma device

NASA Astrophysics Data System (ADS)

Owen, L. W.; Caneses, J. F.; Canik, J.; Lore, J. D.; Corr, C.; Blackwell, B.; Bonnin, X.; Rapp, J.

2017-05-01

Radial transport in helicon heated hydrogen plasmas in the MAGnetized Plasma Interaction Experiment (MAGPIE) is studied with the B2.5-Eirene (SOLPS5.0) code. Radial distributions of plasma density, temperature and ambipolar potential are computed for several magnetic field configurations and compared to double Langmuir probe measurements. Evidence for an unmagnetized ion population is seen in the requirement for a convective pinch term in the continuity equation in order to fit the centrally peaked density profile data. The measured slightly hollow electron temperature profiles are reproduced with combinations of on-axis and edge heating which can be interpreted as helicon and Trivelpiece-Gould wave absorption, respectively. Pressure gradient driven radial charged particle diffusion is chosen to describe the diffusive particle flux since the hollowness of the temperature profiles assists the establishment of on-axis density peaking.

Evaluation of the thermal conductance of flip-chip bonding structure utilizing the measurement based on Fourier's law of heat conduction at steady-state

NASA Astrophysics Data System (ADS)

Wu, Chia-Yu; Huang, Yin-Hsien; Wu, Hsin-Han; Hsieh, Tsung-Eong

2018-06-01

Fourier's law of heat conduction at steady-state was adopted to establish a measurement method utilizing platinum (Pt) thin-film electrodes as the heater and the temperature sensor. The thermal conductivities (κ's) of Pyrex glass, an epoxy resin and a commercial underfill for flip-chip devices were measured and a good agreement with previously reported values was obtained. The thermal boundary resistances (RTBR's) of Pt/sample interfaces were also extracted for discussing their influence on the thermal conduction of samples. Afterward, the flip-chip samples with 2×2 solder joint array utilizing Si wafers as the die and the substrate, without and with the underfills, were prepared and their thermal conductance were measured. For the sample without underfill, the air presenting in the gap of die and the substrate led to the poor thermal conductance of sample. With the insertion of underfills, the thermal conductance of flip-chip samples improved. The resistance to heat transfer across Si/underfill interfaces was also suppressed and to promote the thermal conductance of samples. The thermal properties of underfill and RTBR at Si/underfill interface were further implanted in the calculation of thermal conductance of flip-chip samples containing various solder joint arrays. The increasing number of solder joints diminished the influence of thermal conduction of underfill and RTBR of Si/underfill interface on the thermal conductance of samples. The insertion of underfill with high-κ value might promote the heat conductance of samples containing low-density solder joint arrays; however, it became insignificant in improving the heat conductance of samples containing high-density solder joint arrays.

Losses in radial inflow turbines

NASA Technical Reports Server (NTRS)

Khalil, I. M.; Tabakoff, W.; Hamed, A.

1976-01-01

A study was conducted to determine experimentally and theoretically the losses in radial inflow turbine nozzles. Extensive experimental data was obtained to investigate the flow behavior in a full-scale radial turbine stator annulus. A theoretical model to predict the losses in both the vaned and vaneless regions of the nozzle was developed. In this analysis, the interaction effects between the stator and the rotor are not considered. It was found that the losses incurred due to the end wall boundary layers can be significant, especially if they are characterized by a strong crossflow. The losses estimated using the analytical study are compared with the experimentally determined values.

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.

Oscillatory conductive heat transfer for a fiber in an ideal gas

NASA Technical Reports Server (NTRS)

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

1985-01-01

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

Modeling conductive heat transfer during high-pressure thawing processes: determination of latent heat as a function of pressure.

PubMed

Denys, S; Van Loey, A M; Hendrickx, M E

2000-01-01

A numerical heat transfer model for predicting product temperature profiles during high-pressure thawing processes was recently proposed by the authors. In the present work, the predictive capacity of the model was considerably improved by taking into account the pressure dependence of the latent heat of the product that was used (Tylose). The effect of pressure on the latent heat of Tylose was experimentally determined by a series of freezing experiments conducted at different pressure levels. By combining a numerical heat transfer model for freezing processes with a least sum of squares optimization procedure, the corresponding latent heat at each pressure level was estimated, and the obtained pressure relation was incorporated in the original high-pressure thawing model. Excellent agreement with the experimental temperature profiles for both high-pressure freezing and thawing was observed.

Ionospheric absorption, typical ionization, conductivity, and possible synoptic heating parameters in the upper atmosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, J.K.; Bhatnagar, V.P.

1989-04-01

Relations for the average energetic particle heating and the typical Hall and Pedersen conductances, as functions of the ground-based Hf radio absorption, are determined. Collis and coworkers used the geosynchronous GEOS 2 particle data to relate or ''calibrate'' the auroral absorption on the same magnetic field lines with five levels of D region ionization. These ionospheric models are related to a Chapman layer that extends these models into the E region. The average energetic particle heating is calculated for each of these models using recent expressions for the effective recombination coefficient. The corresponding height-integrated heating rates are determined and relatedmore » to the absorption with a quadratic expression. The average Hall and Pedersen conductivities are calculated for each of the nominal absorption ionospheric models. The corresponding height-integrated conductances for nighttime conditions are determined and related to the absorption. Expressions for these conductances during disturbed sunlit conditions are also determined. These relations can be used in conjunction with simultaneous ground-based riometric and magnetic observations to determines the average Hall and Pedersen currents and the Joule heating. The typical daily rate of temperature increase in the mesosphere for storm conditions is several 10 K for both the energetic particle and the Joule heating. The increasing importance of these parameters of the upper and middle atmospheres is discussed. It is proposed that northern hemisphere ionospheric, current, and heating synoptic models and parameters be investigated for use on a regular basis. copyright American Geophysical Union 1989« less

Application of the Hilbert space average method on heat conduction models.

PubMed

Michel, Mathias; Gemmer, Jochen; Mahler, Günter

2006-01-01

We analyze closed one-dimensional chains of weakly coupled many level systems, by means of the so-called Hilbert space average method (HAM). Subject to some concrete conditions on the Hamiltonian of the system, our theory predicts energy diffusion with respect to a coarse-grained description for almost all initial states. Close to the respective equilibrium, we investigate this behavior in terms of heat transport and derive the heat conduction coefficient. Thus, we are able to show that both heat (energy) diffusive behavior as well as Fourier's law follows from and is compatible with a reversible Schrödinger dynamics on the complete level of description.

A Harmonic Solution for the Hyperbolic Heat Conduction Equation and Its Relationship to the Guyer-Krumhansl Equation

NASA Astrophysics Data System (ADS)

Zhukovsky, K. V.

2018-01-01

A particular solution of the hyperbolic heat-conduction equation was constructed using the method of operators. The evolution of a harmonic solution is studied, which simulates the propagation of electric signals in long wire transmission lines. The structures of the solutions of the telegraph equation and of the Guyer-Krumhansl equation are compared. The influence of the phonon heat-transfer mechanism in the environment is considered from the point of view of heat conductivity. The fulfillment of the maximum principle for the obtained solutions is considered. The frequency dependences of heat conductivity in the telegraph equation and in an equation of the Guyer-Krumhansl type are studied and compared with each other. The influence of the Knudsen number on heat conductivity in the model of thin films is studied.

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

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.

Comparison of microwave and conduction-convection heating autohydrolysis pretreatment for bioethanol production.

PubMed

Aguilar-Reynosa, Alejandra; Romaní, Aloia; Rodríguez-Jasso, Rosa M; Aguilar, Cristóbal N; Garrote, Gil; Ruiz, Héctor A

2017-11-01

This work describes the application of two forms of heating for autohydrolysis pretreatment on isothermal regimen: conduction-convection heating and microwave heating processing using corn stover as raw material for bioethanol production. Pretreatments were performed using different operational conditions: residence time (10-50 min) and temperature (160-200°C) for both pretreatments. Subsequently, the susceptibility of pretreated solids was studied using low enzyme loads, and high substrate loads. The highest conversion was 95.1% for microwave pretreated solids. Also solids pretreated by microwave heating processing showed better ethanol conversion in simultaneous saccharification and fermentation process (92% corresponding to 33.8g/L). Therefore, microwave heating processing is a promising technology in the pretreatment of lignocellulosic materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of soft-sphere contact models for thermal heat conduction in granular flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morris, A. B.; Pannala, S.; Ma, Z.

2016-06-08

Conductive heat transfer to flowing particles occurs when two particles (or a particle and wall) come into contact. The direct conduction between the two bodies depends on the collision dynamics, namely the size of the contact area and the duration of contact. For soft-sphere discrete-particle simulations, it is computationally expensive to resolve the true collision time because doing so would require a restrictively small numerical time step. To improve the computational speed, it is common to increase the 'softness' of the material to artificially increase the collision time, but doing so affects the heat transfer. In this work, two physically-basedmore » correction terms are derived to compensate for the increased contact area and time stemming from artificial particle softening. By including both correction terms, the impact that artificial softening has on the conductive heat transfer is removed, thus enabling simulations at greatly reduced computational times without sacrificing physical accuracy.« less

Evaluation of heat transfer in acupuncture needles: convection and conduction approaches.

PubMed

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. Copyright © 2015. Published by Elsevier B.V.

Axial and radial water transport and internal water storage in tropical forest canopy trees.

Treesearch

Shelley A. James; Frederick C. Meinzer; Guillermo Goldstein; David Woodruff; Timothy Jones; Teresa Restom; Monica Mejia; Michael Clearwater; Paula Campanello

2003-01-01

Heat and stable isotope tracers were used to study axial and radial water transport in relation to sapwood anatomical characteristics and internal water storage in four canopy tree species of a seasonally dry tropical forest in Panama. Anatomical characteristics of the wood and radial profiles of sap flow were measured at the base, upper trunk, and crown of a single...

The electrothermal conductance and heat capacity of black phosphorus

NASA Astrophysics Data System (ADS)

Sengupta, Parijat; Das, Saptarshi; Shi, Junxia

2018-03-01

We study a thermal gradient induced current (It h ) flow in potassium-doped two-dimensional anisotropic black phosphorus (BP) with semi-Dirac dispersion. The prototype device is a BP channel clamped between two contacts maintained at unequal temperatures. The choice of BP lies in the predicted efficient thermoelectric behaviour. A temperature-induced difference in the Fermi levels of the two contacts drives the current (typified by the electro-thermal conductance) which we calculate using the Landauer transport equation. The current shows an initial rise when the device is operated at lower temperatures. The rise stalls at progressively higher temperatures and Ith acquires a plateau-like flat profile indicating a competing effect between a larger number of transmission modes and a corresponding drop in the Fermi level difference between the contacts. The current is computed for both n- and p-type BP, and the difference thereof is attributed to the particle-hole asymmetry. The utility of such calculations lie in conversion of the heat produced in a miniaturized chip to useful thermopower via a prototypical Seebeck power generator. Unlike the flow of Ith that purportedly utilizes the additional removable heat in a nanoscale device heat, the ability of a material to maintain a steady temperature is reflected in its heat capacity through effective absorption of thermal energy. The heat capacity is formulated in this work for BP via a Sommerfeld expansion. In the concluding part, we draw a microscopic connection between the two seemingly disparate processes of heat removal and absorption by pinning down their origin to the underlying density of states. Finally, a qualitative analysis of a Carnot-like efficiency of the considered thermoelectric engine is performed drawing upon the previous results on thermal current and heat capacity.

The electrothermal conductance and heat capacity of black phosphorus.

PubMed

Sengupta, Parijat; Das, Saptarshi; Shi, Junxia

2018-03-14

We study a thermal gradient induced current I th flow in potassium-doped two-dimensional anisotropic black phosphorus (BP) with semi-Dirac dispersion. The prototype device is a BP channel clamped between two contacts maintained at unequal temperatures. The choice of BP lies in the predicted efficient thermoelectric behaviour. A temperature-induced difference in the Fermi levels of the two contacts drives the current (typified by the electro-thermal conductance) which we calculate using the Landauer transport equation. The current shows an initial rise when the device is operated at lower temperatures. The rise stalls at progressively higher temperatures and I th acquires a plateau-like flat profile indicating a competing effect between a larger number of transmission modes and a corresponding drop in the Fermi level difference between the contacts. The current is computed for both n- and p-type BP, and the difference thereof is attributed to the particle-hole asymmetry. The utility of such calculations lie in conversion of the heat produced in a miniaturized chip to useful thermopower via a prototypical Seebeck power generator. Unlike the flow of I th that purportedly utilizes the additional removable heat in a nanoscale device heat, the ability of a material to maintain a steady temperature is reflected in its heat capacity through effective absorption of thermal energy. The heat capacity is formulated in this work for BP via a Sommerfeld expansion. In the concluding part, we draw a microscopic connection between the two seemingly disparate processes of heat removal and absorption by pinning down their origin to the underlying density of states. Finally, a qualitative analysis of a Carnot-like efficiency of the considered thermoelectric engine is performed drawing upon the previous results on thermal current and heat capacity.

Dependence of radiation belt simulations to assumed radial diffusion rates tested for two empirical models of radial transport

NASA Astrophysics Data System (ADS)

Drozdov, Alexander; Shprits, Yuri; Aseev, Nikita; Kellerman, Adam; Reeves, Geoffrey

2017-04-01

Radial diffusion is one of the dominant physical mechanisms that drives acceleration and loss of the radiation belt electrons, which makes it very important for nowcasting and forecasting space weather models. We investigate the sensitivity of the two parameterizations of the radial diffusion of Brautigam and Albert [2000] and Ozeke et al. [2014] on long-term radiation belt modeling using the Versatile Electron Radiation Belt (VERB). Following Brautigam and Albert [2000] and Ozeke et al. [2014], we first perform 1-D radial diffusion simulations. Comparison of the simulation results with observations shows that the difference between simulations with either radial diffusion parameterization is small. To take into account effects of local acceleration and loss, we perform 3-D simulations, including pitch-angle, energy and mixed diffusion. We found that the results of 3-D simulations are even less sensitive to the choice of parameterization of radial diffusion rates than the results of 1-D simulations at various energies (from 0.59 to 1.80 MeV). This result demonstrates that the inclusion of local acceleration and pitch-angle diffusion can provide a negative feedback effect, such that the result is largely indistinguishable simulations conducted with different radial diffusion parameterizations. We also perform a number of sensitivity tests by multiplying radial diffusion rates by constant factors and show that such an approach leads to unrealistic predictions of radiation belt dynamics. References Brautigam, D. H., and J. M. Albert (2000), Radial diffusion analysis of outer radiation belt electrons during the October 9, 1990, magnetic storm, J. Geophys. Res., 105(A1), 291-309, doi:10.1029/1999ja900344. Ozeke, L. G., I. R. Mann, K. R. Murphy, I. Jonathan Rae, and D. K. Milling (2014), Analytic expressions for ULF wave radiation belt radial diffusion coefficients, J. Geophys. Res. [Space Phys.], 119(3), 1587-1605, doi:10.1002/2013JA019204.

Analysis of buoyancy effect on fully developed laminar heat transfer in a rotating tube

NASA Technical Reports Server (NTRS)

Siegel, R.

1985-01-01

Laminar heat transfer is analyzed in a tube rotating about an axis perpendicular to the tube axis. The solution applies for flow that is either radially outward from the axis of rotation, or radially inward toward the axis of rotation. The conditions are fully developed, and there is uniform heat addition at the tube wall. The analysis is performed by expanding velocities and temperature in power series using the Taylor number as a perturbation parameter. Coriolis and buoyancy forces caused by tube rotation are included, and the solution is calculated through second-order terms. The secondary flow induced by the Coriolis terms always tends to increase the heat transfer coefficient; this effect can dominate for small wall heating. For radial inflow, buoyancy also tends to improve heat transfer. For radial outflow, however, buoyancy tends to reduce heat transfer; for large wall heating this effect can dominate, and there is a net reduction in heat transfer coefficient.

Self similar flow behind an exponential shock wave in a self-gravitating, rotating, axisymmetric dusty gas with heat conduction and radiation heat flux

NASA Astrophysics Data System (ADS)

Bajargaan, Ruchi; Patel, Arvind

2018-04-01

One-dimensional unsteady adiabatic flow behind an exponential shock wave propagating in a self-gravitating, rotating, axisymmetric dusty gas with heat conduction and radiation heat flux, which has exponentially varying azimuthal and axial fluid velocities, is investigated. The shock wave is driven out by a piston moving with time according to an exponential law. The dusty gas is taken to be a mixture of a non-ideal gas and small solid particles. The density of the ambient medium is assumed to be constant. The equilibrium flow conditions are maintained and energy is varying exponentially, which is continuously supplied by the piston. The heat conduction is expressed in the terms of Fourier's law, and the radiation is assumed of diffusion type for an optically thick grey gas model. The thermal conductivity and the absorption coefficient are assumed to vary with temperature and density according to a power law. The effects of the variation of heat transfer parameters, gravitation parameter and dusty gas parameters on the shock strength, the distance between the piston and the shock front, and on the flow variables are studied out in detail. It is interesting to note that the similarity solution exists under the constant initial angular velocity, and the shock strength is independent from the self gravitation, heat conduction and radiation heat flux.

Convective heat transfer for a gaseous slip flow in micropipe and parallel-plate microchannel with uniform wall heat flux: effect of axial heat conduction

NASA Astrophysics Data System (ADS)

Haddout, Y.; Essaghir, E.; Oubarra, A.; Lahjomri, J.

2017-12-01

Thermally developing laminar slip flow through a micropipe and a parallel plate microchannel, with axial heat conduction and uniform wall heat flux, is studied analytically by using a powerful method of self-adjoint formalism. This method results from a decomposition of the elliptic energy equation into a system of two first-order partial differential equations. The advantage of this method over other methods, resides in the fact that the decomposition procedure leads to a selfadjoint problem although the initial problem is apparently not a self-adjoint one. The solution is an extension of prior studies and considers a first order slip model boundary conditions at the fluid-wall interface. The analytical expressions for the developing temperature and local Nusselt number in the thermal entrance region are obtained in the general case. Therefore, the solution obtained could be extended easily to any hydrodynamically developed flow and arbitrary heat flux distribution. The analytical results obtained are compared for select simplified cases with available numerical calculations and they both agree. The results show that the heat transfer characteristics of flow in the thermal entrance region are strongly influenced by the axial heat conduction and rarefaction effects which are respectively characterized by Péclet and Knudsen numbers.

Convective heat transfer for a gaseous slip flow in micropipe and parallel-plate microchannel with uniform wall heat flux: effect of axial heat conduction

NASA Astrophysics Data System (ADS)

Haddout, Y.; Essaghir, E.; Oubarra, A.; Lahjomri, J.

2018-06-01

Thermally developing laminar slip flow through a micropipe and a parallel plate microchannel, with axial heat conduction and uniform wall heat flux, is studied analytically by using a powerful method of self-adjoint formalism. This method results from a decomposition of the elliptic energy equation into a system of two first-order partial differential equations. The advantage of this method over other methods, resides in the fact that the decomposition procedure leads to a selfadjoint problem although the initial problem is apparently not a self-adjoint one. The solution is an extension of prior studies and considers a first order slip model boundary conditions at the fluid-wall interface. The analytical expressions for the developing temperature and local Nusselt number in the thermal entrance region are obtained in the general case. Therefore, the solution obtained could be extended easily to any hydrodynamically developed flow and arbitrary heat flux distribution. The analytical results obtained are compared for select simplified cases with available numerical calculations and they both agree. The results show that the heat transfer characteristics of flow in the thermal entrance region are strongly influenced by the axial heat conduction and rarefaction effects which are respectively characterized by Péclet and Knudsen numbers.

High thermal conductivity liquid metal pad for heat dissipation in electronic devices

NASA Astrophysics Data System (ADS)

Lin, Zuoye; Liu, Huiqiang; Li, Qiuguo; Liu, Han; Chu, Sheng; Yang, Yuhua; Chu, Guang

2018-05-01

Novel thermal interface materials using Ag-doped Ga-based liquid metal were proposed for heat dissipation of electronic packaging and precision equipment. On one hand, the viscosity and fluidity of liquid metal was controlled to prevent leakage; on the other hand, the thermal conductivity of the Ga-based liquid metal was increased up to 46 W/mK by incorporating Ag nanoparticles. A series of experiments were performed to evaluate the heat dissipation performance on a CPU of smart-phone. The results demonstrated that the Ag-doped Ga-based liquid metal pad can effectively decrease the CPU temperature and change the heat flow path inside the smart-phone. To understand the heat flow path from CPU to screen through the interface material, heat dissipation mechanism was simulated and discussed.

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

NASA Technical Reports Server (NTRS)

Parker, Hermon M

1953-01-01

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

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 ΔT 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 ΔT was roughly 70 °C, due to distillation of the NaK in the evaporator.

Thermal Conductivity of Advanced Ceramic Thermal Barrier Coatings Determined by a Steady-state Laser Heat-flux Approach

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Miller, Robert A.

2004-01-01

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

A small-plane heat source method for measuring the thermal conductivities of anisotropic materials

NASA Astrophysics Data System (ADS)

Cheng, Liang; Yue, Kai; Wang, Jun; Zhang, Xinxin

2017-07-01

A new small-plane heat source method was proposed in this study to simultaneously measure the in-plane and cross-plane thermal conductivities of anisotropic insulating materials. In this method the size of the heat source element is smaller than the sample size and the boundary condition is thermal insulation due to no heat flux at the edge of the sample during the experiment. A three-dimensional model in a rectangular coordinate system was established to exactly describe the heat transfer process of the measurement system. Using the Laplace transform, variable separation, and Laplace inverse transform methods, the analytical solution of the temperature rise of the sample was derived. The temperature rises calculated by the analytical solution agree well with the results of numerical calculation. The result of the sensitivity analysis shows that the sensitivity coefficients of the estimated thermal conductivities are high and uncorrelated to each other. At room temperature and in a high-temperature environment, experimental measurements of anisotropic silica aerogel were carried out using the traditional one-dimensional plane heat source method and the proposed method, respectively. The results demonstrate that the measurement method developed in this study is effective and feasible for simultaneously obtaining the in-plane and cross-plane thermal conductivities of the anisotropic materials.

Modeling of heat flow and effective thermal conductivity of fractured media: Analytical and numerical methods

NASA Astrophysics Data System (ADS)

Nguyen, S. T.; Vu, M.-H.; Vu, M. N.; Tang, A. M.

2017-05-01

The present work aims to modeling the thermal conductivity of fractured materials using homogenization-based analytical and pattern-based numerical methods. These materials are considered as a network of cracks distributed inside a solid matrix. Heat flow through such media is perturbed by the crack system. The problem of heat flow across a single crack is firstly investigated. The classical Eshelby's solution, extended to the thermal conduction problem of an ellipsoidal inclusion embedding in an infinite homogeneous matrix, gives an analytical solution of temperature discontinuity across a non-conducting penny-shaped crack. This solution is then validated by the numerical simulation based on the finite elements method. The numerical simulation allows analyzing the effect of crack conductivity. The problem of a single crack is then extended to a medium containing multiple cracks. Analytical estimations for effective thermal conductivity, that take into account the interaction between cracks and their spatial distribution, are developed for the case of non-conducting cracks. Pattern-based numerical method is then employed for both cases non-conducting and conducting cracks. In the case of non-conducting cracks, numerical and analytical methods, both account for the spatial distribution of the cracks, fit perfectly. In the case of conducting cracks, the numerical analyzing of crack conductivity effect shows that highly conducting cracks weakly affect heat flow and the effective thermal conductivity of fractured media.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jesudason, Christopher G.

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, ∮{sub C} dS = 0 based on an infinite number of concatenated Carnot engines that approximated the said path and where for each engine ΔQ{sub 1}/T{sub 1}+ΔQ{sub 2}/T{sub 2} = 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 absorptionmore » 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

Numerical Study of Mixing Thermal Conductivity Models for Nanofluid Heat Transfer Enhancement

NASA Astrophysics Data System (ADS)

Pramuanjaroenkij, A.; Tongkratoke, A.; Kakaç, S.

2018-01-01

Researchers have paid attention to nanofluid applications, since nanofluids have revealed their potentials as working fluids in many thermal systems. Numerical studies of convective heat transfer in nanofluids can be based on considering them as single- and two-phase fluids. This work is focused on improving the single-phase nanofluid model performance, since the employment of this model requires less calculation time and it is less complicated due to utilizing the mixing thermal conductivity model, which combines static and dynamic parts used in the simulation domain alternately. The in-house numerical program has been developed to analyze the effects of the grid nodes, effective viscosity model, boundary-layer thickness, and of the mixing thermal conductivity model on the nanofluid heat transfer enhancement. CuO-water, Al2O3-water, and Cu-water nanofluids are chosen, and their laminar fully developed flows through a rectangular channel are considered. The influence of the effective viscosity model on the nanofluid heat transfer enhancement is estimated through the average differences between the numerical and experimental results for the nanofluids mentioned. The nanofluid heat transfer enhancement results show that the mixing thermal conductivity model consisting of the Maxwell model as the static part and the Yu and Choi model as the dynamic part, being applied to all three nanofluids, brings the numerical results closer to the experimental ones. The average differences between those results for CuO-water, Al2O3-water, and CuO-water nanofluid flows are 3.25, 2.74, and 3.02%, respectively. The mixing thermal conductivity model has been proved to increase the accuracy of the single-phase nanofluid simulation and to reveal its potentials in the single-phase nanofluid numerical studies.

Final Report for Project titled High Thermal Conductivity Polymer Composites for Low-Cost Heat Exchangers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thibaud-Erkey, Catherine; Alahyari, Abbas

Heat exchangers (HXs) are critical components in a wide range of heat transfer applications, from HVAC (Heating Ventilation and Cooling) to automobiles to manufacturing plants. They require materials capable of transferring heat at high rates while also minimizing thermal expansion over the usage temperature range. Conventionally, metals are used for applications where effective and efficient heat exchange is required, since many metals exhibit thermal conductivity over 100 W/m K. While metal HXs are constantly being improved, they still have some inherent drawbacks due to their metal construction, in particular corrosion. Polymeric material can offer solution to such durability issues andmore » allow designs that cannot be afforded by metal construction either due to complexity or cost. A major drawback of polymeric material is their low thermal conductivity (0.1-0.5? W/mK) that would lead to large system size. Recent improvements in the area of filled polymers have highlighted the possibility to greatly improve the thermal conductivity of polymeric materials while retaining their inherent manufacturing advantage, and have been applied to heat sink applications. Therefore, the objective of this project was to develop a robust review of materials for the manufacturing of industrial and commercial non-metallic heat exchangers. This review consisted of material identification, literature evaluation, as well as empirical and model characterization, resulting in a database of relevant material properties and characteristics to provide guidance for future heat exchanger development.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miyagi, Lowell; Department of Earth Sciences, Montana State University, Bozeman, Montana 59717; Kanitpanyacharoen, Waruntorn

2013-02-15

To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a Liermann-type diamond anvil cell with radial diffraction geometry (rDAC) was redesigned and developed for synchrotron X-ray diffraction experiments at beamline 12.2.2 of the Advanced Light Source. The rDAC, equipped with graphite heating arrays, allows simultaneous resistive and laser heating while the material is subjected to high pressure. The goals are both to extend the temperature range of external (resistive) heating and to produce environments with lower temperature gradients in a simultaneously resistive- and laser-heated rDAC. Three different geomaterials were used as pilot samples to calibrate andmore » optimize conditions for combined resistive and laser heating. For example, in Run1, FeO was loaded in a boron-mica gasket and compressed to 11 GPa then gradually resistively heated to 1007 K (1073 K at the diamond side). The laser heating was further applied to FeO to raise temperature to 2273 K. In Run2, Fe-Ni alloy was compressed to 18 GPa and resistively heated to 1785 K (1973 K at the diamond side). The combined resistive and laser heating was successfully performed again on (Mg{sub 0.9}Fe{sub 0.1})O in Run3. In this instance, the sample was loaded in a boron-kapton gasket, compressed to 29 GPa, resistive-heated up to 1007 K (1073 K at the diamond side), and further simultaneously laser-heated to achieve a temperature in excess of 2273 K at the sample position. Diffraction patterns obtained from the experiments were deconvoluted using the Rietveld method and quantified for lattice preferred orientation of each material under extreme conditions and during phase transformation.« less

Heat conduction in periodic laminates with probabilistic distribution of material properties

NASA Astrophysics Data System (ADS)

Ostrowski, Piotr; Jędrysiak, Jarosław

2017-04-01

This contribution deals with a problem of heat conduction in a two-phase laminate made of periodically distributed micro-laminas along one direction. In general, the Fourier's Law describing the heat conduction in a considered composite has highly oscillating and discontinuous coefficients. Therefore, the tolerance averaging technique (cf. Woźniak et al. in Thermomechanics of microheterogeneous solids and structures. Monografie - Politechnika Łódzka, Wydawnictwo Politechniki Łódzkiej, Łódź, 2008) is applied. Based on this technique, the averaged differential equations for a tolerance-asymptotic model are derived and solved analytically for given initial-boundary conditions. The second part of this contribution is an investigation of the effect of material properties ratio ω of two components on the total temperature field θ, by the assumption that conductivities of micro-laminas are not necessary uniquely described. Numerical experiments (Monte Carlo simulation) are executed under assumption that ω is a random variable with a fixed probability distribution. At the end, based on the obtained results, a crucial hypothesis is formulated.

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.

Determination of heat conductivity of waste glass feed and its applicability for modeling the batch-to-glass conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hujova, Miroslava; Pokorny, Richard; Klouzek, Jaroslav

The heat conductivity of reacting melter feed affects the heat transfer and conversion process in the cold cap (the reacting feed floating on molten glass). To investigate it, we simulated the feed conditions and morphology in the cold-cap by preparing “fast-dried slurry blocks”, formed by rapidly evaporating water from feed slurry poured onto a 200°C surface. A heat conductivity meter was used to measure heat conductivity of samples cut from the fast-dried slurry blocks, samples of a cold cap retrieved from a laboratory-scale melter, and loose dry powder feed samples. Our study indicates that the heat conductivity of the feedmore » in the cold cap is significantly higher than that of loose dry powder feed, resulting from the feed solidification during the water evaporation from the feed slurry. To assess the heat transfer at higher temperatures when feed turns into foam, we developed a theoretical model that predicts the foam heat conductivity based on morphology data from in-situ X-ray computed tomography. The implications for the mathematical modeling of the cold cap are discussed.« less

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

USGS Publications Warehouse

Nathenson, Menuel; Tilling, Robert I.; ,

1993-01-01

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

A model of heat transfer in sapwood and implications for sap flux density measurements using thermal dissipation probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wullschleger, Stan D; Childs, Kenneth W; King, Anthony Wayne

2011-01-01

A variety of thermal approaches are used to estimate sap flux density in stems of woody plants. Models have proven valuable tools for interpreting the behavior of heat pulse, heat balance, and heat field deformation techniques, but have seldom been used to describe heat transfer dynamics for the heat dissipation method. Therefore, to better understand the behavior of heat dissipation probes, a model was developed that takes into account the thermal properties of wood, the physical dimensions and thermal characteristics of the probes, and the conductive and convective heat transfer that occurs due to water flow in the sapwood. Probesmore » were simulated as aluminum tubes 20 mm in length and 2 mm in diameter, whereas sapwood, heartwood, and bark each had a density and water fraction that determined their thermal properties. Base simulations assumed a constant sap flux density with sapwood depth and no wounding or physical disruption of xylem beyond the 2 mm diameter hole drilled for probe installation. Simulations across a range of sap flux densities showed that the dimensionless quantity k defined as ( Tm T)/ T where Tm is the temperature differential ( T) between the heated and unheated probe under zero flow conditions was dependent on the thermal conductivity of the sapwood. The relationship between sap flux density and k was also sensitive to radial gradients in sap flux density and to xylem disruption near the probe. Monte Carlo analysis in which 1000 simulations were conducted while simultaneously varying thermal conductivity and wound diameter revealed that sap flux density and k showed considerable departure from the original calibration equation used with this technique. The departure was greatest for abrupt patterns of radial variation typical of ring-porous species. Depending on the specific combination of thermal conductivity and wound diameter, use of the original calibration equation resulted in an 81% under- to 48% over-estimation of sap flux

Thermally-Conductive Metallic Coatings and Applications for Heat Removal on In-Space Cryogenic Vehicles

NASA Technical Reports Server (NTRS)

Ameen, Lauren; Hervol, David; Waters, Deborah

2017-01-01

For large in-space cryogenic upper stages, substantial axial heat removal from a forward skirt by vapor-based heat interception may not be achieved by simple attachment methods unless sufficient thermal conductance from the skirt to the cooling fluid can be achieved. Preferable methods would allow for the addition of the cooling system to existing structure with minimal impact on the structure. Otherwise, significant modification to the basic structural design andor novel and complex attachment mechanisms with high effective thermal conductance are likely to be required. The approach being pursued by evolvable Cryogenics (eCryo) is to increase the thermal performance of a relatively simple attachment system by applying metallic or other thermally conductive material coatings to the mating surface area of the fluid channel where it is attached the skirt wall. The expectation of candidate materials is that the dramatic increase in conductivity of pure metals at temperatures close to liquid hydrogen vapor temperature will compensate for the reduced actual contact area typical of mechanical joints. Basic contact conductance data at low temperatures for candidate interface materials is required to enable the test approach. A test rig was designed at NASA Glenn Research Center to provide thermal contact resistance testing between small sample coupons coated with conductive material via electron beam evaporation, a low-temperature option that will not affect physical properties of base materials. Average coating thicknesses were 10 k. The test fixture was designed to mount directly to a cryocooler cold head within a vacuum test chamber. The purpose of this test was to determine qualitative contact conductance between various test samples. Results from this effort will be implemented in a sub-scale vapor-based heat interception test, where the applicability for increased heat removal on large structural skirts will be considered.

Illumination Profile & Dispersion Variation Effects on Radial Velocity Measurements

NASA Astrophysics Data System (ADS)

Grieves, Nolan; Ge, Jian; Thomas, Neil B.; Ma, Bo; Li, Rui; SDSS-III

2015-01-01

The Multi-object APO Radial-Velocity Exoplanet Large-Area Survey (MARVELS) measures radial velocities using a fiber-fed dispersed fixed-delay interferometer (DFDI) with a moderate dispersion spectrograph. This setup allows a unique insight into the 2D illumination profile from the fiber on to the dispersion grating. Illumination profile investigations show large changes in the profile over time and fiber location. These profile changes are correlated with dispersion changes and long-term radial velocity offsets, a major problem within the MARVELS radial velocity data. Characterizing illumination profiles creates a method to both detect and correct radial velocity offsets, allowing for better planet detection. Here we report our early results from this study including improvement of radial velocity data points from detected giant planet candidates. We also report an illumination profile experiment conducted at the Kitt Peak National Observatory using the EXPERT instrument, which has a DFDI mode similar to MARVELS. Using profile controlling octagonal-shaped fibers, long term offsets over a 3 month time period were reduced from ~50 m/s to within the photon limit of ~4 m/s.

NaK Variable Conductance Heat Pipe for Radioisotope Stirling Systems

NASA Technical Reports Server (NTRS)

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

2008-01-01

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

Simulation study on heat conduction of a nanoscale phase-change random access memory cell.

PubMed

Kim, Junho; Song, Ki-Bong

2006-11-01

We have investigated heat transfer characteristics of a nano-scale phase-change random access memory (PRAM) cell using finite element method (FEM) simulation. Our PRAM cell is based on ternary chalcogenide alloy, Ge2Sb2Te5 (GST), which is used as a recording layer. For contact area of 100 x 100 nm2, simulations of crystallization and amorphization processes were carried out. Physical quantities such as electric conductivity, thermal conductivity, and specific heat were treated as temperature-dependent parameters. Through many simulations, it is concluded that one can reduce set current by decreasing both electric conductivities of amorphous GST and crystalline GST, and in addition to these conditions by decreasing electric conductivity of molten GST one can also reduce reset current significantly.

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

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

Thermal conductive heating in fractured bedrock: Screening calculations to assess the effect of groundwater influx

NASA Astrophysics Data System (ADS)

Baston, Daniel P.; Kueper, Bernard H.

2009-02-01

A two-dimensional semi-analytical heat transfer solution is developed and a parameter sensitivity analysis performed to determine the relative importance of rock material properties (density, thermal conductivity and heat capacity) and hydrogeological properties (hydraulic gradient, fracture aperture, fracture spacing) on the ability to heat fractured rock using thermal conductive heating (TCH). The solution is developed using a Green's function approach in which an integral equation is constructed for the temperature in the fracture. Subsurface temperature distributions are far more sensitive to hydrogeological properties than material properties. The bulk ground water influx ( q) can provide a good estimate of the extent of influx cooling when influx is low to moderate, allowing the prediction of temperatures during heating without specific knowledge of the aperture and spacing of fractures. Target temperatures may not be reached or may be significantly delayed when the groundwater influx is large.

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

NASA Technical Reports Server (NTRS)

Chen, Ming-Ming; Faghri, Amir

1990-01-01

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

Reduction of ion thermal diffusivity associated with the transition of the radial electric field in neutral-beam-heated plasmas in the large helical device.

PubMed

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

2001-06-04

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

MHD convective heat transfer in a discretely heated square cavity with conductive inner block using two-phase nanofluid model.

PubMed

Alsabery, A I; Sheremet, M A; Chamkha, A J; Hashim, I

2018-05-09

The problem of steady, laminar natural convection in a discretely heated and cooled square cavity filled by an alumina/water nanofluid with a centered heat-conducting solid block under the effects of inclined uniform magnetic field, Brownian diffusion and thermophoresis is studied numerically by using the finite difference method. Isothermal heaters and coolers are placed along the vertical walls and the bottom horizontal wall, while the upper horizontal wall is kept adiabatic. Water-based nanofluids with alumina nanoparticles are chosen for investigation. The governing parameters of this study are the Rayleigh number (10 3  ≤ Ra ≤ 10 6 ), the Hartmann number (0 ≤ Ha ≤ 50), thermal conductivity ratio (0.28 ≤ k w  ≤ 16), centered solid block size (0.1 ≤ D ≤ 0.7) and the nanoparticles volume fraction (0 ≤ ϕ ≤ 0.04). The developed computational code is validated comprehensively using the grid independency test and numerical and experimental data of other authors. The obtained results reveal that the effects of the thermal conductivity ratio, centered solid block size and the nanoparticles volume fraction are non-linear for the heat transfer rate. Therefore, it is possible to find optimal parameters for the heat transfer enhancement in dependence on the considered system. Moreover, high values of the Rayleigh number and nanoparticles volume fraction characterize homogeneous distributions of nanoparticles inside the cavity. High concentration of nanoparticles can be found near the centered solid block where thermal plumes from the local heaters interact.

Conductivity Rise During Irreversible Electroporation: True Permeabilization or Heat?

PubMed

Ruarus, Alette H; Vroomen, Laurien G P H; Puijk, Robbert S; Scheffer, Hester J; Faes, Theo J C; Meijerink, Martijn R

2018-04-23

Irreversible electroporation (IRE) induces apoptosis with high-voltage electric pulses. Although the working mechanism is non-thermal, development of secondary Joule heating occurs. This study investigated whether the observed conductivity rise during IRE is caused by increased cellular permeabilization or heat development. IRE was performed in a gelatin tissue phantom, in potato tubers, and in 30 patients with unresectable colorectal liver metastases (CRLM). Continuous versus sequential pulsing protocols (10-90 vs. 10-30-30-30) were assessed. Temperature was measured using fiber-optic probes. After temperature had returned to baseline, 100 additional pulses were delivered. The primary technique efficacy of the treated CRLM was compared to the periprocedural current rise. Seven patients received ten additional pulses after a 10-min cool-down period. Temperature and current rise was higher for the continuous pulsing protocol (medians, gel: 13.05 vs. 9.55 °C and 9 amperes (A) vs. 7A; potato: 12.70 vs. 10.53 °C and 6.0A vs. 6.5A). After cooling-down, current returned to baseline in the gel phantom and near baseline values (Δ2A with continuous- and Δ5A with sequential pulsing) in the potato tubers. The current declined after cooling-down in all seven patients with CRLM, although baseline values were not reached. There was a positive correlation between current rise and primary technique efficacy (p = 0.02); however, the previously reported current increase threshold of 12-15A was reached in 13%. The observed conductivity rise during IRE is caused by both cellular permeabilization and heat development. Although a correlation between current rise and efficacy exists, the current increase threshold seems unfeasible for CRLM.

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

NASA Astrophysics Data System (ADS)

Kargel, J. S.; Furfaro, R.

2013-12-01

Thermal gradients within conductive layers of icy satellite and asteroids depend partly on heat flow, which is related to the secular decay of radioactive isotopes, to heat released by chemical phase changes, by conversion of gravitational potential energy to heat during differentiation, tidal energy dissipation, and to release of heat stored from prior periods. Thermal gradients are also dependent on the thermal conductivity of materials, which in turn depends on their composition, crystallinity, porosity, crystal fabric anisotropy, and details of their mixture with other materials. Small impurities can produce lattice defects and changes in polymerization, and thereby have a huge influence on thermal conductivity, as can cage-inclusion (clathrate) compounds. Heat flow and thermal gradients can be affected by fluid phase advection of mass and heat (in oceans or sublimating upper crusts), by refraction related to heterogeneities of thermal conductivity due to lateral variations and composition or porosity. Thermal profiles depend also on the surface temperature controlled by albedo and climate, surface relief, and latitude, orbital obliquity and surface insolation, solid state greenhouses, and endogenic heating of the surface. The thermal state of icy moon interiors and thermal gradients can be limited at depth by fluid phase advection of heat (e.g., percolating meteoric methane or gas emission), by the latent heat of phase transitions (melting, solid-state transitions, and sublimation), by solid-state convective or diapiric heat transfer, and by foundering. Rapid burial of thick volatile deposits can also affect thermal gradients. For geologically inactive or simple icy objects, most of these controls on heat flow and thermal gradients are irrelevant, but for many other icy objects they can be important, in some cases causing large lateral and depth variations in thermal gradients, large variations in heat flow, and dynamically evolving thermal states. Many of

Designing an artificial neural network using radial basis function to model exergetic efficiency of nanofluids in mini double pipe heat exchanger

NASA Astrophysics Data System (ADS)

Ghasemi, Nahid; Aghayari, Reza; Maddah, Heydar

2018-06-01

The present study aims at predicting and optimizing exergetic efficiency of TiO2-Al2O3/water nanofluid at different Reynolds numbers, volume fractions and twisted ratios using Artificial Neural Networks (ANN) and experimental data. Central Composite Design (CCD) and cascade Radial Basis Function (RBF) were used to display the significant levels of the analyzed factors on the exergetic efficiency. The size of TiO2-Al2O3/water nanocomposite was 20-70 nm. The parameters of ANN model were adapted by a training algorithm of radial basis function (RBF) with a wide range of experimental data set. Total mean square error and correlation coefficient were used to evaluate the results which the best result was obtained from double layer perceptron neural network with 30 neurons in which total Mean Square Error(MSE) and correlation coefficient (R2) were equal to 0.002 and 0.999, respectively. This indicated successful prediction of the network. Moreover, the proposed equation for predicting exergetic efficiency was extremely successful. According to the optimal curves, the optimum designing parameters of double pipe heat exchanger with inner twisted tape and nanofluid under the constrains of exergetic efficiency 0.937 are found to be Reynolds number 2500, twisted ratio 2.5 and volume fraction( v/v%) 0.05.

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.

Human body thermal images generated by conduction or radiation heat

NASA Astrophysics Data System (ADS)

Gavriloaia, Gheorghe; Sofron, Emil; Fumarel, Radu

2009-01-01

Humans and animals in general, are usually in a thermal steady state with respect to their surroundings. The tissues heat, generated at normal or diseases states, is lost to environment though several mechanisms: radiation, conduction, convection, evaporation, etc. Skin temperature is not the same on the entire body and a thermal body signature can be got. The temperature at skin level was measured by a thermistor, conduction component and by an IR camera, radiation component. A theoretical analysis using Weinhaum and JIJI model was done. The three images are investigated in order to get a cheap method for the early cancer diagnosis.

Conduction Channel Formation and Dissolution Due to Oxygen Thermophoresis/Diffusion in Hafnium Oxide Memristors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Suhas; Wang, Ziwen; Huang, Xiaopeng

Due to the favorable operating power, endurance, speed, and density., transition-metal-oxide memristors, or resistive random-access memory (RRAM) switches, are under intense development for storage-class memory. Their commercial deployment critically depends on predictive compact models based on understanding nanoscale physiocochemical forces, which remains elusive and controversial owing to the difficulties in directly observing atomic motions during resistive switching, Here, using scanning transmission synchrotron X-ray spectromicroscopy to study in situ switching of hafnium oxide memristors, we directly observed the formation of a localized oxygen-deficiency-derived conductive channel surrounded by a low-conductivity ring of excess oxygen. Subsequent thermal annealing homogenized the segregated oxygen, resettingmore » the cells toward their as-grown resistance state. We show that the formation and dissolution of the conduction channel are successfully modeled by radial thermophoresis and Fick diffusion of oxygen atoms driven by Joule heating. This confirmation and quantification of two opposing nanoscale radial forces that affect bipolar memristor switching are important components for any future physics-based compact model for the electronic switching of these devices.« less

On the stability of the exact solutions of the dual-phase lagging model of heat conduction.

PubMed

Ordonez-Miranda, Jose; Alvarado-Gil, Juan Jose

2011-04-13

The dual-phase lagging (DPL) model has been considered as one of the most promising theoretical approaches to generalize the classical Fourier law for heat conduction involving short time and space scales. Its applicability, potential, equivalences, and possible drawbacks have been discussed in the current literature. In this study, the implications of solving the exact DPL model of heat conduction in a three-dimensional bounded domain solution are explored. Based on the principle of causality, it is shown that the temperature gradient must be always the cause and the heat flux must be the effect in the process of heat transfer under the dual-phase model. This fact establishes explicitly that the single- and DPL models with different physical origins are mathematically equivalent. In addition, taking into account the properties of the Lambert W function and by requiring that the temperature remains stable, in such a way that it does not go to infinity when the time increases, it is shown that the DPL model in its exact form cannot provide a general description of the heat conduction phenomena.

Self-sustained radial oscillating flows between parallel disks

NASA Astrophysics Data System (ADS)

Mochizuki, S.; Yang, W.-J.

1985-05-01

It is pointed out that radial flow between parallel circular disks is of interest in a number of physical systems such as hydrostatic air bearings, radial diffusers, and VTOL aircraft with centrally located downward-positioned jets. The present investigation is concerned with the problem of instability in radial flow between parallel disks. A time-dependent numerical study and experiments are conducted. Both approaches reveal the nucleation, growth, migration, and decay of annular separation bubbles (i.e. vortex or recirculation zones) in the laminar-flow region. A finite-difference technique is utilized to solve the full unsteady vorticity transport equation in the theoretical procedure, while the flow patterns in the experiments are visualized with the aid of dye-injection, hydrogen-bubble, and paraffin-mist methods. It is found that the separation and reattachment of shear layers in the radial flow through parallel disks are unsteady phenomena. The sequence of nucleation, growth, migration, and decay of the vortices is self-sustained.

Evaluation of heat conduction in dental implants after exposure to hot beverages.

PubMed

Livne, Shiri; Harel, Noga; Piek, Dana; Ormianer, Zeev

2014-03-01

It is unknown if the consumption of hot beverages after implant placement poses a danger of overheating at the bone-implant interface. The purpose of this study was to investigate the effect of simulated consumption of hot beverages on the heat transfer to different dental implant types, implant sizes, and the presence of an interim restoration. A model that consisted of 2 plastic containers was constructed to simulate the oral cavity and endosseous region of the jaw. One-piece and 2-piece implants with abutments were placed into a block of bovine mandibular bone without any healing tissue, surrounded by water maintained at 37°C in the lower compartment. The abutments, which extended into the upper container, were covered with water heated to 60°C to simulate consumption of a hot substance and then were cooled down spontaneously to 37°C during 100 to 600 seconds. Five thermocouple electrodes with an accuracy of ±0.1°C were attached to each test specimen and to a computer with data recording and analysis software to record temperature changes. Repeated measures ANOVA (α=.05)was performed to determine the effect of each major factor. Heat conduction from the abutment exposed to hot liquid was significantly higher in the cervical as opposed to the apical areas of the implants. Implant type (1 piece), diameter (wider), and the absence of an interim coping had a significant effect on the maximum temperature measured and on the temperature change rate. Abutment exposure to hot liquids resulted in heat conduction to the cervical region of the implant, which could be biologically harmful in healing tissues. Heat conduction was mitigated by implant design and diameter, and by the presence of an interim prosthesis. Results may differ in clinical models. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Substrate thermal conductivity effect on heat dissipation and lifetime improvement of organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Chung, Seungjun; Lee, Jae-Hyun; Jeong, Jaewook; Kim, Jang-Joo; Hong, Yongtaek

2009-06-01

We report substrate thermal conductivity effect on heat dissipation and lifetime improvement of organic light-emitting diodes (OLEDs). Heat dissipation behavior of top-emission OLEDs fabricated on silicon, glass, and planarized stainless steel substrates was measured by using an infrared camera. Peak temperature measured from the backside of each substrate was saturated to be 21.4, 64.5, and 40.5 °C, 180 s after the OLED was operated at luminance of 10 000 cd/m2 and 80% luminance lifetime was about 198, 31, and 96 h, respectively. Efficient heat dissipation through the highly thermally conductive substrates reduced temperature increase, resulting in much improved OLED lifetime.

Transscleral thermotherapy with laser-induced and conductive heating in hamster Greene melanoma.

PubMed

Rem, Alex I; Oosterhuis, Jendo A; Keunen, Jan E E; Journée-De Korver, Hanneke G

2004-10-01

The purpose of this study was to investigate the cytotoxic effect of heat as induced by transscleral thermotherapy (TSTT), which may be of interest in the treatment of patients with choroidal melanoma. The aim of TSTT is to heat both the sclera and the tumor up to a cytotoxic temperature of about 60 degrees C. TSTT was performed in hamsters with subcutaneously implanted Greene melanoma covered by a specimen of human donor sclera of thickness 0.5, 0.7 or 0.9 mm. A newly developed applicator, which combines conductive episcleral heating at 60 degrees C with laser-induced heating, was used at laser powers ranging from 500 to 1500 mW delivered by an 810 nm diode laser, beam diameter 3 mm, and exposure time 1 min. Temperatures were measured at the scleral surface and at the sclera-tumor interface. The extent of tumor necrosis was examined by light microscopy and the sclera was examined by polarized light microscopy. Maximal depth of tumor necrosis without scleral damage was 4.4 (SD 1.5) mm. The temperature at the scleral surface after TSTT was 58.8 (SD 2.4) degrees C. The temperature at the sclera-tumor interface ranged from 56.4 (SD 3.7) degrees C at 500 mW to 65.3 (SD 4.4) degrees C at 1250 mW laser power. Structural changes to the scleral collagen started to develop at 1250 mW. TSTT with combined laser-induced and conductive heating caused cytotoxic temperatures in the tumor and the sclera, which were well tolerated by the scleral collagen.

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

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 visual study of radial inward choked flow of liquid nitrogen

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Simoneau, R. J.; Hsu, Y. Y.

1973-01-01

A visual study of the radial inward choked flow of liquid nitrogen was conducted. Data and high speed moving pictures were obtained. The study indicated the following: (1) steady radial inward choked flow seems equivalent to steady choked flow through axisymmetric nozzles, (2) transient choked flows through the radial gap are not uniform and the discharge pattern appears as nonuniform impinging jets, and (3) the critical mass flow rate data for the transient case appear different from those of the steady case.

Market Assessment and Commercialization Strategy for the Radial Sandia Cooler

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goetzler, William; Shandross, Richard; Weintraub, Daniel

This market assessment and commercialization report characterizes and assesses the market potential of the rotating heat exchanger technology developed at Sandia National Laboratories (SNL), known as the Radial Sandia Cooler. The RSC is a novel, motor-driven, rotating, finned heat exchanger technology. The RSC was evaluated for the residential, commercial, industrial, and transportation markets. Recommendations for commercialization were made based on assessments of the prototype RSC and the Sandia Cooler technology in general, as well as an in-depth analysis of the six most promising products for initial RSC commercialization.

A Saturnian cam current system driven by asymmetric thermospheric heating

NASA Astrophysics Data System (ADS)

Smith, C. G. A.

2011-02-01

We show that asymmetric heating of Saturn's thermosphere can drive a current system consistent with the magnetospheric ‘cam’ proposed by Espinosa, Southwood & Dougherty. A geometrically simple heating distribution is imposed on the Northern hemisphere of a simplified three-dimensional global circulation model of Saturn's thermosphere. Currents driven by the resulting winds are calculated using a globally averaged ionosphere model. Using a simple assumption about how divergences in these currents close by flowing along dipolar field lines between the Northern and Southern hemispheres, we estimate the magnetic field perturbations in the equatorial plane and show that they are broadly consistent with the proposed cam fields, showing a roughly uniform field implying radial and azimuthal components in quadrature. We also identify a small longitudinal phase drift in the cam current with radial distance as a characteristic of a thermosphere-driven current system. However, at present our model does not produce magnetic field perturbations of the required magnitude, falling short by a factor of ˜100, a discrepancy that may be a consequence of an incomplete model of the ionospheric conductance.

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

PubMed

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.

Influence of heat conducting substrates on explosive crystallization in thin layers

NASA Astrophysics Data System (ADS)

Schneider, Wilhelm

2017-09-01

Crystallization in a thin, initially amorphous layer is considered. The layer is in thermal contact with a substrate of very large dimensions. The energy equation of the layer contains source and sink terms. The source term is due to liberation of latent heat in the crystallization process, while the sink term is due to conduction of heat into the substrate. To determine the latter, the heat diffusion equation for the substrate is solved by applying Duhamel's integral. Thus, the energy equation of the layer becomes a heat diffusion equation with a time integral as an additional term. The latter term indicates that the heat loss due to the substrate depends on the history of the process. To complete the set of equations, the crystallization process is described by a rate equation for the degree of crystallization. The governing equations are then transformed to a moving co-ordinate system in order to analyze crystallization waves that propagate with invariant properties. Dual solutions are found by an asymptotic expansion for large activation energies of molecular diffusion. By introducing suitable variables, the results can be presented in a universal form that comprises the influence of all non-dimensional parameters that govern the process. Of particular interest for applications is the prediction of a critical heat loss parameter for the existence of crystallization waves with invariant properties.

Observation of Electron Bernstein Wave Heating in the RFP

NASA Astrophysics Data System (ADS)

Seltzman, Andrew; Anderson, Jay; Goetz, John; Forest, Cary

2017-10-01

The first observation of RF heating in a reversed field pinch (RFP) using the electron Bernstein wave (EBW) has been demonstrated on MST. Efficient mode conversion of an outboard-launched X mode wave at 5.5 GHz leads to Doppler-shifted resonant absorption (ωrf = nωce-k||v||) for a broad range (n =1-7) of harmonics. The dynamics of EBW-heated electrons are measured using a spatial distribution of solid targets with diametrically opposed x-ray detectors. EBW heating produces a clear supra-thermal electron tail in MST. Radial deposition of the EBW is controlled with |B|and is measured using the HXR flux emitted from an insertable probe. In the thick-shelled MST RFP, the radial accessibility of EBW is limited to r/a >0.8 ( 10cm) by magnetic field error induced by the porthole necessary for the antenna. Experimental measurements show EBW propagation inward through a stochastic magnetic field. EBW-heated test electrons are used as a direct probe of edge (r/a >0.9) radial transport, showing a modest transition from `standard' to reduced-tearing RFP operation. Electron loss is too fast for collisional effects and implies a large non-collisional radial diffusivity. EBW heating has been demonstrated in reduced magnetic stochasticity plasmas with β = 15-20%. Work supported by USDOE.

Microgravity condensing heat exchanger

NASA Technical Reports Server (NTRS)

Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor); North, Andrew (Inventor); Weislogel, Mark M. (Inventor)

2011-01-01

A heat exchanger having a plurality of heat exchanging aluminum fins with hydrophilic condensing surfaces which are stacked and clamped between two cold plates. The cold plates are aligned radially along a plane extending through the axis of a cylindrical duct and hold the stacked and clamped portions of the heat exchanging fins along the axis of the cylindrical duct. The fins extend outwardly from the clamped portions along approximately radial planes. The spacing between fins is symmetric about the cold plates, and are somewhat more closely spaced as the angle they make with the cold plates approaches 90.degree.. Passageways extend through the fins between vertex spaces which provide capillary storage and communicate with passageways formed in the stacked and clamped portions of the fins, which communicate with water drains connected to a pump externally to the duct. Water with no entrained air is drawn from the capillary spaces.

Laser-heated emissive plasma probe.

PubMed

Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K

2008-08-01

Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808 nm wavelength and an output power up to 50 W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hsin; Porter, Wallace D; Bottner, Harold

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)more » 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.« less

Heat capacities and thermal conductivities of AmO 2 and AmO 1.5

NASA Astrophysics Data System (ADS)

Nishi, Tsuyoshi; Itoh, Akinori; Ichise, Kenichi; Arai, Yasuo

2011-07-01

The thermal diffusivity of AmO 2 was measured from 473 to 773 K and that of AmO 1.5 between 473 and 1373 K using a laser flash method. The enthalpy increment of AmO 2 was measured from 335 to 1081 K and that of AmO 1.5 between 335 and 1086 K using drop calorimetry. The heat capacities of AmO 2 and AmO 1.5 were derived from the enthalpy increment measurements. The thermal conductivity was determined from the measured thermal diffusivity, heat capacity and bulk density. The heat capacities of AmO 2 was found larger than that of AmO 1.5. The thermal conductivities of AmO 2 and AmO 1.5 were found to decrease with increasing temperature in the investigated temperature range. The thermal conductivity of AmO 1.5 with A -type hexagonal structure was smaller than that of AmO 2 with C-type fluorite structure but larger than that of sub-stoichiometric AmO 1.73.

Heat conductivity in graphene and related materials: A time-domain modal analysis

NASA Astrophysics Data System (ADS)

Gill-Comeau, Maxime; Lewis, Laurent J.

2015-11-01

We use molecular dynamics (MD) simulations to study heat conductivity in single-layer graphene and graphite. We analyze the MD trajectories through a time-domain modal analysis and show that this is essential for obtaining a reliable representation of the heat flow in graphene and graphite as it permits the proper treatment of collective vibrational excitations, in contrast to a frequency-domain formulation. Our temperature-dependent results are in very good agreement with experiment and, for temperatures in the range 300-1200 K, we find that the ZA branch allows more heat flow than all other branches combined while the contributions of the TA, LA, and ZO branches are comparable at all temperatures. Conductivity mappings reveal strong collective excitations associated with low-frequency ZA modes. We demonstrate that these collective effects are a consequence of the quadratic nature of the ZA branch as they also show up in graphite but are reduced in strained graphene, where the dispersion becomes linear, and are absent in diamond, where acoustic branches are linear. In general, neglecting collective excitations yields errors similar to those from the single-mode relaxation-time approximation.

Experimental study on flame pattern formation and combustion completeness in a radial microchannel

NASA Astrophysics Data System (ADS)

Fan, Aiwu; Minaev, Sergey; Kumar, Sudarshan; Liu, Wei; Maruta, Kaoru

2007-12-01

Combustion behavior in a radial microchannel with a gap of 2.0 mm and a diameter of 50 mm was experimentally investigated. In order to simulate the heat recirculation, which is an essential strategy in microscale combustion devices, positive temperature gradients along the radial flow direction were given to the microchannel by an external heat source. A methane-air mixture was supplied from the center of the top plate through a 4.0 mm diameter delivery tube. A variety of flame patterns, including a stable circular flame and several unstable flame patterns termed unstable circular flame, single and double pelton-like flames, traveling flame and triple flame, were observed in the experiments. The regime diagram of all these flame patterns is presented in this paper. Some characteristics of the various flame patterns, such as the radii of stable and unstable circular flames, major combustion products and combustion efficiencies of all these flame patterns, were also investigated. Furthermore, the effect of the heat recirculation on combustion stability was studied by changing the wall temperature levels.

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).

Manipulating Steady Heat Conduction by Sensu-shaped Thermal Metamaterials

PubMed Central

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

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

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.

Measurements of mineral thermal conductivity at high pressures and temperatures with the laser-heated diamond anvil cell

NASA Astrophysics Data System (ADS)

McGuire, C. P.; Rainey, E.; Kavner, A.

2016-12-01

The high-pressure, high-temperature thermal conductivities of lower mantle oxides and silicates play an important role in governing the heat flow across the core-mantle boundary, and the thermal conductivity of core materials determines, at first order, the power required to run the geodynamo. Uncertainties in the pressure-dependence and compositional-dependence of thermal conductivities has complicated our understanding of the heat flow in the deep earth and has implications for the geodynamo mechanism (Buffett, 2012). The goal of this study is to measure how thermal conductivity varies with pressure and composition using a technique that combines temperature measurements as a function of power input in the laser-heated diamond anvil cell (LHDAC) with a model of three-dimensional heat flow (Rainey & Kavner, 2014). In one set of experiments, we measured temperature versus laser-power for iron, iron silicide, and stainless steel (Fe:Cr:Ni = 70:19:11 wt%), using a variety of insulating layers. In another set of experiments, we measured temperature vs. laser power for a series of Fe-bearing periclase (Mg1-x,FexO) samples, with compositions ranging from x = .24 to x = .78. These experiments were conducted up to pressures of 25 GPa and temperatures of 2800 K. A numerical model for heat conduction in the LHDAC is used to forward model the temperature versus laser power curves at successive pressures, solving for the change in thermal conductivity of the material required to best reproduce the measurements. The heat flow model is implemented using a finite element full-approximation storage (FAS) multi-grid solver, which allows for efficient computation with flexible inputs for geometry and material properties in the diamond anvil cell (Rainey et al., 2013). We use the results of our experiments and model to extract pressure and compositional dependencies of thermal conductivity for the materials described herein. The results are used to help constrain models of the

Simultaneous measurement of thermal conductivity and heat capacity of bulk and thin film materials using frequency-dependent transient thermoreflectance method.

PubMed

Liu, Jun; Zhu, Jie; Tian, Miao; Gu, Xiaokun; Schmidt, Aaron; Yang, Ronggui

2013-03-01

The increasing interest in the extraordinary thermal properties of nanostructures has led to the development of various measurement techniques. Transient thermoreflectance method has emerged as a reliable measurement technique for thermal conductivity of thin films. In this method, the determination of thermal conductivity usually relies much on the accuracy of heat capacity input. For new nanoscale materials with unknown or less-understood thermal properties, it is either questionable to assume bulk heat capacity for nanostructures or difficult to obtain the bulk form of those materials for a conventional heat capacity measurement. In this paper, we describe a technique for simultaneous measurement of thermal conductivity κ and volumetric heat capacity C of both bulk and thin film materials using frequency-dependent time-domain thermoreflectance (TDTR) signals. The heat transfer model is analyzed first to find how different combinations of κ and C determine the frequency-dependent TDTR signals. Simultaneous measurement of thermal conductivity and volumetric heat capacity is then demonstrated with bulk Si and thin film SiO2 samples using frequency-dependent TDTR measurement. This method is further testified by measuring both thermal conductivity and volumetric heat capacity of novel hybrid organic-inorganic thin films fabricated using the atomic∕molecular layer deposition. Simultaneous measurement of thermal conductivity and heat capacity can significantly shorten the development∕discovery cycle of novel materials.

Periodic composites: quasi-uniform heat conduction, Janus thermal illusion, and illusion thermal diodes

NASA Astrophysics Data System (ADS)

Xu, Liujun; Jiang, Chaoran; Shang, Jin; Wang, Ruizhe; Huang, Jiping

2017-11-01

Manipulating thermal conductivities at will plays a crucial role in controlling heat flow. By developing an effective medium theory including periodicity, here we experimentally show that nonuniform media can exhibit quasi-uniform heat conduction. This provides capabilities in proposing Janus thermal illusion and illusion thermal rectification. For the former, we study, via experiment and theory, a big periodic composite containing a small periodic composite with circular or elliptic particles. As a result, we reveal the Janus thermal illusion that describes the whole periodic system with both invisibility illusion along one direction and visibility illusion along the perpendicular direction, which is fundamentally different from the existing thermal illusions for misleading thermal detection. Further, the Janus illusion helps to design two different periodic systems that both work as thermal diodes but with nearly the same temperature distribution, heat fluxes and rectification ratios, thus being called illusion thermal diodes. Such thermal diodes differ from those extensively studied in the literature, and are useful for the areas that require both thermal rectification and thermal camouflage. This work not only opens a door for designing novel periodic composites in thermal camouflage and heat rectification, but also holds for achieving similar composites in other disciplines like electrostatics, magnetostatics, and particle dynamics.

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

NASA Astrophysics Data System (ADS)

Kök, M.; Aydoǧdu, Y.

2007-04-01

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

Mathematical modeling of radiative-conductive heat transfer in semitransparent medium with phase change

NASA Astrophysics Data System (ADS)

Savvinova, Nadezhda A.; Sleptsov, Semen D.; Rubtsov, Nikolai A.

2017-11-01

A mathematical phase change model is a formulation of the Stefan problem. Various formulations of the Stefan problem modeling of radiative-conductive heat transfer during melting or solidification of a semitransparent material are presented. Analysis of numerical results show that the radiative heat transfer has a significant effect on temperature distributions during melting (solidification) of the semitransparent material. In this paper conditions for application of various statements of the Stefan problem are analyzed.

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

NASA Technical Reports Server (NTRS)

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

1976-01-01

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

Soil impact on the radial growth of Taxodium ( Taxodium distichum (L.) Rich.) in Serbia

NASA Astrophysics Data System (ADS)

Jokanovic, D.; Popovic, V.; Vilotic, D.; Mitrovic, S.; Brasanac-Bosanac, Lj.

2012-04-01

This work presents results of analyzed radial development, quantity of radial growth and soil factors in two plantations in Serbia. One of them is located close to Backa Palanka area, and the other is in Belgrade , area of a big war island. Both of them were established at the same type of soil. The research was conducted on 27 years old trees. For both of these locations there were a number of dates which were measured, such as physical-chemical characteristics of the soil and current radial growth that was measured among 20 % widest trees - those parameters were the most important. By comparison between values and form of a current radial growth it was concluded that Taxodium trees in a plantation near Backa Palanka have a culmination of a current radial growth a bit earlier and with some bigger values than those that originate from Belgrade - big war island. There was compared radial development and it was concluded that the trees from Backa Palanka reach bigger radial values than those from Belgrade - big war island at the same age as well. There were some differences between these locations based on physical-chemical analyze conducted on a soil, so the differences in a radial development, form and values of a current radial growth can be explained with a soil influence, and it will be proofed over the following period in this scientific research.

Thermal conductivity study of warm dense matter by differential heating on LCLS and Titan

NASA Astrophysics Data System (ADS)

Hill, M.; McKelvey, A.; Jiang, S.; Shepherd, R.; Hau-Riege, S.; Whitley, H.; Sterne, P.; Hamel, S.; Collins, G.; Ping, Y.; Brown, C.; Floyd, E.; Fyrth, J.; Hoarty, D.; Hua, R.; Bailly-Grandvaux, M.; Beg, F.; Cho, B.; Kim, M.; Lee, J.; Lee, H.; Galtier, E.

2017-10-01

A differential heating platform has been developed for thermal conduction study, where a temperature gradient is induced and subsequent heat flow is probed by time-resolved diagnostics. Multiple experiment using this platform have been carried out at LCLS-MEC and Titan laser facilities for warm dense Al, Fe, amorphous carbon and diamond. Two single-shot time-resolved diagnostics are employed, SOP (streaked optical pyrometry) for surface temperature and FDI (Fourier Domain Interferometry) for surface expansion. Both diagnostics provided excellent data to constrain release equation-of-state (EOS) and thermal conductivity. Data sets with varying target thickness and comparison between simulations with different thermal conductivity models are presented. This work was performed under DOE contract DE-AC52-07NA27344 with support from DOE OFES Early Career program and LLNL LDRD program.

Anterior transposition of the radial nerve--a cadaveric study.

PubMed

Yakkanti, Madhusudhan R; Roberts, Craig S; Murphy, Joshua; Acland, Robert D

2008-01-01

The radial nerve is at risk during the posterior plating of the humerus. The purpose of this anatomic study was to assess the extent of radial nerve dissection required for anterior transposition through the fracture site (transfracture anterior transposition). A cadaver study was conducted approaching the humerus by a posterior midline incision. The extent of dissection of the nerve necessary for plate fixation of the humerus fracture was measured. An osteotomy was created to model a humeral shaft fracture at the spiral groove (OTA classification 12-A2, 12-A3). The radial nerve was then transposed anterior to the humeral shaft through the fracture site. The additional dissection of the radial nerve and the extent of release of soft tissue from the humerus shaft to achieve the transposition were measured. Plating required a dissection of the radial nerve 1.78 cm proximal and 2.13 cm distal to the spiral groove. Transfracture anterior transposition of the radial nerve required an average dissection of 2.24 cm proximal and 2.68 cm distal to the spiral groove. The lateral intermuscular septum had to be released for 2.21 cm on the distal fragment to maintain laxity of the transposed nerve. Transfracture anterior transposition of the radial nerve before plating is feasible with dissection proximal and distal to the spiral groove and elevation of the lateral intermuscular septum. Potential clinical advantages of this technique include enhanced fracture site visualization, application of broader plates, and protection of the radial nerve during the internal fixation.

Structural, dynamic, and vibrational properties during heat transfer in Si/Ge superlattices: A Car-Parrinello molecular dynamics study

NASA Astrophysics Data System (ADS)

Ji, Pengfei; Zhang, Yuwen; Yang, Mo

2013-12-01

The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective.

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.

Estimation of interfacial heat transfer coefficient in inverse heat conduction problems based on artificial fish swarm algorithm

NASA Astrophysics Data System (ADS)

Wang, Xiaowei; Li, Huiping; Li, Zhichao

2018-04-01

The interfacial heat transfer coefficient (IHTC) is one of the most important thermal physical parameters which have significant effects on the calculation accuracy of physical fields in the numerical simulation. In this study, the artificial fish swarm algorithm (AFSA) was used to evaluate the IHTC between the heated sample and the quenchant in a one-dimensional heat conduction problem. AFSA is a global optimization method. In order to speed up the convergence speed, a hybrid method which is the combination of AFSA and normal distribution method (ZAFSA) was presented. The IHTC evaluated by ZAFSA were compared with those attained by AFSA and the advanced-retreat method and golden section method. The results show that the reasonable IHTC is obtained by using ZAFSA, the convergence of hybrid method is well. The algorithm based on ZAFSA can not only accelerate the convergence speed, but also reduce the numerical oscillation in the evaluation of IHTC.

Integral methods of solving boundary-value problems of nonstationary heat conduction and their comparative analysis

NASA Astrophysics Data System (ADS)

Kot, V. A.

2017-11-01

The modern state of approximate integral methods used in applications, where the processes of heat conduction and heat and mass transfer are of first importance, is considered. Integral methods have found a wide utility in different fields of knowledge: problems of heat conduction with different heat-exchange conditions, simulation of thermal protection, Stefantype problems, microwave heating of a substance, problems on a boundary layer, simulation of a fluid flow in a channel, thermal explosion, laser and plasma treatment of materials, simulation of the formation and melting of ice, inverse heat problems, temperature and thermal definition of nanoparticles and nanoliquids, and others. Moreover, polynomial solutions are of interest because the determination of a temperature (concentration) field is an intermediate stage in the mathematical description of any other process. The following main methods were investigated on the basis of the error norms: the Tsoi and Postol’nik methods, the method of integral relations, the Gudman integral method of heat balance, the improved Volkov integral method, the matched integral method, the modified Hristov method, the Mayer integral method, the Kudinov method of additional boundary conditions, the Fedorov boundary method, the method of weighted temperature function, the integral method of boundary characteristics. It was established that the two last-mentioned methods are characterized by high convergence and frequently give solutions whose accuracy is not worse that the accuracy of numerical solutions.

Below and above boiling point comparison of microwave irradiation and conductive heating for municipal sludge digestion under identical heating/cooling profiles.

PubMed

Hosseini Koupaie, E; Eskicioglu, C

2015-01-01

This research provides a comprehensive comparison between microwave (MW) and conductive heating (CH) sludge pretreatments under identical heating/cooling profiles at below and above boiling point temperatures. Previous comparison studies were constrained to an uncontrolled or a single heating rate due to lack of a CH equipment simulating MW under identical thermal profiles. In this research, a novel custom-built pressure-sealed vessel which could simulate MW pretreatment under identical heating/cooling profiles was used for CH pretreatment. No statistically significant difference was proven between MW and CH pretreatments in terms of sludge solubilization, anaerobic biogas yield and organics biodegradation rate (p-value>0.05), while statistically significant effects of temperature and heating rate were observed (p-value<0.05). These results explain the contradictory results of previous studies in which only the final temperature (not heating/cooling rates) was controlled. Copyright © 2015 Elsevier Ltd. All rights reserved.

Heat transfer in rotating serpentine passages with selected model orientation for smooth or skewed trip walls

NASA Technical Reports Server (NTRS)

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

1993-01-01

Experiments were conducted to determine the effects of model orientation as well as buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. Turbine blades have internal coolant passage surfaces at the leading and trailing edges of the airfoil with surfaces at angles which are as large as +/- 50 to 60 degrees to the axis of rotation. Most of the previously-presented, multiple-passage, rotating heat transfer experiments have focused on radial passages aligned with the axis of rotation. Results from serpentine passages with orientations 0 and 45 degrees to the axis of rotation which simulate the coolant passages for the mid chord and trailing edge regions of the rotating airfoil are compared. The experiments were conducted with rotation in both directions to simulate serpentine coolant passages with the rearward flow of coolant or with the forward flow of coolant. The experiments were conducted for passages with smooth surfaces and with 45 degree trips adjacent to airfoil surfaces for the radial portion of the serpentine passages. At a typical flow condition, the heat transfer on the leading surfaces for flow outward in the first passage with smooth walls was twice as much for the model at 45 degrees compared to the model at 0 degrees. However, the differences for the other passages and with trips were less. In addition, the effects of buoyancy and Coriolis forces on heat transfer in the rotating passage were decreased with the model at 45 degrees, compared to the results at 0 degrees. The heat transfer in the turn regions and immediately downstream of the turns in the second passage with flow inward and in the third passage with flow outward was also a function of model orientation with differences as large as 40 to 50 percent occurring between the model orientations with forward flow and rearward flow of coolant.

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

Thermally stratified flow of second grade fluid with non-Fourier heat flux and temperature dependent thermal conductivity

NASA Astrophysics Data System (ADS)

Khan, M. Ijaz; Zia, Q. M. Zaigham; Alsaedi, A.; Hayat, T.

2018-03-01

This attempt explores stagnation point flow of second grade material towards an impermeable stretched cylinder. Non-Fourier heat flux and thermal stratification are considered. Thermal conductivity dependents upon temperature. Governing non-linear differential system is solved using homotopic procedure. Interval of convergence for the obtained series solutions is explicitly determined. Physical quantities of interest have been examined for the influential variables entering into the problems. It is examined that curvature parameter leads to an enhancement in velocity and temperature. Further temperature for non-Fourier heat flux model is less than Fourier's heat conduction law.

A genetic algorithm-based optimization model for pool boiling heat transfer on horizontal rod heaters at isolated bubble regime

NASA Astrophysics Data System (ADS)

Alavi Fazel, S. Ali

2017-09-01

A new optimized model which can predict the heat transfer in the nucleate boiling at isolated bubble regime is proposed for pool boiling on a horizontal rod heater. This model is developed based on the results of direct observations of the physical boiling phenomena. Boiling heat flux, wall temperature, bubble departing diameter, bubble generation frequency and bubble nucleation site density have been experimentally measured. Water and ethanol have been used as two different boiling fluids. Heating surface was made by several metals and various degrees of roughness. The mentioned model considers various mechanisms such as latent heat transfer due to micro-layer evaporation, transient conduction due to thermal boundary layer reformation, natural convection, heat transfer due to the sliding bubbles and bubble super-heating. The fractional contributions of individual mentioned heat transfer mechanisms have been calculated by genetic algorithm. The results show that at wall temperature difference more that about 3 K, bubble sliding transient conduction, non-sliding transient conduction, micro-layer evaporation, natural convection, radial forced convection and bubble super-heating have higher to lower fractional contributions respectively. The performance of the new optimized model has been verified by comparison of the existing experimental data.

Conduction block of mammalian myelinated nerve by local cooling to 15–30°C after a brief heating

PubMed Central

Zhang, Zhaocun; Lyon, Timothy D.; Kadow, Brian T.; Shen, Bing; Wang, Jicheng; Lee, Andy; Kang, Audry; Roppolo, James R.; de Groat, William C.

2016-01-01

This study aimed at understanding thermal effects on nerve conduction and developing new methods to produce a reversible thermal block of axonal conduction in mammalian myelinated nerves. In 13 cats under α-chloralose anesthesia, conduction block of pudendal nerves (n = 20) by cooling (5–30°C) or heating (42–54°C) a small segment (9 mm) of the nerve was monitored by the urethral striated muscle contractions and increases in intraurethral pressure induced by intermittent (5 s on and 20 s off) electrical stimulation (50 Hz, 0.2 ms) of the nerve. Cold block was observed at 5–15°C while heat block occurred at 50–54°C. A complete cold block up to 10 min was fully reversible, but a complete heat block was only reversible when the heating duration was less than 1.3 ± 0.1 min. A brief (<1 min) reversible complete heat block at 50–54°C or 15 min of nonblock mild heating at 46–48°C significantly increased the cold block temperature to 15–30°C. The effect of heating on cold block fully reversed within ∼40 min. This study discovered a novel method to block mammalian myelinated nerves at 15–30°C, providing the possibility to develop an implantable device to block axonal conduction and treat many chronic disorders. The effect of heating on cold block is of considerable interest because it raises many basic scientific questions that may help reveal the mechanisms underlying cold or heat block of axonal conduction. PMID:26740534

Thermophoretically induced large-scale deformations around microscopic heat centers

NASA Astrophysics Data System (ADS)

Puljiz, Mate; Orlishausen, Michael; Köhler, Werner; Menzel, Andreas M.

2016-05-01

Selectively heating a microscopic colloidal particle embedded in a soft elastic matrix is a situation of high practical relevance. For instance, during hyperthermic cancer treatment, cell tissue surrounding heated magnetic colloidal particles is destroyed. Experiments on soft elastic polymeric matrices suggest a very long-ranged, non-decaying radial component of the thermophoretically induced displacement fields around the microscopic heat centers. We theoretically confirm this conjecture using a macroscopic hydrodynamic two-fluid description. Both thermophoretic and elastic effects are included in this theory. Indeed, we find that the elasticity of the environment can cause the experimentally observed large-scale radial displacements in the embedding matrix. Additional experiments confirm the central role of elasticity. Finally, a linearly decaying radial component of the displacement field in the experiments is attributed to the finite size of the experimental sample. Similar results are obtained from our theoretical analysis under modified boundary conditions.

Effect of Cattaneo-Christov heat flux on Jeffrey fluid flow with variable thermal conductivity

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Javed, Mehwish; Imtiaz, Maria; Alsaedi, Ahmed

2018-03-01

This paper presents the study of Jeffrey fluid flow by a rotating disk with variable thickness. Energy equation is constructed by using Cattaneo-Christov heat flux model with variable thermal conductivity. A system of equations governing the model is obtained by applying boundary layer approximation. Resulting nonlinear partial differential system is transformed to ordinary differential system. Homotopy concept leads to the convergent solutions development. Graphical analysis for velocities and temperature is made to examine the influence of different involved parameters. Thermal relaxation time parameter signifies that temperature for Fourier's heat law is more than Cattaneo-Christov heat flux. A constitutional analysis is made for skin friction coefficient and heat transfer rate. Effects of Prandtl number on temperature distribution and heat transfer rate are scrutinized. It is observed that larger Reynolds number gives illustrious temperature distribution.

Heat transfer device

NASA Technical Reports Server (NTRS)

Kalkbrenner, R. W. (Inventor)

1974-01-01

A heat transfer device is characterized by an hermetically sealed tubular housing including a tubular shell terminating in spaced end plates, and a tubular mesh wick concentrically arranged and operatively supported within said housing. The invention provides an improved wicking restraint formed as an elongated and radially expanded tubular helix concentrically related to the wick and adapted to be axially foreshortened and radially expanded into engagement with the wick in response to an axially applied compressive load. The wick is continuously supported in a contiguous relationship with the internal surfaces of the shell.

Experiments on Thermal Convection in Rotating Spherical Shells With Radial Gravity: The Geophysical Fluid Flow Cell

NASA Technical Reports Server (NTRS)

Hart, John E.

1996-01-01

Experiments designed to study the fluid dynamics of buoyancy driven circulations in rotating spherical shells were conducted on the United States Microgravity Laboratory 2 spacelab mission. These experiments address several aspects of prototypical global convection relevant to large scale motions on the Sun, Earth, and on the giant planets. The key feature is the consistent modeling of radially directed gravity in spherical geometry by using dielectric polarization forces. Imagery of the planforms of thermally driven flows for rapidly-rotating regimes shows an initial separation and eventual merger of equatorial and polar convection as the heating (i.e. the Rayleigh number) is increased. At low rotation rates, multiple-states of motion for the same external parameters were observed.

Effects of applied dc radial electric fields on particle transport in a bumpy torus plasma

NASA Technical Reports Server (NTRS)

Roth, J. R.

1978-01-01

The influence of applied dc radial electric fields on particle transport in a bumpy torus plasma is studied. The plasma, magnetic field, and ion heating mechanism are operated in steady state. Ion kinetic temperature is more than a factor of ten higher than electron temperature. The electric fields raise the ions to energies on the order of kilovolts and then point radially inward or outward. Plasma number density profiles are flat or triangular across the plasma diameter. It is suggested that the radial transport processes are nondiffusional and dominated by strong radial electric fields. These characteristics are caused by the absence of a second derivative in the density profile and the flat electron temperature profiles. If the electric field acting on the minor radius of the toroidal plasma points inward, plasma number density and confinement time are increased.

Heat conduction in a chain of colliding particles with a stiff repulsive potential

NASA Astrophysics Data System (ADS)

Gendelman, Oleg V.; Savin, Alexander V.

2016-11-01

One-dimensional billiards, i.e., a chain of colliding particles with equal masses, is a well-known example of a completely integrable system. Billiards with different particle masses is generically not integrable, but it still exhibits divergence of a heat conduction coefficient (HCC) in the thermodynamic limit. Traditional billiards models imply instantaneous (zero-time) collisions between the particles. We relax this condition of instantaneous impact and consider heat transport in a chain of stiff colliding particles with the power-law potential of the nearest-neighbor interaction. The instantaneous collisions correspond to the limit of infinite power in the interaction potential; for finite powers, the interactions take nonzero time. This modification of the model leads to a profound physical consequence—the probability of multiple (in particular triple) -particle collisions becomes nonzero. Contrary to the integrable billiards of equal particles, the modified model exhibits saturation of the heat conduction coefficient for a large system size. Moreover, the identification of scattering events with triple-particle collisions leads to a simple definition of the characteristic mean free path and a kinetic description of heat transport. This approach allows us to predict both the temperature and density dependencies for the HCC limit values. The latter dependence is quite counterintuitive—the HCC is inversely proportional to the particle density in the chain. Both predictions are confirmed by direct numerical simulations.

Modeling transient heat transfer in nuclear waste repositories.

PubMed

Yang, Shaw-Yang; Yeh, Hund-Der

2009-09-30

The heat of high-level nuclear waste may be generated and released from a canister at final disposal sites. The waste heat may affect the engineering properties of waste canisters, buffers, and backfill material in the emplacement tunnel and the host rock. This study addresses the problem of the heat generated from the waste canister and analyzes the heat distribution between the buffer and the host rock, which is considered as a radial two-layer heat flux problem. A conceptual model is first constructed for the heat conduction in a nuclear waste repository and then mathematical equations are formulated for modeling heat flow distribution at repository sites. The Laplace transforms are employed to develop a solution for the temperature distributions in the buffer and the host rock in the Laplace domain, which is numerically inverted to the time-domain solution using the modified Crump method. The transient temperature distributions for both the single- and multi-borehole cases are simulated in the hypothetical geological repositories of nuclear waste. The results show that the temperature distributions in the thermal field are significantly affected by the decay heat of the waste canister, the thermal properties of the buffer and the host rock, the disposal spacing, and the thickness of the host rock at a nuclear waste repository.

Numerical modeling of thermal conductive heating in fractured bedrock.

PubMed

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

2010-01-01

Numerical modeling was employed to study the performance of thermal conductive heating (TCH) in fractured shale under a variety of hydrogeological conditions. Model results show that groundwater flow in fractures does not significantly affect the minimum treatment zone temperature, except near the beginning of heating or when groundwater influx is high. However, fracture and rock matrix properties can significantly influence the time necessary to remove all liquid water (i.e., reach superheated steam conditions) in the treatment area. Low matrix permeability, high matrix porosity, and wide fracture spacing can contribute to boiling point elevation in the rock matrix. Consequently, knowledge of these properties is important for the estimation of treatment times. Because of the variability in boiling point throughout a fractured rock treatment zone and the absence of a well-defined constant temperature boiling plateau in the rock matrix, it may be difficult to monitor the progress of thermal treatment using temperature measurements alone. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.

Radial basis functions in mathematical modelling of flow boiling in minichannels

NASA Astrophysics Data System (ADS)

Hożejowska, Sylwia; Hożejowski, Leszek; Piasecka, Magdalena

The paper addresses heat transfer processes in flow boiling in a vertical minichannel of 1.7 mm depth with a smooth heated surface contacting fluid. The heated element for FC-72 flowing in a minichannel was a 0.45 mm thick plate made of Haynes-230 alloy. An infrared camera positioned opposite the central, axially symmetric part of the channel measured the plate temperature. K-type thermocouples and pressure converters were installed at the inlet and outlet of the minichannel. In the study radial basis functions were used to solve a problem concerning heat transfer in a heated plate supplied with the controlled direct current. According to the model assumptions, the problem is treated as twodimensional and governed by the Poisson equation. The aim of the study lies in determining the temperature field and the heat transfer coefficient. The results were verified by comparing them with those obtained by the Trefftz method.

Fourier's law of heat conduction: quantum mechanical master equation analysis.

PubMed

Wu, Lian-Ao; Segal, Dvira

2008-06-01

We derive the macroscopic Fourier's Law of heat conduction from the exact gain-loss time convolutionless quantum master equation under three assumptions for the interaction kernel. To second order in the interaction, we show that the first two assumptions are natural results of the long time limit. The third assumption can be satisfied by a family of interactions consisting of an exchange effect. The pure exchange model directly leads to energy diffusion in a weakly coupled spin- 12 chain.

Dependence of radiation belt simulations to assumed radial diffusion rates

NASA Astrophysics Data System (ADS)

Drozdov, A.; Shprits, Y.; Aseev, N.; Kellerman, A. C.; Reeves, G. D.

2017-12-01

Radial diffusion is one of the dominant physical mechanisms that drives acceleration and loss of the radiation belt electrons due to wave-particle interaction with ultra low frequency (ULF) waves, which makes it very important for radiation belt modeling and forecasting. We investigate the sensitivity of several parameterizations of the radial diffusion including Brautigam and Albert [2000], Ozeke et al. [2014] and Ali et al. [2016] on long-term radiation belt modeling using the Versatile Electron Radiation Belt (VERB). Following previous studies, we first perform 1-D radial diffusion simulations. To take into account effects of local acceleration and loss, we perform additional 3-D simulations, including pitch-angle, energy and mixed diffusion. The obtained result demonstrates that the inclusion of local acceleration and pitch-angle diffusion can provide a negative feedback effect, such that the result is largely indistinguishable between simulations conducted with different radial diffusion parameterizations. We also perform a number of sensitivity tests by multiplying radial diffusion rates by constant factors and show that such an approach leads to unrealistic predictions of radiation belt dynamics.

Oculoauriculovertebral spectrum with radial anomaly in child.

PubMed

Taksande, Amar; Vilhekar, Krishna

2013-01-01

Oculoauriculovertebral spectrum (OAVS) or Goldenhar syndrome is a wide spectrum of congenital anomalies that involves structures arising from the first and second branchial arches. It is characterized by a wide spectrum of symptoms and physical features. These abnormalities mainly involve the cheekbones, jaws, mouth, ears, eyes, or vertebrae. Other conditions with ear and/or radial involvement, such as, the Nager syndrome, Holt-Oram syndrome, Radial-renal syndrome, facioauriculoradial dysplasia, Fanconi anemia, and Vertebral, Anal atresia, Cardiac, Trachea, Esophageal, Renal, and Limb (VACTERL) association should be considered for differential diagnosis. Here we report a child who had facial asymmetry, microsomia, microtia, congenital facial nerve palsy, conductive hearing loss, skin tags, iris coloboma, and preaxial polydactyly.

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.

Negative differential thermal conductance and heat amplification in superconducting hybrid devices

NASA Astrophysics Data System (ADS)

Fornieri, Antonio; Timossi, Giuliano; Bosisio, Riccardo; Solinas, Paolo; Giazotto, Francesco

2016-04-01

We investigate the thermal transport properties of a temperature-biased Josephson tunnel junction composed of two different superconductors. We show that this simple system can provide a large negative differential thermal conductance (NDTC) with a peak-to-valley ratio of ˜3 in the transmitted electronic heat current. The NDTC is then exploited to outline the caloritronic analog of the tunnel diode, which can exhibit a modulation of the output temperature as large as 80 mK at a bath temperature of 50 mK. Moreover, this device may work in a regime of thermal hysteresis that can be used to store information as a thermal memory. On the other hand, the NDTC effect offers the opportunity to conceive two different designs of a thermal transistor, which might operate as a thermal switch or as an amplifier/modulator. The latter shows a heat amplification factor >1 in a 500-mK-wide working region of the gate temperature. After the successful realization of heat interferometers and thermal diodes, this kind of structures would complete the conversion of the most important electronic devices in their thermal counterparts, breaking ground for coherent caloritronics nanocircuits where heat currents can be manipulated at will.

Structural, dynamic, and vibrational properties during heat transfer in Si/Ge superlattices: A Car-Parrinello molecular dynamics study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Pengfei; Zhang, Yuwen, E-mail: zhangyu@missouri.edu; Yang, Mo

The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heatmore » transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective.« less

Numerical Investigation of the Thermal Regime of Underground Channel Heat Pipelines Under Flooding Conditions with the Use of a Conductive-Convective Heat Transfer Model

NASA Astrophysics Data System (ADS)

Polovnikov, V. Yu.

2018-05-01

This paper presents the results of numerical analysis of thermal regimes and heat losses of underground channel heating systems under flooding conditions with the use of a convective-conductive heat transfer model with the example of the configuration of the heat pipeline widely used in the Russian Federation — a nonpassage ferroconcrete channel (crawlway) and pipelines insulated with mineral wool and a protective covering layer. It has been shown that convective motion of water in the channel cavity of the heat pipeline under flooding conditions has no marked effect on the intensification of heat losses. It has been established that for the case under consideration, heat losses of the heat pipeline under flooding conditions increase from 0.75 to 52.39% due to the sharp increase in the effective thermal characteristics of the covering layer and the heat insulator caused by their moistening.

Numerical Investigation of the Thermal Regime of Underground Channel Heat Pipelines Under Flooding Conditions with the Use of a Conductive-Convective Heat Transfer Model

NASA Astrophysics Data System (ADS)

Polovnikov, V. Yu.

2018-03-01

This paper presents the results of numerical analysis of thermal regimes and heat losses of underground channel heating systems under flooding conditions with the use of a convective-conductive heat transfer model with the example of the configuration of the heat pipeline widely used in the Russian Federation — a nonpassage ferroconcrete channel (crawlway) and pipelines insulated with mineral wool and a protective covering layer. It has been shown that convective motion of water in the channel cavity of the heat pipeline under flooding conditions has no marked effect on the intensification of heat losses. It has been established that for the case under consideration, heat losses of the heat pipeline under flooding conditions increase from 0.75 to 52.39% due to the sharp increase in the effective thermal characteristics of the covering layer and the heat insulator caused by their moistening.

Anelastic spherical dynamos with radially variable electrical conductivity

NASA Astrophysics Data System (ADS)

Dietrich, W.; Jones, C. A.

2018-05-01

A series of numerical simulations of the dynamo process operating inside gas giant planets has been performed. We use an anelastic, fully nonlinear, three-dimensional, benchmarked MHD code to evolve the flow, entropy and magnetic field. Our models take into account the varying electrical conductivity, high in the ionised metallic hydrogen region, low in the molecular outer region. Our suite of electrical conductivity profiles ranges from Jupiter-like, where the outer hydrodynamic region is quite thin, to Saturn-like, where there is a thick non-conducting shell. The rapid rotation leads to the formation of two distinct dynamical regimes which are separated by a magnetic tangent cylinder - mTC. Outside the mTC there are strong zonal flows, where Reynolds stress balances turbulent viscosity, but inside the mTC Lorentz force reduces the zonal flow. The dynamic interaction between both regions induces meridional circulation. We find a rich diversity of magnetic field morphologies. There are Jupiter-like steady dipolar fields, and a belt of quadrupolar dominated dynamos spanning the range of models between Jupiter-like and Saturn-like conductivity profiles. This diversity may be linked to the appearance of reversed sign helicity in the metallic regions of our dynamos. With Saturn-like conductivity profiles we find models with dipolar magnetic fields, whose axisymmetric components resemble those of Saturn, and which oscillate on a very long time-scale. However, the non-axisymmetric field components of our models are at least ten times larger than those of Saturn, possibly due to the absence of any stably stratified layer.

Radial-probe EBUS for the diagnosis of peripheral pulmonary lesions

PubMed Central

Jacomelli, Marcia; Demarzo, Sergio Eduardo; Cardoso, Paulo Francisco Guerreiro; Palomino, Addy Lidvina Mejia; Figueiredo, Viviane Rossi

2016-01-01

ABSTRACT Objective: Conventional bronchoscopy has a low diagnostic yield for peripheral pulmonary lesions. Radial-probe EBUS employs a rotating ultrasound transducer at the end of a probe that is passed through the working channel of the bronchoscope. Radial-probe EBUS facilitates the localization of peripheral pulmonary nodules, thus increasing the diagnostic yield. The objective of this study was to present our initial experience using radial-probe EBUS in the diagnosis of peripheral pulmonary lesions at a tertiary hospital. Methods: We conducted a retrospective analysis of 54 patients who underwent radial-probe EBUS-guided bronchoscopy for the investigation of pulmonary nodules or masses between February of 2012 and September of 2013. Radial-probe EBUS was performed with a flexible 20-MHz probe, which was passed through the working channel of the bronchoscope and advanced through the bronchus to the target lesion. For localization of the lesion and for collection procedures (bronchial brushing, transbronchial needle aspiration, and transbronchial biopsy), we used fluoroscopy. Results: Radial-probe EBUS identified 39 nodules (mean diameter, 1.9 ∓ 0.7 cm) and 19 masses (mean diameter, 4.1 ∓ 0.9 cm). The overall sensitivity of the method was 66.7% (79.5% and 25.0%, respectively, for lesions that were visible and not visible by radial-probe EBUS). Among the lesions that were visible by radial-probe EBUS, the sensitivity was 91.7% for masses and 74.1% for nodules. The complications were pneumothorax (in 3.7%) and bronchial bleeding, which was controlled bronchoscopically (in 9.3%). Conclusions: Radial-probe EBUS shows a good safety profile, a low complication rate, and high sensitivity for the diagnosis of peripheral pulmonary lesions. PMID:27832231

Determination of thermophysical characteristics of solid materials by electrical modelling of the solutions to the inverse problems in nonsteady heat conduction

NASA Technical Reports Server (NTRS)

Kozdoba, L. A.; Krivoshei, F. A.

1985-01-01

The solution of the inverse problem of nonsteady heat conduction is discussed, based on finding the coefficient of the heat conduction and the coefficient of specific volumetric heat capacity. These findings are included in the equation used for the electrical model of this phenomenon.

Flow structure and heat exchange analysis in internal cooling channel of gas turbine blade

NASA Astrophysics Data System (ADS)

Szwaba, Ryszard; Kaczynski, Piotr; Doerffer, Piotr; Telega, Janusz

2016-08-01

This paper presents the study of the flow structure and heat transfer, and also their correlations on the four walls of a radial cooling passage model of a gas turbine blade. The investigations focus on heat transfer and aerodynamic measurements in the channel, which is an accurate representation of the configuration used in aeroengines. Correlations for the heat transfer coefficient and the pressure drop used in the design of radial cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include corner fillet, ribs with fillet radii and special orientation. Therefore, this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which possesses very realistic features.

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.

Production and physiological responses of heat-stressed lactating dairy cattle to conductive cooling.

PubMed

Perano, Kristen M; Usack, Joseph G; Angenent, Largus T; Gebremedhin, Kifle G

2015-08-01

The objective of this research was to test the effectiveness of conductive cooling in alleviating heat stress of lactating dairy cows. A conductive cooling system was built with waterbeds (Dual Chamber Cow Waterbeds, Advanced Comfort Technology Inc., Reedsburg, WI) modified to circulate chilled water. The experiment lasted 7 wk. Eight first-lactation Holstein cows producing 34.4±3.7kg/d of milk at 166±28 d in milk were used in the study. Milk yield, dry matter intake (DMI), and rectal temperature were recorded twice daily, and respiration rate was recorded 5 times per day. During wk 1, the cows were not exposed to experimental heat stress or conductive cooling. For the remaining 6 wk, the cows were exposed to heat stress from 0900 to 1700h each day. During these 6 wk, 4 of the 8 cows were cooled with conductive cooling (experimental cows), and the other 4 were not cooled (control cows). The study consisted of 2 thermal environment exposures (temperature-humidity index mean ± standard deviation of 80.7±0.9 and 79.0±1.0) and 2 cooling water temperatures (circulating water through the water mattresses at temperatures of 4.5°C and 10°C). Thus, a total of 4 conductive cooling treatments were tested, with each treatment lasting 1 wk. During wk 6, the experimental and control cows were switched and the temperature-humidity index of 79.0±1.0 with 4.5°C cooling water treatment was repeated. During wk 7, waterbeds were placed directly on concrete stalls without actively cooling the water. Least squares means and P-values for the different treatments were calculated with multivariate mixed models. Conductively cooling the cows with 4.5°C water decreased rectal temperature by 1.0°C, decreased respiration rate by 18 breaths/min, increased milk yield by 5%, and increased DMI by 14% compared with the controls. When the results from the 2 cooling water temperatures (4.5°C and 10°C circulating water) were compared, we found that the rectal temperature from 4.5�

Lighting system with heat distribution face plate

DOEpatents

Arik, Mehmet; Weaver, Stanton Earl; Stecher, Thomas Elliot; Kuenzler, Glenn Howard; Wolfe, Jr., Charles Franklin; Li, Ri

2013-09-10

Lighting systems having a light source and a thermal management system are provided. The thermal management system includes synthetic jet devices, a heat sink and a heat distribution face plate. The synthetic jet devices are arranged in parallel to one and other and are configured to actively cool the lighting system. The heat distribution face plate is configured to radially transfer heat from the light source into the ambient air.

(abstract) Ulysses Solar Wind Ion Temperatures: Radial, Latitudinal, and Dynamical Dependencies

NASA Technical Reports Server (NTRS)

Goldstein, B. E.; Smith, E. J.; Gosling, J. T.; McComas, D. J.; Balogh, A.

1996-01-01

Observations of the Ulysses SWOOPS plasma experiment are used to determine the dependencies of solar wind ion temperatures upon radial distance, speed, and other parameters, and to estimate solar wind heating. Comparisons with three dimensional temperature estimates determined from the ion spectra by a least squares fitting program will be provided (only small samples of data have been reduced with this program).

Constitutive restrictions for deformable simple media that are heat conducting and electrically polarizable

NASA Astrophysics Data System (ADS)

Montanaro, Adriano

2017-07-01

We present the constitutive restrictions for a deformable simple medium that is heat conducting, electrically polarizable and interacting with the electric field, either of elastic type or with a fading memory. The used theory is an extension of the well known Green-Naghdi thermo-mechanical theories of continua, mainly devoted to thermoelastic bodies or rigid conductors. Hence the theory that is used here is based on an entropy balance law rather than an entropy imbalance, uses the notion of thermal displacement, and predicts heat propagation by thermal waves at finite speed.

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

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.

Radial Clearance Found To Play a Key Role in the Performance of Compliant Foil Air Bearings

NASA Technical Reports Server (NTRS)

Radil, Kevin C.

2003-01-01

Compliant foil air bearings are at the forefront of the Oil-Free turbomachinery revolution, which supports gas turbine engines with hydrodynamic bearings that use air instead of oil as the working fluid. These types of bearings have been around for almost 50 years and have found a home in several commercial applications, such as in air cycle machines, turbocompressors, and microturbines, but are now being aggressively pursued for use in small and midrange aircraft gas turbine engines. Benefits include higher operating speeds and temperatures, lower maintenance costs, and greater reliability. The Oil-Free Turbomachinery team at the NASA Glenn Research Center is working to foster the transition of Oil-Free technology into gas turbine engines by performing in-house experiments on foil air bearings in order to gain a greater insight into their complex operating principles. A research program recently undertaken at Glenn focused on the concept of radial clearance and its influence on bearing performance. The tests were conducted on foil bearings with different radial clearances. As defined for a foil bearing, radial clearance is a measure of the small amount of shaft radial motion that is present from play that exists in the elastic support structure, such as between the top and bump foils and the bump foils and bearing shell (see the drawing). With an insufficient amount of radial clearance, the bearing imparts a high preload on the shaft, which when excessive, can reduce the loadcarrying capability of the bearing. On the other hand, systems using foil bearings with excessive radial clearance may experience rotordynamic instabilities because of low bearing preload. Therefore, without a more thorough understanding of radial clearance, it is difficult to accurately predict the performance of a given bearing design. The test program demonstrated that there is a direct correlation between radial clearance and the performance of foil air bearings. As shown in the graph, an

Universal Scaling of Robust Thermal Hot Spot and Ionic Current Enhancement by Focused Ohmic Heating in a Conic Nanopore

PubMed Central

Pan, Zehao; Wang, Ceming; Li, Meng; Chang, Hsueh-Chia

2017-01-01

A stable nanoscale thermal hot spot, with temperature approaching 100 °C, is shown to be sustained by localized Ohmic heating of a focused electric field at the tip of a slender conic nanopore. The self-similar (length-independent) conic geometry allows us to match the singular heat source at the tip to the singular radial heat loss from the slender cone to obtain a self-similar steady temperature profile along the cone and the resulting ionic current conductance enhancement due to viscosity reduction. The universal scaling, which depends only on a single dimensionless parameter Z, collapses the measured conductance data and computed temperature profiles in ion-track conic nanopores and conic nanopipettes. The collapsed numerical data reveal universal values for the hot-spot location and temperature in an aqueous electrolyte. PMID:27715110

Universal Scaling of Robust Thermal Hot Spot and Ionic Current Enhancement by Focused Ohmic Heating in a Conic Nanopore

NASA Astrophysics Data System (ADS)

Pan, Zehao; Wang, Ceming; Li, Meng; Chang, Hsueh-Chia

2016-09-01

A stable nanoscale thermal hot spot, with temperature approaching 100 °C , is shown to be sustained by localized Ohmic heating of a focused electric field at the tip of a slender conic nanopore. The self-similar (length-independent) conic geometry allows us to match the singular heat source at the tip to the singular radial heat loss from the slender cone to obtain a self-similar steady temperature profile along the cone and the resulting ionic current conductance enhancement due to viscosity reduction. The universal scaling, which depends only on a single dimensionless parameter Z , collapses the measured conductance data and computed temperature profiles in ion-track conic nanopores and conic nanopipettes. The collapsed numerical data reveal universal values for the hot-spot location and temperature in an aqueous electrolyte.

Universal Scaling of Robust Thermal Hot Spot and Ionic Current Enhancement by Focused Ohmic Heating in a Conic Nanopore.

PubMed

Pan, Zehao; Wang, Ceming; Li, Meng; Chang, Hsueh-Chia

2016-09-23

A stable nanoscale thermal hot spot, with temperature approaching 100 °C, is shown to be sustained by localized Ohmic heating of a focused electric field at the tip of a slender conic nanopore. The self-similar (length-independent) conic geometry allows us to match the singular heat source at the tip to the singular radial heat loss from the slender cone to obtain a self-similar steady temperature profile along the cone and the resulting ionic current conductance enhancement due to viscosity reduction. The universal scaling, which depends only on a single dimensionless parameter Z, collapses the measured conductance data and computed temperature profiles in ion-track conic nanopores and conic nanopipettes. The collapsed numerical data reveal universal values for the hot-spot location and temperature in an aqueous electrolyte.

Radial arm strike rail

DOEpatents

McKeown, Mark H.; Beason, Steven C.

1991-01-01

The radial arm strike rail assembly is a system for measurement of bearings, directions, and stereophotography for geologic mapping, particularly where magnetic compasses are not appropriate. The radial arm, pivoting around a shaft axis, provides a reference direction determination for geologic mapping and bearing or direction determination. The centerable and levelable pedestal provide a base for the radial arm strike rail and the telescoping camera pedestal. The telescoping feature of the radial arm strike rail allows positioning the end of the rail for strike direction or bearing measurement with a goniometer.

Numerical heat transfer study in a scattering, absorbing and emitting semi-transparent porous medium in a cylindrical enclosure

NASA Astrophysics Data System (ADS)

Timoumi, M.; Chérif, B.; Sifaoui, M. S.

2005-12-01

In this paper, heat transfer problem through a semi-transparent porous medium in a cylindrical enclosure is investigated. The governing equations for this problem and the boundary conditions are non-linear differential equations depending on the dimensionless radial coordinate, Planck number N, scattering albedo ω, walls emissivity and thermal conductivity ratio kr. The set of differential equations are solved by a numerical technique taken from the IMSL MATH/LIBRARY. Various results are obtained for the dimensionless temperature profiles in the solid and fluid phases and the radiative heat flux. The effects of some radiative properties of the medium on the heat transfer rate are examined.

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

NASA Technical Reports Server (NTRS)

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

1995-01-01

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

[Seasonal variation of soil heat conduction in a larch plantation and its relations to environmental factors].

PubMed

Wang, Wen-Jie; Cui, Song; Liu, Wei; Zu, Yuan-Gang; Sun, Wei; Wang, Hui-Min

2008-10-01

Based on a 3-year (2003-2005) observation of soil heat flux (SHF) in a larch (Larix gmelinii) plantation, the characteristics of soil heat conduction in the plantation and their relationships with environment factors were analyzed. The results showed that there was an obvious seasonal variation of SHF in different years and sampling sites. The SHF was positive from April to August and mostly negative from September to next March, with an almost balance between heat income and outcome at annual scale. Solar net radiation had significant effects on the SHF and soil heat conductance (k), and an obvious time-lag effect was found, with 4-5 hours' time-lag in winter and 2-3 hours' time-lag in summer. Based on the real-time measurement of SHF and soil temperature difference at the study sites, the k value was significantly higher in early spring (P < 0.05), but no significant difference was observed in other seasons (P > 0.05). Therefore, when we use the observation data of soil temperature from weather stations to estimate soil heat flux, the k value in spring (from March to May) could induce a bias estimation.

Triple acting radial seal

DOEpatents

Ebert, Todd A [West Palm Beach, FL; Carella, John A [Jupiter, FL

2012-03-13

A triple acting radial seal used as an interstage seal assembly in a gas turbine engine, where the seal assembly includes an interstage seal support extending from a stationary inner shroud of a vane ring, the interstage seal support includes a larger annular radial inward facing groove in which an outer annular floating seal assembly is secured for radial displacement, and the outer annular floating seal assembly includes a smaller annular radial inward facing groove in which an inner annular floating seal assembly is secured also for radial displacement. A compliant seal is secured to the inner annular floating seal assembly. The outer annular floating seal assembly encapsulates the inner annular floating seal assembly which is made from a very low alpha material in order to reduce thermal stress.

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

USDA-ARS?s Scientific Manuscript database

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...

Divertor-leg instability for finite beta and radially-tilted divertor plate

NASA Astrophysics Data System (ADS)

Cohen, R. H.; Ryutov, D. D.

2004-11-01

Plasma in the divertor leg may experience a fast instability caused by sheath boundary conditions (BC). Perturbations cannot penetrate beyond the X point because of very strong shearing in its vicinity. Accordingly, this instability could increase cross-field transport in the divertor leg, and thereby reduce the heat load on the divertor plate, without having any appreciable negative effect on core plasma confinement. A way of describing the role of shearing in terms of the surface resistivity attributed to a ``control plane'' below the X point has recently been suggested (Contr. Plasma Phys., v. 44, p. 168, 2004). We use this BC, plus sheath BC at the divertor plate. We include effects of finite beta and of the radial tilt of the divertor plate. We optimize the radial tilt in order to maximize radial transport in divertor legs. We discuss experimental signatures of the instability: i) phase velocity and wave-numbers of the most unstable modes; ii) correlations between fluctuations of various parameters; and iii) the differences between fluctuations in the common and private flux regions.

Requirements for Radial Migration: How does the migrating fraction depend on stellar velocity dispersion?

NASA Astrophysics Data System (ADS)

Tolfree, Kathryne; Wyse, R. F.

2014-01-01

Radial migration is a way to rearrange the orbital angular momentum of stars in an spiral disk without inducing kinematic heating. When radial migration is very efficient, a large fraction of disk stars experience significant changes in their orbital angular momenta in a short period of time. Such scenarios have strong implications for the chemical and kinematic evolution of disk galaxies. We have undertaken an investigation of the physical dependencies of the efficiency of radial migration on stellar kinematics and spiral structure by deriving the fraction of stars that can migrate radially given certain conditions. In order for a star in a spiral disk to migrate radially, it must first be “captured" in a family of resonant orbits near the radius of corotation with a spiral pattern. Thus far, the only analytic criterion for capture has been for stars in circular orbits. We present the capture criterion for stars on non-circular orbits in a disk galaxy. We then use our analytically derived capture criteria to model the radial distribution of the captured fraction in an exponential disk with a flat rotation curve as well as the dependence of the total captured fraction in the disk on the radial component of the stellar velocity dispersion (σR) and the amplitude of the spiral perturbation to the underlying potential at corotation (|Φs|CR). We find that the captured fraction goes as Exp[-σR2/|Φs|CR].

Requirements for Radial Migration: How Does the Migrating Fraction Depend on Stellar Velocity Dispersion?

NASA Astrophysics Data System (ADS)

Tolfree, K. J. D.; Wyse, R. F. G.

2014-03-01

Radial migration is a mechanism that can rearrange the orbital angular momentum of stars in a spiral disk without inducing kinematic heating. When radial migration is very efficient, a large fraction of disk stars experience significant changes in their orbital angular momenta over a short period of time. Such scenarios have strong implications for the chemical and kinematic evolution of disk galaxies. We have undertaken an investigation of the physical dependencies of the efficiency of radial migration on stellar kinematics and spiral structure by deriving the fraction of stars that can migrate radially. In order for a star in a spiral disk to migrate radially, it must first be “captured” in a family of resonant orbits near the radius of corotation with a transient spiral pattern. To date, the only analytic criterion for capture has been for stars in circular orbits. We present the capture criterion for disk stars on non-circular orbits. We then use our analytically derived capture criterion to model the radial distribution of the captured fraction in an exponential disk with a flat rotation curve. Further, we derive the dependence of the total captured fraction in the disk on the radial component of the stellar velocity dispersion (σR) and the amplitude of the spiral perturbation to the underlying potential evaluated at corotation (|Φs|CR). We find that within an annulus centered around corotation where σR is constant, the captured fraction goes as e-σR2/|Φs|CR.

Genetic variability for stomatal conductance in Pima cotton and its relation to improvements of heat adaptation.

PubMed Central

Radin, J W; Lu, Z; Percy, R G; Zeiger, E

1994-01-01

Responses of stomata to environment have been intensively studied, but little is known of genetic effects on stomatal conductance or their consequences. In Pima cotton (Gossypium barbadense L.), a crop that is bred for irrigated production in very hot environments, stomatal conductance varies genetically over a wide range and has increased with each release of new higher-yielding cultivars. A cross between heat-adapted (high-yielding) and unadapted genotypes produced F2 progeny cosegregating for stomatal conductance and leaf temperature. Within segregating populations in the field, conductance was negatively correlated with foliar temperature because of evaporative cooling. Plants were selected from the F2 generation specifically and solely for differing stomatal conductance. Among F3 and F4 populations derived from these selections, conductance and leaf cooling were significantly correlated with fruiting prolificacy during the hottest period of the year and with yield. Conductance was not associated with other factors that might have affected yield potential (single-leaf photosynthetic rate, leaf water potential). As breeders have increased the yield of this crop, genetic variability for conductance has allowed inadvertent selection for "heat avoidance" (evaporative cooling) in a hot environment. PMID:11607487

Simultaneous Measurement of Thermal Conductivity and Specific Heat in a Single TDTR Experiment

NASA Astrophysics Data System (ADS)

Sun, Fangyuan; Wang, Xinwei; Yang, Ming; Chen, Zhe; Zhang, Hang; Tang, Dawei

2018-01-01

Time-domain thermoreflectance (TDTR) technique is a powerful thermal property measurement method, especially for nano-structures and material interfaces. Thermal properties can be obtained by fitting TDTR experimental data with a proper thermal transport model. In a single TDTR experiment, thermal properties with different sensitivity trends can be extracted simultaneously. However, thermal conductivity and volumetric heat capacity usually have similar trends in sensitivity for most materials; it is difficult to measure them simultaneously. In this work, we present a two-step data fitting method to measure the thermal conductivity and volumetric heat capacity simultaneously from a set of TDTR experimental data at single modulation frequency. This method takes full advantage of the information carried by both amplitude and phase signals; it is a more convenient and effective solution compared with the frequency-domain thermoreflectance method. The relative error is lower than 5 % for most cases. A silicon wafer sample was measured by TDTR method to verify the two-step fitting method.

The Role of Radial Clearance on the Performance of Foil Air Bearings

NASA Technical Reports Server (NTRS)

Radil, Kevin; Howard, Samuel; Dykas, Brian

2002-01-01

Load capacity tests were conducted to determine how radial clearance variations affect the load capacity coefficient of foil air bearings. Two Generation III foil air bearings with the same design but possessing different initial radial clearances were tested at room temperature against an as-ground PS304 coated journal operating at 30,000 rpm. Increases in radial clearance were accomplished by reducing the journal's outside diameter via an in-place grinding system. From each load capacity test the bearing load capacity coefficient was calculated from the rule-of-thumb (ROT) model developed for foil air bearings. The test results indicate that, in terms of the load capacity coefficient, radial clearance has a direct impact on the performance of the foil air bearing. Each test bearing exhibited an optimum radial clearance that resulted in a maximum load capacity coefficient. Relative to this optimum value are two separate operating regimes that are governed by different modes of failure. Bearings operating with radial clearances less than the optimum exhibit load capacity coefficients that are a strong function of radial clearance and are prone to a thermal runaway failure mechanism and bearing seizure. Conversely, a bearing operating with a radial clearance twice the optimum suffered only a 20 percent decline in its maximum load capacity coefficient and did not experience any thermal management problems. However, it is unknown to what degree these changes in radial clearance had on other performance parameters, such as the stiffness and damping properties of the bearings.

Heat transfer to an unconfined ceiling from an impinging buoyant diffusion flame

NASA Astrophysics Data System (ADS)

Weng, W. G.; Hasemi, Y.

2006-05-01

Impinging flames are used in fire safety research, industrial heating and melting, and aerospace applications. Multiple modes of heat transfer, such as natural convection, forced convection and thermal radiation, etc. are commonly important in those processes. However, the detailed heat transfer mechanisms are not well understood. In this paper, a model is developed to calculate the thermal response of an unconfined nonburning ceiling from an impinging buoyant diffusion flame. This model uses an algorithm for conduction into the ceiling material. It takes account of heat transfer due to radiation from the fire source to the ceiling surface, and due to reradiation from the ceiling surface to other items. Using experimental data, the convective heat transfer coefficient at lower surface is deduced from this model. In addition, the predicted heat fluxes are compared with the existing experimental data, and the comparison results validate the presented model. It is indicated that this model can be used to predict radial-dependent surface temperature histories under a variety of different realistic levels of fire energy generation rates and fire-to-ceiling separation distance.

Advanced radial inflow turbine rotor program: Design and dynamic testing

NASA Technical Reports Server (NTRS)

Rodgers, C.

1976-01-01

The advancement of small, cooled, radial inflow turbine technology in the area of operation at higher turbine inlet temperature is discussed. The first step was accomplished by designing, fabricating, and subjecting to limited mechanical testing an advanced gas generator rotating assembly comprising a radial inflow turbine and two-stage centrifugal compressor. The radial inflow turbine and second-stage compressor were designed as an integrally machined monorotor with turbine cooling taking place basically by conduction to the compressor. Design turbine inlet rotor gas temperature, rotational speed, and overall gas generator compressor pressure ratio were 1422 K (2560 R), 71,222 rpm, and 10/1 respectively. Mechanical testing on a fabricated rotating assembly and bearing system covered 1,000 cold start/stop cycles and three spins to 120 percent design speed (85,466 rpm).

Spontaneous radial nerve palsy subsequent to non-traumatic neuroma.

PubMed

Ebrahimpour, Adel; Nazerani, Shahram; Tavakoli Darestani, Reza; Khani, Salim

2013-09-01

Spontaneous radial palsy is a not rare finding in hand clinics. The anatomy of the radial nerve renders it prone to pressure paralysis as often called "Saturday night palsy". This problem is a transient nerve lesion and an acute one but the case presented here is very unusual in that it seems this entity can also occur as an acute on chronic situation with neuroma formation. A 61 year-old man presented with the chief complaint of inability to extend the wrist and the fingers of the left hand which began suddenly the night before admission, following a three-week history of pain, numbness and tingling sensation of the affected extremity. He had no history of trauma to the extremity. Electromyography revealed a severe conductive defect of the left radial nerve with significant axonal loss at the upper arm. Surgical exploration identified a neuroma of the radial nerve measuring 1.5 cm in length as the cause of the paralysis. The neuroma was removed and an end-to-end nerve coaption was performed. Complete recovery of the hand and finger extension was achieved in nine months.

Thermophysical fundamentals of cyclonic recirculating heating devices

NASA Astrophysics Data System (ADS)

Karpov, S. V.; Zagoskin, A. A.

2017-10-01

This report presents the results of experimental and theoretical research of aerodynamics and convective heat transfer in cyclone devices with the new system of external recirculation of heating gas under the influence of radial pressure gradient in a heat carrier’s swirling turbulent flow. The dynamic problem of tangential velocity distribution in a clearance volume is solved at various re-circulation ratio values including limiting quantities (kr = 0; 1) and variations in cyclonic combustion chamber’s design parameters and operating conditions (Rer); the integrated calculation ratios for fundamental aerodynamic characteristics of a recirculation device are derived. The first experimental and numerical studies of convective heat transfer on internal and external surfaces of a hollow shaft in a swirling recirculation flow are derived through the instrumentality of OpenFOAM, these studies are also conducted for a setting of several cylindrical solid inserts. The external surface heat problem of a hollow cylindrical insert is solved with integral and digital methods; generalized similarity equations for the internal and external surfaces extended in range of Reynolds number are derived. The experimental data is in reasonable agreement with the derived curves and the results of mathematic modelling of convective heat transfer. Calculation recommendations for optimal selection of kr values at various ratios of their geometric characteristics and products utilization rate are obtained.

Heat transfer in a cover-plate preswirl rotating-disk system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pilbrow, R.; Karabay, H.; Wilson, M.

1999-04-01

In most gas turbines, blade-cooling air is supplied from stationary preswirl nozzles that swirl the air in the direction of rotation of the turbine disk. In the cover-plate system, the preswirl nozzles are located radially inward of the blade-cooling holes in the disk, and the swirling air flows radially outward in the cavity between the disk and a cover-plate attached to it. In this combined computational and experimental paper, an axisymmetric elliptic solver, incorporating the Launder-Sharma and the Morse low-Reynolds-number {kappa}-{epsilon} turbulence models, is used to compute the flow and heat transfer. The computed Nusselt numbers for the heated turbinemore » disk are compared with measured values obtained from a rotating-disk rig. Comparisons are presented, for a wide range of coolant flow rates, for rotational Reynolds numbers in the range 0.5 {times} 10{sup 6} to 1.5 {times} 10{sup 6}, and for 0.9 < {beta}{sub p} < 3.1, where {beta}{sub p} is the preswirl ratio (or ratio of the tangential component of velocity of the cooling air at inlet to the system to that of the disk). Agreement between the computed and measured Nusselt numbers is reasonably good, particularly at the larger Reynolds numbers. A simplified numerical simulation is also conducted to show the effect of the swirl ratio and the other flow parameters on the flow and heat transfer in the cover-plate system.« less

Theoretical analysis of oscillatory terms in lattice heat-current time correlation functions and their contributions to thermal conductivity

NASA Astrophysics Data System (ADS)

Pereverzev, Andrey; Sewell, Tommy

2018-03-01

Lattice heat-current time correlation functions for insulators and semiconductors obtained using molecular dynamics (MD) simulations exhibit features of both pure exponential decay and oscillatory-exponential decay. For some materials the oscillatory terms contribute significantly to the lattice heat conductivity calculated from the correlation functions. However, the origin of the oscillatory terms is not well understood, and their contribution to the heat conductivity is accounted for by fitting them to empirical functions. Here, a translationally invariant expression for the heat current in terms of creation and annihilation operators is derived. By using this full phonon-picture definition of the heat current and applying the relaxation-time approximation we explain, at least in part, the origin of the oscillatory terms in the lattice heat-current correlation function. We discuss the relationship between the crystal Hamiltonian and the magnitude of the oscillatory terms. A solvable one-dimensional model is used to illustrate the potential importance of terms that are omitted in the commonly used phonon-picture expression for the heat current. While the derivations are fully quantum mechanical, classical-limit expressions are provided that enable direct contact with classical quantities obtainable from MD.

Dynamics of charged bulk viscous collapsing cylindrical source with heat flux

NASA Astrophysics Data System (ADS)

Shah, S. M.; Abbas, G.

2017-04-01

In this paper, we have explored the effects of dissipation on the dynamics of charged bulk viscous collapsing cylindrical source which allows the out-flow of heat flux in the form of radiations. The Misner-Sharp formalism has been implemented to drive the dynamical equation in terms of proper time and radial derivatives. We have investigated the effects of charge and bulk viscosity on the dynamics of collapsing cylinder. To determine the effects of radial heat flux, we have formulated the heat transport equations in the context of Müller-Israel-Stewart theory by assuming that thermodynamics viscous/heat coupling coefficients can be neglected within some approximations. In our discussion, we have introduced the viscosity by the standard (non-causal) thermodynamics approach. The dynamical equations have been coupled with the heat transport equation; the consequences of the resulting coupled heat equation have been analyzed in detail.

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

PubMed Central

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

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

PubMed

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

2013-09-22

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.

Diffusion approximation of the radiative-conductive heat transfer model with Fresnel matching conditions

NASA Astrophysics Data System (ADS)

Chebotarev, Alexander Yu.; Grenkin, Gleb V.; Kovtanyuk, Andrey E.; Botkin, Nikolai D.; Hoffmann, Karl-Heinz

2018-04-01

The paper is concerned with a problem of diffraction type. The study starts with equations of complex (radiative and conductive) heat transfer in a multicomponent domain with Fresnel matching conditions at the interfaces. Applying the diffusion, P1, approximation yields a pair of coupled nonlinear PDEs describing the radiation intensity and temperature for each component of the domain. Matching conditions for these PDEs, imposed at the interfaces between the domain components, are derived. The unique solvability of the obtained problem is proven, and numerical experiments are conducted.

Heat and mass transport during a groundwater replenishment trial in a highly heterogeneous aquifer

NASA Astrophysics Data System (ADS)

Seibert, Simone; Prommer, Henning; Siade, Adam; Harris, Brett; Trefry, Mike; Martin, Michael

2014-12-01

Changes in subsurface temperature distribution resulting from the injection of fluids into aquifers may impact physiochemical and microbial processes as well as basin resource management strategies. We have completed a 2 year field trial in a hydrogeologically and geochemically heterogeneous aquifer below Perth, Western Australia in which highly treated wastewater was injected for large-scale groundwater replenishment. During the trial, chloride and temperature data were collected from conventional monitoring wells and by time-lapse temperature logging. We used a joint inversion of these solute tracer and temperature data to parameterize a numerical flow and multispecies transport model and to analyze the solute and heat propagation characteristics that prevailed during the trial. The simulation results illustrate that while solute transport is largely confined to the most permeable lithological units, heat transport was also affected by heat exchange with lithological units that have a much lower hydraulic conductivity. Heat transfer by heat conduction was found to significantly influence the complex temporal and spatial temperature distribution, especially with growing radial distance and in aquifer sequences with a heterogeneous hydraulic conductivity distribution. We attempted to estimate spatially varying thermal transport parameters during the data inversion to illustrate the anticipated correlations of these parameters with lithological heterogeneities, but estimates could not be uniquely determined on the basis of the collected data.

One-Particle Representation of Heat Conduction Described within the Scope of the Second Law.

PubMed

Jesudason, Christopher Gunaseelan

2016-01-01

The Carnot cycle and its deduction of maximum conversion efficiency of heat inputted and outputted isothermally at different temperatures necessitated the construction of isothermal and adiabatic pathways within the cycle that were mechanically "reversible", leading eventually to the Kelvin-Clausius development of the entropy function S with differential dS = dq/T such that [symbol: see text]C dS = 0 where the heat absorption occurs at the isothermal paths of the elementary Carnot cycle. Another required condition is that the heat transfer processes take place infinitely slowly and "reversibly", implying that rates of transfer are not explicitly featured in the theory. The definition of 'heat' as that form of energy that is transferred as a result of a temperature difference suggests that the local mode of transfer of "heat" in the isothermal segments of the pathway implies a Fourier-like heat conduction mechanism which is apparently irreversible, leading to an increase in entropy of the combined reservoirs at either end of the conducting material, and which is deemed reversible mechanically. These paradoxes are circumvented here by first clarifying the terms used before modeling heat transfer as a thermodynamically reversible but mechanically irreversible process and applied to a one dimensional atomic lattice chain of interacting particles subjected to a temperature difference exemplifying Fourier heat conduction. The basis of a "recoverable trajectory" i.e. that which follows a zero entropy trajectory is identified. The Second Law is strictly maintained in this development. A corollary to this zero entropy trajectory is the generalization of the Zeroth law for steady state non-equilibrium systems with varying temperature, and thus to a statement about "equilibrium" in steady state non-thermostatic conditions. An energy transfer rate term is explicitly identified for each particle and agrees quantitatively (and independently) with the rate of heat absorbed at the

Equivalent Thermal Conductivities for Twisted Flat Windings

NASA Astrophysics Data System (ADS)

Glises, R.; Bernard, R.; Chamagne, D.; Kauffmann, J. M.

1996-10-01

The authors of this paper intend to develop a method of determination of equivalent thermal conductivities for twisted flat windings. The conductivities determined are radial and parallel to the principal directions of the windings. A design has been realized thanks to the thermal modulus of the computation software Flux2D using a finite elements method. Following that phase, numerical correlations permitting to express the radial conductivities as a function of temperature, filling rate and insulation conductivities are proposed. Les auteurs de cet article se proposent de développer une étude de détermination de conductivités thermiques équivalentes d'empilements de bobinages plats torsadés. Les conductivités sont déterminées dans le plan radial (perpendiculaire à l'axe des bobinages) et parallèlement aux directions principales de la structure. La méthode utilisée est exclusivement numérique et est réalisée à l'aide du logiciel de calculs bidimensionnels par éléments finis Flux2D. Des corrélations numériques exploitables permettent d'obtenir directement les conductivités radiales en fonction du taux de remplissage, de la température du milieu et des conductivités des isolants électriques.

Anatomic fit of six different radial head plates: comparison of precontoured low-profile radial head plates.

PubMed

Burkhart, Klaus Josef; Nowak, Tobias E; Kim, Yoon-Joo; Rommens, Pol M; Müller, Lars P

2011-04-01

Bulky implants may lead to symptomatic soft tissue irritation after open reduction and internal fixation of radial head and neck fractures. The purpose of our study was to compare the anatomic fit of precontoured radial head plates. We stripped 22 embalmed human cadaveric radiuses of soft tissues. We investigated 6 radial head plates: (1) the Medartis radial head buttress plate (MBP), (2) the Medartis radial head rim plate (MRP), (3) the Synthes radial neck plate (SNP), (4) the Synthes radial head plate (SHP), (5) the Acumed radial head plate (AHP), and (6) the Wright radial head plate (WHP). Each plate was applied to each radial head at the place of best fit within the safe zone. We tested 4 parameters of anatomic fit: (1) plate-to-bone distance, (2) plate contact judged by 3 different observers, (3) pin-subchondral zone distance, and (4) plate-to-bone contact after adjustment of the plates. The MBP and MRP showed the lowest profile by objective measurements, the SNP and AHP had a moderate profile, and the SHP and WHP demonstrated the bulkiest profile. The subjective assessments also demonstrated the best fit for the MBP, a good fit for the SNP, a moderate fit for the MRP and AHP, and a poor fit for the SHP and WHP. The MBP, MRP, and AHP could always provide pin-subchondral zone contact, unlike the SHP, SNP, and WHP. After bending, significant improvement of plate-to-bone distance could only be seen for the MBP, MRP, and WHP. The ranking among plates remained the same except for the WHP, which showed a significantly lower plate-to-bone distance than the SHP. Currently available radial head implants are heterogeneous. The MBP and MRP showed the lowest profile and best anatomic fit. Owing to the complex radial head anatomy, to date there is no one radial head plate that perfectly fits all radial heads. Conformance of existing plates to the radial head and neck is not perfect. Careful plate selection and modification, when necessary, may minimize interference of this

Magnetogasdynamic spherical shock wave in a non-ideal gas under gravitational field with conductive and radiative heat fluxes

NASA Astrophysics Data System (ADS)

Nath, G.; Vishwakarma, J. P.

2016-11-01

Similarity solutions are obtained for the flow behind a spherical shock wave in a non-ideal gas under gravitational field with conductive and radiative heat fluxes, in the presence of a spatially decreasing azimuthal magnetic field. The shock wave is driven by a piston moving with time according to power law. The radiation is considered to be of the diffusion type for an optically thick grey gas model and the heat conduction is expressed in terms of Fourier's law for heat conduction. Similarity solutions exist only when the surrounding medium is of constant density. The gas is assumed to have infinite electrical conductivity and to obey a simplified van der Waals equation of state. It is shown that an increase of the gravitational parameter or the Alfven-Mach number or the parameter of the non-idealness of the gas decreases the compressibility of the gas in the flow-field behind the shock, and hence there is a decrease in the shock strength. The pressure and density vanish at the inner surface (piston) and hence a vacuum is formed at the center of symmetry. The shock waves in conducting non-ideal gas under gravitational field with conductive and radiative heat fluxes can be important for description of shocks in supernova explosions, in the study of a flare produced shock in the solar wind, central part of star burst galaxies, nuclear explosion etc. The solutions obtained can be used to interpret measurements carried out by space craft in the solar wind and in neighborhood of the Earth's magnetosphere.

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

USGS Publications Warehouse

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

2007-01-01

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

Electrical conductivity and rate-capability of Li 4Ti 5O 12 as a function of heat-treatment atmosphere

NASA Astrophysics Data System (ADS)

Wolfenstine, J.; Lee, U.; Allen, J. L.

Recently there has considerable interest in Li 4Ti 5O 12 as a potential anode for use in Li-ion batteries [1-8]. It has many advantages compared to the currently used graphite. For example, it is a zero-strain lithium insertion host suggesting virtually unlimited cycle life. It features a flat, operating voltage of about 1.5 V versus lithium, above the reduction potential of common electrolyte solvents thus, it does not form a solid electrolyte interface based on solvent reduction which should be a favorable property for high rate and low temperature operation. This voltage also is sufficiently high such that the dangers of lithium plating that can occur at high rate and/or low temperature are removed. However, several disadvantages exist compared to graphite. These include low rate-capability as a result of its low electronic conductivity [6]. Consequently, there have been several studies which have focused on improving electronic conductivity with the intent of improving its rate-capability [4,6,8]. For example, recently Huang et al. [8] have shown that the formation of a Li 4Ti 5O 12/Cu xO composite anode that was formed by heat-treatment under a 3 vol.% H 2 in N 2 atmosphere at high rates (>2C) had a higher capacity over a similar powders heat-treated under air. For example, at 10C the capacity of the powders heated under the 3 vol.% H 2 in N 2 atmosphere was about 1.8 X that for the powders heated under air and was attributed to the higher electrical conductivity of the composite heated under the reducing atmosphere compared to under air. The electrical conductivity of the composite formed under the reducing atmosphere was about an order magnitude higher than that for the composite heated under air. Huang et al. [8] suggested that the improved electrical conductivity was a result of the reduction of some Ti 4+ to Ti 3+ in Li 4Ti 5O 12 and/or reduction of Cu 2+/Cu + in Cu xO to Cu metal under the reducing atmosphere. However, they did not separate these effects

Increased Thermal Conductivity in Metal-Organic Heat Carrier Nanofluids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nandasiri, Manjula I.; Liu, Jian; McGrail, B. Peter

2016-06-15

Metal organic heat carriers (MOHCs) are recently developed nanofluids containing metal organic framework (MOF) nanoparticles dispersed in various base fluids including refrigerants (R245Fa) and methanol. MOHCs utilize the MOF properties to improve the thermo-physical properties of base fluids. Here, we report the synthesis and characterization of MOHCs containing nanoMIL-101(Cr) and graphene oxide (GO) in an effort to improve the thermo-physical properties of various base fluids. MOHC containing MIL-101(Cr)/GO nanocomposites showed enhanced surface area, porosity, and nitrogen adsorption compared with the intrinsic nano MIL-101(Cr) and the properties depend on the amount of GO added. Powder X-ray diffraction (PXRD) confirmed the preservedmore » crystallinity of MIL-101(Cr) in all nanocomposites with the absence of any unreacted GO. Scanning electron microscopy images confirmed the presence of near spherical MIL-101(Cr) nanoparticles in the range of 40-80 nm in diameter. MOHC nanofluids containing MIL-101(Cr)/GO in methanol exhibited significant enhancement in the thermal conductivity (by approxi-mately 50%) relative to that of the intrinsic nano MIL-101(Cr) in methanol. The thermal conductivity of base fluid (methanol) was enhanced by about 20 %. The enhancement in the thermal conductivity of nanoMIL-101(Cr) MOHCs due to graphene oxide functionalization is explained using a classical Maxwell model.« less

Constraints on the Efficiency of Radial Migration in Spiral Galaxies

NASA Astrophysics Data System (ADS)

Daniel, Kathryne J.; Wyse, Rosemary F. G.

2015-01-01

A transient spiral arm can permanently rearrange the orbital angular momentum of the stellar disk without inducing kinematic heating. This phenomenon is called radial migration because a star's orbital angular momentum determines its mean orbital radius. Should radial migration be an efficient process it could cause a large fraction of disk stars to experience significant changes in their individual orbital angular momenta on dynamically short timescales. Such scenarios have strong implications for the chemical, structural and kinematic evolution of disk galaxies. We have undertaken an investigation into the physical dependencies of the efficiency of radial migration on stellar kinematics and spiral structure. In order for a disk star to migrate radially, it must first be 'trapped' in a particular family of orbits, called horseshoe orbits, that occur near the radius of corotation with a spiral pattern. Thus far, the only analytic criterion for horseshoe orbits has been for stars with zero random orbital energy. We present our analytically derived 'capture criterion' for stars with some finite random orbital energy in a disk with a given rotation curve. Our capture criterion predict that trapping in a horseshoe orbit is primarily determined by whether or not the position of a star's mean orbital radius (determined by its orbital angular momentum) is within the 'capture region', the location and shape of which can be derived from the capture criterion. We visualize and confirm this prediction via numerically integrated orbits. We then apply our capture criterion to snap shot models of disk galaxies to determine (1) the radial distribution of the fraction of stars initially trapped in horseshoe orbits, and (2) the dependence of the total fraction of captured stars in the disk on the radial component of the stellar velocity dispersion (σR) and the amplitude of the spiral perturbation to the underlying potential at corotation. We here present a model of an exponential

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

USGS Publications Warehouse

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

2007-01-01

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

Radial Distribution of Absorption in a Cesium Heat Pipe with Axial Laser Heating

DTIC Science & Technology

2011-03-01

The spring is used to maintain a clear circular path through the heat pipe and secure the mesh. Two copper crush gaskets attach the Brewster angled ...necessary. The pump beam is assumed to be a Gaussian beam and has been focused through a convex lens to position the beam waist at the center of

Cooling characteristics of air cooled radial turbine blades

NASA Astrophysics Data System (ADS)

Sato, T.; Takeishi, K.; Matsuura, M.; Miyauchi, J.

The cooling design and the cooling characteristics of air cooled radial turbine wheels, which are designed for use with the gas generator turbine for the 400 horse power truck gas turbine engine, are presented. A high temperature and high speed test was performed under aerodynamically similar conditions to that of the prototype engine in order to confirm the metal temperature of the newly developed integrated casting wheels constructed of the superalloys INCO 713C. The test results compared with the analytical value, which was established on the basis of the results of the heat transfer test and the water flow test, are discussed.

Experimental and theoretical analysis of nanofluids based on high temperature-heat transfer fluid with enhanced thermal properties

NASA Astrophysics Data System (ADS)

Navas, Javier; Sánchez-Coronilla, Antonio; Martín, Elisa I.; Gómez-Villarejo, Roberto; Teruel, Miriam; Gallardo, Juan Jesús; Aguilar, Teresa; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; Martín-Calleja, Joaquín

2017-04-01

In this work, nanofluids were prepared using commercial Cu nanoparticles and a commercial high temperature-heat transfer Fluid (eutectic mixture of diphenyl oxide and biphenyl) as the base fluid, which is used in concentrating solar power (CSP) plants. Different properties such as density, viscosity, heat capacity and thermal conductivity were characterized. Nanofluids showed enhanced heat transfer efficiency. In detail, the incorporation of Cu nanoparticles led to an increase of the heat capacity up to 14%. Also, thermal conductivity was increased up to 13%. Finally, the performance of the nanofluids prepared increased up to 11% according to the Dittus-Boelter correlation. On the other hand, equilibrium molecular dynamics simulation was used to model the experimental nanofluid system studied. Thermodynamic properties such as heat capacity and thermal conductivity were calculated and the results were compared with experimental data. The analysis of the radial function distributions (RDFs) and the inspection of the spatial distribution functions (SDFs) indicate the important role that plays the metal-oxygen interaction in the system. Dynamic properties such as the diffusion coefficients of base fluid and nanofluid were computed according to Einstein relation by computing the mean square displacement (MSD). Supplementary online material is available in electronic form at http://www.epjap.org

Investigation of Conjugate Heat Transfer in Turbine Blades and Vanes

NASA Technical Reports Server (NTRS)

Kassab, A. J.; Kapat, J. S.

2001-01-01

We report on work carried out to develop a 3-D coupled Finite Volume/BEM-based temperature forward/flux back (TFFB) coupling algorithm to solve the conjugate heat transfer (CHT) which arises naturally in analysis of systems exposed to a convective environment. Here, heat conduction within a structure is coupled to heat transfer to the external fluid which is convecting heat into or out of the solid structure. There are two basic approaches to solving coupled fluid structural systems. The first is a direct coupling where the solution of the different fields is solved simultaneously in one large set of equations. The second approach is a loose coupling strategy where each set of field equations is solved to provide boundary conditions for the other. The equations are solved in turn until an iterated convergence criterion is met at the fluid-solid interface. The loose coupling strategy is particularly attractive when coupling auxiliary field equations to computational fluid dynamics codes. We adopt the latter method in which the BEM is used to solve heat conduction inside a structure which is exposed to a convective field which in turn is resolved by solving the NASA Glenn compressible Navier-Stokes finite volume code Glenn-HT. The BEM code features constant and bi-linear discontinuous elements and an ILU-preconditioned GMRES iterative solver for the resulting non-symmetric algebraic set arising in the conduction solution. Interface of flux and temperature is enforced at the solid/fluid interface, and a radial-basis function scheme is used to interpolated information between the CFD and BEM surface grids. Additionally, relaxation is implemented in passing the fluxes from the conduction solution to the fluid solution. Results from a simple test example are reported.

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

NASA Technical Reports Server (NTRS)

Tabakoff, W.

1975-01-01

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

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

NASA Astrophysics Data System (ADS)

Talmage, G.

1994-05-01

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

Effect of narrow band nonuniformity on unsteady heat up of water vapor under radiation-conduction combined heat transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okamoto, Tatsuyuki; Tanaka, Tomohiro; Morimune, Atsushi

Effect of narrow band nonuniformity on unsteady heat up process of water vapor under radiation-conduction combined heat transfer is examined by comparing the result of numerical simulations with and without incorporation of narrow band nonuniformity. The authors propose a rational and comprehensive computational approach for incorporating the narrow band nonuniformity into numerical simulations of radiative heat transfer when the considered field is nonisothermal. Results of examination exhibited that the contribution of radiative heat transfer to the heat up rate of water vapor may be almost twice overestimated, if the narrow band nonuniformity effect is neglected. Separate analyses of radiative energymore » attributed to wall emission and gas emission clarified that the absorption of wall emission is overestimated and, on the contrary, the absorption of radiation energy emitted by water vapor itself is underestimated if the narrow band nonuniformity is neglected. The reason why such over- or under-estimation is induced is understood by examining the influence of line overlap parameter on the transmittance averaged within a narrow band. Smaller value of line overlap parameter {gamma}/d means more violent narrow band nonuniformity. The broken lines show the narrow band transmittance for flat incident power spectrum, and the solid lines show that for the radiative emission from the absorbing gas itself. It is also clarified that the disregard of the narrow band nonuniformity give rise to serious error in the estimation of absorption rate of wall and gas emission even in the case where the disregard of narrow band nonuniformity bring little change to the temperature distribution. The results illustrated in this paper suggest that the narrow band nonuniformity should not be neglected.« less

Efficiently modelling urban heat storage: an interface conduction scheme in an urban land surface model (aTEB v2.0)

NASA Astrophysics Data System (ADS)

Lipson, Mathew J.; Hart, Melissa A.; Thatcher, Marcus

2017-03-01

Intercomparison studies of models simulating the partitioning of energy over urban land surfaces have shown that the heat storage term is often poorly represented. In this study, two implicit discrete schemes representing heat conduction through urban materials are compared. We show that a well-established method of representing conduction systematically underestimates the magnitude of heat storage compared with exact solutions of one-dimensional heat transfer. We propose an alternative method of similar complexity that is better able to match exact solutions at typically employed resolutions. The proposed interface conduction scheme is implemented in an urban land surface model and its impact assessed over a 15-month observation period for a site in Melbourne, Australia, resulting in improved overall model performance for a variety of common material parameter choices and aerodynamic heat transfer parameterisations. The proposed scheme has the potential to benefit land surface models where computational constraints require a high level of discretisation in time and space, for example at neighbourhood/city scales, and where realistic material properties are preferred, for example in studies investigating impacts of urban planning changes.

FORTRAN 77 programs for conductive cooling of dikes with temperature-dependent thermal properties and heat of crystallization

USGS Publications Warehouse

Delaney, P.T.

1988-01-01

Temperature histories obtained from transient heat-conduction theory are applicable to most dikes despite potential complicating effects related to magma flow during emplacement, groundwater circulation, and metamorphic reaction during cooling. Here. machine-independent FORTRAN 77 programs are presented to calculate temperatures in and around dikes as they cool conductively. Analytical solutions can treat thermal-property contrasts between the dike and host rocks, but cannot address the release of magmatic heat of crystallization after the early stages of cooling or the appreciable temperature dependence of thermal conductivity and diffusivity displayed by most rock types. Numerical solutions can incorporate these additional factors. The heat of crystallization can raise the initial temperature at the dike contact, ??c1, about 100??C above that which would be estimated if it were neglected, and can decrease the rate at which the front of solidified magma moves to the dike center by a factor of as much as three. Thermal conductivity and diffusivity of rocks increase with decreasing temperature and, at low temperatures, these properties increase more if the rocks are saturated with water. Models that treat these temperature dependencies yield estimates of ??c1 that are as much as 75??C beneath those which would be predicted if they were neglected. ?? 1988.

Extraction of temperature dependent electrical resistivity and thermal conductivity from silicon microwires self-heated to melting temperature

NASA Astrophysics Data System (ADS)

Bakan, Gokhan; Adnane, Lhacene; Gokirmak, Ali; Silva, Helena

2012-09-01

Temperature-dependent electrical resistivity, ρ(T), and thermal conductivity, k(T), of nanocrystalline silicon microwires self-heated to melt are extracted by matching simulated current-voltage (I-V) characteristics to experimental I-V characteristics. Electrical resistivity is extracted from highly doped p-type wires on silicon dioxide in which the heat losses are predominantly to the substrate and the self-heating depends mainly on ρ(T) of the wires. The extracted ρ(T) decreases from 11.8 mΩ cm at room-temperature to 5.2 mΩ cm at 1690 K, in reasonable agreement with the values measured up to ˜650 K. Electrical resistivity and thermal conductivity are extracted from suspended highly doped n-type silicon wires in which the heat losses are predominantly through the wires. In this case, measured ρ(T) (decreasing from 20.5 mΩ cm at room temperature to 12 mΩ cm at 620 K) is used to extract ρ(T) at higher temperatures (decreasing to 1 mΩ cm at 1690 K) and k(T) (decreasing from 30 W m-1 K-1 at room temperature to 20 W m-1 K-1 at 1690 K). The method is tested by using the extracted parameters to model wires with different dimensions. The experimental and simulated I-V curves for these wires show good agreement up to high voltage and temperature levels. This technique allows extraction of the electrical resistivity and thermal conductivity up to very high temperatures from self-heated microstructures.

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

NASA Technical Reports Server (NTRS)

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

2005-01-01

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

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.

Heat amplification and negative differential thermal conductance in a strongly coupled nonequilibrium spin-boson system

NASA Astrophysics Data System (ADS)

Wang, Chen; Chen, Xu-Min; Sun, Ke-Wei; Ren, Jie

2018-05-01

We investigate the nonequilibrium quantum heat transfer in a quantum thermal transistor, constructed by a triangle-coupled spin-boson system in a three-terminal setup. By exploiting the nonequilibrium noninteracting blip approximation approach combined with full counting statistics, we obtain the steady-state thermal transport, such as heat currents. We identify the giant heat amplification feature in a strong coupling regime, which results from the negative differential thermal conductance with respect to the gate temperature. Analysis shows that the strong coupling between the gate qubit and corresponding gate thermal bath plays the crucial role in exhibiting these far-from-equilibrium features. These results would have potential implications in designing efficient quantum thermal transistors in the future.

Symmetric flows for compressible heat-conducting fluids with temperature dependent viscosity coefficients

NASA Astrophysics Data System (ADS)

Wan, Ling; Wang, Tao

2017-06-01

We consider the Navier-Stokes equations for compressible heat-conducting ideal polytropic gases in a bounded annular domain when the viscosity and thermal conductivity coefficients are general smooth functions of temperature. A global-in-time, spherically or cylindrically symmetric, classical solution to the initial boundary value problem is shown to exist uniquely and converge exponentially to the constant state as the time tends to infinity under certain assumptions on the initial data and the adiabatic exponent γ. The initial data can be large if γ is sufficiently close to 1. These results are of Nishida-Smoller type and extend the work (Liu et al. (2014) [16]) restricted to the one-dimensional flows.

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

USGS Publications Warehouse

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.

Pressure dependence of thermal conductivity and specific heat in CeRh2Si2 measured by an extended thermal relaxation method

NASA Astrophysics Data System (ADS)

Nishigori, Shijo; Seida, Osamu

2018-05-01

We have developed a new technique for measuring thermal conductivity and specific heat under pressure by improving a thermal relaxation method. In this technique, a cylindrical sample with a small disc heater is embedded in the pressure-transmitting medium, then temperature variations of the sample and heater were directly measured by thermocouples during a heating and cooling process. Thermal conductivity and specific heat are estimated by comparing the experimental data with temperature variations simulated by a finite element method. The obtained thermal conductivity and specific heat of the test sample CeRh2Si2 exhibit a small enhancement and a clear peak arising from antiferromagnetic transition, respectively. The observation of these typical behaviors for magnetic compounds indicate that the technique is valid for the study on thermal properties under pressure.

One-dimensional analysis of plane and radial thin film flows including solid-body rotation

NASA Technical Reports Server (NTRS)

Thomas, S.; Hankey, W.; Faghri, A.; Swanson, T.

1989-01-01

The flow of a thin liquid film with a free surface along a horizontal plate which emanates from a pressurized vessel is examined by integrating the equations of motion across the thin liquid layer and discretizing the integrated equations using finite difference techniques. The effects of 0-g and solid-body rotation will be discussed. The two cases of interest are plane flow and radial flow. In plane flow, the liquid is considered to be flowing along a channel with no change in the width of the channel, whereas in radial flow the liquid spreads out radially over a disk, so that the area changes along the radius. It is desired to determine the height of the liquid film at any location along the plate of disk, so that the heat transfer from the plate or disk can be found. The possibility that the flow could encounter a hydraulic jump is accounted for.

Hyperbolic heat conduction problems involving non-Fourier effects - Numerical simulations via explicit Lax-Wendroff/Taylor-Galerkin finite element formulations

NASA Technical Reports Server (NTRS)

Tamma, Kumar K.; Namburu, Raju R.

1989-01-01

Numerical simulations are presented for hyperbolic heat-conduction problems that involve non-Fourier effects, using explicit, Lax-Wendroff/Taylor-Galerkin FEM formulations as the principal computational tool. Also employed are smoothing techniques which stabilize the numerical noise and accurately predict the propagating thermal disturbances. The accurate capture of propagating thermal disturbances at characteristic time-step values is achieved; numerical test cases are presented which validate the proposed hyperbolic heat-conduction problem concepts.

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.

Novel 18650 lithium-ion battery surrogate cell design with anisotropic thermophysical properties for studying failure events

NASA Astrophysics Data System (ADS)

Spinner, Neil S.; Hinnant, Katherine M.; Mazurick, Ryan; Brandon, Andrew; Rose-Pehrsson, Susan L.; Tuttle, Steven G.

2016-04-01

Cylindrical 18650-type surrogate cells were designed and fabricated to mimic the thermophysical properties and behavior of active lithium-ion batteries. An internal jelly roll geometry consisting of alternating stainless steel and mica layers was created, and numerous techniques were used to estimate thermophysical properties. Surrogate cell density was measured to be 1593 ± 30 kg/m3, and heat capacity was found to be 727 ± 18 J/kg-K. Axial thermal conductivity was determined to be 5.1 ± 0.6 W/m-K, which was over an order of magnitude higher than radial thermal conductivity due to jelly roll anisotropy. Radial heating experiments were combined with numerical and analytical solutions to the time-dependent, radial heat conduction equation, and from the numerical method an additional estimate for heat capacity of 805 ± 23 J/kg-K was found. Using both heat capacities and analysis techniques, values for radial thermal conductivity were between 0.120 and 0.197 W/m-K. Under normal operating conditions, relatively low radial temperature distributions were observed; however, during extreme battery failure with a hexagonal cell package, instantaneous radial temperature distributions as high as 43-71 °C were seen. For a vertical cell package, even during adjacent cell failure, similar homogeneity in internal temperatures were observed, demonstrating thermal anisotropy.

Temporal and radial variation of the solar wind temperature-speed relationship

NASA Astrophysics Data System (ADS)

Elliott, H. A.; Henney, C. J.; McComas, D. J.; Smith, C. W.; Vasquez, B. J.

2012-09-01

The solar wind temperature (T) and speed (V) are generally well correlated at ˜1 AU, except in Interplanetary Coronal Mass Ejections where this correlation breaks down. We perform a comprehensive analysis of both the temporal and radial variation in the temperature-speed (T-V) relationship of the non-transient wind, and our analysis provides insight into both the causes of the T-V relationship and the sources of the temperature variability. Often at 1 AU the speed-temperature relationship is well represented by a single linear fit over a speed range spanning both the slow and fast wind. However, at times the fast wind from coronal holes can have a different T-V relationship than the slow wind. A good example of this was in 2003 when there was a very large and long-lived outward magnetic polarity coronal hole at low latitudes that emitted wind with speeds as fast as a polar coronal hole. The long-lived nature of the hole made it possible to clearly distinguish that some holes can have a different T-V relationship. In an earlier ACE study, we found that both the compressions and rarefactions T-V curves are linear, but the compression curve is shifted to higher temperatures. By separating compressions and rarefactions prior to determining the radial profiles of the solar wind parameters, the importance of dynamic interactions on the radial evolution of the solar wind parameters is revealed. Although the T-V relationship at 1 AU is often well described by a single linear curve, we find that the T-V relationship continually evolves with distance. Beyond ˜2.5 AU the differences between the compressions and rarefactions are quite significant and affect the shape of the overall T-V distribution to the point that a simple linear fit no longer describes the distribution well. Since additional heating of the ambient solar wind outside of interaction regions can be associated with Alfvénic fluctuations and the turbulent energy cascade, we also estimate the heating rate

Holographic heat current as Noether current

NASA Astrophysics Data System (ADS)

Liu, Hai-Shan; Lü, H.; Pope, C. N.

2017-09-01

We employ the Noether procedure to derive a general formula for the radially conserved heat current in AdS planar black holes with certain transverse and traceless perturbations, for a general class of gravity theories. For Einstein gravity, the general higher-order Lovelock gravities and also a class of Horndeski gravities, we derive the boundary stress tensor and show that the resulting boundary heat current matches precisely the bulk Noether current.

Simulating Remediation of Trichloroethylene in Fractured Bedrock by Thermal Conductive Heating Using the Numerical Model TMVOC

DTIC Science & Technology

2013-01-01

in the well and the process of conductive heating occurs away from the well ( Baston and Kueper, 2009). This process is highly effective for...of an extra row of heater wells outside of the treatment zone to preheat the water ( Baston and Kueper, 2009). To reduce the amount of cooling that...concrete slab ( Baston and Kueper, 2009). This not only reduces heat loss, but also reduces the amount of infiltration of precipitation into the

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

ERIC Educational Resources Information Center

Mendez, Sergio; AungYong, Lisa

2014-01-01

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

One-Particle Representation of Heat Conduction Described within the Scope of the Second Law

PubMed Central

Jesudason, Christopher Gunaseelan

2016-01-01

The Carnot cycle and its deduction of maximum conversion efficiency of heat inputted and outputted isothermally at different temperatures necessitated the construction of isothermal and adiabatic pathways within the cycle that were mechanically “reversible”, leading eventually to the Kelvin-Clausius development of the entropy function S with differential dS=dq/T such that ∮CdS=0 where the heat absorption occurs at the isothermal paths of the elementary Carnot cycle. Another required condition is that the heat transfer processes take place infinitely slowly and “reversibly”, implying that rates of transfer are not explicitly featured in the theory. The definition of ‘heat’ as that form of energy that is transferred as a result of a temperature difference suggests that the local mode of transfer of “heat” in the isothermal segments of the pathway implies a Fourier-like heat conduction mechanism which is apparently irreversible, leading to an increase in entropy of the combined reservoirs at either end of the conducting material, and which is deemed reversible mechanically. These paradoxes are circumvented here by first clarifying the terms used before modeling heat transfer as a thermodynamically reversible but mechanically irreversible process and applied to a one dimensional atomic lattice chain of interacting particles subjected to a temperature difference exemplifying Fourier heat conduction. The basis of a “recoverable trajectory” i.e. that which follows a zero entropy trajectory is identified. The Second Law is strictly maintained in this development. A corollary to this zero entropy trajectory is the generalization of the Zeroth law for steady state non-equilibrium systems with varying temperature, and thus to a statement about “equilibrium” in steady state non-thermostatic conditions. An energy transfer rate term is explicitly identified for each particle and agrees quantitatively (and independently) with the rate of heat absorbed at

Heating device for semiconductor wafers

DOEpatents

Vosen, Steven R.

1999-01-01

An apparatus for heat treating semiconductor wafers is disclosed. The apparatus includes a heating device which contains an assembly of light energy sources for emitting light energy onto a wafer. In particular, the light energy sources are positioned such that many different radial heating zones are created on a wafer being heated. For instance, in one embodiment, the light energy sources form a spiral configuration. In an alternative embodiment, the light energy sources appear to be randomly dispersed with respect to each other so that no discernable pattern is present. In a third alternative embodiment of the present invention, the light energy sources form concentric rings. Tuning light sources are then placed in between the concentric rings of light.

Optimization method for an evolutional type inverse heat conduction problem

NASA Astrophysics Data System (ADS)

Deng, Zui-Cha; Yu, Jian-Ning; Yang, Liu

2008-01-01

This paper deals with the determination of a pair (q, u) in the heat conduction equation u_t-u_{xx}+q(x,t)u=0, with initial and boundary conditions u(x,0)=u_0(x),\\qquad u_x|_{x=0}=u_x|_{x=1}=0, from the overspecified data u(x, t) = g(x, t). By the time semi-discrete scheme, the problem is transformed into a sequence of inverse problems in which the unknown coefficients are purely space dependent. Based on the optimal control framework, the existence, uniqueness and stability of the solution (q, u) are proved. A necessary condition which is a couple system of a parabolic equation and parabolic variational inequality is deduced.

Design characteristics of a heat pipe test chamber

NASA Technical Reports Server (NTRS)

Baker, Karl W.; Jang, J. Hoon; Yu, Juin S.

1992-01-01

LeRC has designed a heat pipe test facility which will be used to provide data for validating heat pipe computer codes. A heat pipe test chamber that uses helium gas for enhancing heat transfer was investigated. The conceptual design employs the technique of guarded heating and guarded cooling to facilitate accurate measurements of heat transfer rates to the evaporator and from the condenser. The design parameters are selected for a baseline heat pipe made of stainless steel with an inner diameter of 38.10 mm and a wall thickness of 1.016 mm. The heat pipe operates at a design temperature of 1000 K with an evaporator radial heat flux of 53 W/sq. cm.

Modal Contributions to Heat Conduction across Crystalline and Amorphous Si/Ge Interfaces

NASA Astrophysics Data System (ADS)

Gordiz, Kiarash; Henry, Asegun

Until now, our entire understanding of interfacial heat transfer has been based on the phonon gas model and Landauer formalism. Based on this framework, it is difficult to offer any intuition on heat transfer between two solid materials if one side of the interface is an amorphous structure. Here, using the interface conductance modal analysis (ICMA) method, we investigate the modal contributions to thermal interface conductance (TIC) through crystalline (c) and amorphous (a) Si/Ge interfaces. It is revealed that around 15% of the conductance through the cSi/cGe interface arises from less than 0.1% of the modes of vibration in the structure that exist between 12-13THz and because of their large eigenvectors around the interface are classified as interfacial modes. Correlation maps show that these interfacial modes exhibit strong correlations with all the other modes. The physics behind this strong coupling ability is studied by calculating the mode-level harmonic and anharmonic energy distribution among all the atoms in the system. It is found that these interfacial modes are enabled by the large degree of anharmonicity near the interface, which is higher than the bulk and ultimately allows this small group of modes to couple to other modes of vibration. In addition, unlike the cSi/cGe, correlation maps for aSi/cGe, cSi/aGe, and aSi/aGe interfaces show that the majority of contributions to TIC arise from auto-correlations instead of cross-correlations. The provided analysis sheds light on the nature of localized vibrations at interfaces and can be enlightening for other investigations of localization.

Convection effects on radial segregation and crystal melt interface in vertical Bridgman growth

NASA Technical Reports Server (NTRS)

Tanveer, S.

1993-01-01

We analytically study the influence of convection caused by horizontal heat transfer through the sides of a vertical Bridgman apparatus. We consider the case when the heat transfer across the side walls is small so that the resulting interfacial deformation and fluid velocities are also small. This allows us to linearize the Navier-Stokes equations and express the interfacial conditions about a planar interface through a Taylor expansion. Using a no tangential stress conditions on the side walls, asymptotic expressions for both the interfacial slope, and radial segregation at the crystal-melt interface are obtained in closed form in the limit of large thermal Rayleigh number. It is suggested that these can be reduced by appropriately controlling a specific heat transfer property at the edge of the insulation zone in the solid side.

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

NASA Astrophysics Data System (ADS)

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

2012-09-01

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

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

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-06

... INTERNATIONAL TRADE COMMISSION [Docket No. 2899] Certain Integrated Circuit Packages Provided With... complaint entitled Certain Integrated Circuit Packages Provided With Multiple Heat-Conducting Paths and..., telephone (202) 205-2000. The public version of the complaint can be accessed on the Commission's electronic...

Calculation of thermal conductivity, thermal diffusivity and specific heat capacity of sedimentary rocks using petrophysical well logs

NASA Astrophysics Data System (ADS)

Fuchs, Sven; Balling, Niels; Förster, Andrea

2015-12-01

In this study, equations are developed that predict for synthetic sedimentary rocks (clastics, carbonates and evapourates) thermal properties comprising thermal conductivity, specific heat capacity and thermal diffusivity. The rock groups are composed of mineral assemblages with variable contents of 15 major rock-forming minerals and porosities of 0-30 per cent. Petrophysical properties and their well-logging-tool-characteristic readings were assigned to these rock-forming minerals and to pore-filling fluids. Relationships are explored between each thermal property and other petrophysical properties (density, sonic interval transit time, hydrogen index, volume fraction of shale and photoelectric absorption index) using multivariate statistics. The application of these relations allows computing continuous borehole profiles for each rock thermal property. The uncertainties in the prediction of each property vary depending on the selected well-log combination. Best prediction is in the range of 2-8 per cent for the specific heat capacity, of 5-10 per cent for the thermal conductivity, and of 8-15 for the thermal diffusivity, respectively. Well-log derived thermal conductivity is validated by laboratory data measured on cores from deep boreholes of the Danish Basin, the North German Basin, and the Molasse Basin. Additional validation of thermal conductivity was performed by comparing predicted and measured temperature logs. The maximum deviation between these logs is <3 °C. The thermal-conductivity calculation allowed an evaluation of the depth range in which the palaeoclimatic effect on the subsurface temperature field can be observed in the North German Basin. This effect reduces the surface heat-flow density by 25 mW m-2.

A new Eulerian model for viscous and heat conducting compressible flows

NASA Astrophysics Data System (ADS)

Svärd, Magnus

2018-09-01

In this article, a suite of physically inconsistent properties of the Navier-Stokes equations, associated with the lack of mass diffusion and the definition of velocity, is presented. We show that these inconsistencies are consequences of the Lagrangian derivation that models viscous stresses rather than diffusion. A new model for compressible and diffusive (viscous and heat conducting) flows of an ideal gas, is derived in a purely Eulerian framework. We propose that these equations supersede the Navier-Stokes equations. A few numerical experiments demonstrate some differences and similarities between the new system and the Navier-Stokes equations.

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

NASA Technical Reports Server (NTRS)

Maise, G.; Rossi, M. J.

1974-01-01

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

Radial retinotomy in the macula.

PubMed

Bovino, J A; Marcus, D F

1984-01-01

Radial retinotomy is an operative procedure usually performed in the peripheral or equatorial retina. To facilitate retinal attachment, the authors used intraocular scissors to perform radial retinotomy in the macula of two patients during vitrectomy surgery. In the first patient, a retinal detachment complicated by periretinal proliferation and macula hole formation was successfully reoperated with the aid of three radial cuts in the retina at the edges of the macular hole. In the second patient, an intraoperative retinal tear in the macula during diabetic vitrectomy was also successfully repaired with the aid of radial retinotomy. In both patients, retinotomy in the macula was required because epiretinal membranes, which could not be easily delaminated, were hindering retinal reattachment.

Heat transfer in thermal barrier coated rods with circumferential and radial temperature gradients

NASA Astrophysics Data System (ADS)

Chung, B. T. F.; Kermani, M. M.; Braun, M. J.; Padovan, J.; Hendricks, R.

1984-06-01

To study the heat transfer in ceramic coatings applied to the heated side of internally cooled hot section components of the gas turbine engine, a mathematical model is developed for the thermal response of plasma-sprayed ZrO2-Y2O3 ceramic materials with a Ni-Cr-AL-Y bond coat on a Rene 41 rod substrate subject to thermal cycling. This multilayered cylinder with temperature dependent thermal properties is heated in a cross-flow by a high velocity flame and then cooled by ambient air. Due to high temperature and high velocity of the flame, both gas radiation and forced convection are taken into consideration. Furthermore, the local turbulent heat transfer coefficient is employed which varies with angular position as well as the surface temperature. The transient two-dimensional (heat transfer along axial direction is neglected) temperature distribution of the composite cylinder is determined numerically.

Heat transfer in thermal barrier coated rods with circumferential and radial temperature gradients

NASA Technical Reports Server (NTRS)

Chung, B. T. F.; Kermani, M. M.; Braun, M. J.; Padovan, J.; Hendricks, R.

1984-01-01

To study the heat transfer in ceramic coatings applied to the heated side of internally cooled hot section components of the gas turbine engine, a mathematical model is developed for the thermal response of plasma-sprayed ZrO2-Y2O3 ceramic materials with a Ni-Cr-AL-Y bond coat on a Rene 41 rod substrate subject to thermal cycling. This multilayered cylinder with temperature dependent thermal properties is heated in a cross-flow by a high velocity flame and then cooled by ambient air. Due to high temperature and high velocity of the flame, both gas radiation and forced convection are taken into consideration. Furthermore, the local turbulent heat transfer coefficient is employed which varies with angular position as well as the surface temperature. The transient two-dimensional (heat transfer along axial direction is neglected) temperature distribution of the composite cylinder is determined numerically.

On Electromagnetic Modulation of Flow Instabilities, Mixing and Heat Transfer in Conducting and Magnetized Fluids

NASA Astrophysics Data System (ADS)

Kenjeres, S.

2016-09-01

In the present paper we give a concise review of some recent highlights of our research dealing with electromagnetic control of flow, mixing and heat transfer of electrically conductive or magnetized fluids. We apply a combination of state-of-art numerical (DNS and LES) and experimental (PIV and LIF) techniques to provide fundamental insights into the complex phenomena of interactions between imposed (or induced) electromagnetic fields and underlying fluid flow. Our analysis covers an extensive range of working fluids, i.e. weakly- and highly-electrically-conductive, as well as magnetized fluids. These interactions are defined through the presence of different types of body forces acting per volume of fluid. A fully closed system of governing equations containing an extended set of the Navier-Stokes and a simplified set of the Maxwell equations is presented. The four characteristic examples are selected: the electromagnetic control of self-sustained jet oscillations, the electromagnetic enhancement of heat transfer in thermal convection, the wake interactions behind magnetic obstacles and finally, the thermo-magnetic convection in differentially heated cubical enclosure. The comparative assessment between experimental and numerical results is presented. It is concluded that generally good agreement between simulations and experiments is obtained for all cases considered, proving the concept of electromagnetic modulation, which can be used in numerous technological applications.

Electrophysiological examination and high frequency ultrasonography for diagnosis of radial nerve torsion and compression

PubMed Central

Shi, Miao; Qi, Hengtao; Ding, Hongyu; Chen, Feng; Xin, Zhaoqin; Zhao, Qinghua; Guan, Shibing; Shi, Hao

2018-01-01

Abstract This study aims to evaluate the value of electrophysiological examination and high frequency ultrasonography in the differential diagnosis of radial nerve torsion and radial nerve compression. Patients with radial nerve torsion (n = 14) and radial nerve compression (n = 14) were enrolled. The results of neurophysiological and high frequency ultrasonography were compared. Electrophysiological examination and high-frequency ultrasonography had a high diagnostic rate for both diseases with consistent results. Of the 28 patients, 23 were positive for electrophysiological examination, showing decreased amplitude and decreased conduction velocity of radial nerve; however, electrophysiological examination cannot distinguish torsion from compression. A total of 27 cases showed positive in ultrasound examinations among all 28 cases. On ultrasound images, the nerve was thinned at torsion site whereas thickened at the distal ends of torsion. The diameter and cross-sectional area of torsion or compression determined the nerve damage, and ultrasound could locate the nerve injury site and measure the length of the nerve. Electrophysiological examination and high-frequency ultrasonography can diagnose radial neuropathy, with electrophysiological examination reflecting the neurological function, and high-frequency ultrasound differentiating nerve torsion from compression. PMID:29480857

Thermal Conductivity Change Kinetics of Ceramic Thermal Barrier Coatings Determined by the Steady-State Laser Heat Flux Technique

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.

2000-01-01

A steady-state laser heat flux technique has been developed at the NASA Glenn Research Center at Lewis Field to obtain critical thermal conductivity data of ceramic thermal barrier coatings under the temperature and thermal gradients that are realistically expected to be encountered in advanced engine systems. In this study, thermal conductivity change kinetics of a plasma-sprayed, 254-mm-thick ZrO2-8 wt % Y2O3 ceramic coating were obtained at high temperatures. During the testing, the temperature gradients across the coating system were carefully measured by the surface and back pyrometers and an embedded miniature thermocouple in the substrate. The actual heat flux passing through the coating system was determined from the metal substrate temperature drop (measured by the embedded miniature thermocouple and the back pyrometer) combined with one-dimensional heat transfer models.

Unsteady Sisko magneto-nanofluid flow with heat absorption and temperature dependent thermal conductivity: A 3D numerical study

NASA Astrophysics Data System (ADS)

Khan, Masood; Ahmad, Latif; Gulzar, M. Mudassar

2018-03-01

The impact of temperature dependent thermal conductivity and convective surface conditions on unsteady 3D Sisko nanofluid flow over a stretching surface is studied in the presence of heat generation/absorption and magnetic field. The numerical solution of nonlinear coupled equations has been carried out to explore the properties of different physical profiles of the fluid flow with varying of parameters. Specifically, the application of generalized Biot numbers and heat generation/absorption parameter in the sketching of temperature and concentration profiles are explored. The effect of all three parameters is noticed in the increasing order for shear thinning (0 < n < 1) and for shear thickening (n > 1) fluids. Moreover, the influence of Biot number γ1 on heat and mass transfer rates, are found in the enhancement and diminishing conducts respectively, in both cases of shear thinning as well as shear thickening fluids and a reverse trend is observed with the variation of Biot number γ2 . Additionally, the present results are validated through skin friction, heat and mass transfer rate values with the comparable values in the existing previous values.

Combination radial and thrust magnetic bearing

NASA Technical Reports Server (NTRS)

Blumenstock, Kenneth A. (Inventor)

2002-01-01

A combination radial and thrust magnetic bearing is disclosed that allows for both radial and thrust axes control of an associated shaft. The combination radial and thrust magnetic bearing comprises a rotor and a stator. The rotor comprises a shaft, and first and second rotor pairs each having respective rotor elements. The stator comprises first and second stator elements and a magnet-sensor disk. In one embodiment, each stator element has a plurality of split-poles and a corresponding plurality of radial force coils and, in another embodiment, each stator element does not require thrust force coils, and radial force coils are replaced by double the plurality of coils serving as an outer member of each split-pole half.

Radial turbine cooling

NASA Technical Reports Server (NTRS)

Roelke, Richard J.

1992-01-01

Radial turbines have been used extensively in many applications including small ground based electrical power generators, automotive engine turbochargers and aircraft auxiliary power units. In all of these applications the turbine inlet temperature is limited to a value commensurate with the material strength limitations and life requirements of uncooled metal rotors. To take advantage of all the benefits that higher temperatures offer, such as increased turbine specific power output or higher cycle thermal efficiency, requires improved high temperature materials and/or blade cooling. Extensive research is on-going to advance the material properties of high temperature superalloys as well as composite materials including ceramics. The use of ceramics with their high temperature potential and low cost is particularly appealing for radial turbines. However until these programs reach fruition the only way to make significant step increases beyond the present material temperature barriers is to cool the radial blading.

Radial q-space sampling for DSI.

PubMed

Baete, Steven H; Yutzy, Stephen; Boada, Fernando E

2016-09-01

Diffusion spectrum imaging (DSI) has been shown to be an effective tool for noninvasively depicting the anatomical details of brain microstructure. Existing implementations of DSI sample the diffusion encoding space using a rectangular grid. Here we present a different implementation of DSI whereby a radially symmetric q-space sampling scheme for DSI is used to improve the angular resolution and accuracy of the reconstructed orientation distribution functions. Q-space is sampled by acquiring several q-space samples along a number of radial lines. Each of these radial lines in q-space is analytically connected to a value of the orientation distribution functions at the same angular location by the Fourier slice theorem. Computer simulations and in vivo brain results demonstrate that radial diffusion spectrum imaging correctly estimates the orientation distribution functions when moderately high b-values (4000 s/mm2) and number of q-space samples (236) are used. The nominal angular resolution of radial diffusion spectrum imaging depends on the number of radial lines used in the sampling scheme, and only weakly on the maximum b-value. In addition, the radial analytical reconstruction reduces truncation artifacts which affect Cartesian reconstructions. Hence, a radial acquisition of q-space can be favorable for DSI. Magn Reson Med 76:769-780, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Heat transfer between a heated plate and an impinging transient diesel spray

NASA Astrophysics Data System (ADS)

Arcoumanis, C.; Chang, J.-C.

1993-12-01

An experimental investigation was performed to determine the heat-transfer distribution in the vicinity of a transient diesel spray impinging on a heated flat plate. The spray prior to impingement was characterised in terms of simultaneous droplet sizes and velocities by phase-Doppler anemometry while during its impingement on the plate, which was heated at temperatures between 150 205°C, the instantaneous surface temperature and associated rates of wall heat transfer were monitored by fast response thermocouples. The parameters examined in this work included the distance between the nozzle and the wall surface, the radial distance from the impingement point, the injection frequency, the injected volume and the pre-impingement wall temperature. The results showed that the wall heat transfer rates are dependent on the spray characteristics prior to impingement; the higher the “velocity of arrival” of the droplet is, the higher the heat transfer. A correlation was thus developed for the instantaneous and spatially-resolved spray/wall heat transfer based on experimentally-determined Nusselt, Reynolds, Prandtl and Weber numbers over a wide range of test conditions.

Two dimensional finite element heat transfer models for softwood

Treesearch

Hongmei Gu; John F. Hunt

2004-01-01

The anisotropy of wood creates a complex problem for solving heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models use average thermal properties across either the radial or tangential directions and have not differentiated the effects of cellular alignment, earlywood/latewood...

Nuclear reactor removable radial shielding assembly having a self-bowing feature

DOEpatents

Pennell, William E.; Kalinowski, Joseph E.; Waldby, Robert N.; Rylatt, John A.; Swenson, Daniel V.

1978-01-01

A removable radial shielding assembly for use in the periphery of the core of a liquid-metal-cooled fast-breeder reactor, for closing interassembly gaps in the reactor core assembly load plane prior to reactor criticality and power operation to prevent positive reactivity insertion. The assembly has a lower nozzle portion for inserting into the core support and a flexible heat-sensitive bimetallic central spine surrounded by blocks of shielding material. At refueling temperature and below the spine is relaxed and in a vertical position so that the tolerances permitted by the interassembly gaps allow removal and replacement of the various reactor core assemblies. During an increase in reactor temperature from refueling to hot standby, the bimetallic spine expands, bowing the assembly toward the core center line, exerting a radially inward gap-closing-force on the above core load plane of the reactor core assembly, closing load plane interassembly gaps throughout the core prior to startup and preventing positive reactivity insertion.

Radial Halbach Magnetic Bearings

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2009-01-01

Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while

Thermal performance of an integrated collector storage solar water heater (ICSSWH) with a storage tank equipped with radial fins of rectangular profile

NASA Astrophysics Data System (ADS)

Chaabane, Monia; Mhiri, Hatem; Bournot, Philippe

2013-01-01

The thermal behavior of an integrated collector storage solar water heater (ICSSWH) is numerically studied using the package Fluent 6.3. Based on the good agreement between the numerical results and the experimental data of Chaouachi and Gabsi (Renew Energy Revue 9(2):75-82, 2006), an attempt to improve this solar system operating was made by equipping the storage tank with radial fins of rectangular profile. A second 3D CFD model was developed and a series of numerical simulations were conducted for various SWH designs which differ in the depth of this extended surface for heat exchange. As the modified surface presents a higher characteristic length for convective heat transfer from the storage tank to the water, the fins equipped storage tank based SWH is determined to have a higher water temperature and a reduced thermal losses coefficient during the day-time period. Regarding the night operating of this water heater, the results suggest that the modified system presents higher thermal losses.

Conductive Critical Thinking

ERIC Educational Resources Information Center

Paetkau, Mark

2007-01-01

One of my goals as an instructor is to teach students critical thinking skills. This paper presents an example of a student-led discussion of heat conduction at the first-year level. Heat loss from a human head is calculated using conduction and radiation models. The results of these plausible (but wrong) models of heat transfer contradict what…

Methods for making radially anisotropic thin-film magnetic torroidal cores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qiu, Jizheng; Sullivan, Charles R.

2017-05-23

A method of forming a radially anisotropic toroidal magnetic core includes providing apparatus having a first magnet for providing a radial magnetic field extending across a cavity from an axial spindle to a surrounding second magnetic element, placing a substrate in the cavity, the substrate having a hole fitting around the head of the spindle; and sputter-depositing a film of ferromagnetic material onto the substrate. In an embodiment, the spindle is magnetically coupled to a first pole of the first magnet, the second magnetic element is coupled to a second pole of the first magnet, and a thermally conductive, nonmagnetic,more » insert separates the spindle and the second magnetic element.« less

Hydrodynamic structure of the boundary layers in a rotating cylindrical cavity with radial inflow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herrmann-Priesnitz, Benjamín, E-mail: bherrman@ing.uchile.cl; Torres, Diego A.; Advanced Mining Technology Center, Universidad de Chile, Av. Tupper 2007, Santiago

A flow model is formulated to investigate the hydrodynamic structure of the boundary layers of incompressible fluid in a rotating cylindrical cavity with steady radial inflow. The model considers mass and momentum transfer coupled between boundary layers and an inviscid core region. Dimensionless equations of motion are solved using integral methods and a space-marching technique. As the fluid moves radially inward, entraining boundary layers develop which can either meet or become non-entraining. Pressure and wall shear stress distributions, as well as velocity profiles predicted by the model, are compared to numerical simulations using the software OpenFOAM. Hydrodynamic structure of themore » boundary layers is governed by a Reynolds number, Re, a Rossby number, Ro, and the dimensionless radial velocity component at the periphery of the cavity, U{sub o}. Results show that boundary layers merge for Re < < 10 and Ro > > 0.1, and boundary layers become predominantly non-entraining for low Ro, low Re, and high U{sub o}. Results may contribute to improve the design of technology, such as heat exchange devices, and turbomachinery.« less

Heating device for semiconductor wafers

DOEpatents

Vosen, S.R.

1999-07-27

An apparatus for heat treating semiconductor wafers is disclosed. The apparatus includes a heating device which contains an assembly of light energy sources for emitting light energy onto a wafer. In particular, the light energy sources are positioned such that many different radial heating zones are created on a wafer being heated. For instance, in one embodiment, the light energy sources form a spiral configuration. In an alternative embodiment, the light energy sources appear to be randomly dispersed with respect to each other so that no discernible pattern is present. In a third alternative embodiment of the present invention, the light energy sources form concentric rings. Tuning light sources are then placed in between the concentric rings of light. 4 figs.

Comparative investigation of five nanoparticles in flow of viscous fluid with Joule heating and slip due to rotating disk

NASA Astrophysics Data System (ADS)

Qayyum, Sumaira; Khan, Muhammad Ijaz; Hayat, Tasawar; Alsaedi, Ahmed

2018-04-01

Present article addresses the comparative study for flow of five water based nanofluids. Flow in presence of Joule heating is generated by rotating disk with variable thickness. Nanofluids are suspension of Silver (Ag), Copper (Cu), Copper oxide (CuO), Aluminum oxide or Alumina (Al2O3), Titanium oxide or titania (TiO2) and water. Boundary layer approximation is applied to partial differential equations. Using Von Karman transformations the partial differential equations are converted to ordinary differential equations. Convergent series solutions are obtained. Graphical results are presented to examine the behaviors of axial, radial and tangential velocities, temperature, skin friction and Nusselt number. It is observed that radial, axial and tangential velocities decay for slip parameters. Axial velocity decays for larger nanoparticle volume fraction. Effect of nanofluids on velocities dominant than base material. Temperature rises for larger Eckert number and temperature of silver water nanofluid is more because of its higher thermal conductivity. Surface drag force reduces for higher slip parameters. Transfer of heat is more for larger disk thickness index.

Radial-probe EBUS for the diagnosis of peripheral pulmonary lesions.

PubMed

Jacomelli, Marcia; Demarzo, Sergio Eduardo; Cardoso, Paulo Francisco Guerreiro; Palomino, Addy Lidvina Mejia; Figueiredo, Viviane Rossi

2016-01-01

Conventional bronchoscopy has a low diagnostic yield for peripheral pulmonary lesions. Radial-probe EBUS employs a rotating ultrasound transducer at the end of a probe that is passed through the working channel of the bronchoscope. Radial-probe EBUS facilitates the localization of peripheral pulmonary nodules, thus increasing the diagnostic yield. The objective of this study was to present our initial experience using radial-probe EBUS in the diagnosis of peripheral pulmonary lesions at a tertiary hospital. We conducted a retrospective analysis of 54 patients who underwent radial-probe EBUS-guided bronchoscopy for the investigation of pulmonary nodules or masses between February of 2012 and September of 2013. Radial-probe EBUS was performed with a flexible 20-MHz probe, which was passed through the working channel of the bronchoscope and advanced through the bronchus to the target lesion. For localization of the lesion and for collection procedures (bronchial brushing, transbronchial needle aspiration, and transbronchial biopsy), we used fluoroscopy. Radial-probe EBUS identified 39 nodules (mean diameter, 1.9 ± 0.7 cm) and 19 masses (mean diameter, 4.1 ± 0.9 cm). The overall sensitivity of the method was 66.7% (79.5% and 25.0%, respectively, for lesions that were visible and not visible by radial-probe EBUS). Among the lesions that were visible by radial-probe EBUS, the sensitivity was 91.7% for masses and 74.1% for nodules. The complications were pneumothorax (in 3.7%) and bronchial bleeding, which was controlled bronchoscopically (in 9.3%). Radial-probe EBUS shows a good safety profile, a low complication rate, and high sensitivity for the diagnosis of peripheral pulmonary lesions. A broncoscopia convencional possui baixo rendimento diagnóstico para lesões pulmonares periféricas. A ecobroncoscopia radial (EBUS radial) emprega um transdutor ultrassonográfico rotatório na extremidade de uma sonda que é inserida no canal de trabalho do broncoscópio. O EBUS

Development of a Compact, Deep-Penetrating Heat Flow Instrument for Lunar Landers: In-Situ Thermal Conductivity System

NASA Technical Reports Server (NTRS)

Nagihara, S.; Zacny, K.; Hedlund, M.; Taylor, P. T.

2012-01-01

Geothermal heat flow is obtained as a product of the geothermal gradient and the thermal conductivity of the vertical soil/rock/regolith interval penetrated by the instrument. Heat flow measurements are a high priority for the geophysical network missions to the Moon recommended by the latest Decadal Survey and previously the International Lunar Network. One of the difficulties associated with lunar heat flow measurement on a robotic mission is that it requires excavation of a relatively deep (approx 3 m) hole in order to avoid the long-term temporal changes in lunar surface thermal environment affecting the subsurface temperature measurements. Such changes may be due to the 18.6-year-cylcle lunar precession, or may be initiated by presence of the lander itself. Therefore, a key science requirement for heat flow instruments for future lunar missions is to penetrate 3 m into the regolith and to measure both thermal gradient and thermal conductivity. Engineering requirements are that the instrument itself has minimal impact on the subsurface thermal regime and that it must be a low-mass and low-power system like any other science instrumentation on planetary landers. It would be very difficult to meet the engineering requirements, if the instrument utilizes a long (> 3 m) probe driven into the ground by a rotary or percussive drill. Here we report progress in our efforts to develop a new, compact lunar heat flow instrumentation that meets all of these science and engineering requirements.

Resolving electrical conductivities from collisionally damped plasmons in isochorically heated warm dense aluminum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sperling, P.; Fletcher, L. B.; Chung, H. -K.

2016-03-29

We measure the highly-resolved inelastic x-ray scattering spectrum of isochorically ultrafast heated aluminum. In the x-ray forward scattering spectra the electron temperature could be measured from the down- and upshifted plasmon, where the electron density of ne = 1:8 1023 cm 3 is known a priori. We have studied the plasmon damping by applying electron-particle collision models beyond the Born approximation determining the electrical conductivity of warm dense aluminum.

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

NASA Technical Reports Server (NTRS)

Padovan, Joe; Krishna, Lala

1986-01-01

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

Quasiballistic heat removal from small sources studied from first principles

NASA Astrophysics Data System (ADS)

Vermeersch, Bjorn; Mingo, Natalio

2018-01-01

Heat sources whose characteristic dimension R is comparable to phonon mean free paths display thermal resistances that exceed conventional diffusive predictions. This has direct implications to (opto)electronics thermal management and phonon spectroscopy. Theoretical analyses have so far limited themselves to particular experimental configurations. Here, we build upon the multidimensional Boltzmann transport equation (BTE) to derive universal expressions for the apparent conductivity suppression S (R ) =κeff(R ) /κbulk experienced by radially symmetric 2D and 3D sources. In striking analogy to cross-plane heat conduction in thin films, a distinct quasiballistic regime emerges between ballistic (κeff˜R ) and diffusive (κeff≃κbulk ) asymptotes that displays a logarithmic dependence κeff˜ln(R ) in single crystals and fractional power dependence κeff˜R2 -α in alloys (with α the Lévy superdiffusion exponent). Analytical solutions and Monte Carlo simulations for spherical and circular heat sources in Si, GaAs, Si0.99Ge0.01 , and Si0.82Ge0.18 , all carried out from first principles, confirm the predicted generic tendencies. Contrary to the thin film case, common approximations like kinetic theory estimates κeff≃∑Sωgreyκω and modified Fourier temperature curves perform relatively poorly. Up to threefold deviations from the BTE solutions for sub-100 nm sources underline the need for rigorous treatment of multidimensional nondiffusive transport.

High heat flux Langmuir probe array for the DIII-D divertor platesa)

NASA Astrophysics Data System (ADS)

Watkins, J. G.; Taussig, D.; Boivin, R. L.; Mahdavi, M. A.; Nygren, R. E.

2008-10-01

Two modular arrays of Langmuir probes designed to handle a heat flux of up to 25 MW/m2 for 10 s exposures have been installed in the lower divertor target plates of the DIII-D tokamak. The 20 pyrolytic graphite probe tips have more than three times higher thermal conductivity and 16 times larger mass than the original DIII-D isotropic graphite probes. The probe tips have a fixed 12.5° surface angle to distribute the heat flux more uniformly than the previous 6 mm diameter domed collectors and a symmetric "rooftop" design to allow operation with reversed toroidal magnetic field. A large spring-loaded contact area improves heat conduction from each probe tip through a ceramic insulator into a cooled graphite divertor floor tile. The probe tips, brazed to molybdenum foil to ensure good electrical contact, are mounted in a ceramic tray for electrical isolation and reliable cable connections. The new probes are located 1.5 cm radially apart in a staggered arrangement near the entrance to the lower divertor pumping baffle and are linearly spaced 3 cm apart on the shelf above the in-vessel cryopump. Typical target plate profiles of Jsat, Te, and Vf with 4 mm spatial resolution are shown.

Memory behaviors of entropy production rates in heat conduction

NASA Astrophysics Data System (ADS)

Li, Shu-Nan; Cao, Bing-Yang

2018-02-01

Based on the relaxation time approximation and first-order expansion, memory behaviors in heat conduction are found between the macroscopic and Boltzmann-Gibbs-Shannon (BGS) entropy production rates with exponentially decaying memory kernels. In the frameworks of classical irreversible thermodynamics (CIT) and BGS statistical mechanics, the memory dependency on the integrated history is unidirectional, while for the extended irreversible thermodynamics (EIT) and BGS entropy production rates, the memory dependences are bidirectional and coexist with the linear terms. When macroscopic and microscopic relaxation times satisfy a specific relationship, the entropic memory dependences will be eliminated. There also exist initial effects in entropic memory behaviors, which decay exponentially. The second-order term are also discussed, which can be understood as the global non-equilibrium degree. The effects of the second-order term are consisted of three parts: memory dependency, initial value and linear term. The corresponding memory kernels are still exponential and the initial effects of the global non-equilibrium degree also decay exponentially.

Heat transfer and hydrodynamic investigations of a baffled slurry bubble column

NASA Astrophysics Data System (ADS)

Saxena, S. C.; Chen, Z. D.

1992-09-01

Heat transfer and hydrodynamic investigations have been conducted in a 0.108 m internal diameter bubble column at ambient conditions. The column is equipped with seven 19mm diameter tubes arranged in an equilateral triangular pitch of 36.5 mm. A Monsanto synthetic heat transfer fluid, Therminol-66 having a viscosity of 39.8 cP at 303 K, is used as a liquid medium. Magnetite powders, average diameters 27.7 and 36.6 µm, in five concentrations up to 50 weight percent in the slurry, are used. As a gas phase, industrial grade nitrogen of purity 99.6 percent is employed. Gas holdup in different operating modes and regimes have been measured for the two- and three-phase systems over a superficial gas velocity range up to 0.20 m/s in the semi-batch mode. Heat transfer coefficients are measured at different tube locations in the bundle at different radial and vertical locations over a range of operating conditions. All these data are compared with the existing literature correlations and models. New correlations are proposed.

Radial/axial power divider/combiner

NASA Technical Reports Server (NTRS)

Vaddiparty, Yerriah P. (Inventor)

1987-01-01

An electromagnetic power divider/combiner comprises N radial outputs (31) having equal powers and preferably equal phases, and a single axial output (20). A divider structure (1) and a preferably identical combiner structure (2) are broadside coupled across a dielectric substrate (30) containing on one side the network of N radial outputs (31) and on its other side a set of N equispaced stubs (42) which are capacitively coupled through the dielectric substrate (30) to the N radial outputs (31). The divider structure (1) and the combiner structure (2) each comprise a dielectric disk (12, 22, respectively) on which is mounted a set of N radial impedance transformers (14, 24, respectively). Gross axial coupling is determined by the thickness of the dielectric layer (30). Rotating the disks (12, 22) with respect to each other effectuates fine adjustment in the degree of axial coupling.

Three-dimensional flow measurements in a vaneless radial turbine scroll

NASA Technical Reports Server (NTRS)

Tabakoff, W.; Wood, B.; Vittal, B. V. R.

1982-01-01

The flow behavior in a vaneless radial turbine scroll was examined experimentally. The data was obtained using the slant sensor technique of hot film anemometry. This method used the unsymmetric heat transfer characteristics of a constant temperature hot film sensor to detect the flow direction and magnitude. This was achieved by obtaining a velocity vector measurement at three sensor positions with respect to the flow. The true magnitude and direction of the velocity vector was then found using these values and a Newton-Raphson numerical technique. The through flow and secondary flow velocity components are measured at various points in three scroll sections.

Computation of the temperature distribution in cooled radial inflow turbine guide vanes

NASA Technical Reports Server (NTRS)

Tabakoff, W.; Hosny, W.; Hamed, A.

1977-01-01

A two-dimensional finite-difference numerical technique is presented to determine the temperature distribution of an internally-cooled blade of radial turbine guide vanes. A simple convection cooling is assumed inside the guide vane. Such an arrangement results in relatively small cooling effectiveness at the leading edge and at the trailing edge. Heat transfer augmentation in these critical areas may be achieved by using impingement jets and film cooling. A computer program is written in Fortran IV for IBM 370/165 computer.

Utility of nerve conduction studies for diagnosis of injury to the medial branch of the superficial radial nerve.

PubMed

Kon, Tomoya; Suzuki, Chieko; Hotta, Ryotaro; Funamizu, Yukihisa; Haga, Rie; Ueno, Tatsuya; Nishijima, Haruo; Arai, Akira; Nunomura, Jinichi; Nukada, Hitoshi; Tomiyama, Masahiko; Baba, Masayuki

2017-09-01

The clinical utility of nerve conduction study (NCS) for the distal medial branch of the superficial radial nerve (SRN) has not yet been clarified. Therefore, we investigated the clinical utility of NCS in patients with suspected SRN injury and compared the results with those in healthy control subjects. Bilateral NCS of the medial branch of the SRN was performed in two patients with suspected injury of the medial branch of the SRN, and in 20 healthy control subjects. A surface recording electrode was placed at the medial side of the metacarpophalangeal joint of the thumb. The SRN was then stimulated at a location 12 cm proximal from the recording electrode. The mean sensory nerve action potential in the two patients was significantly lower than that of the controls (6.75 ± 0.92 vs. 23.8 ± 8.2 μV, P  < 0.05). The side-to-side differences in sensory nerve action potential in the two patients were significantly higher than in the controls (55 ± 7.1 vs. 11 ± 7.8%, P  < 0.05). NCS may be useful for diagnosing injury of the medial branch of the SRN.

A radial transmission line material measurement apparatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warne, L.K.; Moyer, R.D.; Koontz, T.E.

1993-05-01

A radial transmission line material measurement sample apparatus (sample holder, offset short standards, measurement software, and instrumentation) is described which has been proposed, analyzed, designed, constructed, and tested. The purpose of the apparatus is to obtain accurate surface impedance measurements of lossy, possibly anisotropic, samples at low and intermediate frequencies (vhf and low uhf). The samples typically take the form of sections of the material coatings on conducting objects. Such measurements thus provide the key input data for predictive numerical scattering codes. Prediction of the sample surface impedance from the coaxial input impedance measurement is carried out by two techniques.more » The first is an analytical model for the coaxial-to-radial transmission line junction. The second is an empirical determination of the bilinear transformation model of the junction by the measurement of three full standards. The standards take the form of three offset shorts (and an additional lossy Salisbury load), which have also been constructed. The accuracy achievable with the device appears to be near one percent.« less

Development of a spinning wave heat engine

NASA Technical Reports Server (NTRS)

Zinn, B. T.; Powell, E. A.; Hubbartt, J. E.

1982-01-01

A theoretical analysis and an experimental investigation were conducted to assess the feasibility of developing a spinning wave heat engine. Such as engine would utilize a large amplitude traveling acoustic wave rotating around a cylindrica chamber, and it should not suffer from the inefficiency, noise, and intermittent thrust which characterizes pulse jet engines. The objective of this investigation was to determine whether an artificially driven large amplitude spinning transverse wave could induce a steady flow of air through the combustion chamber under cold flow conditions. In the theoretical analysis the Maslen and Moore perturbation technique was extended to study flat cylinders (pancake geometry) with completely open side walls and a central opening. In the parallel experimental study, a test moel was used to determine resonant frequencies and radial pressure distributions, as well as oscillatory and steady flow velocities at the inner and outer peripheries. The experimental frequency was nearly the same as the theoretical acoustic value for a model of the same outer diameter but without a central hole. Although the theoretical analysis did not predict a steady velocity component, simulaneous measurements of hotwire and microphone responses have shown that the spinning wave pumps a mean flow radially outward through the cavity.

A model for particle confinement in a toroidal plasma subject to strong radial electric fields

NASA Technical Reports Server (NTRS)

Roth, J. R.

1977-01-01

The approach adopted in the NASA Lewis Bumpy Torus experiment is to confine and heat a toroidal plasma by the simultaneous application of strong dc magnetic fields and electric fields. Strong radial electric fields (about 1 kV/cm) are imposed by biasing the plasma with up to 12 negative electrode rings which surround its minor circumference. The plasma containment is consistent with a balance of two processes: a radial infusion of ions in those sectors not containing electrode rings, resulting from the radially inward electric fields; and ion losses to the electrode rings, each of which acts as a sink and draws ions out the plasma in the manner of a Langmuir probe in the ion saturation regime. The highest density on axis which has been observed so far in this steady-state plasma is 6.2 trillion particles per cu cm, for which the particle containment time is 2.5 msec. The deuterium ion kinetic temperature for these conditions was in the range of 360 to 520 eV.

Use of impure inert gases in the controlled heating and cooling of mixed conducting metal oxide materials

DOEpatents

Carolan, Michael Francis [Allentown, PA; Bernhart, John Charles [Fleetwood, PA

2012-08-21

Method for processing an article comprising mixed conducting metal oxide material. The method comprises contacting the article with an oxygen-containing gas and either reducing the temperature of the oxygen-containing gas during a cooling period or increasing the temperature of the oxygen-containing gas during a heating period; during the cooling period, reducing the oxygen activity in the oxygen-containing gas during at least a portion of the cooling period and increasing the rate at which the temperature of the oxygen-containing gas is reduced during at least a portion of the cooling period; and during the heating period, increasing the oxygen activity in the oxygen-containing gas during at least a portion of the heating period and decreasing the rate at which the temperature of the oxygen-containing gas is increased during at least a portion of the heating period.

Axial flow heat exchanger devices and methods for heat transfer using axial flow devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koplow, Jeffrey P.

Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferredmore » across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.« less

14 CFR 73.5 - Bearings; radials; miles.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 2 2011-01-01 2011-01-01 false Bearings; radials; miles. 73.5 Section 73.5... SPECIAL USE AIRSPACE General § 73.5 Bearings; radials; miles. (a) All bearings and radials in this part... statute miles. ...

14 CFR 73.5 - Bearings; radials; miles.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 2 2013-01-01 2013-01-01 false Bearings; radials; miles. 73.5 Section 73.5... SPECIAL USE AIRSPACE General § 73.5 Bearings; radials; miles. (a) All bearings and radials in this part... statute miles. ...

14 CFR 73.5 - Bearings; radials; miles.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 2 2014-01-01 2014-01-01 false Bearings; radials; miles. 73.5 Section 73.5... SPECIAL USE AIRSPACE General § 73.5 Bearings; radials; miles. (a) All bearings and radials in this part... statute miles. ...

14 CFR 73.5 - Bearings; radials; miles.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 2 2010-01-01 2010-01-01 false Bearings; radials; miles. 73.5 Section 73.5... SPECIAL USE AIRSPACE General § 73.5 Bearings; radials; miles. (a) All bearings and radials in this part... statute miles. ...

14 CFR 73.5 - Bearings; radials; miles.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 2 2012-01-01 2012-01-01 false Bearings; radials; miles. 73.5 Section 73.5... SPECIAL USE AIRSPACE General § 73.5 Bearings; radials; miles. (a) All bearings and radials in this part... statute miles. ...

Melt Segregation and Tidal Heating at Io

NASA Astrophysics Data System (ADS)

Rajendar, A.; Dufek, J.; Roberts, J. H.; Paty, C. S.

2011-12-01

Recent evidence of melt beneath Io's surface (Khurana et al., 2010) and repeated observation of volcanic activity and features consistent with volcanic activity at the surface (e.g. Veeder et al, 1994; Rathbun et al., 2004; Lopes-Gautier et al., 1999; Smith et al., 1979) has raised further questions about the structure of the Galilean moon and the processes that shape it. In this study we examine the thermal state, melt fraction, and multiphase dynamics of melt segregation within Io's interior. Using a coupled multiphase dynamics and tidal heating model we explore the location, spatial extent, and temporal residence times of melt in Io's subsurface, as well as response to orbital parameters. In a thermally evolving body subject to tidal forcing, in which melt production and migration takes place, feedback can occur with respect to the physical and thermal properties. We explore this feedback to produce a thermal model of Io, taking into account the rate of tidal heating and fluid motion within the interior. First, a layered model of the internal structure is assumed. The equations of motion for forced oscillations in a layered spherical body are then solved using the propagator matrix method (Sabadini and Vermeesen, 2004) to obtain the displacements and strains due to tidal motion (Roberts and Nimmo, 2008). From this, the radial distribution of tidal heat generation within Io is calculated. This radial heating profile is then used as input for a multi-phase fluid model in order to obtain an estimate of the radial temperature distribution and thus the material properties and melt fractions. In the multiphase model individual phases (melt and solid residue) separately conserve mass, momentum and enthalpy (Dufek and Bachmann, 2010) allowing us to explore melt segregation phenomena. Enthalpy closure is provided by the MELTS (Ghiorso and Sack, 1995) thermodynamics algorithm, which is called at each point in space. This accounts for the partitioning between latent and

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

NASA Technical Reports Server (NTRS)

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

1977-01-01

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

Ion heating and characteristics of ST plasma used by double-pulsing CHI on HIST

NASA Astrophysics Data System (ADS)

Hanao, Takafumi; Hirono, Hidetoshi; Hyobu, Takahiro; Ito, Kengo; Matsumoto, Keisuke; Nakayama, Takashi; Oki, Nobuharu; Kikuchi, Yusuke; Fukumoto, Naoyuki; Nagata, Masayoshi

2013-10-01

Multi-pulsing Coaxial Helicity Injection (M-CHI) is an efficient current drive and sustainment method used in spheromak and spherical torus (ST). We have observed plasma current/flux amplification by double pulsing CHI. Poloidal ion temperature measured by Ion Doppler Spectrometer (IDS) has a peak at plasma core region. In this region, radial electric field has a negative peak. At more inboard side that is called separatrix between closed flux region and inner open flux region, poloidal flow has a large shear and radial electric field changes the polarity. After the second CHI pulse, we observed sharp and rapid ion heating at plasma core region and separatrix. In this region, the poloidal ion temperature is selective heating because electron temperature is almost uniform. At this time, flow shear become larger and radial electric field is amplified at separatorix. These effects produce direct heating of ion through the viscous flow damping. Furthermore, we observed decrease of electron density at separatrix. Decreased density makes Hall dynamo electric field as two-fluid effect. When the ion temperature is increasing, dynamo electric field is observed at separatrix. It may have influence with the ion heating. We will discuss characteristic of double pulsing CHI driven ST plasmas and correlation of direct heating of ion with dynamo electric field and any other parameters.

Radial wave crystals: radially periodic structures from anisotropic metamaterials for engineering acoustic or electromagnetic waves.

PubMed

Torrent, Daniel; Sánchez-Dehesa, José

2009-08-07

We demonstrate that metamaterials with anisotropic properties can be used to develop a new class of periodic structures that has been named radial wave crystals. They can be sonic or photonic, and wave propagation along the radial directions is obtained through Bloch states like in usual sonic or photonic crystals. The band structure of the proposed structures can be tailored in a large amount to get exciting novel wave phenomena. For example, it is shown that acoustical cavities based on radial sonic crystals can be employed as passive devices for beam forming or dynamically orientated antennas for sound localization.

Magnetogasdynamics shock waves in a rotational axisymmetric non-ideal gas with increasing energy and conductive and radiative heat-fluxes

NASA Astrophysics Data System (ADS)

Nath, Gorakh

2016-07-01

Self-similar solutions are obtained for one-dimensional adiabatic flow behind a magnetogasdynamics cylindrical shock wave propagating in a rotational axisymmetric non ideal gas with increasing energy and conductive and radiative heat fluxes in presence of an azimuthal magnetic field. The fluid velocities and the azimuthal magnetic field in the ambient medium are assume to be varying and obeying power laws. In order to find the similarity solutions the angular velocity of the ambient medium is taken to be decreasing as the distance from the axis increases. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be the diffusion type for an optically thick grey gas model. The thermal conductivity and the absorption coefficient are assumed to vary with temperature and density. The effects of the presence of radiation and conduction, the non-idealness of the gas and the magnetic field on the shock propagation and the flow behind the shock are investigated.

Radial q-space sampling for DSI

PubMed Central

Baete, Steven H.; Yutzy, Stephen; Boada, Fernando, E.

2015-01-01

Purpose Diffusion Spectrum Imaging (DSI) has been shown to be an effective tool for non-invasively depicting the anatomical details of brain microstructure. Existing implementations of DSI sample the diffusion encoding space using a rectangular grid. Here we present a different implementation of DSI whereby a radially symmetric q-space sampling scheme for DSI (RDSI) is used to improve the angular resolution and accuracy of the reconstructed Orientation Distribution Functions (ODF). Methods Q-space is sampled by acquiring several q-space samples along a number of radial lines. Each of these radial lines in q-space is analytically connected to a value of the ODF at the same angular location by the Fourier slice theorem. Results Computer simulations and in vivo brain results demonstrate that RDSI correctly estimates the ODF when moderately high b-values (4000 s/mm2) and number of q-space samples (236) are used. Conclusion The nominal angular resolution of RDSI depends on the number of radial lines used in the sampling scheme, and only weakly on the maximum b-value. In addition, the radial analytical reconstruction reduces truncation artifacts which affect Cartesian reconstructions. Hence, a radial acquisition of q-space can be favorable for DSI. PMID:26363002

Radial Neck Dilatory Remodeling After Radial Head Arthroplasty With an Uncemented, Press Fit, Fully Chemically Etched Stem Design.

PubMed

Sullivan, Matthew P; Firoozabadi, Reza; Kennedy, Stephen A; Agel, Julie; Magnusson, Eric; Schiffman, Brett; Folchert, Matthew; Beingessner, Daphne

2017-09-01

To compare the radiographic outcomes of 2 widely used side loading, press fit, RHA implants used to reconstruct complex elbow trauma. Retrospective cohort study. Level-1 Academic trauma center. Patients undergoing RHA. Cohort 1 received Synthes Radial Head Prosthesis. Cohort 2 received Biomet ExploR Radial Head Replacement. Radial neck dilatory remodeling. Eighty-two subjects were included in final analysis, 63 from the Biomet Cohort, and 19 from Synthes cohort. Demographic and injury characteristics were similar among cohorts. Radial neck dilatory remodeling as well as periprosthetic radiographic lucency were seen significantly more frequently and to a significantly greater degree in the Synthes cohort. The average percentage of dilatory remodeling of the Synthes cohort was 34.9% and that of the Biomet cohort was 2.7%. There were no differences in rates of revision surgery. Our study demonstrates significant radiographic differences between 2 frequently used RHA implants. Radial neck dilatory remodeling is a common, rapidly progressive, and dramatic finding frequently seen with the Synthes Radial Head Prosthesis. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Global strong solutions to the one-dimensional heat-conductive model for planar non-resistive magnetohydrodynamics with large data

NASA Astrophysics Data System (ADS)

Li, Yang

2018-06-01

In this paper, we consider the initial-boundary value problem to the one-dimensional compressible heat-conductive model for planar non-resistive magnetohydrodynamics. By making full use of the effective viscous flux and an analogue, together with the structure of the equations, global existence and uniqueness of strong solutions are obtained on condition that the initial density is bounded below away from vacuum and the heat conductivity coefficient κ satisfies the growth condition κ _1(1+θ^{α })≤ κ (θ)≤ κ _2(1+θ^{α }),\\quad { for some }0< α < ∞, with κ _1,κ _2 being positive constants. Moreover, global solvability of strong solutions is shown with the initial vacuum. The results are obtained without any smallness restriction to the initial data.

High Thermal Conductivity Polymer Composites for Low Cost Heat Exchangers

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2017-08-01

This factsheet describes a project that identified and evaluated commercially available and state-of-the-art polymer-based material options for manufacturing industrial and commercial non-metallic heat exchangers. A heat exchanger concept was also developed and its performance evaluated with heat transfer modeling tools.

An Exact Formula for Calculating Inverse Radial Lens Distortions

PubMed Central

Drap, Pierre; Lefèvre, Julien

2016-01-01

This article presents a new approach to calculating the inverse of radial distortions. The method presented here provides a model of reverse radial distortion, currently modeled by a polynomial expression, that proposes another polynomial expression where the new coefficients are a function of the original ones. After describing the state of the art, the proposed method is developed. It is based on a formal calculus involving a power series used to deduce a recursive formula for the new coefficients. We present several implementations of this method and describe the experiments conducted to assess the validity of the new approach. Such an approach, non-iterative, using another polynomial expression, able to be deduced from the first one, can actually be interesting in terms of performance, reuse of existing software, or bridging between different existing software tools that do not consider distortion from the same point of view. PMID:27258288

Martian thermal boundary layers: Subhourly variations induced by radiative-conductive heat transfer within the dust-laden atmosphere-ground system

NASA Technical Reports Server (NTRS)

Pallmann, A. J.; Dannevik, W. P.; Frisella, S. P.

1973-01-01

Radiative-conductive heat transfer has been investigated for the ground-atmosphere system of the planet Mars. The basic goal was the quantitative determination of time dependent vertical distributions of temperature and static stability for Southern-Hemispheric summer season and middle and polar latitudes, for both dust-free and dust-laden atmospheric conditions. The numerical algorithm which models at high spatial and temporal resolution the thermal energy transports in the dual ground-atmosphere system, is based on solution of the applicable heating rate equation, including radiative and molecular-conductive heat transport terms. The two subsystems are coupled by an internal thermal boundary condition applied at the ground-atmosphere interface level. Initial data and input parameters are based on Mariner 4, 6, 7, and 9 measurements and the JPL Mars Scientific Model. Numerical experiments were run for dust-free and dust-laden conditions in the midlatitudes, as well as ice-free and ice-covered polar regions. Representative results and their interpretation are presented. Finally, the theoretical framework of the generalized problem with nonconservative Mie scattering and explicit thermal-convective heat transfer is formulated, and applicable solution algorithms are outlined.

Radial lean direct injection burner

DOEpatents

Khan, Abdul Rafey; Kraemer, Gilbert Otto; Stevenson, Christian Xavier

2012-09-04

A burner for use in a gas turbine engine includes a burner tube having an inlet end and an outlet end; a plurality of air passages extending axially in the burner tube configured to convey air flows from the inlet end to the outlet end; a plurality of fuel passages extending axially along the burner tube and spaced around the plurality of air passage configured to convey fuel from the inlet end to the outlet end; and a radial air swirler provided at the outlet end configured to direct the air flows radially toward the outlet end and impart swirl to the air flows. The radial air swirler includes a plurality of vanes to direct and swirl the air flows and an end plate. The end plate includes a plurality of fuel injection holes to inject the fuel radially into the swirling air flows. A method of mixing air and fuel in a burner of a gas turbine is also provided. The burner includes a burner tube including an inlet end, an outlet end, a plurality of axial air passages, and a plurality of axial fuel passages. The method includes introducing an air flow into the air passages at the inlet end; introducing a fuel into fuel passages; swirling the air flow at the outlet end; and radially injecting the fuel into the swirling air flow.

Transpiration-induced axial and radial tension gradients in trunks of Douglas-fir trees.

Treesearch

J.C. Domec; F. C. Meinzer; B. L. Gartner; D. Woodruff

2006-01-01

We determined the axial and radial xylem tension gradients in trunks of young Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees. Axial specific conductivity (ks-a) and sap flux density (Js) were measured at four consecutive depths within the sapwood at a...

Invisibility problem in acoustics, electromagnetism and heat transfer. Inverse design method

NASA Astrophysics Data System (ADS)

Alekseev, G.; Tokhtina, A.; Soboleva, O.

2017-10-01

Two approaches (direct design and inverse design methods) for solving problems of designing devices providing invisibility of material bodies of detection using different physical fields - electromagnetic, acoustic and static are discussed. The second method is applied for solving problems of designing cloaking devices for the 3D stationary thermal scattering model. Based on this method the design problems under study are reduced to respective control problems. The material parameters (radial and tangential heat conductivities) of the inhomogeneous anisotropic medium filling the thermal cloak and the density of auxiliary heat sources play the role of controls. A unique solvability of direct thermal scattering problem in the Sobolev space is proved and the new estimates of solutions are established. Using these results, the solvability of control problem is proved and the optimality system is derived. Based on analysis of optimality system, the stability estimates of optimal solutions are established and numerical algorithms for solving particular thermal cloaking problem are proposed.

Confirmation of radial velocity variability in Arcturus

NASA Technical Reports Server (NTRS)

Cochran, William D.

1988-01-01

The paper presents results of high-precision measurements of radial-velocity variations in Alpha Boo. Significant radial-velocity variability is detected well in excess of the random and systematic measurement errors. The radial velocity varies by an amount greater than 200 m/sec with a period of around 2 days.

Using Actively Heated Fibre Optics (AHFO) to determine soil thermal conductivity and soil moisture content at high spatial and temporal resolution

NASA Astrophysics Data System (ADS)

Ciocca, Francesco; Abesser, Corinna; Hannah, David; Blaen, Philip; Chalari, Athena; Mondanos, Michael; Krause, Stefan

2017-04-01

Optical fibre distributed temperature sensing (DTS) is increasingly used in environmental monitoring and for subsurface characterisation, e.g. to obtain precise measurements of soil temperature at high spatio-temporal resolution, over several kilometres of optical fibre cable. When combined with active heating of metal elements embedded in the optical fibre cable (active-DTS), the temperature response of the soil to heating provides valuable information from which other important soil parameters, such as thermal conductivity and soil moisture content, can be inferred. In this presentation, we report the development of an Actively Heated Fibre Optics (AHFO) method for the characterisation of soil thermal conductivity and soil moisture dynamics at high temporal and spatial resolutions at a vegetated hillslope site in central England. The study site is located within a juvenile forest adjacent to the Birmingham Institute of Forest Research (BIFoR) experimental site. It is instrumented with three loops of a 500m hybrid-optical cable installed at 10cm, 25cm and 40cm depths. Active DTS surveys were undertaken in June and October 2016, collecting soil temperature data at 0.25m intervals along the cable, prior to, during and after the 900s heating phase. Soil thermal conductivity and soil moisture were determined according to Ciocca et al. 2012, applied to both the cooling and the heating phase. Independent measurements of soil thermal conductivity and soil moisture content were collected using thermal needle probes, calibrated capacitance-based probes and laboratory methods. Results from both the active DTS survey and independent in-situ and laboratory measurements will be presented, including the observed relationship between thermal conductivity and moisture content at the study site and how it compares against theoretical curves used by the AHFO methods. The spatial variability of soil thermal conductivity and soil moisture content, as observed using the different

Fungistatic activity of heat-treated flaxseed determined by response surface methodology.

PubMed

Xu, Y; Hall, C; Wolf-Hall, C

2008-08-01

The objective of this study was to evaluate the effect of heat treatment on the fungistatic activity of flaxseed (Linum usitatissimum) in potato dextrose agar (PDA) medium and a fresh noodle system. The radial growth of Penicilliumn chrysogenum, Aspergillus flavus, and a Penicillium sp. isolated from moldy noodles, as well as the mold count of fresh noodle enriched with heat treated flaxseed, were used to assess antifungal activity. A central composite design in the response surface methodology was used to predict the effect of heating temperature and time on antifungal activity of flaxseed flour (FF). Statistical analysis determined that the linear terms of both variables (that is, heating temperature and time) and the quadratic terms of the heating temperature had significant (P<0.05) effects on the radial growth of all 3 test fungi and the mold count log-cycle reduction of fresh noodle. The interactions between the temperature and time were significant for all dependent variables (P<0.05). Significant reductions in antifungal activities were found when FF was subjected to high temperatures, regardless of heating time. In contrast, prolonging the heating time did not substantially affect the antifungal activities of FF at low temperature. However, 60% of the antifungal activity was retained after FF was heated at 100 degrees C for 15 min, which suggests a potential use of FF as an antifungal additive in food products subjected to low to mild heat treatments.

Heating-frequency-dependent thermal conductivity: An analytical solution from diffusive to ballistic regime and its relevance to phonon scattering measurements

NASA Astrophysics Data System (ADS)

Yang, Fan; Dames, Chris

2015-04-01

The heating-frequency dependence of the apparent thermal conductivity in a semi-infinite body with periodic planar surface heating is explained by an analytical solution to the Boltzmann transport equation. This solution is obtained using a two-flux model and gray mean free time approximation and verified numerically with a lattice Boltzmann method and numerical results from the literature. Extending the gray solution to the nongray regime leads to an integral transform and accumulation-function representation of the phonon scattering spectrum, where the natural variable is mean free time rather than mean free path, as often used in previous work. The derivation leads to an approximate cutoff conduction similar in spirit to that of Koh and Cahill [Phys. Rev. B 76, 075207 (2007), 10.1103/PhysRevB.76.075207] except that the most appropriate criterion involves the heater frequency rather than thermal diffusion length. The nongray calculations are consistent with Koh and Cahill's experimental observation that the apparent thermal conductivity shows a stronger heater-frequency dependence in a SiGe alloy than in natural Si. Finally these results are demonstrated using a virtual experiment, which fits the phase lag between surface temperature and heat flux to obtain the apparent thermal conductivity and accumulation function.

Analysis of higher harmonics on bidirectional heat pulse propagation experiment in helical and tokamak plasmas

NASA Astrophysics Data System (ADS)

Kobayashi, T.; Ida, K.; Inagaki, S.; Tsuchiya, H.; Tamura, N.; Choe, G. H.; Yun, G. S.; Park, H. K.; Ko, W. H.; Evans, T. E.; Austin, M. E.; Shafer, M. W.; Ono, M.; López-bruna, D.; Ochando, M. A.; Estrada, T.; Hidalgo, C.; Moon, C.; Igami, H.; Yoshimura, Y.; Tsujimura, T. Ii.; Itoh, S.-I.; Itoh, K.

2017-07-01

In this contribution we analyze modulation electron cyclotron resonance heating (MECH) experiment and discuss higher harmonic frequency dependence of transport coefficients. We use the bidirectional heat pulse propagation method, in which both inward propagating heat pulse and outward propagating heat pulse are analyzed at a radial range, in order to distinguish frequency dependence of transport coefficients due to hysteresis from that due to other reasons, such as radially dependent transport coefficients, a finite damping term, or boundary effects. The method is applied to MECH experiments performed in various helical and tokamak devices, i.e. Large Helical Device (LHD), TJ-II, Korea Superconducting Tokamak Advanced Research (KSTAR), and Doublet III-D (DIII-D) with different plasma conditions. The frequency dependence of transport coefficients are clearly observed, showing a possibility of existence of transport hysteresis in flux-gradient relation.

Influence of internal channel geometry of gas turbine blade on flow structure and heat transfer

NASA Astrophysics Data System (ADS)

Szwaba, Ryszard; Kaczynski, Piotr; Telega, Janusz; Doerffer, Piotr

2017-12-01

This paper presents the study of the influence of channel geometry on the flow structure and heat transfer, and also their correlations on all the walls of a radial cooling passage model of a gas turbine blade. The investigations focus on the heat transfer and aerodynamic measurements in the channel, which is an accurate representation of the configuration used in aeroengines. Correlations for the heat transfer coefficient and the pressure drop used in the design of internal cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include a corner fillets, ribs with fillet radii and a special orientation. Therefore, this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which has very realistic features.

Heat conduction in chain polymer liquids: molecular dynamics study on the contributions of inter- and intramolecular energy transfer.

PubMed

Ohara, Taku; Yuan, Tan Chia; Torii, Daichi; Kikugawa, Gota; Kosugi, Naohiro

2011-07-21

In this paper, the molecular mechanisms which determine the thermal conductivity of long chain polymer liquids are discussed, based on the results observed in molecular dynamics simulations. Linear n-alkanes, which are typical polymer molecules, were chosen as the target of our studies. Non-equilibrium molecular dynamics simulations of bulk liquid n-alkanes under a constant temperature gradient were performed. Saturated liquids of n-alkanes with six different chain lengths were examined at the same reduced temperature (0.7T(c)), and the contributions of inter- and intramolecular energy transfer to heat conduction flux, which were identified as components of heat flux by the authors' previous study [J. Chem. Phys. 128, 044504 (2008)], were observed. The present study compared n-alkane liquids with various molecular lengths at the same reduced temperature and corresponding saturated densities, and found that the contribution of intramolecular energy transfer to the total heat flux, relative to that of intermolecular energy transfer, increased with the molecular length. The study revealed that in long chain polymer liquids, thermal energy is mainly transferred in the space along the stiff intramolecular bonds. This finding implies a connection between anisotropic thermal conductivity and the orientation of molecules in various organized structures with long polymer molecules aligned in a certain direction, which includes confined polymer liquids and self-organized structures such as membranes of amphiphilic molecules in water.

Methods and apparatus for radially compliant component mounting

DOEpatents

Bulman, David Edward [Cincinnati, OH; Darkins, Jr., Toby George; Stumpf, James Anthony [Columbus, IN; Schroder, Mark S [Greenville, SC; Lipinski, John Joseph [Simpsonville, SC

2012-03-27

Methods and apparatus for a mounting assembly for a liner of a gas turbine engine combustor are provided. The combustor includes a combustor liner and a radially outer annular flow sleeve. The mounting assembly includes an inner ring surrounding a radially outer surface of the liner and including a plurality of axially extending fingers. The mounting assembly also includes a radially outer ring coupled to the inner ring through a plurality of spacers that extend radially from a radially outer surface of the inner ring to the outer ring.

[Clinical observation on the different treatments targeted at different types of radial head fracture and radial neck fracture].

PubMed

Zhang, Ying-Ze; Guo, Ming-Ke; Zheng, Zhan-le; Zhang, Qi; Chen, Wei

2009-06-15

To assess the effect of the different treatments targeted at different types of radial head fracture and radial neck fracture. A retrospective study was performed in 87 patients from February 2006 to March 2007. Fifty-four patients with radial head fractures included 36 males and 18 females, aged from 18 to 65 years (the average age was 33); Forty of them resulted from crashing, 8 from traffic injury and 6 from falling injury. According to Mason classification system, there were 15 type I, 23 type II and 16 type III. Thirty-three patients with radial neck fractures included 21 males and 12 females, aged from 9 to 17 years (the average age was 13), 29 of them resulted from crashing, 1 from traffic injury and 3 from falling injury. According to O'Brien classification system, there were 8 type I, 14 type II and 11 type III. Type I of radial head fractures and radial neck fractures were immobilization with cast, the patients with type II of radial head fractures were treated with open reduction and micro-screw or T-trapezoid and bridge-shaped plate fixation and type III had operations to fix with bridge-shaped locked plate and repair the broken annular ligament, or replace heads with prosthesis. All patients with type II and type III of radial neck fractures were treated with closed reduction by leverage and percutaneous intra-medullary nailing. The patients were followed up for 4-12 months (mean 7.2 months). The functional recovery degrees were evaluated with Wheeler's evaluation system. In group of radial head fractures, the results were excellent in 26 patients, good in 20, fair in 6 and poor in 2, the excellent and good rate was 85.2%. In group of radial neck fractures, the results were excellent in 20 patients, good in 9, fair in 4 and poor in no patient, and the excellent and good rate was 87.9%. Different types of fractures should choose different surgical methods according to their characters. The excellent functional recovery depend on anatomical reduction

Investigation of second grade fluid through temperature dependent thermal conductivity and non-Fourier heat flux

NASA Astrophysics Data System (ADS)

Hayat, T.; Ahmad, Salman; Khan, M. Ijaz; Alsaedi, A.; Waqas, M.

2018-06-01

Here we investigated stagnation point flow of second grade fluid over a stretchable cylinder. Heat transfer is characterized by non-Fourier law of heat flux and thermal stratification. Temperature dependent thermal conductivity and activation energy are also accounted. Transformations procedure is applying to transform the governing PDE's into ODE's. Obtained system of ODE's are solved analytically by HAM. Influence of flow variables on velocity, temperature, concentration, skin friction and Sherwood number are analyzed. Obtained outcome shows that velocity enhanced through curvature parameter, viscoelastic parameter and velocities ratio variable. Temperature decays for larger Prandtl number, thermal stratification, thermal relaxation and curvature parameter. Sherwood number and concentration field show opposite behavior for higher estimation of activation energy, reaction rate, curvature parameter and Schmidt number.

Novel Integration Radial and Axial Magnetic Bearing

NASA Technical Reports Server (NTRS)

Blumenstock, Kenneth; Brown, Gary

2000-01-01

Typically, fully active magnetically suspended systems require one axial and two radial magnetic bearings. Combining radial and axial functions into a single device allows for more compact and elegant packaging. Furthermore, in the case of high-speed devices such as energy storage flywheels, it is beneficial to minimize shaft length to keep rotor mode frequencies as high as possible. Attempts have been made to combine radial and axial functionality, but with certain drawbacks. One approach requires magnetic control flux to flow through a bias magnet reducing control effectiveness, thus resulting in increased resistive losses. This approach also requires axial force producing magnetic flux to flow in a direction into the rotor laminate that is undesirable for minimizing eddy-current losses resulting in rotational losses. Another approach applies a conical rotor shape to what otherwise would be a radial heteropolar magnetic bearing configuration. However, positional non-linear effects are introduced with this scheme and the same windings are used for bias, radial, and axial control adding complexity to the controller and electronics. For this approach, the amount of axial capability must be limited. It would be desirable for an integrated radial and axial magnetic bearing to have the following characteristics; separate inputs for radial and axial control for electronics and control simplicity, all magnetic control fluxes should only flow through their respective air gaps and should not flow through any bias magnets for minimal resistive losses, be of a homopolar design to minimize rotational losses, position related non-linear effects should be minimized, and dependent upon the design parameters, be able to achieve any radial/axial force or power ratio as desired. The integrated radial and axial magnetic bearing described in this paper exhibits all these characteristics. Magnetic circuit design, design equations, and magnetic field modeling results will be presented.

Novel Integrated Radial and Axial Magnetic Bearing

NASA Technical Reports Server (NTRS)

Blumenstock, Kenneth A.; Brown, Gary L.; Powers, Edward I. (Technical Monitor)

2000-01-01

Typically, fully active magnetically suspended systems require one axial and two radial magnetic bearings. Combining radial and axial functions into a single device allows for more compact and elegant packaging. Furthermore, in the case of high-speed devices such as energy storage flywheels, it is beneficial to minimize shaft length to keep rotor mode frequencies as high as possible. Attempts have been made to combine radial and axial functionality, but with certain drawbacks. One approach requires magnetic control flux to flow through a bias magnet reducing control effectiveness, thus resulting in increased resistive losses. This approach also requires axial force producing magnetic flux to flow in a direction into the rotor laminate that is undesirable for minimizing eddy-current losses resulting in rotational losses. Another approach applies a conical rotor shape to what otherwise would be a radial heteropolar magnetic bearing configuration. However, positional non-linear effects are introduced with this scheme and the same windings are used for bias, radial, and axial control adding complexity to the controller and electronics. For this approach, the amount of axial capability must be limited. It would be desirable for an integrated radial and axial magnetic bearing to have the following characteristics, separate inputs for radial and axial control for electronics and control simplicity, all magnetic control fluxes should only flow through their respective air gaps and should not flow through any bias magnets for minimal resistive losses, be of a homopolar design to minimize rotational losses, position related non-linear effects should be minimized, and dependent upon the design parameters, be able to achieve any radial/axial force or power ratio as desired. The integrated radial and axial magnetic bearing described in this paper exhibits all these characteristics. Magnetic circuit design, design equations, and analysis results will be presented.

Design of Refractory Metal Life Test Heat Pipe and Calorimeter

NASA Technical Reports Server (NTRS)

Martin, J. J.; Reid, R. S.; Bragg-Sitton, S. M.

2010-01-01

Heat pipe life tests have seldom been conducted on a systematic basis. Typically, one or more heat pipes are built and tested for an extended period at a single temperature with simple condenser loading. Results are often reported describing the wall material, working fluid, test temperature, test duration, and occasionally the nature of any failure. Important information such as design details, processing procedures, material assay, power throughput, and radial power density are usually not mentioned. We propose to develop methods to generate carefully controlled data that conclusively establish heat pipe operating life with material-fluid combinations capable of extended operation. The test approach detailed in this Technical Publication will use 16 Mo-44.5%Re alloy/sodium heat pipe units that have an approximate12-in length and 5/8-in diameter. Two specific test series have been identified: (1) Long-term corrosion rates based on ASTM-G-68-80 (G-series) and (2) corrosion trends in a cross-correlation sequence at various temperatures and mass fluences based on a Fisher multifactor design (F-series). Evaluation of the heat pipe hardware will be performed in test chambers purged with an inert purified gas (helium or helium/argon mixture) at low pressure (10-100 torr) to provide thermal coupling between the heat pipe condenser and calorimeter. The final pressure will be selected to minimize the potential for voltage breakdown between the heat pipe and radio frequency (RF) induction coil (RF heating is currently the planned method of powering the heat pipes). The proposed calorimeter is constructed from a copper alloy and relies on a laminar flow water-coolant channel design to absorb and transport energy

Spurious heat conduction behavior of finite-size graphene nanoribbon under extreme uniaxial strain caused by the AIREBO potential

NASA Astrophysics Data System (ADS)

Yang, Xueming; Wu, Sihan; Xu, Jiangxin; Cao, Bingyang; To, Albert C.

2018-02-01

Although the AIREBO potential can well describe the mechanical and thermal transport of the carbon nanostructures under normal conditions, previous studies have shown that it may overestimate the simulated mechanical properties of carbon nanostructures in extreme strains near fracture. It is still unknown whether such overestimation would also appear in the thermal transport of nanostructrues. In this paper, the mechanical and thermal transport of graphene nanoribbon under extreme deformation conditions are studied by MD simulations using both the original and modified AIREBO potential. Results show that the cutoff function of the original AIREBO potential produces an overestimation on thermal conductivity in extreme strains near fracture stage. Spurious heat conduction behavior appears, e.g., the thermal conductivity of GNRs does not monotonically decrease with increasing strain, and even shows a ;V; shaped reversed and nonphysical trend. Phonon spectrum analysis show that it also results in an artificial blue shift of G peak and phonon stiffening of the optical phonon modes. The correlation between spurious heat conduction behavior and overestimation of mechanical properties near the fracture stage caused by the original AIREBO potential are explored and revealed.