NASA Astrophysics Data System (ADS)
Hedayati, F.; Ganji, D. D.; Hamidi, S. M.; Malvandi, A.
2012-06-01
The coupling of the homotopy perturbation method (HPM) and the variational iteration method (VIM) is a strong technique for solving higher dimensional initial boundary value problems. In this article, after a brief explanation of the mentioned method, the coupled techniques are applied to one-dimensional heat transfer in a rectangular radial fin with a temperature-dependent thermal conductivity to show the effectiveness and accuracy of the method in comparison with other methods. The graphical results show the best agreement of the three methods; however, the amount of calculations of each iteration for the combination of HPM and VIM was reduced markedly for multiple iterations. It was found that the variation of the dimensionless temperature strongly depends on the dimensionless small parameter {\\varepsilon_1}. Moreover, as the dimensionless length increases, the thermal conductivity of the fin decreases along the fin.
NASA Technical Reports Server (NTRS)
Basiulis, A.; Buzzard, R. J.
1971-01-01
Unit moves heat radially from small diameter shell to larger diameter shell, or vice versa, with negligible temperature drop, making device useful wherever heating or cooling of concentrically arranged materials, substances, and structures is desired.
Valenzuela, Javier (Hanover, NH)
2001-01-01
A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.
NASA Astrophysics Data System (ADS)
Meydaneri, Fatma; Saatçi, Buket; Gündüz, Mehmet; Özdemir, Mehmet
2013-11-01
The variations of thermal conductivities of solid phases versus temperature for pure Sn, pure Zn and Sn-9 wt.% Zn, Sn-14 wt.% Zn, Sn-50 wt.% Zn, Sn-80 wt.% Zn binary alloys were measured with a radial heat flow apparatus. The thermal conductivity ratios of liquid phase to solid phase for the pure Sn, pure Zn and eutectic Sn-9 wt.% Zn alloy at their melting temperature are found with a Bridgman-type directional solidification apparatus. Thus, the thermal conductivities of liquid phases for pure Sn, pure Zn and eutectic Sn-9 wt.% Zn binary alloy at their melting temperature were evaluated by using the values of solid phase thermal conductivities and the thermal conductivity ratios of liquid phase to solid phase.
New constraints on Earth's radial conductivity structure
NASA Astrophysics Data System (ADS)
Püthe, Christoph; Kuvshinov, Alexey; Olsen, Nils; Sabaka, Terence
2014-05-01
We present a new model of Earth's radial (1-D) conductivity structure at depths between 10 km and the core-mantle boundary. It is based on CM5, the latest version in the Comprehensive Model series that has been derived using 13 years (September 2000 to September 2013) of magnetic data collected by the three satellites Oersted, CHAMP and SAC-C and at the global network of geomagnetic observatories. CM5 describes contributions due to sources in core, lithosphere, ionosphere and magnetosphere (and corresponding induced parts) in form of spherical harmonic expansion (SHE) coefficients. Removing predictions of the core, lithospheric and ionospheric field contributions as given by CM5 from the observations, we determine time series of the dominating external and induced SHE coefficients of the magnetic potential due to the magnetospheric ring current. Scalar Q-responses are estimated from these coefficients. An iterative approach is used to correct the estimated responses for 3-D effects arising from lateral heterogeneities in the top 10 km. The corrected Q-responses are converted to C-responses; the latter are subsequently inverted for the layered 1-D mantle conductivity profile with the Newton method. The Hessian matrix of the misfit function, which is derived analytically, is used to estimate confidence limits for the conductivity of each layer. The resulting conductivity-depth profile is compared to 1-D conductivity models of Earth's mantle recovered in previous studies.
Conduction heat transfer solutions
VanSant, J.H.
1983-08-01
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. The introduction presents a synopsis on the theory, differential equations, and boundary conditions for conduction heat transfer. Some discussion is given on the use and interpretation of solutions. Supplementary data such as mathematical functions, convection correlations, and thermal properties are included for aiding the user in computing numerical values from the solutions. 155 figs., 92 refs., 9 tabs.
Conduction heat transfer solutions
VanSant, J.H.
1980-03-01
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. This material is useful for engineers, scientists, technologists, and designers of all disciplines, particularly those who design thermal systems or estimate temperatures and heat transfer rates in structures. More than 500 problem solutions and relevant data are tabulated for easy retrieval. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. A case number is assigned to each problem for cross-referencing, and also for future reference. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. At least one source reference is given so that the user can review the methods used to derive the solutions. Problem solutions are given in the form of equations, graphs, and tables of data, all of which are also identified by problem case numbers and source references.
The Usefulness of Proximal Radial Motor Conduction in Acute Compressive Radial Neuropathy
Kim, Kun Hyun; Park, Kee-Duk; Chung, Pil-Wook; Moon, Heui-Soo; Kim, Yong Bum; Yoon, Won Tae
2015-01-01
Background and Purpose The objective of this study was to determine diagnostic and prognostic values of proximal radial motor conduction in acute compressive radial neuropathy. Methods Thirty-nine consecutive cases of acute compressive radial neuropathy with radial conduction studies-including stimulation at Erb's point-performed within 14 days from clinical onset were reviewed. The radial conduction data of 39 control subjects were used as reference data. Results Thirty-one men and eight women (age, 45.2±12.7 years, mean±SD) were enrolled. All 33 patients in whom clinical follow-up data were available experienced complete recovery, with a recovery time of 46.8±34.3 days. Partial conduction block was found frequently (17 patients) on radial conduction studies. The decrease in the compound muscle action potential area between the arm and Erb's point was an independent predictor for recovery time. Conclusions Proximal radial motor conduction appears to be a useful method for the early detection and prediction of prognosis of acute compressive radial neuropathy.
Performance of a variable conductance heat pipe heat exchanger
P. D. Chancelor
1983-01-01
The performance of an air to air heat exchanger in which heat is transferred to a finned evaporator and from a finned condenser via a heat pipe was evaluated. The variable conductance heat pipe is to the condenser fins a heat source and to the evaporator fins a heat sink. The principal advantage of the variable conductance heat pipe heat
Heat Transfer Experiments in the Internal Cooling Passages of a Cooled Radial Turbine Rotor
NASA Technical Reports Server (NTRS)
Johnson, B. V.; Wagner, J. H.
1996-01-01
An experimental study was conducted (1) to experimentally measure, assess and analyze the heat transfer within the internal cooling configuration of a radial turbine rotor blade and (2) to obtain heat transfer data to evaluate and improve computational fluid dynamics (CFD) procedures and turbulent transport models of internal coolant flows. A 1.15 times scale model of the coolant passages within the NASA LERC High Temperature Radial Turbine was designed, fabricated of Lucite and instrumented for transient beat transfer tests using thin film surface thermocouples and liquid crystals to indicate temperatures. Transient heat transfer tests were conducted for Reynolds numbers of one-fourth, one-half, and equal to the operating Reynolds number for the NASA Turbine. Tests were conducted for stationary and rotating conditions with rotation numbers in the range occurring in the NASA Turbine. Results from the experiments showed the heat transfer characteristics within the coolant passage were affected by rotation. In general, the heat transfer increased and decreased on the sides of the straight radial passages with rotation as previously reported from NASA-HOST-sponsored experiments. The heat transfer in the tri-passage axial flow region adjacent to the blade exit was relatively unaffected by rotation. However, the heat transfer on one surface, in the transitional region between the radial inflow passage and axial, constant radius passages, decreased to approximately 20 percent of the values without rotation. Comparisons with previous 3-D numerical studies indicated regions where the heat transfer characteristics agreed and disagreed with the present experiment.
Heat Transfer from an ESF Radial Plate Clutch Surface
D. J. Ellam; W. A. Bullough; V. Oravskı
2003-01-01
The aim of this work was to investigate the rate of heat transfer from a radial plate clutch surface. The paper presents experimental results over a range of angular speeds (&OHgr;) and fluid gap widths (h), which are then favourably compared to analytical and computational fluid dynamics (CFD) solutions for the same geometry and operating conditions. Verifying the heat transfer
Radial heat transfer from a moving plasma
Johnson, James Randall
1966-01-01
!red to the arc. Although the heat flux data appeared to be a linear fui, ction of the power supplied to the arc, no correlation was given, Wet! arri (6) has also considered three models for predirtirig the stagnation heat flux to an object mme rsed in an air... plasma. Tse modi- f ied Fay-Riddel1 equation was used as a bas ' s for the three models wh. ich are 1. equil. 'brium boundary layer, 2. f rozen flow and a fully catalytic wall 3. arid f r seri flow a d noncatalytic wall. On comparison...
Mathematical model for solar drying of potato cylinders with thermal conductivity radially modulated
NASA Astrophysics Data System (ADS)
Trujillo Arredondo, Mariana
2014-05-01
A mathematical model for drying potato cylinders using solar radiation is proposed and solved analytically. The model incorporates the energy balance for the heat capacity of the potato, the radiation heat transfer from the potato toward the drying chamber and the solar radiation absorbed by the potato during the drying process. Potato cylinders are assumed to exhibit a thermal conductivity which is radially modulated. The method of the Laplace transform, with integral Bromwich and residue theorem will be applied and the analytic solutions for the temperature profiles in the potato cylinder will be derived in the form of an infinite series of Bessel functions, when the thermal conductivity is constant; and in the form of an infinite series of Heun functions, when the thermal conductivity has a linear radial modulation. All computations are performed using computer algebra, specifically Maple. It is expected that the analytical results obtained will be useful in food engineering and industry. Our results suggest some lines for future investigations such as the adoption of more general forms of radial modulation for the thermal conductivity of potato cylinders; and possible applications of other computer algebra software such as Maxima and Mathematica.
Ballistic-Diffusive Heat-Conduction Equations
Gang Chen; Gang
2001-01-01
We present new heat-conduction equations, named ballistic-diffusive equations, which are derived from the Boltzmann equation. We show that the new equations are a better approximation than the Fourier law and the Cattaneo equation for heat conduction at the scales when the device characteristic length, such as film thickness, is comparable to the heat-carrier mean free path and\\/or the characteristic time,
Resistive Heating in Radial Geometry Diamond Anvil Cell
NASA Astrophysics Data System (ADS)
Zepeda-Alarcon, E.; Knight, J. W.; MacDowell, A.; Miyagi, L. M.; Kaercher, P. M.; Kanitpanyacharoen, W.; Wenk, H.; Williams, Q. C.
2012-12-01
High temperature and pressure experiments are important for understanding deep Earth geodynamics. Radial x-ray diffraction from samples under high pressure within a diamond anvil cell(DAC) provide information on lattice strain and crystallite preferred orientation. Understanding the development of crystallographic preferred orientation is essential for identifying deformation mechanisms as well as assessing anisotropy of bulk physical properties. Many high pressure radial diffraction experiments in the diamond anvil cell are performed at room temperature. For high temperatures, laser heating can be used but this technique produces large temperature gradients. Resistive heating provides a more homogeneous temperature distribution and covers the inaccessible low temperature range (<~1400K) of laser heating. Another advantage of this technique is stability, allowing long time period in-situ temperature experiments to be possible. Applying both heating techniques simultaneously covers a wider temperature range while minimizing temperature gradients. We are developing a resistive heating system for diamond anvil cells in radial geometry (rDAC) at beamline 12.2.2 of the Advanced Light Source (ALS) of Lawrence Berkeley Laboratory to recreate deep Earth deformation conditions. The design is based on a previous one by Due et al., in revision. The heater is laser-milled from high-purity solid graphite, and designed to fit slightly displaced from the diamond culets. Due to the low inherent resistivity and small size of the graphite heater, 6x3x0.5mm, we can achieve temperatures at the cullet of 300 to >1300 K at relatively low power loads of ~ 200 watts. The laser machining produces very uniform heater geometry which allows us to obtain reproducible temperatures in the rDAC. The assembly is modular and self supporting which allows for ease of assembly a requirement if users are to install the heater in a cell themselves. We are currently applying this technique to study lattice preferred orientation changes during phase transformations. We study the transformation of coesite and stishovite that occurs in the deep crust, and olivine transforming to ringwoodite and then to magnesiowuestite and perovskite in the lower mantle.
The heat transfer characteristics of the jacket-type radial heat pipe
NASA Astrophysics Data System (ADS)
Jiao, Yonggang; Xia, Guodong; Wang, Dan
2013-07-01
A simple, rapid mathematical model to calculate the non-steady-state startup process of the jacket-type radial heat pipe is presented in this paper. The model is based on the special structure and using conditions of the jacket-type radial heat pipe, the vapor temperature in heat pipe only changes over time. The startup performance of the heat pipe with variation input heat flux and the filling rate is analyzed. The results manifest that the filling rate increased will reduce the maximum operating temperature of the heat pipe and shorten the startup time of the heat pipe. With the increase of input heat flux, the operating temperature increases and the time to reach the steady state of the heat pipe is added. The total thermal resistance of heat pipe decreases with the increase of the input heat flux and filling rate. The variation of the local convective heat transfer coefficient and the maximum temperature of the water are investigated with different cooling water inlet conditions.
Light dynamics in materials with radially inhomogeneous thermal conductivity.
Kartashov, Yaroslav V; Vysloukh, Victor A; Torner, Lluis
2013-11-01
We study the properties of bright and vortex solitons in thermal media with nonuniform thermal conductivity and homogeneous refractive index, whereby the local modulation of the thermal conductivity strongly affects the entire refractive index distribution. While regions where the thermal conductivity is increased effectively expel light, self-trapping may occur in the regions with reduced thermal conductivity, even if such regions are located close to the material boundary. As a result, strongly asymmetric self-trapped beams may form inside a ring with reduced thermal conductivity and perform persistent rotary motion. Also, such rings are shown to support stable vortex solitons, which may feature strongly noncanonical shapes. PMID:24177108
Radial disk heating by more than one spiral density wave
I. Minchev; A. C. Quillen
2005-10-28
We consider a differentially rotating, 2D stellar disk perturbed by two steady state spiral density waves moving at different patterns speeds. Our investigation is based on direct numerical integration of initially circular test-particle orbits. We examine a range of spiral strengths and spiral speeds and show that stars in this time dependent gravitational field can be heated (their random motions increased). This is particularly noticeable in the simultaneous propagation of a 2-armed spiral density wave near the corotation resonance (CR), and a weak 4-armed one near the inner and outer 4:1 Lindblad resonances. In simulations with 2 spiral waves moving at different pattern speeds we find: (1) the variance of the radial velocity, sigma_R^2, exceeds the sum of the variances measured from simulations with each individual pattern; (2) sigma_R^2 can grow with time throughout the entire simulation; (3) sigma_R^2 is increased over a wider range of radii compared to that seen with one spiral pattern; (4) particles diffuse radially in real space whereas they don't when only one spiral density wave is present. Near the CR with the stronger, 2-armed pattern, test particles are observed to migrate radially. These effects take place at or near resonances of both spirals so we interpret them as the result of stochastic motions. This provides a possible new mechanism for increasing the stellar velocity dispersion in galactic disks. If multiple spiral patterns are present in the Galaxy we predict that there should be large variations in the stellar velocity dispersion as a function of radius.
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.
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.
Heat transfer in a radially rotating square duct fitted with in-line transverse ribs
S. W. Chang; W. D. Morris
2003-01-01
This paper describes an experimental study of heat transfer in a radially rotating square duct with two opposite walls fitted by transverse ribs. The manner in which rotation modifies the forced heat convection is considered for the case where the duct rotates about an axis perpendicular to the duct's axis of symmetry and the flow within is radially outward with
Finite Heat conduction in 2D Lattices
Lei Yang; Yang Kongqing
2001-07-30
This paper gives a 2D hamonic lattices model with missing bond defects, when the capacity ratio of defects is enough large, the temperature gradient can be formed and the finite heat conduction is found in the model. The defects in the 2D harmonic lattices impede the energy carriers free propagation, by another words, the mean free paths of the energy carrier are relatively short. The microscopic dynamics leads to the finite conduction in the model.
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 conductivity of a pion gas
Antonio Dobado Gonzalez; Felipe J. Llanes-Estrada; Juan M. Torres Rincon
2007-02-13
We evaluate the heat conductivity of a dilute pion gas employing the Uehling-Uehlenbeck equation and experimental phase-shifts parameterized by means of the SU(2) Inverse Amplitude Method. Our results are consistent with previous evaluations. For comparison we also give results for an (unphysical) hard sphere gas.
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.
R. I. Nigmatulin; N. S. Khabeev
1980-01-01
Vapor (gas) bubbles executing free radial oscillations in a liquid are considered. Expressions are obtained for the frequency and decay rate of small free oscillations of the bubbles. The effective coefficients of heat transfer between the radially pulsating bubbles and the liquid are determined.
J. B. Henderson; A. C. Caolo
1983-01-01
An experimental investigation was performed for free convection heat transfer from radial fin tube heat exchangers operating in water. Experimental heat transfer data were obtained as a function of the Rayleigh number for copper and aluminum fin tubes for two fin diameters and four fin spacings. The experimental data covered a Rayleigh number range of 1 to 10âµ. The experimental
Phonon heat conduction in layered anisotropic crystals
NASA Astrophysics Data System (ADS)
Minnich, A. J.
2015-02-01
The thermal properties of anisotropic crystals are of both fundamental and practical interest, but transport phenomena in anisotropic materials such as graphite remain poorly understood because solutions of the Boltzmann equation often assume isotropy. Here, we extend an analytic solution of the transient, frequency-dependent Boltzmann equation to highly anisotropic solids and examine its predictions for graphite. We show that this simple model predicts key results, such as long c -axis phonon mean free paths and a negative correlation of cross-plane thermal conductivity with in-plane group velocity, that were previously observed with computationally expensive molecular-dynamics simulations. Further, using our analytic solution, we demonstrate a method to reconstruct the anisotropic mean free path spectrum of crystals with arbitrary dispersion relations without any prior knowledge of their harmonic or anharmonic properties using observations of quasiballistic heat conduction. These results provide a useful analytic framework to understand thermal transport in anisotropic crystals.
Matthew W. Becker; Randall J. Charbeneau
2000-01-01
Forced-gradient groundwater tracer tests may be conducted using a variety of hydraulic schemes, so it is useful to have simple semi-analytic models available that can examine various injection\\/withdrawal scenarios. Models for radially convergent tracer tests are formulated here as transfer functions, which allow complex tracer test designs to be simulated by a series of simple mathematical expressions. These mathematical expressions
CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011
Dyer, Bill
ME 525 CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011 Office: 201C Roberts Hall Lecture Room of conduction heat transfer. Important results which are useful for engineering application will also: 121 Roberts Hall Phone: 994-6295 Lecture Periods: 12:45- 2:00, TR TEXT: Heat Conduction, M. N. Ozisik
Radiative Heat Conduction and the Magnetorotational Instability
Rafael A. Araya-Gochez; Ethan Vishniac
2003-11-21
A photon or neutrino gas--semi-contained by a baryonic species through scattering--comprises a rather peculiar MHD fluid where the magnetic field is truly frozen only to the co-moving volume associated with the mass density. Although radiative diffusion precludes an adiabatic treatment of compressive perturbations, we show that the energy equation may be cast in "quasi-adiabatic" form for exponentially growing non-propagating wave modes. Defining a generalized quasi-adiabatic index leads to a relatively straightforward dispersion relation for non-axisymmetric magnetorotational modes in the horizontal regime when an accretion disk has comparable stress contributions from diffusive and non-diffusive particle species. This analysis is generally applicable to optically thick, neutrino-cooled disks since the pressure contributions from photons, pairs and neutrinos, all have the same temperature dependence whereas only the neutrino component has radiative heat conduction properties on the time and length scales of the instability. We discuss the energy deposition process and the temporal and spatial properties of the ensuing turbulent disk structure on the basis of the derived dispersion relation.
Transport analysis through heat waves driven at different radial positions
U. Gasparino; V. Erckmann; H. J. Hartfuß; H. Maaßberg; M. Romé
1998-01-01
In W7-AS, electron cyclotron resonance heating (ECRH) discharges sustained by three gyrotrons, one resonant on-axis and two off-axis, were investigated by a perturbative square-wave modulation of the on- and the off-axis deposited power, respectively. The absorption profile of the modulated ECRH power as well as the transport coefficients, were determined from the response of the amplitude and phase delay of
Mamoru Hirata; Hisataka Sakakibara
2007-01-01
Objective The present study aimed to clarify the range of involvement for hand-arm vibration syndrome (VS) in the median, ulnar and\\u000a radial nerves of the hand.\\u000a \\u000a \\u000a \\u000a Methods Sensory nerve conduction velocities (SCVs) for 3 nerves in the hands and arms were examined for 34 patients with VS and 23\\u000a age-matched controls. Neuropathy types were classified by possible carpal tunnel syndrome (CTS), Guyon’s
Finite element procedure for heat conduction problems with internal heating
Pham, Q.T. [Univ. of New South Wales, Sydney (Australia). School of Chemical Engineering and Industrial Chemistry
1995-05-01
Heat transfer problems involving temperature-dependent heat generation are formally equivalent to those involving variable specific heat such as occur in phase change situations. The use of distributed and lumped capacitance finite element methods for solving these problems is investigated. The technique is successfully applied to very severe internal heating problems such as the self-ignition of biological materials.
Falabella, S.
1988-05-11
A small Radial Energy Analyzer (REA) was used on the Tandem Mirror Experiment-Upgrade (TMX-U), at Lawerence Livermore National Laboratory, to investigate the radial profiles of ion temperature, density, and plasma potential during Ion Cyclotron Resonance Heating (ICRH). The probe has been inserted into the central-cell plasma at temperatures of 200 eV and densities of 3 x 10/sup 12/cm/sup /minus 3// without damage to the probe, or major degradation of the plasma. This analyzer has indicated an increase in ion temperature from near 20 eV before ICRH to near 150 eV during ICRH, with about 60 kW of broadcast power. The REA measurements were cross-checked against other diagnostics on TMX-U and found to be consistent. The ion density measurement was compared to the line-density measured by microwave interferometry and found to agree within 10 to 20%. A radial intergral of n/sub i/T/sub i/ as measured by the REA shows good agreement with the diamagnetic loop measurement of plasma energy. The radial density profile is observed to broaden during the RF heating pulses, without inducing additional radial losses in the core plasma. The radial profile of plasma is seen to vary from axially peaked, to nearly flat as the plasma conditions carried over the series of experiments. To relate the increase in ion temperature to power absorbed by the plasma, a power balance as a function of radius was performed. The RF power absorbed is set equal to the sum of the losses during ICRH, minus those without ICRH. This method accounts for more than 70% of the broadcast power using a simple power balance model. The measured radial profile of the RF heating was compared to the calculations of two codes, ANTENA and GARFIELD, to test their effectiveness as predictors of power absorption profiles for TMX-U. 62 refs., 63 figs., 7 tabs.
Radial and temporal variations in surface heat transfer during cryogen spray cooling
NASA Astrophysics Data System (ADS)
Franco, Walfre; Liu, Jie; Wang, Guo-Xiang; Nelson, J. Stuart; Aguilar, Guillermo
2005-01-01
Cryogen spray cooling (CSC) is a heat extraction process that protects the epidermis from thermal damage during dermatologic laser surgery. The objective of the present work is to investigate radial and temporal variations in the heat transferred through the surface of a skin phantom during CSC. A fast-response thermal sensor is used to measure surface temperatures every 1 mm across a 16 mm diameter of the sprayed surface of the phantom. An analytical expression based on Fourier's law and Duhamel's theorem is used to compute surface heat fluxes from temperature measurements. Results show that radial and temporal variations of the boundary conditions have a strong influence on the homogeneity of heat extraction from the skin phantom. However, there is a subregion of uniform cooling whose size is time dependent. It is also observed that the surface heat flux undergoes a marked dynamic variation, with a maximum heat flux occurring at the centre of the sprayed surface early in the spurt followed by a quick decrease. The study shows that radial and temporal variations of boundary conditions must be taken into account and ideally controlled to guarantee uniform protection during CSC of human skin.
Superfluid heat conduction and the cooling of magnetized neutron stars
Cirigliano, Vincenzo [Los Alamos National Laboratory; Reddy, Sanjay [Los Alamos National Laboratory; Sharma, Rishi [Los Alamos National Laboratory; Aguilera, Deborah N [BUENOS AIRES
2008-01-01
We report on a new mechanism for heat conduction in the neutron star crust. We find that collective modes of superftuid neutron matter, called superfiuid phonons (sPhs), can influence heat conduction in magnetized neutron stars. They can dominate the heat conduction transverse to magnetic field when the magnetic field B {approx}> 10{sup 13} C. At density p {approx_equal} 10{sup 12}--10{sup 14} g/cm{sup 3} the conductivity due to sPhs is significantly larger than that due to lattice phonons and is comparable to electron conductivity at when temperature {approx_equal} 10{sup 8} K. This new mode of heat conduction can limit the surface anisotropy in highly magnetized neutron stars. Cooling curves of magnetized neutron stars with and without superfluid heat conduction show observationally discernible differences.
Control of heat source in a heat conduction problem
NASA Astrophysics Data System (ADS)
Lyashenko, V.; Kobilskaya, E.
2014-11-01
The mathematical model of thermal processes during the heat treatment of a moving axisymmetric environment, for example wire. is considered. The wire is heated by internal constantly or periodically operating heat source. It is presented in the form of initial-boundary value problem for the unsteady heat equation with internal constantly or periodically operating heat source. The purpose of the work is the definition of control parameter of temperature field of a moving area, which is heated by internal heat source. The control parameters are determined by solving a nonlocal problem for the heat equation. The problem of getting an adequate temperature distribution throughout the heating area is considered. Therefore, a problem of heat source control is solved, in particular, control by electric current. Control of the heat source allows to maintain the necessary, from a technological point of view, temperature in the heating area. In this paper, to find additional information about the source of heat. The integral condition is used in the control problem. Integral condition, which is considered in the work, determines the energy balance of the heating zone and connects the desired temperature distribution in the internal points of area with temperatures at the boundaries. Control quality in an extremum formulation of the problem is assessed using the quadratic functional. In function space, from a physical point of view, proposed functional is the absolute difference between the actual emission of energy and absorbed energy in the heating zone. The absorbed energy is calculated by solving of the boundary value problem. Methods of determining the control parameters of temperature field are proposed. The resulting problem is solved by iterative methods. At different physical conditions, numerical calculations are carried out, control parameters of the heat treatment process are obtained.
Theory and design of variable conductance heat pipes
NASA Technical Reports Server (NTRS)
Marcus, B. D.
1972-01-01
A comprehensive review and analysis of all aspects of heat pipe technology pertinent to the design of self-controlled, variable conductance devices for spacecraft thermal control is presented. Subjects considered include hydrostatics, hydrodynamics, heat transfer into and out of the pipe, fluid selection, materials compatibility and variable conductance control techniques. The report includes a selected bibliography of pertinent literature, analytical formulations of various models and theories describing variable conductance heat pipe behavior, and the results of numerous experiments on the steady state and transient performance of gas controlled variable conductance heat pipes. Also included is a discussion of VCHP design techniques.
Conduction, convection, and radiation in heat transport by BEM
K. Onishi; N. Tosaka; M. Tanaka
1985-01-01
Simultaneous conduction and convection of heat is analyzed using the boundary element method. Combined calculations of heat transfer involving transient conduction in solids, natural and forced convection in fluid under various boundary conditions for a complex two-dimensional geometry are presented. The flow equations for the thermal fluid are based on the Boussinesq approximation. The stream function, vorticity, and temperature are
Qualitative aspects in dualphaselag heat conduction Ram on Quintanilla 1
Racke, Reinhard
at low temperature has been observed to propagate by means of waves. These aspects have caused intenseQualitative aspects in dualÂphaseÂlag heat conduction Ramâ?? on Quintanilla 1 Department of Applied.racke@uniÂkonstanz.de Abstract: We consider the system of dualÂphaseÂlag heat conduction proposed by Tzou [21]. First, we prove
Efficient Reformulation of HOTFGM: Heat Conduction with Variable Thermal Conductivity
NASA Technical Reports Server (NTRS)
Zhong, Yi; Pindera, Marek-Jerzy; Arnold, Steven M. (Technical Monitor)
2002-01-01
Functionally graded materials (FGMs) have become one of the major research topics in the mechanics of materials community during the past fifteen years. FGMs are heterogeneous materials, characterized by spatially variable microstructure, and thus spatially variable macroscopic properties, introduced to enhance material or structural performance. The spatially variable material properties make FGMs challenging to analyze. The review of the various techniques employed to analyze the thermodynamical response of FGMs reveals two distinct and fundamentally different computational strategies, called uncoupled macromechanical and coupled micromechanical approaches by some investigators. The uncoupled macromechanical approaches ignore the effect of microstructural gradation by employing specific spatial variations of material properties, which are either assumed or obtained by local homogenization, thereby resulting in erroneous results under certain circumstances. In contrast, the coupled approaches explicitly account for the micro-macrostructural interaction, albeit at a significantly higher computational cost. The higher-order theory for functionally graded materials (HOTFGM) developed by Aboudi et al. is representative of the coupled approach. However, despite its demonstrated utility in applications where micro-macrostructural coupling effects are important, the theory's full potential is yet to be realized because the original formulation of HOTFGM is computationally intensive. This, in turn, limits the size of problems that can be solved due to the large number of equations required to mimic realistic material microstructures. Therefore, a basis for an efficient reformulation of HOTFGM, referred to as user-friendly formulation, is developed herein, and subsequently employed in the construction of the efficient reformulation using the local/global conductivity matrix approach. In order to extend HOTFGM's range of applicability, spatially variable thermal conductivity capability at the local level is incorporated into the efficient reformulation. Analytical solutions to validate both the user-friendly and efficient reformulations am also developed. Volume discretization sensitivity and validation studies, as well as a practical application of the developed efficient reformulation are subsequently carried out. The presented results illustrate the accuracy and implementability of both the user-friendly formulation and the efficient reformulation of HOTFGM.
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.
Thermal Conductivity of Composites Under Di erent Heating Scenarios
composite sample, and (iii) a continuous heat source. 1 Introduction Adhesives such as epoxies, gels thermal conductivities, such as diamond dust, carbon #12;bers, or aluminum particles, are added to create material with a pulsed heat source (laser) at one end, a heat sink at the other end (ambient air
Transport of radial heat flux and second sound in fusion plasmas
Guercan, Oe. D.; Berionni, V.; Hennequin, P.; Morel, P.; Vermare, L. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex (France); Diamond, P. H. [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of); CMTFO and CASS, UCSD, California 92093 (United States); Garbet, X.; Dif-Pradalier, G. [CEA, IRFM, F-13108 Saint Paul Lez Durance (France); Kosuga, Y. [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of)
2013-02-15
Simple flux-gradient relations that involve time delay and radial coupling are discussed. Such a formulation leads to a rather simple description of avalanches and may explain breaking of gyroBohm transport scaling. The generalization of the flux-gradient relation (i.e., constitutive relation), which involve both time delay and spatial coupling, is derived from drift-kinetic equation, leading to kinetic definitions of constitutive elements such as the flux of radial heat flux. This allows numerical simulations to compute these cubic quantities directly. The formulation introduced here can be viewed as an extension of turbulence spreading to include the effect of spreading of cross-phase as well as turbulence intensity, combined in such a way to give the flux. The link between turbulence spreading and entropy production is highlighted. An extension of this formulation to general quasi-linear theory for the distribution function in the phase space of radial position and parallel velocity is also discussed.
E × B shear pattern formation by radial propagation of heat flux waves
Kosuga, Y., E-mail: kosuga@riam.kyushu-u.ac.jp [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of); IAS and RIAM, Kyushu University, Fukuoka (Japan); Diamond, P. H. [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of) [WCI Center for Fusion Theory, NFRI, Daejeon (Korea, Republic of); CASS and CMTFO, University of California, San Diego, California 92093 (United States); Dif-Pradalier, G. [CEA, IRFM, Paul-lez-Durance Cedex (France)] [CEA, IRFM, Paul-lez-Durance Cedex (France); Gürcan, Ö. D. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau (France)] [Laboratoire de Physique des Plasmas, Ecole Polytechnique, Palaiseau (France)
2014-05-15
A novel theory to describe the formation of E×B flow patterns by radially propagating heat flux waves is presented. A model for heat avalanche dynamics is extended to include a finite delay time between the instantaneous heat flux and the mean flux, based on an analogy between heat avalanche dynamics and traffic flow dynamics. The response time introduced here is an analogue of the drivers' response time in traffic dynamics. The microscopic foundation for the time delay is the time for mixing of the phase space density. The inclusion of the finite response time changes the model equation for avalanche dynamics from Burgers equation to a nonlinear telegraph equation. Based on the telegraph equation, the formation of heat flux jams is predicted. The growth rate and typical interval of jams are calculated. The connection of the jam interval to the typical step size of the E×B staircase is discussed.
E × B shear pattern formation by radial propagation of heat flux wavesa)
NASA Astrophysics Data System (ADS)
Kosuga, Y.; Diamond, P. H.; Dif-Pradalier, G.; Gürcan, Ã.-. D.
2014-05-01
A novel theory to describe the formation of E ×B flow patterns by radially propagating heat flux waves is presented. A model for heat avalanche dynamics is extended to include a finite delay time between the instantaneous heat flux and the mean flux, based on an analogy between heat avalanche dynamics and traffic flow dynamics. The response time introduced here is an analogue of the drivers' response time in traffic dynamics. The microscopic foundation for the time delay is the time for mixing of the phase space density. The inclusion of the finite response time changes the model equation for avalanche dynamics from Burgers equation to a nonlinear telegraph equation. Based on the telegraph equation, the formation of heat flux jams is predicted. The growth rate and typical interval of jams are calculated. The connection of the jam interval to the typical step size of the E ×B staircase is discussed.
Heat conduction in relativistic neutral gases revisited
A. L. Garcia-Perciante; A. R. Mendez
2010-09-30
The kinetic theory of dilute gases to first order in the gradients yields linear relations between forces and fluxes. The heat flux for the relativistic gas has been shown to be related not only to the temperature gradient but also to the density gradient in the representation where number density, temperature and hydrodynamic velocity are the independent state variables. In this work we show the calculation of the corresponding transport coefficients from the full Boltzmann equation and compare the magnitude of the relativistic correction.
Coupling heat conduction, radiation and convection in complex geometries
I. Rupp; C. Péniguel
1999-01-01
In many industrial applications, convection radiation and conduction participate simultaneously to the heat transfers. A numerical approach able to cope with such problems has been developed. The code SYRTHES is tackling conduction and radiation (limited to non participating medium). Radiation is solved by a radiosity approach, and conduction by a finite element method. Accurate and efficient algorithms based on a
Heat conduction through the Trombe wall
NASA Astrophysics Data System (ADS)
Carter, C.
1980-07-01
This paper aims to add to the theoretical understanding of Trombe walls, and to consider the most appropriate calculation methods for simulation purposes. Various control strategies can be used to improve the wall performance, but only movable insulation outside the wall produces any substantial improvement. In this case, total heat flow over a periodic cycle increases with thermal capacity to an easily calculable upper limit which can be approached quite closely with practically realizable walls. An exact solution for a two-state Trombe wall is compared with approximate solutions obtained using finite difference methods and the author's modal expansion method. The Crank-Nicholson method has oscillatory errors in some problems, but adequate overall accuracy can be obtained using time steps up to four hours. The modal expansion method is generally very accurate and efficient.
Natural Convection Heat Transfer around Heated Cylinders Inside a Cavity with Conducting Walls
Marcel Lacroix; Antoine Joyeux
1995-01-01
A numerical study has been conducted for natural convection heat transfer for air around two vertically separated horizontal heated cylinders placed inside a rectangular enclosure having finite wall conductances. The interaction between convection in the fluid-filled cavity and conduction in the walls surrounding the cavity is investigated. Results have been obtained for Rayleigh numbers Ra between 10 and 10, dimensionless
Kohlrausch Heat Conductivity Apparatus for Intermediate or Advanced Laboratory
ERIC Educational Resources Information Center
Jensen, H. G.
1970-01-01
Describes student experiment in measuring heat conductivity according to Kohlrausch's method. Theory, apparatus design, and experimental procedure is outlined. Results for copper are consistent to within 2 percent. (LC)
Ballistic heat conduction and mass disorder in one dimension
NASA Astrophysics Data System (ADS)
Ong, Zhun-Yong; Zhang, Gang
2014-08-01
It is well-known that in the disordered harmonic chain, heat conduction is subballistic and the thermal conductivity (?) scales asymptotically as \\lim_{L\\rightarrow\\infty}\\kappa\\propto L^{0.5} where L is the chain length. However, using the nonequilibrium Green's function (NEGF) method and analytical modelling, we show that there exists a critical crossover length scale (LC) below which ballistic heat conduction (\\kappa\\propto L) can coexist with mass disorder. This ballistic-to-subballistic heat conduction crossover is connected to the exponential attenuation of the phonon transmittance function ? i.e. ?(?, L) = exp[-L/?(?)], where ? is the frequency-dependent attenuation length. The crossover length can be determined from the minimum attenuation length, which depends on the maximum transmitted frequency. We numerically determine the dependence of the transmittance on frequency and mass composition as well as derive a closed form estimate, which agrees closely with the numerical results. For the length-dependent thermal conductance, we also derive a closed form expression which agrees closely with numerical results and reproduces the ballistic to subballistic thermal conduction crossover. This allows us to characterize the crossover in terms of changes in the length, mass composition and temperature dependence, and also to determine the conditions under which heat conduction enters the ballistic regime. We describe how the mass composition can be modified to increase ballistic heat conduction.
Ballistic heat conduction and mass disorder in one dimension.
Ong, Zhun-Yong; Zhang, Gang
2014-08-20
It is well-known that in the disordered harmonic chain, heat conduction is subballistic and the thermal conductivity (?) scales asymptotically as lim(L--> ?) ? ? L(0.5) where L is the chain length. However, using the nonequilibrium Green's function (NEGF) method and analytical modelling, we show that there exists a critical crossover length scale (LC) below which ballistic heat conduction (? ? L) can coexist with mass disorder. This ballistic-to-subballistic heat conduction crossover is connected to the exponential attenuation of the phonon transmittance function ? i.e. ?(?, L) = exp[-L/?(?)], where ? is the frequency-dependent attenuation length. The crossover length can be determined from the minimum attenuation length, which depends on the maximum transmitted frequency. We numerically determine the dependence of the transmittance on frequency and mass composition as well as derive a closed form estimate, which agrees closely with the numerical results. For the length-dependent thermal conductance, we also derive a closed form expression which agrees closely with numerical results and reproduces the ballistic to subballistic thermal conduction crossover. This allows us to characterize the crossover in terms of changes in the length, mass composition and temperature dependence, and also to determine the conditions under which heat conduction enters the ballistic regime. We describe how the mass composition can be modified to increase ballistic heat conduction. PMID:25077430
Finite element solution of transient heat conduction using iterative solvers
Mile R. Vuji?i?
2006-01-01
Purpose – To provide an analysis of transient heat conduction, which is solved using different iterative solvers for graduate and postgraduate students (researchers) which can help them develop their own research. Design\\/methodology\\/approach – Three-dimensional transient heat conduction in homogeneous materials using different time-stepping methods such as finite difference (? explicit, implicit and Crank-Nicolson) and finite element (weighted residual and least
Use of Spreadsheets in Solving Heat Conduction Problems in Fins
NSDL National Science Digital Library
Karimi, Amir
Excel is an effective and inexpensive tool available on all computers equipped with Microsoft Office. This software has the necessary functions for solving a large class of engineering problems, including those related to heat transfer. This paper provides several examples to demonstrate the application of Excel in solving problems involving one-dimensional heat conduction in various fin configurations. It provides formulas for the temperature distribution and heat transfer for several different fin profiles.
Analogous studies of simultaneous conductive and radiative heat transfer
D W Stops; R E Pearson
1966-01-01
The process of radiative heat transfer is electrically simulated by using voltage-dependent resistors in conjunction with current transference circuits, and so an analogue is devised which shows how the overall uni-directional heat transfer by simultaneous conduction and radiation across a transparent gas space is a function of the positions of radiation shields which may be interposed between the bounding surfaces.
Entropy and temperature gradients thermomechanics: dissipation, heat conduction
Boyer, Edmond
Entropy and temperature gradients thermomechanics: dissipation, heat conduction inequality and heat Rendus MÃ©canique 340, 6 (2012) 434-443" DOI : 10.1016/j.crme.2012.04.001 #12;temperature and its gradient and the first n spatial gradients of the temperature, they showed that the internal energy and the en- tropy
Electron Heat Conduction in the Phaedrus Tandem Mirror
Donna Lynn Smatlak
1982-01-01
Experiments to investigate electron heat conduction have been performed on the University of Wisconsin tandem mirror Phaedrus. Electron temperature differences along the magnetic field were generated using a mircowave heat pulse. Probe techniques were developed for the continuous measurement of local electron temperatures with a time resolution of less than one microsecond. Parameter studies indicated that the temperature differences were
Radiative heat conduction and the magnetorotational instability
NASA Astrophysics Data System (ADS)
Araya-Góchez, Rafael A.; Vishniac, Ethan T.
2004-12-01
A photon or a neutrino gas, semicontained by a non-diffusive particle species through scattering, comprises a rather peculiar magnetohydrodynamic fluid where the magnetic field is truly frozen only to the comoving volume associated with the mass density. Although radiative diffusion precludes a formal adiabatic treatment of compressive perturbations, we cast the energy equation in quasi-adiabatic form by assuming a negligible rate of energy exchange among species on the time-scale of the perturbation. This leads to a simplified dispersion relation for toroidal, non-axisymmetric magnetorotational modes when the accretion disc has comparable stress contributions from diffusive and non-diffusive components. The properties of the modes of fastest growth are shown to depend strongly on the compressibility of the mode, with a reduction in growth rate consistent with the results of Blaes & Socrates for axisymmetric modes. A clumpy disc structure is anticipated on the basis of the polarization properties of the fastest-growing modes. This analysis is accurate in the near-hole region of locally cooled, hyper-accreting flows if the electron gas becomes moderately degenerate such that non-conductive, thermalizing processes with associated electron-positron release (i.e. neutrino annihilation and neutrino absorption on to nuclei) are effectively blocked by high occupation of the Fermi levels.
In situ laser heating and radial synchrotron X-ray diffraction ina diamond anvil cell
Kunz, Martin; Caldwell, Wendel A.; Miyagi, Lowell; Wenk,Hans-Rudolf
2007-06-29
We report a first combination of diamond anvil cell radialx-ray diffraction with in situ laser heating. The laser-heating setup ofALS beamline 12.2.2 was modified to allow one-sided heating of a samplein a diamond anvil cell with an 80 W yttrium lithium fluoride laser whileprobing the sample with radial x-ray diffraction. The diamond anvil cellis placed with its compressional axis vertical, and perpendicular to thebeam. The laser beam is focused onto the sample from the top while thesample is probed with hard x-rays through an x-ray transparentboron-epoxy gasket. The temperature response of preferred orientation of(Fe,Mg)O is probed as a test experiment. Recrystallization was observedabove 1500 K, accompanied by a decrease in stress.
NASA Astrophysics Data System (ADS)
Farthing, P. R.; Long, C. A.; Rogers, R. H.
1991-06-01
An internal theory is used to model the flow, and predict heat transfer rates, for corotating compressor disks with a superposed radial inflow of air. Measurements of heat transfer are also made, both in an experimental rig and in an engine. The flow structure comprises source and sink regions, Ekman-type layers and an inviscid central core. Entrainment occurs in the source region, the fluid being distributed into the two nonentraining Ekman-type layers. Fluid leaves the cavity via the sink region. The integral model is validated against the experimental data, although there are some uncertainties in modeling the exact thermal conditions of the experiment. The magnitude of the Nusselt numbers is affected by the rotational Reynolds number and dimensionless flowrate; the maximum value of Nu is found to occur near the edge of the source region. The heat transfer measurements using the engine data show acceptable agreement with theory and experiment.
DSMC Convergence for Microscale Gas-Phase Heat Conduction
D. J. Rader; M. A. Gallis; J. R. Torczynski
2004-01-01
The convergence of Bird's Direct Simulation Monte Carlo (DSMC) method is investigated for gas-phase heat conduction at typical microscale conditions. A hard-sphere gas is confined between two fully accommodating walls of unequal temperature. Simulations are performed for small system and local Knudsen numbers, so continuum flow exists outside the Knudsen layers. The ratio of the DSMC thermal conductivity to the
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…
Fourier analysis of conductive heat transfer for glazed roofing materials
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah [Faculty of Computer and Mathematical Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia); Zakaria, Nor Zaini [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia)
2014-07-10
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
Fourier analysis of conductive heat transfer for glazed roofing materials
NASA Astrophysics Data System (ADS)
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah; Zakaria, Nor Zaini
2014-07-01
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
Gas heat conduction in an evacuated tube solar collector
Beikircher, T.; Goldemund, G. [Ludwig-Maximilians-Universitaet Muenchen (Germany)] [Ludwig-Maximilians-Universitaet Muenchen (Germany); Benz, N. [ZAE Bayern, Muenchen (Germany)] [ZAE Bayern, Muenchen (Germany)
1996-10-01
We investigated experimentally the pressure dependency of the gas heat conduction in an evacuated plate-in-tube solar collector. A stationary heat loss experiment was built up with an electrically heated real-size collector model. The gas pressure was varied from 10{sup -3} to 10{sup 4} Pa, the temperatures of the absorber and the casing were held at 150{degree}C (electrical heaters) and 30{degree}C (water cooling), respectively. Losses by radiation and solid conduction were determined experimentally at pressures below 0.1 Pa. At higher pressures these background losses were subtracted from the total heat losses, to receive the heat losses by gas heat conduction. The experimental results were compared with approximate theoretical models. The onset of convection is in agreement with the usual theories for parallel plates taking the largest distance between the absorber and the gas tube as the plate distance. As a first approximation the pressure dependency of the gas heat conduction is described by the usual theory for parallel plates, taking the smallest distance between the absorber and the glass tube as the plate distance. 11 refs., 3 figs.
S. Narasimha Murthy; N. Rudraiah; B. V. Mariyappa
1972-01-01
The linear and nonlinear stability of a heterogeneous incompressible inviscid perfectly conducting fluid between two cylinders is investigated in the presence of a radial gravitational force and geostrophic force. The stability for linear disturbances is investigated using the normal mode method, while the nonlinear stability is investigated by applying the energy method. In the case of linear theory, it is
Quantal Heating of Conducting Electrons with Discrete Spectrum
Vitkalov, S. A. [Department of Physics, The City College of New York, New York, NY 10031 (United States); Bykov, A. A. [Institute of Semiconductor Physics, 630090 Novosibirsk (Russian Federation)
2011-12-23
Usually heating of conducting electrons by dc electric field results in an increase of electron temperature. In this paper we show that the dc heating of 2D electrons, placed in quantized magnetic fields, results in a peculiar electron distribution, which has the same broadening or an effective 'temperature' as the unbiased electron system. The quantal heating, however, violates strongly the Ohm's Law. In the conducting system with discrete electron spectrum the quantal heating results in spectacular decrease of electron resistance and transition of the electrons into a state with zero differential resistance (ZDR). Finally the heating leads to apparent dc driven metal-insulator transition, which correlates with the transition into the ZDR state. The correlation is very unexpected and is not understood.
M. Bahrami ENSC 388 (F09) Steady Conduction Heat Transfer 1 Steady Heat Conduction
Bahrami, Majid
requirement for heat transfer is the presence of a temperature difference. The temperature difference gradient, which is the slope of the temperature curve (the rate of change of temperature T with length x and surface area A. The temperature difference across the wall is T = T2 Â T1. Note that heat transfer
NASA Astrophysics Data System (ADS)
Akbarzadeh, A. H.; Chen, Z. T.
2012-06-01
The transient heat conduction in a functionally graded cylindrical panel is investigated based on the dual phase lag (DPL) theory in this article. Except for the phase lags which are assumed to be constant, all the other material properties of the panel are assumed to change continuously along the radial direction according to a power-law formulation with different non-homogeneity indices. The heat conduction equations based on the DPL theory in the cylindrical coordinate system are written in a general form which are then used for the analyses of four different geometries: (1) a hollow cylinder of an infinite length; (2) a hollow cylinder of a finite length; (3) a cylindrical panel of an infinite length; and (4) a cylindrical panel of a finite length. Using the Laplace transform, the analytical solutions for temperature and heat flux are obtained in the Laplace domain. The solutions are then converted into the time domain by employing the fast Laplace inversion technique. The exact expressions for the radial thermal wave speed are obtained for the four different geometries. The numerical results are displayed to reveal the effect of different approximations of the DPL theory on the temperature distribution for various non-homogeneity indices. The results are verified with those reported in the literature.
THERM3D -- A boundary element computer program for transient heat conduction problems
Ingber, M.S. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Mechanical Engineering
1994-02-01
The computer code THERM3D implements the direct boundary element method (BEM) to solve transient heat conduction problems in arbitrary three-dimensional domains. This particular implementation of the BEM avoids performing time-consuming domain integrations by approximating a ``generalized forcing function`` in the interior of the domain with the use of radial basis functions. An approximate particular solution is then constructed, and the original problem is transformed into a sequence of Laplace problems. The code is capable of handling a large variety of boundary conditions including isothermal, specified flux, convection, radiation, and combined convection and radiation conditions. The computer code is benchmarked by comparisons with analytic and finite element results.
Heat conductance in nonlinear lattices at small temperature gradients
T. Yu. Astakhova; V. N. Likhachev; G. A. Vinogradov
2010-06-09
This paper proposes a new methodological framework within which the heat conductance in 1D lattices can be studied. The total process of heat conductance is separated into two parts where the first one is the equilibrium process at equal temperatures $T$ of both ends and the second one -- non-equilibrium with the temperature $\\Delta T$ of one end and zero temperature of the other. This approach allows significant decrease of computational time at $\\Delta T \\to 0$. The threshold temperature $T_{\\rm thr}$ is found which scales $T_{\\rm thr}(N) \\sim N^{-3}$ with the lattice size $N$ and by convention separates two mechanisms of heat conductance: phonon mechanism dominates at $T temperature at $T > T_{\\rm thr}$. Solitons and breathers are directly visualized in numerical experiments. The problem of heat conductance in non-linear lattices in the limit $\\Delta T \\to 0$ can be reduced to the heat conductance of harmonic lattice with time-dependent stochastic rigidities determined by the equilibrium process at temperature $T$. The detailed analysis is done for the $\\beta$-FPU lattice though main results are valid for one-dimensional lattices with arbitrary potentials.
Thermally conductive cementitious grout for geothermal heat pump systems
Allan, Marita (Old Field, NY)
2001-01-01
A thermally conductive cement-sand grout for use with a geothermal heat pump system. The cement sand grout contains cement, silica sand, a superplasticizer, water and optionally bentonite. The present invention also includes a method of filling boreholes used for geothermal heat pump systems with the thermally conductive cement-sand grout. The cement-sand grout has improved thermal conductivity over neat cement and bentonite grouts, which allows shallower bore holes to be used to provide an equivalent heat transfer capacity. In addition, the cement-sand grouts of the present invention also provide improved bond strengths and decreased permeabilities. The cement-sand grouts can also contain blast furnace slag, fly ash, a thermoplastic air entraining agent, latex, a shrinkage reducing admixture, calcium oxide and combinations thereof.
Mechanical control of heat conductivity in molecular chains
NASA Astrophysics Data System (ADS)
Savin, A. V.; Gendelman, O. V.
2014-01-01
We discuss a possibility to control heat conductivity in molecular chains by means of external mechanical loads. To illustrate such possibilities we consider first well-studied one-dimensional chain with degenerate double-well potential of the nearest-neighbor interaction. We consider varying lengths of the chain with fixed number of particles. Number of possible energetically degenerate ground states strongly depends on the overall length of the chain, or, in other terms, on average length of the link between neighboring particles. These degenerate states correspond to mechanical equilibria; therefore, one can say that formation of such structures mimics a process of plastic deformation. We demonstrate that such modification of the chain length can lead to quite profound (almost fivefold) reduction of the heat conduction coefficient. Even more profound effect is revealed for a model with a single-well nonconvex potential. It is demonstrated that in a certain range of constant external forcing, this model becomes effectively double-well and has a multitude of possible states of equilibrium for fixed value of the external load. Due to this degeneracy, the heat-conduction coefficient can be reduced by two orders of magnitude. We suggest a mechanical model of a chain with periodic double-well potential, which allows control of the heat transport. The models considered may be useful for description of heat transfer in biological macromolecules and for control of the heat transport in microsystems. The possibility of the heat transport control in more realistic three-dimensional systems is illustrated by simulation of a three-dimensional model of polymer ?-helix. In this model, the mechanical stretching also brings about the structural inhomogeneity and, in turn, to essential reduction of the heat conductivity.
Assessing the RELAPS-3D Heat Conduction Enclosure Model
McCann, Larry D.
2008-09-30
Three heat conduction problems that have exact solutions are modeled with RELAP5-3D using the conduction enclosure model. These comparisons are designed to be used in the RELAP5-3D development assessment scheduled to be completed in 2009. It is shown that with proper input choices and adequate model detail the exact solutions can be matched. In addition, this analysis identified an error and the required correction in the cylindrical and spherical heat conductor models in RELAP5-3D which will be corrected in a future version of RELAP5-3D.
A Mechanical Model for Fourier's Law of Heat Conduction
NASA Astrophysics Data System (ADS)
Ruelle, David
2012-05-01
Nonequilibrium statistical mechanics close to equilibrium is a physically satisfactory theory centered on the linear response formula of Green-Kubo. This formula results from a formal first order perturbation calculation without rigorous justification. A rigorous derivation of Fourier's law for heat conduction from the laws of mechanics remains thus a major unsolved problem. In this note we present a deterministic mechanical model of a heat-conducting chain with nontrivial interactions, where kinetic energy fluctuations at the nodes of the chain are removed. In this model the derivation of Fourier's law can proceed rigorously.
NASA Astrophysics Data System (ADS)
Arbaban, M.; Salimpour, M. R.
2015-03-01
In the present study, laminar natural convection of nanofluids confined between two horizontal concentric cylinders with eight radial fins attached to the inner cylinder is studied. Governing equations are solved using the finite volume method. The computations are performed for various Rayleigh numbers, nanofluids and volume fractions of nanoparticles. From the results, it is found that the average Nusselt number enhances when volume fraction and thermal conductivity of nanoparticles increases. Also, it is observed that the average Nusselt number of Cu-water nanofluid is highest among the nanofluids of the present study. Moreover, it is seen that the temperature gradient and absolute value of stream function decrease by addition of nanoparticles.
Federal Register 2010, 2011, 2012, 2013, 2014
2012-06-06
...Circuit Packages Provided With Multiple Heat- Conducting Paths and Products Containing...Circuit Packages Provided With Multiple Heat-Conducting Paths and Products Containing...circuit packages provided with multiple heat-conducting paths and products...
Federal Register 2010, 2011, 2012, 2013, 2014
2012-07-05
...Circuit Packages Provided With Multiple Heat- Conducting Paths and Products Containing...circuit packages provided with multiple heat-conducting paths and products containing...circuit packages provided with multiple heat-conducting paths and products...
Minimizing RF heating of conducting wires in MRI.
Yeung, Christopher J; Karmarkar, Parag; McVeigh, Elliot R
2007-11-01
Performing interventions using long conducting wires in MRI introduces the risk of focal RF heating at the wire tip. Comprehensive EM simulations are combined with carefully measured experimental data to show that method-of-moments EM field modeling coupled with heat transfer modeling can adequately predict RF heating with wires partially inserted into the patient-mimicking phantom. The effects of total wire length, inserted length, wire position in the phantom, phantom position in the scanner, and phantom size are examined. Increasing phantom size can shift a wire's length of maximum tip heating from about a half wave toward a quarter wave. In any event, with wires parallel to the scanner bore, wire tip heating is minimized by keeping the patient and wires as close as possible to the central axis of the scanner bore. At 1.5T, heating is minimized if bare wires are shorter than 0.6 m or between approximately 2.4 m and approximately 3.0 m. Heating is further minimized if wire insertion into phantoms equivalent to most aqueous soft tissues is less than 13 cm or greater than 40 cm (longer for fatty tissues, bone, and lung). The methods demonstrated can be used to estimate the absolute amount of heating in order to set RF power safety thresholds. PMID:17969097
Zhiyun Wang; Mo Yang; Ling Li; Yuwen Zhang
2011-01-01
Combined heat transfer by natural convection-conduction and surface radiation in an open cavity heated by constant flux is studied here. The laminar flow is solved numerically by employing the SIMPLE algorithm with QUICK scheme. The numerical results show that both radiation and solid conduction increase the average total Nusselt number. The average total Nusselt number is a linear increasing function
Generalized thermoelastic diffusive waves in heat conducting materials
J. N. Sharma
2007-01-01
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
Human body thermal images generated by conduction or radiation heat
Gheorghe Gavriloaia; Emil Sofron; Radu Fumarel
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
Numeric modeling method usage for heat conductivity equations solution
NASA Astrophysics Data System (ADS)
Loginov, Vladimir; Stolyarova, Alla; Parpiev, Azad
2015-01-01
The sweep method applicability for non-stationary one-dimensional differential heat conductivity equations solving is proved in this work. The sweep method applicability check is made by using exact analytical method and approximate analytical method. The confrontation carried out has shown that the obtained numeric results error isn't more 2%.
Element-by-element factorization algorithms for heat conduction
NASA Technical Reports Server (NTRS)
Hughes, T. J. R.; Winget, J. M.; Park, K. C.
1983-01-01
Element-by-element solution strategies are developed for transient heat conduction problems. Results of numerical tests indicate the effectiveness of the procedures proposed. The small database requirements and attractive architectural features of the algorithms suggest considerable potential for solving large scale problems.
A spectral stochastic approach to the inverse heat conduction problem
Zabaras, Nicholas J.
by employing orthogonal poly- nomials as the trial basis in the random space. Solution to the ill-posed SIHCPA spectral stochastic approach to the inverse heat conduction problem Velamur Asokan Badri Narayanan, Nicholas Zabaras 1 Materials Process Design and Control Laboratory, Sibley School of Mechanical
Subramaniam, Anandh
Vacuum Induction Melting Unit Induction heating is a process wherein induced eddy currents heat conductive materials. This heating can be used to melt metals and make alloys. Vacuum Induction melting on the melting process. The induction melting facility (Figure 1) was established in the Symmetry Lab (WL-207
Hierarchical Bayesian models for inverse problems in heat conduction
NASA Astrophysics Data System (ADS)
Wang, Jingbo; Zabaras, Nicholas
2005-02-01
Stochastic inverse problems in heat conduction with consideration of uncertainties in the measured temperature data, temperature sensor locations and thermophysical properties are addressed using a Bayesian statistical inference method. Both parameter estimation and thermal history reconstruction problems, including boundary heat flux and heat source reconstruction, are studied. Probabilistic specification of the unknown variables is deduced from temperature measurements. Hierarchical Bayesian models are adopted to relax the prior assumptions on the unknowns. The use of a hierarchical Bayesian method for automatic selection of the regularization parameter in the function estimation inverse problem is discussed. In addition, the method explores the length scales in the estimation of thermal variables varying in space and time. Markov chain Monte Carlo (MCMC) simulation is conducted to explore the high dimensional posterior state space. The methodologies presented are general and applicable to a number of data-driven engineering inverse problems.
Parsons, J.A.; Han, J.C. [Texas A and M Univ., College Station, TX (United States); Lee, C.P. [GE Aircraft Engines, Cincinnati, OH (United States)
1998-01-01
The effect of channel rotation on jet impingement cooling by arrays of circular jets in two channels was studied. Jet flow direction was in the direction of rotation in one channel and opposite to the rotation direction in the other channel. The jets impinged normally on two smooth target walls. Heat transfer results are presented for these two target walls, for the jet walls containing the jet producing orifices, and for side walls connecting the target and jet walls. The flow exited the channels in a single direction, radially outward, creating a crossflow on jets at larger radii. The mean test model radius-to-jet diameter ratio was 397. The jet rotation number was varied from 0.0 to 0.0028 and the isolated effects of jet Reynolds number (5000 and 10,000), and wall-to-coolant temperature difference ratio (0.0855 and 0.129) were measured. The results for nonrotating conditions show that the Nusselt numbers for the target and jet walls in both channels are about the same and are greater than those for the side walls of both channels. However, as rotation number increases, the heat transfer coefficients for all walls in both channels decrease up to 20% below those results that correspond to nonrotating conditions. As the wall-to-coolant temperature difference ratio increases, heat transfer coefficient decreases up to 10% with other parameters held constant.
Variable conductance heat pipes from the laboratory to space
NASA Technical Reports Server (NTRS)
Kirkpatrick, J. P.
1973-01-01
Heat pipes were developed which can be used as (1) a variable conductance link between a heat source and sink which provides temperature stability; (2) a feedback control mechanism that acts to directly maintain the source at a constant temperature; (3) or as a thermal diode that allows heat to be transferred in one direction only. To establish flight level confidence in these basic control techniques, the Ames Heat Pipe Experiment (AHPE) was launched in August 1972 and the Advanced Thermal Control Flight Experiment (ATFE) is scheduled for launch in May 1973. The major efforts of the technology development, initial flight results of the AHPE, and ground test data of the ATFE are discussed.
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.
Specific heat and thermal conductivity of amorphous boron
NASA Astrophysics Data System (ADS)
Medwick, P. A.; Cahill, David G.; Raychaudhuri, A. K.; Pohl, R. O.; Gompf, F.; Nücker, N.; Tanaka, T.
1991-07-01
From inelastic neutron scattering the phonon density of states of amorphous boron has been determined, and from this the specific heat between 30 and 500 K has been calculated. The results have been compared with the specific heat measured for amorphous boron, crystalline ?-B and Y B66. The thermal conductivity of single crystals of Y B58 and Y B67, has been measured, and has been found to be indistinguishable from that of Y B66 crystals grown in a different laboratory, in spite of very different physical and chemical perfection. This result provides further evidence that the low thermal conductivity of these crystals is intrinsic. At higher temperatures, it approaches the theoretical minimum thermal conductivity of this boron-rich compound, which in turn is equal to that of amorphous boron.
Specific heat and thermal conductivity of amorphous boron
Medwick, P.A.; Cahill, D.G.; Raychaudhuri, A.K.; Pohl, R.O. (Laboratory for Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853-2501 (United States)); Gompf, F.; Nuecker, N. (Kernforschungszentrum Karlsruhe, Institute for Nuclear and Solid State Physics, P.O. Box 3640, D-7500 (Germany)); Tanaka, T. (National Institute for Research in Inorganic Materials, Namiki 1-1, Tsukuba, Ibaraki 305 (Japan))
1991-07-01
From inelastic neutron scattering the phonon density of states of amorphous boron has been determined, and from this the specific heat between 30 and 500 K has been calculated. The results have been compared with the specific heat measured for amorphous boron, crystalline {beta}--{ital B} and {ital Y} {ital B}{sub 66}. The thermal conductivity of single crystals of {ital Y} {ital B}{sub 58} and {ital Y} {ital B}{sub 67}, has been measured, and has been found to be indistinguishable from that of {ital Y} {ital B}{sub 66} crystals grown in a different laboratory, in spite of very different physical and chemical perfection. This result provides further evidence that the low thermal conductivity of these crystals is intrinsic. At higher temperatures, it approaches the theoretical minimum thermal conductivity of this boron-rich compound, which in turn is equal to that of amorphous boron.
Thermal conductivity, electrical conductivity and specific heat of copper-carbon fiber composite
NASA Technical Reports Server (NTRS)
Kuniya, Keiichi; Arakawa, Hideo; Kanai, Tsuneyuki; Chiba, Akio
1988-01-01
A new material of copper/carbon fiber composite is developed which retains the properties of copper, i.e., its excellent electrical and thermal conductivity, and the property of carbon, i.e., a small thermal expansion coefficient. These properties of the composite are adjustable within a certain range by changing the volume and/or the orientation of the carbon fibers. The effects of carbon fiber volume and arrangement changes on the thermal and electrical conductivity, and specific heat of the composite are studied. Results obtained are as follows: the thermal and electrical conductivity of the composite decrease as the volume of the carbon fiber increases, and were influenced by the fiber orientation. The results are predictable from a careful application of the rule of mixtures for composites. The specific heat of the composite was dependent, not on fiber orientation, but on fiber volume. In the thermal fatigue tests, no degradation in the electrical conductivity of this composite was observed.
Correlations and scaling in one-dimensional heat conduction.
Deutsch, J M; Narayan, Onuttom
2003-10-01
We examine numerically the full spatiotemporal correlation functions for all hydrodynamic quantities for the random collision model introduced recently. The autocorrelation function of the heat current, through the Kubo formula, gives a thermal conductivity exponent of 1/3 in agreement with the analytical prediction and previous numerical work. Remarkably, this result depends crucially on the choice of boundary conditions: for periodic boundary conditions (as opposed to open boundary conditions with heat baths) the exponent is approximately 1/2. All primitive hydrodynamic quantities scale with the dynamic critical exponent predicted analytically. PMID:14682932
Heating rate controller for thermally stimulated conductivity and thermoluminescence measurements.
NASA Technical Reports Server (NTRS)
Manning, E. G.; Littlejohn, M. A.; Oakley, E. M.; Hutchby , J. A.
1972-01-01
A temperature controller is described which enables the temperature of a sample mounted on a cold finger to be varied linearly with time. Heating rates between 0.5 and 10 K/min can be achieved for temperatures between 90 and 300 K. Provision for terminating the sample heating at any temperature between these extremes is available. The temperature can be held at the terminating temperature or be reduced to the starting temperature in a matter of minutes. The controller has been used for thermally stimulated conductivity measurements and should be useful for thermoluminescence measurements as well.
Peletier, Mark A., E-mail: m.a.peletier@tue.nl [Department of Mathematics and Computer Science and Institute for Complex Molecular Systems, Technische Universiteit Eindhoven, Postbus 513, 5600 MB Eindhoven (Netherlands); Redig, Frank, E-mail: f.h.j.redig@tudelft.nl [Delft Institute of Applied Mathematics, Technische Universiteit Delft, Mekelweg 4, 2628 CD Delft (Netherlands); Vafayi, Kiamars, E-mail: k.vafayi@tue.nl [Department of Mathematics and Computer Science, Technische Universiteit Eindhoven, Postbus 513, 5600 MB Eindhoven (Netherlands)
2014-09-15
We consider three one-dimensional continuous-time Markov processes on a lattice, each of which models the conduction of heat: the family of Brownian Energy Processes with parameter m (BEP(m)), a Generalized Brownian Energy Process, and the Kipnis-Marchioro-Presutti (KMP) process. The hydrodynamic limit of each of these three processes is a parabolic equation, the linear heat equation in the case of the BEP(m) and the KMP, and a nonlinear heat equation for the Generalized Brownian Energy Process with parameter a (GBEP(a)). We prove the hydrodynamic limit rigorously for the BEP(m), and give a formal derivation for the GBEP(a). We then formally derive the pathwise large-deviation rate functional for the empirical measure of the three processes. These rate functionals imply gradient-flow structures for the limiting linear and nonlinear heat equations. We contrast these gradient-flow structures with those for processes describing the diffusion of mass, most importantly the class of Wasserstein gradient-flow systems. The linear and nonlinear heat-equation gradient-flow structures are each driven by entropy terms of the form ?log??; they involve dissipation or mobility terms of order ?{sup 2} for the linear heat equation, and a nonlinear function of ? for the nonlinear heat equation.
Heat conduction nanocalorimeter for pl-scale single cell measurements
NASA Astrophysics Data System (ADS)
Johannessen, E. A.; Weaver, J. M. R.; Cobbold, P. H.; Cooper, J. M.
2002-03-01
An ultrasensitive nanocalorimeter for use with pl-scale biological samples using silicon microfabrication technology has been developed in which a 720 pl reaction vessel, a calibration heater, and a thermoelectric transducer of 125 ?K sensitivity were integrated into a single multilayer thin-film configuration. The resolution of the system ranged from 10 to 25 nW depending on the heat capacity, conductance and power density of the samples studied. The device has been used in heat conduction measurements of the energy released from the enzyme catalyzed hydrolysis of hydrogen peroxide using purified catalase, and for the determination of the catalase activity within a single mouse hepatocyte. The nanocalorimeter has the potential for integration in a high-density array format, where the change in temperature from ultralow volume cellular assays could be used as a generic analytical tool for high throughput screening of bioactive compounds.
Modelling of transient heat conduction with diffuse interface methods
NASA Astrophysics Data System (ADS)
Ettrich, J.; Choudhury, A.; Tschukin, O.; Schoof, E.; August, A.; Nestler, B.
2014-12-01
We present a survey on different numerical interpolation schemes used for two-phase transient heat conduction problems in the context of interface capturing phase-field methods. Examples are general transport problems in the context of diffuse interface methods with a non-equal heat conductivity in normal and tangential directions to the interface. We extend the tonsorial approach recently published by Nicoli M et al (2011 Phys. Rev. E 84 1–6) to the general three-dimensional (3D) transient evolution equations. Validations for one-dimensional, two-dimensional and 3D transient test cases are provided, and the results are in good agreement with analytical and numerical reference solutions.
New Critical Divergences in the Heat Conductivity in the Presence of a Temperature Gradient
Ehud Meron; Itamar Procaccia
1983-01-01
New effects in heat-conducting nonequilibrium fluids near critical points are predicted theoretically: The heat conductivity gains a new divergent contribution and the heat diffusivity becomes strongly nonisotropic.
Experimental study of convective heat transfer of compressed air flow in radially rotating ducts
Hwang, G.J,; Tzeng, S.C.; Mao, C.P.
1999-07-01
The convective heat transfer of pressurized air flow in radially rotating serpentine channel is investigated experimentally in the present study. The main governing parameters are the Prandtl number, the Reynolds number for forced convection, the rotation number for the Coriolis force induced cross stream secondary flow and the Grashof number for natural convection. To simulate the operation conditions of a real gas turbine, the present study kept the parameters in the test rig approximately the same as those in a real engine. The air in the present serpentine channel was pressurized to increase the air density for making up the low rotational speed in the experiment. Before entering the rotating ducts, the air was also cooled to gain a high density ratio of approximately 1/3 in the ducts. This high density ratio will give a similar order of magnitude of Grashof number in a real operation condition. The local heat transfer rate on the four channel walls are present and compared with that in existing literature.
Fuzzy and interval finite element method for heat conduction problem
Sarangam Majumdar; Sukanta Nayak; S. Chakraverty
2012-09-26
Traditional finite element method is a well-established method to solve various problems of science and engineering. Different authors have used various methods to solve governing differential equation of heat conduction problem. In this study, heat conduction in a circular rod has been considered which is made up of two different materials viz. aluminum and copper. In earlier studies parameters in the differential equation have been taken as fixed (crisp) numbers which actually may not. Those parameters are found in general by some measurements or experiments. So the material properties are actually uncertain and may be considered to vary in an interval or as fuzzy and in that case complex interval arithmetic or fuzzy arithmetic has to be considered in the analysis. As such the problem is discretized into finite number of elements which depend on interval/fuzzy parameters. Representation of interval/fuzzy numbers may give the clear picture of uncertainty. Hence interval/fuzzy arithmetic is applied in the finite element method to solve a steady state heat conduction problem. Application of fuzzy finite element method in the said problem gives fuzzy system of linear equations in general. Here new methods have also been proposed to handle such type of fuzzy system of linear equations. Corresponding results are computed and has been reported here.
Superdiffusive heat conduction in semiconductor alloys. I. Theoretical foundations
NASA Astrophysics Data System (ADS)
Vermeersch, Bjorn; Carrete, Jesús; Mingo, Natalio; Shakouri, Ali
2015-02-01
Semiconductor alloys exhibit a strong dependence of effective thermal conductivity on measurement frequency. So far this quasiballistic behavior has only been interpreted phenomenologically, providing limited insight into the underlying thermal transport dynamics. Here, we show that quasiballistic heat conduction in semiconductor alloys is governed by Lévy superdiffusion. By solving the Boltzmann transport equation (BTE) with ab initio phonon dispersions and scattering rates, we reveal a transport regime with fractal space dimension 1 3 ) and cumulative conductivity spectra ??(? ;? ) ˜(?;? ) ? resolved for relaxation times or mean free paths through the simple relations ? =3 -? =1 +3 /n =2 -? . The quasiballistic transport inside alloys is no longer governed by Brownian motion, but instead is dominated by Lévy dynamics. This has important implications for the interpretation of thermoreflectance (TR) measurements with modified Fourier theory. Experimental ? values for InGaAs and SiGe, determined through TR analysis with a novel Lévy heat formalism, match ab initio BTE predictions within a few percent. Our findings lead to a deeper and more accurate quantitative understanding of the physics of nanoscale heat-flow experiments.
El-Genk, M.S.; Gao, C. [Univ. of New Mexico, Albuquerque, NM (United States)
1996-05-10
Quenching experiments were performed to determine the effect of wall material properties on pool boiling heat transfer for downward facing convex surfaces (radius of curvature 218.5 mm) in saturated water. Experiments employed 303e-type stainless steel and copper test sections having identical dimensions (75 mm in diameter and 20 mm thick). Pool boiling curves were constructed on the basis of two-dimensional numerical solution of transient heat conduction in spherical coordinates, (r, {theta}) in test sections during quenching. The measured temperature histories at nine interior locations near the boiling surface ({approximately}0.5 mm) provided a time-dependent boundary condition for the numerical solution. To ensure stability and reduce both computer storage and execution time, the numerical solution used the alternating direction implicit (ADI) method with control volume representations. A sensitivity analysis was conducted to assess the effect of grid size on computation time as well as the accuracy of calculated temperatures and pool boiling heat flux values. Best results were obtained using a 20 x 20 network of control volumes and a noniterative approach, whereas the computation time on a Pentium 90-MHz PC for the entire pool boiling curve was about 7% of real time. Calculated temperatures near the top surface ({approximately}5 mm) agreed with measured values to within 0.5 and 2.5 K for copper and stainless steel, respectively. The error in the overall energy balance in the test section, performed after each time interval, was less than 0.001%. The thermal diffusivity of test section material strongly affected both radial conduction within the section and lateral conduction near the boiling surface and, hence, the local pool boiling curves as well as the maximum and minimum pool boiling heat flux values.
Petra Pichler; Walter Oberhuber
2007-01-01
The record-breaking heat-wave in summer 2003 was expected to have a strong impact on tree growth, especially where trees occur at their ecological limits. We studied radial growth response of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) exposed to dry inner Alpine climate (Tyrol, Austria) to extreme hot and dry conditions in 2003. Tree ring
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.
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.
Fabrication and test of a variable conductance heat pipe
NASA Technical Reports Server (NTRS)
Lehtinen, A. M.
1978-01-01
A variable conductance heat pipe (VCHP) with feedback control was fabricated with a reservoir-condenser volume ratio of 10 and an axially grooved action section. Tests of the heat transport capability were greater than or equal to the analytical predictions for the no gas case. When gas was added, the pipe performance degraded by 18% at zero tilt as was expected. The placement of the reservoir heater and the test fixture cooling fins are believed to have caused a superheated vapor condition in the reservoir. Erroneously high reservoir temperature indications resulted from this condition. The observed temperature gradients in the reservoir lend support to this theory. The net result was higher than predicted reservoir temperatures. Also, significant increases in minimum heat load resulted for controller set point temperatures higher than 0 C. At 30 C, control within the tolerance band was maintained, but high reservoir heater power was required. Analyses showed that control is not possible for reasonably low reservoir heater power. This is supported by the observation of a significant reservoir heat leak through the condenser.
Manipulating Steady Heat Conduction by Sensu-shaped Thermal Metamaterials
Han, Tiancheng; Liu, Dan; Gao, Dongliang; Li, Baowen; Thong, John T L; Qiu, Cheng-Wei
2014-01-01
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. However, to realize one advanced control function of thermal flux, one needs to design one sophisticated, multilayered and inhomogeneous thermal structure with different composition/shape at different regions of one device. In this work, we employ one identical sensu-unit with facile natural composition to experimentally realize a new class of thermal metamaterials for controlling thermal conduction (e.g., thermal concentrator, focusing/resolving, uniform heating), only resorting to positioning and locating the same unit element of sensu-shape structure. The thermal metamaterial unit and the proper arrangement of multiple identical units are capable of transferring, redistributing and managing thermal energy in a versatile fashion. It is al...
The stationary state and the heat equation for a variant of Davies' model of heat conduction
NASA Astrophysics Data System (ADS)
Artuso, R.; Benza, V.; Frigerio, A.; Gorini, V.; Montaldi, E.
1985-03-01
We study a variant of Davies' model of heat conduction, consisting of a chain of (classical or quantum) harmonic oscillators, whose ends are coupled to thermal reservoirs at different temperatures, and where neighboring oscillators interact via intermediate reservoirs. In the weak coupling limit, we show that a unique stationary state exists, and that a discretized heat equation holds. We give an explicit expression of the stationary state in the case of two classical oscillators. The heat equation is obtained in the hydrodynamic limit, and it is proved that it completely describes the macroscopic behavior of the model.
NASA Technical Reports Server (NTRS)
Anderson, W. T.; Edwards, D. K.; Eninger, J. E.; Marcus, B. D.
1974-01-01
A research and development program in variable conductance heat pipe technology is reported. The project involved: (1) theoretical and/or experimental studies in hydrostatics, (2) hydrodynamics, (3) heat transfer into and out of the pipe, (4) fluid selection, and (5) materials compatibility. The development, fabrication, and test of the space hardware resulted in a successful flight of the heat pipe experiment on the OAO-3 satellite. A summary of the program is provided and a guide to the location of publications on the project is included.
Combined conduction and radiation heat transfer in concentric cylindrical media
NASA Technical Reports Server (NTRS)
Pandey, D. K.
1987-01-01
The exact radiative transfer expressions for gray and nongray gases which are absorbing, emitting and nonscattering, contained between infinitely long concentric cylinders with black surfaces, are given in local thermodynamic equilibrium. Resulting energy equations due to the combination of conduction and radiation modes of heat transfer, under steady state conditions for gray and nongray media, are solved numerically using the undetermined parameters method. A single 4.3-micron band of CO2 is considered for the nongray problems. The present solutions for gray and nongray gases obtained in the plane-parallel limit (radius ratio approaches to one) are compared with the plane-parallel results reported in the literature.
Homogeneous Thermal Cloak with Constant Conductivity and Tunable Heat Localization
Han, Tiancheng; Yuan, Tao; Li, Baowen; Qiu, Cheng-Wei
2013-01-01
Invisible cloak has long captivated the popular conjecture and attracted intensive research in various communities of wave dynamics, e.g., optics, electromagnetics, acoustics, etc. However, their inhomogeneous and extreme parameters imposed by transformation-optic method will usually require challenging realization with metamaterials, resulting in narrow bandwidth, loss, polarization-dependence, etc. In this paper, we demonstrate that thermodynamic cloak can be achieved with homogeneous and finite conductivity only employing naturally available materials. It is demonstrated that the thermal localization inside the coating layer can be tuned and controlled robustly by anisotropy, which enables an incomplete cloak to function perfectly. Practical realization of such homogeneous thermal cloak has been suggested by using two naturally occurring conductive materials, which provides an unprecedentedly plausible way to flexibly realize thermal cloak and manipulate heat flow with phonons. PMID:23549139
Time fractional dual-phase-lag heat conduction equation
NASA Astrophysics Data System (ADS)
Xu, Huan-Ying; Jiang, Xiao-Yun
2015-03-01
We build a fractional dual-phase-lag model and the corresponding bioheat transfer equation, which we use to interpret the experiment results for processed meat that have been explained by applying the hyperbolic conduction. Analytical solutions expressed by H-functions are obtained by using the Laplace and Fourier transforms method. The inverse fractional dual-phase-lag heat conduction problem for the simultaneous estimation of two relaxation times and orders of fractionality is solved by applying the nonlinear least-square method. The estimated model parameters are given. Finally, the measured and the calculated temperatures versus time are compared and discussed. Some numerical examples are also given and discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11102102, 11472161, and 91130017), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2014AQ015), and the Independent Innovation Foundation of Shandong University, China (Grant No. 2013ZRYQ002).
Anelastic dynamo models with radially varying conductivity: application to gas giants
NASA Astrophysics Data System (ADS)
Duarte, Lúcia; Gastine, Thomas; Wicht, Johannes
2013-04-01
Observations of the two gas giants show that both planets have dipolar magnetic fields: Jupiter's is very similar to Earth's magnetic field and Saturn's is very axisymmetric. Our main goal is to construct realistic numerical models that explain these features. While the small density jump across terrestrial iron cores allows to use the Boussinesq approximation, the picture is different for the gas giants. Here, the density decreases by a factor of around 5000 from the deep interior to the surface (1 bar level). Though most of this density jump is accommodated in the outer molecular envelopes, it may still be significant in the metallic dynamo region. Among other properties, the electrical conductivity also varies significantly with radius, being roughly constant in the metallic hydrogen region and decaying exponentially in the molecular envelope. We solve an anelastic numerical dynamo model (which differs from a fully compressible model by neglecting sound waves) to explore the effects of density stratification and electrical conductivity variation on magnetic field generation. We use an anelastic version of the MHD code MagIC with density jumps up to 245 and an electrical conductivity that decays exponentially in the outer 10-20% of the simulated shell. Previous simulations using constant conductivity showed that dipole dominated magnetic fields are only found up to a density jump of 6. An increasing stratification progressively confines the most active convective region close to the outer boundary equator. Mean field models have shown that such a configuration prefers non-axisymmetric modes. The exponential conductivity decrease helps by separating magnetic field generation from the dominant convective region. For intermediate stratifications (6 < density jump < 148), the dipole component clearly dominates during short periods. Stable strongly dipolar solutions are found when a large stratification (density jump > 148) more clearly separates the dynamo from the dominant convective region.
High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems
NASA Technical Reports Server (NTRS)
Tarau, Calin; Walker, Kara L.; Anderson, William G.
2009-01-01
In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) is under development to allow multiple stops and restarts of the Stirling convertor. The status of the ongoing effort in developing this technology is presented in this paper. An earlier, preliminary design had a radiator outside the Advanced Stirling Radioisotope Generator (ASRG) casing, used NaK as the working fluid, and had the reservoir located on the cold side adapter flange. The revised design has an internal radiator inside the casing, with the reservoir embedded inside the insulation. A large set of advantages are offered by this new design. In addition to reducing the overall size and mass of the VCHP, simplicity, compactness and easiness in assembling the VCHP with the ASRG are significantly enhanced. Also, the permanently elevated temperatures of the entire VCHP allows the change of the working fluid from a binary compound (NaK) to single compound (Na). The latter, by its properties, allows higher performance and further mass reduction of the system. Preliminary design and analysis shows an acceptable peak temperature of the ASRG case of 140 C while the heat losses caused by the addition of the VCHP are 1.8 W.
High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems
NASA Astrophysics Data System (ADS)
Tarau, Calin; Walker, Kara L.; Anderson, William G.
2009-03-01
In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling converter provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) is under development to allow multiple stops and restarts of the Stirling engine. The status of the ongoing effort in developing this technology is presented in this paper. An earlier, preliminary design had a radiator outside the Advanced Stirling Radioisotope Generator (ASRG) casing, used NaK as the working fluid, and had the reservoir located on the cold side adapter flange. The revised design has an internal radiator inside the casing, with the reservoir embedded inside the insulation. A large set of advantages are offered by this new design. In addition to reducing the overall size and mass of the VCHP, simplicity, compactness and easiness in assembling the VCHP with the ASRG are significantly enhanced. Also, the permanently elevated temperatures of the entire VCHP allows the change of the working fluid from a binary compound (NaK) to single compound (Na). The latter, by its properties, allows higher performance and further mass reduction of the system. Preliminary design and analysis shows an acceptable peak temperature of the ASRG case of 140° C while the heat losses caused by the addition of the VCHP are 1.8 W.
Satouh, Yuhkoh; Padma, Potturi; Toda, Toshifusa; Satoh, Nori; Ide, Hiroyuki; Inaba, Kazuo
2005-02-01
Members of the heat-shock protein (HSP)40 regulate the protein folding activity of HSP70 proteins and help the functional specialization of this molecular chaperone system in various types of cellular events. We have recently identified Hsp40 as a component of flagellar axoneme in the ascidian Ciona intestinalis, suggesting a correlation between Hsp40 related chaperone system and flagellar function. In this study, we have found that Ciona 37-kDa Hsp40 is extracted from KCl-treated axonemes with 0.5 M KI solution and comigrates with radial spoke protein (RSP)3 along with several proteins as a complex through gel filtration and ion exchange columns. Peptide mass fingerprinting with matrix-assisted laser desorption ionization/time of flight/mass spectrometry revealed that other proteins in the complex include a homolog of sea urchin spokehead protein (homolog of RSP4/6), a membrane occupation and recognition nexus repeat protein with sequence similarity with meichroacidin, and a functionally unknown 33-kDa protein. A spoke head protein, LRR37, is not included in the complex, suggesting that the complex constructs the stalk of radial spoke. Immunoelectron microscopy indicates that Hsp40 is localized in the distal portion of spoke stalk, possibly at the junction between spoke head and the stalk. PMID:15563603
Satouh, Yuhkoh; Padma, Potturi; Toda, Toshifusa; Satoh, Nori; Ide, Hiroyuki; Inaba, Kazuo
2005-01-01
Members of the heat-shock protein (HSP)40 regulate the protein folding activity of HSP70 proteins and help the functional specialization of this molecular chaperone system in various types of cellular events. We have recently identified Hsp40 as a component of flagellar axoneme in the ascidian Ciona intestinalis, suggesting a correlation between Hsp40 related chaperone system and flagellar function. In this study, we have found that Ciona 37-kDa Hsp40 is extracted from KCl-treated axonemes with 0.5 M KI solution and comigrates with radial spoke protein (RSP)3 along with several proteins as a complex through gel filtration and ion exchange columns. Peptide mass fingerprinting with matrix-assisted laser desorption ionization/time of flight/mass spectrometry revealed that other proteins in the complex include a homolog of sea urchin spokehead protein (homolog of RSP4/6), a membrane occupation and recognition nexus repeat protein with sequence similarity with meichroacidin, and a functionally unknown 33-kDa protein. A spoke head protein, LRR37, is not included in the complex, suggesting that the complex constructs the stalk of radial spoke. Immunoelectron microscopy indicates that Hsp40 is localized in the distal portion of spoke stalk, possibly at the junction between spoke head and the stalk. PMID:15563603
Variable Conductance Heat Pipes for Radioisotope Stirling Systems
NASA Astrophysics Data System (ADS)
Anderson, William G.; Tarau, Calin
2008-01-01
In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) was designed to allow multiple stops and restarts of the Stirling engine. A VCHP was designed for the Advanced Stirling Radioisotope Generator, with a 850 °C heater head temperature. The VCHP turns on with a ?T of 30 °C, which is high enough to not risk standard ASRG operation but low enough to save most heater head life. This VCHP has a low mass, and low thermal losses for normal operation. In addition to the design, a proof-of-concept NaK VCHP was fabricated and tested. While NaK is normally not used in heat pipes, it has an advantage in that it is liquid at the reservoir operating temperature, while Na or K alone would freeze. The VCHP had two condensers, one simulating the heater head, and the other simulating the radiator. The experiments successfully demonstrated operation with the simulated heater head condenser off and on, while allowing the reservoir temperature to vary over 40 to 120 °C, the maximum range expected. In agreement with previous NaK heat pipe tests, the evaporator ?T was roughly 70 °C, due to distillation of the NaK in the evaporator.
NASA Astrophysics Data System (ADS)
Bunker, R. S.; Metzger, D. E.; Wittig, S.
1990-06-01
The detailed radial distributions of rotor heat-transfer coefficients for three basic disk-cavity geometries applicable to gas turbines are presented. The coefficients are obtained over a range of parameters including disk rotational Reynolds numbers of 200,000 to 50,000, rotor/stator spacing-to-disk ratios of 0.025 to 0.15, and jet mass flow rates between 0.10 and 0.40 times the turbulent pumped flow rate of a free disk. The effects of a parallel rotor are analyzed, and strong variations in local Nusselt numbers for all but the rotational speed are pointed out and compared with the associated hub-injection data from a previous study. It is demonstrated that the overall rotor heat transfer is optimized by either the hub injection or radial location injection of a coolant, dependent on the configuration.
Federal Register 2010, 2011, 2012, 2013, 2014
2012-12-12
...Certain Integrated Circuit Packages Provided with Multiple Heat- Conducting Paths and Products Containing Same; Commission...of certain integrated circuit packages provided with multiple heat-conducting paths and products containing same by reason...
Application of the boundary element method to transient heat conduction
NASA Technical Reports Server (NTRS)
Dargush, G. F.; Banerjee, P. K.
1991-01-01
An advanced boundary element method (BEM) is presented for the transient heat conduction analysis of engineering components. The numerical implementation necessarily includes higher-order conforming elements, self-adaptive integration and a multiregion capability. Planar, three-dimensional and axisymmetric analyses are all addressed with a consistent time-domain convolution approach, which completely eliminates the need for volume discretization for most practical analyses. The resulting general purpose algorithm establishes BEM as an attractive alternative to the more familiar finite difference and finite element methods for this class of problems. Several detailed numerical examples are included to emphasize the accuracy, stability and generality of the present BEM. Furthermore, a new efficient treatment is introduced for bodies with embedded holes. This development provides a powerful analytical tool for transient solutions of components, such as casting moulds and turbine blades, which are cumbersome to model when employing the conventional domain-based methods.
Heat conduction in nanoscale materials: a statistical-mechanics derivation of the local heat flux.
Li, Xiantao
2014-09-01
We derive a coarse-grained model for heat conduction in nanoscale mechanical systems. Starting with an all-atom description, this approach yields a reduced model, in the form of conservation laws of momentum and energy. The model closure is accomplished by introducing a quasilocal thermodynamic equilibrium, followed by a linear response approximation. Of particular interest is the constitutive relation for the heat flux, which is expressed nonlocally in terms of the spatial and temporal variation of the temperature. Nanowires made of copper and silicon are presented as examples. PMID:25314400
NASA Astrophysics Data System (ADS)
Diligenskaya, A. N.; Rapoport, É. Ya.
2014-09-01
Consideration is given to inverse heat-conduction problems on identification of the strength of internal heat sources or the law of their spatial distribution. The problems have been formulated in an extremum statement as problems of optimum control over an object with distributed parameters when the set of control actions is limited to the class of continuous and continuously differentiable functions. On the basis of parametrization of control actions, the problem is reduced to an unsmooth problem of mathematical programming for the solution of which we use a special method taking account of the alternance properties of the sought optimum solutions.
High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems
Tarau, Calin; Walker, Kara L.; Anderson, William G. [Advanced Cooling Technologies, Inc. 1046 New Holland Ave. Lancaster, PA 17601 (United States)
2009-03-16
In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling converter provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) is under development to allow multiple stops and restarts of the Stirling engine. The status of the ongoing effort in developing this technology is presented in this paper. An earlier, preliminary design had a radiator outside the Advanced Stirling Radioisotope Generator (ASRG) casing, used NaK as the working fluid, and had the reservoir located on the cold side adapter flange. The revised design has an internal radiator inside the casing, with the reservoir embedded inside the insulation. A large set of advantages are offered by this new design. In addition to reducing the overall size and mass of the VCHP, simplicity, compactness and easiness in assembling the VCHP with the ASRG are significantly enhanced. Also, the permanently elevated temperatures of the entire VCHP allows the change of the working fluid from a binary compound (NaK) to single compound (Na). The latter, by its properties, allows higher performance and further mass reduction of the system. Preliminary design and analysis shows an acceptable peak temperature of the ASRG case of 140 deg. C while the heat losses caused by the addition of the VCHP are 1.8 W.
Maruyama, Shigeo
-ballistic feature. This gives rise to some unique stationary and non-stationary heat conduction [7, 8]. OneDiffusive-Ballistic Heat Conduction of Carbon Nanotubes and Nanographene Ribbons Junichiro Shiomi-3-5800-6983 Abstract Investigations of diffusive-ballistic heat conduction of finite-length single-walled carbon
Coupling of wall conduction with natural convection from heated cylinders in a rectangular enclosure
Marcel Lacroix; Antoine Joyeux
1996-01-01
A numerical study has been conducted for natural convection heat transfer for air from two vertically separated horizontal heated cylinders confined to a rectangular enclosure having vertical walls of finite conductances and horizontal walls at the heat sink temperature. The interaction between convection in the fluid filled cavity and conduction in the vertical walls is investigated. Results have been obtained
Incompressible Perturbations in Uniformally Stratified Viscous Heat-Conducting Fluid
NASA Astrophysics Data System (ADS)
Gorodtsov, V. A.
2012-04-01
One-component model of dissipative medium with two-parametric equation of state allows us to formulate a simple model of a stratified viscous heat-conducting fluid. At local thermodynamic equilibrium description and the simplifying assumption of constancy of the kinetic coefficients the complete system of equations of a viscous fluid can be written in the form of the equations of conservation of mass, momentum balance, entropy balance and state equation. Consequence of the equation of state is a linear relationship between changes in density and changes in pressure and entropy. In the case of an incompressible fluid change in the density does not occur when the pressure changes. This corresponds to an infinite speed of sound. As a result, change in the density is proportional to the temperature change and thermal expansion coefficient. Accordingly, the velocity of fluid flow is not solenoidal. At the constant heat capacity the entropy balance equation reduces to the heat equation, which in turn takes the form of the evolution equation of the density. This equation completes the equation of conservation of mass and the equation of fluid motion. We assume that fluid flow occurs in the gravity field and is caused by small external forces, a small source of mass and small thermal source. Let the initial state of the fluid is rest with the vertical coordinate-dependent density distribution. For simplicity it is assumed also that the stratification is uniform, i.e. the buoyancy frequency is constant. Then the weak current caused by the sources will be described by the linearized equations with constant coefficients in Boussinesq approximation. In this approximation, square of buoyancy frequency, the density at a fixed level and the transport coefficients are the basic constant coefficients of the equations. Gravity selects the vertical direction, and therefore it is convenient to divide vector characteristics of the perturbation in the horizontal and vertical parts. In turn, the horizontal components of vectors is conveniently represented by pairs of scalar potentials using the Helmholtz decomposition. Taking into account these relations complete system of equations for small perturbations can be reduced to separate equations for the characteristics of the perturbations. As a result, small perturbations of density, pressure and vectors of velocity and vorticity can be expressed in the form of various derivatives of the five quasipotentials. Four of these quasipotentials obey the same equation of sixth order with the mass, force and heat sources, respectively, on the right side. The operator left-hand side of these equations reflects the behavior of internal waves, as well as viscous and thermal relaxation. In addition to the viscosity this operator includes the kinetic coefficient, which is directly proportional to the coefficient of thermal conductivity and is inversely proportional to the specific heat. In this case the vertical componen
Theory and design of variable conductance heat pipes: Steady state and transient performance
NASA Technical Reports Server (NTRS)
Edwards, D. K.; Fleischman, G. L.; Marcus, B. D.
1972-01-01
Heat pipe technology pertinent to the design and application of self-controlled, variable conductance heat pipes for spacecraft thermal control is discussed. Investigations were conducted to: (1) provide additional confidence in existing design tools, (2) to generate new design tools, and (3) to develop superior variable conductance heat pipe designs. A computer program for designing and predicting the performance of the heat pipe systems was developed.
DPL model analysis of non-Fourier heat conduction restricted by continuous boundary interface
NASA Astrophysics Data System (ADS)
Jiang, Fangming; Liu, Dengying
2001-03-01
Dual-phase lag (DPL) model is used to describe the non-Fourier heat conduction in a finite medium where the boundary at x=0 is heated by a rectangular pulsed energy source and the other boundary is tightly contacted with another medium and satisfies the continuous boundary condition. Numerical solution of this kind of non-Fourier heat conduction is presented in this paper. The results are compared with those predicted by the hyperbolic heat conduction (HHC) equation.
Analysis of heat conduction in a disk brake system
Faramarz Talati; Salman Jalalifar
2009-01-01
In this paper, the governing heat equations for the disk and the pad are extracted in the form of transient heat equations\\u000a with heat generation that is dependant to time and space. In the derivation of the heat equations, parameters such as the\\u000a duration of braking, vehicle velocity, geometries and the dimensions of the brake components, materials of the disk
SEP BIMOD variable conductance heat pipes acceptance and characterization tests
NASA Technical Reports Server (NTRS)
Hemminger, J. A.
1981-01-01
A series of six heat pipes, similar in design to those flown on the Comunications Technology Satellite Hermes, for use in a prototype Solar Electric Propulsion BIMOD thrust module are evaluated. The results of acceptance and characterization tests performed on the heat pipe subassemble are reported. The performance of all the heat pipes met, or exceeded, design specifications.
Lopez, Jose M; Avila, Marc
2015-01-01
The flow of fluid confined between a heated rotating cylinder and a cooled stationary cylinder is a canonical experiment for the study of heat transfer in engineering. The theoretical treatment of this system is greatly simplified if the cylinders are assumed to be of infinite length or periodic in the axial direction, in which cases heat transfer occurs only through conduction as in a solid. We here investigate numerically heat transfer and the onset of turbulence in such flows by using both periodic and no-slip boundary conditions in the axial direction. We obtain a simple linear criterion that determines whether the infinite-cylinder assumption can be employed. The curvature of the cylinders enters this linear relationship through the slope and additive constant. For a given length-to-gap aspect ratio there is a critical Rayleigh number beyond which the laminar flow in the finite system is convective and so the behaviour is entirely different from the periodic case. The criterion does not depend on the Pra...
Martin, Timothy
Summary Weusedthreemethodstomeasureboundarylayer conductance to heat transfer (gbH) and water vapor of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become diffusion, the boundary layer around a leaf also provides resistance to the transfer of heat between a leaf
Maruyama, Shigeo
is expected to be a good heat conductor with the extraordinary long phonon mean free paths. This gives rise not only give rise to thermal boundary resistances but also influence the intrinsic heat conductionInfluence of interfaces on diffusive-ballistic heat conduction of carbon nanotubes Shiomi
Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes
Maruyama, Shigeo
effect gives rise to the long-time heat flux correlation.11) More recently, the length dependenceMolecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes-3-1 Hongo, Bunkyo-ku Tokyo 113-8656, Japan Diffusive-ballistic heat conduction of finite-length single
Li, Baowen
Wave transmission, phonon localization, and heat conduction of a one-dimensional Frenkel the fundamental properties, such as the wave transmission, heat conduction, and other low these related properties, namely, the wave transmission, the heat conduc- tion, and the phonon localization in 1
Maruyama, Shigeo
to predict the heat conduction due to the lack of local diffusion. It is shown that this can be remedied. In a typical macroscopic description, a well-known model of heat wave propagation was formulated by Cattaneo = + , (1) where heat is conducted as a wave whose amplitude decays with an effective relaxation time . Here
Thermographic validation of a novel, laminate body, analytical heat conduction model
NASA Astrophysics Data System (ADS)
Desgrosseilliers, Louis; Groulx, Dominic; White, Mary Anne
2014-07-01
The two-region fin model captures the heat spreading behaviour in multilayered composite bodies (i.e., laminates), heated only over a small part of their domains (finite heat source), where there is an inner layer that has a substantial capacity for heat conduction parallel to the heat exchange surface (convection cooling). This resulting heat conduction behaviour improves the overall heat transfer process when compared to heat conduction in homogeneous bodies. Long-term heat storage using supercooling salt hydrate phase change materials, stovetop cookware, and electronics cooling applications could all benefit from this kind of heat-spreading in laminates. Experiments using laminate films reclaimed from post-consumer Tetra Brik cartons were conducted with thin rectangular and circular heaters to confirm the laminate body, steady-state, heat conduction behaviour predicted by the two-region fin model. Medium to high accuracy experimental validation of the two-region fin model was achieved in Cartesian and cylindrical coordinates for forced external convection and natural convection, the latter for Cartesian only. These were conducted using constant heat flux finite heat source temperature profiles that were measured by infrared thermography. This validation is also deemed valid for constant temperature heat sources.
A. Nakayama; F. Kuwahara; G. Xu; F. Kato
2004-01-01
An analytical procedure has been proposed to attack a highly conjugate thermal problem associated with radiation, convection and conduction within a heat insulating wall structure. Firstly, an analytical solution is derived for fully-developed mixed convective flow through parallel plates. Secondly, the resulting expressions for convection are coupled with radiation and conduction equations to form a set of heat balance equations
Chancelor
1983-01-01
The primary objective of the work is to evaluate the performance of an air to air variable conductance heat pipe heat exchanger (VCHPHX). This type of heat exchanger is of particular interest to the commercial aircraft industry because of its unique control system. The results from this research will help to provide the engineer with experimental data necessary to design
Heat conduction problem of an evaporating liquid T. Barta, V. Janecek, D. Prazak
BÃ¡rta, TomÃ¡s
in industrial applications, e.g. boiling heat exchangers or heat pipes. Special case of such problem as heat exchange fluid. A common interest is avoiding boiling of this cooling medium, i.e. nucleationHeat conduction problem of an evaporating liquid wedge T. BÂ´arta, V. Janecek, D. PrazÂ´ak Abstract
Radiation and gas conduction heat transport across a helium dewar multilayer insulation system
M. A. Green
1994-01-01
This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulate a 4 K liquid helium cryostat. The method described here permits one to estimate the insulation potential for a multilayer insulation system from first principles. The heat transfer regimes included are: radiation, conduction by free molecule gas conduction, and conduction through continuum gas
Constructal-theory network of conducting paths for cooling a heat generating volume
Adrian Bejan
1997-01-01
This paper develops a solution to the fundamental problem of how to collect and ‘channel’ to one point the heat generated volumetrically in a low conductivity volume of given size. The amount of high conductivity material that is available for building channels (high conductivity paths) through the volume is fixed. The total heat generation rate is also fixed. The solution
Chen, Lin; Li, Zhen; Guo, Zeng-Yuan [Department of Engineering Mechanics, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing 100084 (China)
2009-07-15
In this paper, two modified types of polypropylene (PP) with high thermal conductivity up to 2.3 W/m K and 16.5 W/m K are used to manufacture the finned-tube heat exchangers, which are prospected to be used in liquid desiccant air conditioning, heat recovery, water source heat pump, sea water desalination, etc. A third plastic heat exchanger is also manufactured with ordinary PP for validation and comparison. Experiments are carried out to determine the thermal performance of the plastic heat exchangers. It is found that the plastic finned-tube heat exchanger with thermal conductivity of 16.5 W/m K can achieve overall heat transfer coefficient of 34 W/m{sup 2} K. The experimental results are compared with calculation and they agree well with each other. Finally, the effect of material thermal conductivity on heat exchanger thermal performance is studied in detail. The results show that there is a threshold value of material thermal conductivity. Below this value improving thermal conductivity can considerably improve the heat exchanger performance while over this value improving thermal conductivity contributes very little to performance enhancement. For the finned-tube heat exchanger designed in this paper, when the plastic thermal conductivity can reach over 15 W/m K, it can achieve more than 95% of the titanium heat exchanger performance and 84% of the aluminum or copper heat exchanger performance with the same dimension. (author)
Y. Liu; N. Phan-Thien
1999-01-01
The complete conjugate heat conduction, convection and radiation problem for a heated block in a differentially heated square\\u000a enclosure is solved by an operator-splitting pseudo-time-stepping finite element method. The main feature of the solution\\u000a procedure is that the multi-phases are treated as a single computational domain with unknown interfacial boundary conditions.\\u000a The temperature distribution in the heated block and in
Performance tests of a conductive magnetic refrigerator using a 4.5 K heat sink
NASA Astrophysics Data System (ADS)
Prenger, F. C.; Hill, D. D.; Trueblood, J.; Servais, T.; Laatsch, J.; Barclay, J. A.
Initial performance test results of a prototype, conductive magnetic refrigerator rejecting heat to a 4.5 K heat sink are presented. The prototype uses Gadolinium Gallium Garnet as the working material, operates in a Carnot cycle, uses NbTi magnets and employs conduction heat transfer internally. The data presented are used to validate an analytical model of the device. Performance limitations from circumferential conduction and internal friction are identified and discussed.
Shrestha, R.; Lee, K. M.; Chang, W. S.; Kim, D. S.; Rhee, G. H.; Choi, T. Y.
2013-01-01
In this paper, we describe the thermal conductivity measurement of single-walled carbon nanotubes thin film using a laser point source-based steady state heat conduction method. A high precision micropipette thermal sensor fabricated with a sensing tip size varying from 2 ?m to 5 ?m and capable of measuring thermal fluctuation with resolution of ±0.01 K was used to measure the temperature gradient across the suspended carbon nanotubes (CNT) film with a thickness of 100 nm. We used a steady heat conduction model to correlate the temperature gradient to the thermal conductivity of the film. We measured the average thermal conductivity of CNT film as 74.3 ± 7.9 W m?1 K?1 at room temperature. PMID:23556837
The correlation of radial heat transfer data from a moving plasma
Choksi, Nitinchandra Mafatlal
1967-01-01
immersed in an air plasma, Wethern (5) has considered three model ~ which are equilibrium boundary layer, Z. frozen flow and a fully catalytic wall, and 3. frozen flow and noncatalytic wall. On comparison with the heat transfer coefficient which...
October 2011 SDI FEP Issues Heat Conduction Issues (HC)
the heaters. Background: Halite thermal conductivity (k) is inversely related to porosity. The higher porosity additional information on the higher temperature-lower thermally conductive nature of halite and its affect on distal temperatures. Background: Halite thermal k is inversely related to temperature. A higher
Solving Heat Conduction Problems by the Direct Meshless Local Petrov-Galerkin (DMLPG) method
Schaback, Robert
Solving Heat Conduction Problems by the Direct Meshless Local Petrov-Galerkin (DMLPG) method DavoudÂ¨ottingen, Germany. SUMMARY As an improvement of the Meshless Local PetrovÂGalerkin (MLPG), the Direct Meshless Local; Meshless methods; MLPG methods; DMLPG methods; Heat conduction problem. 1. INTRODUCTION Meshless methods
Quantitative analyses of damp-heat-induced degradation in transparent conducting oxides
Park, Byungwoo
Quantitative analyses of damp-heat-induced degradation in transparent conducting oxides Jae Ik Kim online 9 January 2014 Keywords: Transparent conducting oxides Al-doped ZnO Damp-heat test Photovoltaics atmosphere) for sputter-deposited aluminum-doped zinc oxide (ZnO:Al) thin films were quantitatively studied
Satoru Yamamoto; Daisuke Niiyama; Byeong Rog Shin
2004-01-01
Natural convection around a horizontal circular pipe coupled with heat conduction in the solid structure is numerically investigated using a preconditioning method for solving incompressible and compressible Navier–Stokes equations. In this method, fundamental equations are completely reduced to an equation of heat conduction when the flow field is static (zero velocity). Therefore, not only compressible flows but also very slow
Estimating thermal diffusivity and specific heat from needle probe thermal conductivity data
William F. Waite; Lauren Y. Gilbert; William J. Winters; David H. Mason
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
Li, Baowen
Nonballistic heat conduction in an integrable random-exchange Ising chain studied with quantum numerically investigate the heat conduction in a random-exchange Ising spin chain by using the quantum master equation. The chain is subject to a uniform transverse field h, while the exchange couplings Qn between
Thermal conductivity and specific heat of sorghum grain
Miller, Clinton Frank
1963-01-01
to three volt range, the voltmeter resistance was 300 ohms. Leads for this meter were soldered to the element to provide good electrical connections. Prior to any testing this meter was calibrated by the Electrical Engineering Department of the A &. M... is the length of the heating element in the voltmeter circuit. Length b could only be measured accurately after the voltmeter leads were soldered to the heating element. Two working equations were then developed by substituting the value of Q in Equation 2...
on the total window heat transfer rates may be much larger. This effect is even greater in low on a literature review and an evaluation of current methods of modeling heat transfer through window frames, we evaluating heat transfer through the low-conductance frames. We conclude that the near-term priorities
Maruyama, Shigeo
-length in many applications even at room temperature. This gives rise to unique steady and unsteady heat/sources is expected to determine the overall heat transfer performance. Such interfaces not only give rise to thermalInfluence of surrounding materials on heat conduction of carbon nanotubes: Molecular dynamics
Thermal conductivity and diffusivity of biomaterials measured with self-heated thermistors
J. W. Valvano; J. R. Cochran; K. R. Diller
1985-01-01
This paper presents an experimental method to measure the thermal conductivity and thermal diffusivity of biomaterials. Self-heated thermistor probes, inserted into the tissue of interest, are used to deliver heat as well as to monitor the rate of heat removal. An empirical calibration procedure allows accurate thermal-property measurements over a wide range of tissue temperatures. Operation of the instrument in
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…
NASA Astrophysics Data System (ADS)
Chen, Lingen; Ma, Kang; Sun, Fengrui
2011-06-01
The optimal configuration of the expansion process of a heated working fluid inside a cylinder for maximum work output with a movable piston and time-dependent heat conductance is determined in this paper using finite-time thermodynamics. The heat transfer between the working fluid and the external heat bath is assumed to obey the generalized radiative heat transfer law (
Variable Conductance Heat Pipe Cooling of Stirling Convertor and General Purpose Heat Source
NASA Technical Reports Server (NTRS)
Tarau, Calin; Schwendeman, Carl; Anderson, William G.; Cornell, Peggy A.; Schifer, Nicholas A.
2013-01-01
In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental results from integrating the VCHP with an operating Stirling convertor and describes the methodology used to achieve their successful combined operation.
A high reliability variable conductance heat pipe space radiator
G. L. Fleischman; G. F. Pasley; R. J. McGrath; L. D. Loudenback
1978-01-01
The heat pipes in this radiator for space applications incorporate a central-core wrapped screen wick, which primes and reprimes under adverse conditions in the presence of noncondensable gas. A step change in mesh size provides low resistance to liquid flow in the condenser while at the same time retaining high pumping capability in the evaporator region. The envelope and wick
DPL model analysis of non-Fourier heat conduction restricted by continuous boundary interface
Fangming Jiang; Dengying Liu
2001-01-01
Dual-phase lag (DPL) model is used to describe the non-Fourier heat conduction in a finite medium where the boundary at x=0 is heated by a rectangular pulsed energy source and the other boundary is tightly contacted with another medium and satisfies\\u000a the continuous boundary condition. Numerical solution of this kind of non-Fourier heat conduction is presented in this paper.\\u000a The
NASA Technical Reports Server (NTRS)
Brandon, S.; Derby, J. J.
1992-01-01
In the present investigation of crystalline phase internal radiation and heat conduction during the vertical Bridgman growth of a YAG-like oxide crystal, where transport through the melt is dominated by convection and conduction, heat is also noted to be conducted through ampoule walls via natural convection and enclosure radiation. The results of a quasi-steady-state axisymmetric Galerkin FEM indicate that heat transfer through the system is powerfully affected by the optical absorption coefficient of the crystal. The coupling of internal radiation through the crystal with conduction through the ampoule walls promotes melt/crystal interface shapes that are highly reflected near the ampoule wall.
Mohammad M. Rahman; K. M. Salahuddin
2010-01-01
The effects of variable electric conductivity and temperature dependent viscosity on hydromagnetic heat and mass transfer flow along a radiate isothermal inclined permeable surface in a stationary fluid in the presence of internal heat generation (or absorption) are analyzed numerically presenting local similarity solutions for various values of the physical parameters. The research shows that the difference in the results
J. P. Vishwakarma; G. Nath
2010-01-01
A self-similar solution for the propagation of a cylindrical shock wave in a dusty gas with heat conduction and radiation heat flux, which is rotating about the axis of symmetry, is investigated. The shock is assumed to be driven out by a piston (an inner expanding surface) and the dusty gas is assumed to be a mixture of non-ideal gas
J. P. Vishwakarma; G. Nath
2012-01-01
The propagation of shock waves in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux, which has a variable azimuthally fluid velocity together with a variable axial fluid velocity, is investigated. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It
Lin Chen; Zhen Li; Zeng-Yuan Guo
2009-01-01
In this paper, two modified types of polypropylene (PP) with high thermal conductivity up to 2.3W\\/m K and 16.5W\\/m K are used to manufacture the finned-tube heat exchangers, which are prospected to be used in liquid desiccant air conditioning, heat recovery, water source heat pump, sea water desalination, etc. A third plastic heat exchanger is also manufactured with ordinary PP
Lin Chen; Zhen Li; Zeng-Yuan Guo
2009-01-01
In this paper, two modified types of polypropylene (PP) with high thermal conductivity up to 2.3 W\\/m K and 16.5 W\\/m K are used to manufacture the finned-tube heat exchangers, which are prospected to be used in liquid desiccant air conditioning, heat recovery, water source heat pump, sea water desalination, etc. A third plastic heat exchanger is also manufactured with
Pokorny, Richard; Rice, Jarrett A.; Schweiger, Michael J.; Hrma, Pavel R.
2013-06-01
The cold cap is a layer of reacting glass batch floating on the surface of melt in an all-electric continuous glass melter. The heat needed for the conversion of the melter feed to molten glass must be transferred to and through the cold cap. Since the heat flux into the cold cap determines the rate of melting, the heat conductivity is a key property of the reacting feed. We designed an experimental setup consisting of a large cylindrical crucible with an assembly of thermocouples that monitors the evolution of the temperature field while the crucible is heated at a constant rate. Then we used two methods to calculate the heat conductivity and thermal diffusivity of the reacting feed: the approximation of the temperature field by polynomial functions and the finite-volume method coupled with least-squares analysis. Up to 680°C, the heat conductivity of the reacting melter feed was represented by a linear function of temperature.
Comparison of HAM and HPM methods in nonlinear heat conduction and convection equations
M. Sajid; T. Hayat
2008-01-01
Recently, Rajabi et al. (Application of homotopy perturbation method in nonlinear heat conduction and convection equations, Phys. Lett. A 360 (2007) 570–573.) discussed the solutions of temperature distribution in lumped system of combined convection–radiation. They solved a nonlinear equation of the steady conduction in a slab with variable thermal conductivity using both perturbation and homotopy perturbation methods. They claim that
Thermal conductivity in nanostructured materials and analysis of local angle between heat fluxes
NASA Astrophysics Data System (ADS)
Fu, B.; Tang, G. H.; Bi, C.
2014-09-01
The phonon Boltzmann transport equation with the frequency-dependent model is solved numerically to study the thermal conductivity in nanoporous thin film and nanocomposite. Local angle between heat fluxes, defined as the angle between the directions of heat flux component qx and the local heat flux q, is introduced. At a fixed porosity or interface area, the thermal conductivity, local angle distribution, and the average angle of the two-dimensional nanoporous thin films with circular, hexagonal, square, and triangular pores are reported, and the thermal conductivity decreases with the increase in the interface area or porosity. Furthermore, the relationship between the thermal conductivity and average angle is also discussed for the three-dimensional nanoporous thin films with aligned or staggered pores, and silicon-germanium embedded and compacted nanocomposites. All the results show that the nanostructured material with a larger average angle between heat fluxes has a lower thermal conductivity.
Tables for solution of the heat-conduction equation with a time-dependent heating rate
Bergles A. E.
1962-01-01
Tables are presented for the solution of the transient onedimensional heat flow in a solid body of constant material properties with the heating rate at one boundary dependent on time. These tables allow convenient and ...
Phonon Transport in Graphene: Umklapp Quenching and Heat Conduction
NASA Astrophysics Data System (ADS)
Balandin, Alexander
2009-11-01
Since its exfoliation, graphene attracted tremendous attention of the research community. Graphene, which consists of a single atomic plane of carbon atoms, revealed many unique properties including extremely high electron mobility. In this talk I will show that unusual properties of graphene are not limited to electrons alone. Phonons also behave differently in two-dimensional (2D) system such as graphene. We have recently discovered experimentally that thermal conductivity of suspended graphene layers is extremely high and exceeds that of diamond or graphite [2-3]. We explained our results theoretically by considering the Umklapp and edge scattering of phonons in graphene [3]. Unlike in bulk graphite, the phonon transport in graphene is pure 2D for all phonon energies. As a result, the thermal conductivity of graphene can become extremely high. The extraordinary high thermal conductivity of graphene can be used for thermal management of nanoscale electronic devices. This work was supported by SRC-DARPA Functional Engineered Nano Architectonics (FENA) center and Interconnect Focus Center (IFC). [1] A.A. Balandin, et al. Nano Letters, 8, 902 (2008); S. Ghosh, et al., Appl. Phys. Lett., 92, 151911 (2008). [2] D.L. Nika, et al., Phys. Rev. B, 79, 155413 (2009); D.L. Nika et al., Appl. Phys. Lett., 94, 203103 (2009)
Author's personal copy Pyroelectric waste heat energy harvesting using heat conduction
Pilon, Laurent
-product of power, refrigeration, or heat pump cycles according to the second law of thermodynamics [1]. In 2009 pump, cryogenic refrigeration, and air liquefaction applications [3]. Organic Rankine cycles use heat harvesting Olsen cycle a b s t r a c t Waste heat can be directly converted into electrical energy
Heat conduction in a chain of dissociating particles: Effect of dimensionality
NASA Astrophysics Data System (ADS)
Zolotarevskiy, V.; Savin, A. V.; Gendelman, O. V.
2015-03-01
The paper considers heat conduction in a model chain of composite particles with hard core and elastic external shell. Such model mimics three main features of realistic interatomic potentials—hard repulsive core, quasilinear behavior in a ground state, and possibility of dissociation. It has become clear recently that this latter feature has crucial effect on convergence of the heat conduction coefficient in thermodynamic limit. We demonstrate that in one-dimensional chain of elastic particles with hard core the heat conduction coefficient also converges, as one could expect. Then we explore effect of dimensionality on the heat transport in this model. For this sake, longitudinal and transversal motions of the particles are allowed in a long narrow channel. With varying width of the channel, we observe sharp transition from "one-dimensional" to "two-dimensional" behavior. Namely, the heat conduction coefficient drops by about order of magnitude for relatively small widening of the channel. This transition is not unique for the considered system. Similar phenomenon of transition to quasi-1D behavior with growth of aspect ratio of the channel is observed also in a gas of densely packed hard (billiard) particles, both for two- and three-dimensional cases. It is the case despite the fact that the character of transition in these two systems is not similar, due to different convergence properties of the heat conductivity. In the billiard model, the divergence pattern of the heat conduction coefficient smoothly changes from logarithmic to power-like law with increase of the length.
Precise measurements of radial temperature gradients in the laser-heated diamond anvil cell.
Kavner, A; Nugent, C
2008-02-01
A new spectroradiometry system specialized for measuring two-dimensional temperature gradients for samples at high pressure in the laser heated diamond anvil cell has been designed and constructed at UCLA. Emitted light intensity from sample hotspots is imaged by a videocamera for real time monitoring, an imaging spectroradiometer for temperature measurement, and a high-dynamic-range camera that examines a magnified image of the two-dimensional intensity distribution of the heated spot, yielding precise measurements of temperature gradients. With this new system, most systematic errors in temperature measurement due to chromatic aberration are bypassed. We use this system to compare several different geometries of temperature measurement found in the literature, including scanning a pinhole aperture, and narrow-slit and wide-slit entrance apertures placed before the imaging spectrometer. We find that the most accurate way of measuring a temperature is to use the spectrometer to measure an average hotspot temperature and to use information from the imaging charge coupled device to calculate the temperature distribution to the hotspot. We investigate the effects of possible wavelength- and temperature-dependent emissivity, and evaluate their errors. We apply this technique to measure the anisotropy in temperature distribution of highly oriented graphite at room temperature and also at high pressures. A comparison between model and experiment demonstrates that this system is capable of measuring thermal diffusivity in anisotropic single crystals and is also capable of measuring relative thermal diffusivity at high pressures and temperatures among different materials. This shows the possibility of using this system to provide information about thermal diffusivity of materials at high pressure and temperature. PMID:18315322
Molecular dynamics analysis of spectral characteristics of phonon heat conduction in silicon
Henry, Asegun Sekou Famake
2006-01-01
Due to the technological significance of silicon, its heat conduction mechanisms have been studied extensively. However, there have been some lingering questions surrounding the phonon mean free path and importance of ...
Effect of viscosity and wall heat conduction on shock attenuation in narrow channels
NASA Astrophysics Data System (ADS)
Deshpande, A.; Puranik, B.
2015-02-01
In the present work, the effects due to viscosity and wall heat conduction on shock propagation and attenuation in narrow channels are numerically investigated. A two-dimensional viscous shock tube configuration is simulated, and heat conduction in the channel walls is explicitly included. The simulation results indicate that the shock attenuation is significantly less in case of an adiabatic wall, and the use of an isothermal wall model is adequate to take into account the wall heat conduction. A parametric study is performed to characterize the effects of viscous forces and wall heat conduction on shock attenuation, and the behaviour is explained on the basis of boundary layer formation in the post-shock region. A dimensionless parameter that describes the shock attenuation is correlated with the diaphragm pressure ratio and a dimensionless parameter which is expressed using the characteristic Reynolds number and the dimensionless shock travel.
Transition from near-field thermal radiation to phonon heat conduction at sub-nanometre gaps.
Chiloyan, Vazrik; Garg, Jivtesh; Esfarjani, Keivan; Chen, Gang
2015-01-01
When the separation of two surfaces approaches sub-nanometre scale, the boundary between the two most fundamental heat transfer modes, heat conduction by phonons and radiation by photons, is blurred. Here we develop an atomistic framework based on microscopic Maxwell's equations and lattice dynamics to describe the convergence of these heat transfer modes and the transition from one to the other. For gaps >1?nm, the predicted conductance values are in excellent agreement with the continuum theory of fluctuating electrodynamics. However, for sub-nanometre gaps we find the conductance is enhanced up to four times compared with the continuum approach, while avoiding its prediction of divergent conductance at contact. Furthermore, low-frequency acoustic phonons tunnel through the vacuum gap by coupling to evanescent electric fields, providing additional channels for energy transfer and leading to the observed enhancement. When the two surfaces are in or near contact, acoustic phonons become dominant heat carriers. PMID:25849305
Conjugate conduction-convection heat transfer with a high-speed boundary layer
Frederick L. Shope
1994-01-01
A space-marching boundary-layer program has been extensively modified to model conjugate conduction-convection heat transfer for the case of co-flowing high-speed gas and liquid coolant. Solid body conduction is modeled as one-dimensional, constant property heat transfer. The coolant is modeled empirically as a bulk fluid with combined forced convection and subcooled nucleate boiling. The flow solver was modified to solve the
Effect of heat treatment on the thermal conductivity of plasma-sprayed thermal barrier coatings
Rollie Dutton; Robert Wheeler; K. S. Ravichandran; K. An
2000-01-01
The effect of heat treatment on the thermal conductivity of plasma-sprayed Y2O3 stabilized ZrO2 (YSZ) and Al2O3 coatings was investigated. A heat treatment of 1300 °C in flowing argon for 50 h was found to significantly increase the\\u000a thermal conductivity of the coatings when compared to measurements in the assprayed condition. Transmission electron microscopy\\u000a (TEM) examination of the microstructures of
The Boundary Element Method for the Solution of the Backward Heat Conduction Equation
H. Han; D. B. Ingham; Y. Yuan
1995-01-01
In this paper we consider the numerical solution of the one-dimensional, unsteady heat conduction equation in which Dirichlet boundary conditions are specified at two space locations and the temperature distribution at a particular time, say T0, is given. The temperature distribution for all times, t < T0, is now required and this backward heat conduction problem is a well-known improperly
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.
Simulation of convective-conductive-radiative heat transfer in a cooling basin
P. Vaitiek?nas; D. Paliulis
The three-dimensional mathematical model of complex research of heat and mass transfer in water media was used. This allows examining the interaction of some transfer processes in the natural cooling basin (lake Dr?kšiai): heat convection and conduction, direct and diffusive solar radiation, variable density of the water and heat transfer coefficient of the water-air interface. The combined effect of these
M. Epstein; F. B. Cheung; T. C. Chawla; G. M. Hauser
1981-01-01
The effective thermal conductivity for radiative heat transfer within an optically thick fluid layer undergoing high Rayleigh number convection is derived. This result is combined with available ''pure'' free-convection heat-transfer correlations to obtain closed-form analytical descriptions of the gross properties of a radiating fluid layer heated internally or form below. These simple solutions compare favorably with recent work in which
Jan-Patrice Simoneau; Julien Champigny; Brian Mays; Lewis Lommers
2007-01-01
A three-dimensional model has been constructed to simulate the passive heat removal in a modular prismatic-block high temperature reactor during a loss of active cooling accident. This model, developed using the STAR-CD general computational fluid dynamics code, solves the combined conductive, convective, and radiative heat transfer within a 30° section of the core and reactor vessel. To accommodate the different
Irving Langmuir; John Bradshaw Taylor
1936-01-01
The theory and the equations governing the temperature distribution, resistance, and heat flow in a tungsten filament as affected by its leads are given for the low temperature range (<600°K), both for the general case and for several special cases. A low temperature vs. current scale for tungsten is calculated from these equations using measurements of heat conductivity given in
J. Sladek; V. Sladek; Ch. Zhang
2003-01-01
Advanced computational method for transient heat conduction analysis in continuously nonhomogeneous functionally graded materials (FGM) is proposed. The method is based on the local boundary integral equations with moving least square approximation of the temperature and heat flux. The initial-boundary value problem is solved by the Laplace transform technique. Both Papoulis and Stehfest algorithms are applied for the numerical Laplace
Influence of convection, conduction, and radiation on the frequency response of heat fluxmeters
H. Malcorps
1982-01-01
A simple model for a heat fluxmeter, exchanging heat by radiation, convection, and conduction with the surrounding air is introduced. The final analytical solution is interpreted by means of electronic analog circuits and an explanation of the properties of the radiometer of Gier and Dunkle (AIEE Trans. 70, 107–114, 1953) is given.
Simultaneous radiative, convective and conductive heat transfer from a developed surface
T. Kunitomo; S. Tanaka
1976-01-01
The paper considers the simultaneous radiative, conductive and convective heat transfer from three types of developed systems: (1) a longitudinally ribbed flat surface, (2) a longitudinally ribbed cylinder, and (3) a peripherally ribbed cylinder. The Monte Carlo method is used to analyze the radiation characteristics of the surfaces. Attention is given to the effects of heat transfer parameters and geometrical
Conjugate heat transfer by natural convection, conduction and radiation in open cavities
H. Nouanegue; A. Muftuoglu; E. Bilgen
2008-01-01
In this paper, we investigate conjugate heat transfer by natural convection, conduction and radiation in open cavities in which a uniform heat flux is applied to the inside surface of the solid wall facing the opening. Conservation equations are solved by finite difference–control volume numerical method. The relevant governing parameters are: the Rayleigh numbers from 109 to 1012, the Prandtl
Fygenson, Deborah Kuchnir
-BeÂ´nard convection Guenter Ahlers Department of Physics and iQUEST, University of California, Santa Barbara transport in Rayleigh-BeÂ´nard convection the correction for the sidewall conductance is usually neglected convection of a fluid heated from below is the global heat transport of the system 1 , as expressed
Qualitative aspects in dual-phase-lag heat conduction Ramon Quintanilla1
Racke, Reinhard
at low temperature has been observed to propagate by means of waves. These aspects have caused intense+ corresponds to the heat flux vector at the same point at time t+q. The delay time is causedQualitative aspects in dual-phase-lag heat conduction RamÂ´on Quintanilla1 Department of Applied
Analysis of dielectric heating and conductive cooling of pyrite in coal
D. D. Bluhm; G. E. Fanslow; S. O. Nelson
1981-01-01
Electrical and thermal properties of pyrite and coal were used to obtain a theoretical analysis of dielectric heating and conductive cooling of pyrite in coal. The results were used to establish radiation levels required to produce pyrite-coal temperature differentials in solid coals. The objective of dielectric heating of pyrite in coal is to raise its temperature to a point where
RELAP5-3D multidimensional heat conduction enclosure model for RBMK reactor application
Paik
1999-01-01
A heat conduction enclosure model is conceived and implemented by RELAP5-3D between heat structures. The suggested model uses a lumped parameter model that is generally applicable to multidimensional calculational domain. This new model is applied to calculation of RBMK reactor core graphite blocks and is compared to the commercially available Fluid Dynamics Analysis Package (FIDAP) finite element code. Reasonably good
Zabaras, Nicholas J.
probability density function (PPDF) of the boundary heat flux is computed given temperature measurements state space is exploited using Markov Chain Monte Carlo (MCMC) algorithms in order to obtain estimates inverse heat conduction examples are presented to demonstrate the potential of the MCMC-based Bayesian
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.
Demko, Jonathan Alexander
1980-01-01
(December 19SO) Jonathan Alexander Demko, B. S. M. E. , Texas A&M University Chairman of Advisory Committee: Dr. Louis C. Chow A flat plate heat exchanger (PHE) was examined analytically with focus on assessing the effects of axial conduction along... AND DISCUSSION 15 Bulk Temperature Heat Exchanger Performance Fully Developed Flows Unbalanced Flows 17 25 30 CHAPTER IV SUMMARY AND CONCLUSIONS REFERENCES APPENDIX 3B 40 VITA 56 LIST OF FIGURES ~Fi ure ~Pa e Model of a flat plate heat exchanger...
Numerical simulation of a latent heat thermal energy storage system with enhanced heat conduction
M. Costa; D. Buddhi; A. Oliva
1998-01-01
A latent heat storage system has been designed to take advantage of the off-peak electrical energy for space heating. Using an enthalpy formation and a fully implicit finite difference method, the thermal performance of such a storage system with and without fins has been analysed. For the one-dimensional simulation model, calculations have been made for the melt fraction and energy
Microwave absorption in powders of small conducting particles for heating applications.
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 ? (specifically, by the condition a = 2.41?). This means that for particles of any conductivity, optimized magnetic absorption (and hence microwave heating by magnetic induction) can be achieved by simple selection of the mean particle size. For weakly conducting samples, electric dipole absorption dominates, and is maximized when the conductivity is approximately ? ? 3??(0) ? 0.4 S m(-1), independent of particle radius. Therefore, although electric dipole heating can be as effective as magnetic dipole heating for a powder sample of the same volume, it is harder to obtain optimized conditions at a fixed frequency of microwave field. The absorption of sub-micron particles is ineffective in both magnetic and electric fields. However, if the particles are magnetic, with a lossy part to their complex permeability, then magnetic dipole losses are dramatically enhanced compared to their values for non-magnetic particles. An interesting application of this is the use of very small magnetic particles for the selective microwave heating of biological samples. PMID:23321957
Joaquín Zueco; O. Anwar Bég; H. S. Takhar; V. R. Prasad
2009-01-01
A two-dimensional mathematical model is presented for the laminar heat and mass transfer of an electrically-conducting, heat generating\\/absorbing fluid past a perforated horizontal surface in the presence of viscous and Joule (Ohmic) heating. The Talbot–Cheng–Scheffer–Willis formulation (1980) is used to introduce a thermophoretic coefficient into the concentration boundary layer equation. The governing partial differential equations are non-dimensionalized and transformed into
Thermoelasticity of thin shells based on the time-fractional heat conduction equation
NASA Astrophysics Data System (ADS)
Povstenko, Yuriy
2013-06-01
The time-nonlocal generalizations of Fourier's law are analyzed and the equations of the generalized thermoelasticity based on the time-fractional heat conduction equation with the Caputo fractional derivative of order 0 < ? ? 2 are presented. The equations of thermoelasticity of thin shells are obtained under the assumption of linear dependence of temperature on the coordinate normal to the median surface of a shell. The conditions of Newton's convective heat exchange between a shell and the environment have been assumed. In the particular case of classical heat conduction ( ? = 1) the obtained equations coincide with those known in the literature.
Thermoelasticity of thin shells based on the time-fractional heat conduction equation
NASA Astrophysics Data System (ADS)
Povstenko, Yuriy
2013-06-01
The time-nonlocal generalizations of Fourier's law are analyzed and the equations of the generalized thermoelasticity based on the time-fractional heat conduction equation with the Caputo fractional derivative of order 0 < ? ? 2 are presented. The equations of thermoelasticity of thin shells are obtained under the assumption of linear dependence of temperature on the coordinate normal to the median surface of a shell. The conditions of Newton's convective heat exchange between a shell and the environment have been assumed. In the particular case of classical heat conduction (? = 1) the obtained equations coincide with those known in the literature.
About influence of gravity on heat conductivity process of the Planets
Gladkov, S O; Ray, Saibal; Rahaman, F
2015-01-01
In the present study it is shown that the interaction of a quasi-static gravitational wave through density fluctuations gives rise to a heat conductivity coefficient and hence temperature. This fact is a very important characteristics to establish a heat equilibrium process of such massive body as the Earth and other Planets. To carry out this exercise general mechanism has been provided, which makes a bridge between classical physics and quantum theory, and specific dependence of heat conductivity coefficient in wide region is also calculated.
About influence of gravity on heat conductivity process of the Planets
S. O. Gladkov; Anil Yadav; Saibal Ray; F. Rahaman
2014-07-30
In the present study it is shown that the interaction of a quasi-static gravitational wave through density fluctuations gives rise to a heat conductivity coefficient and hence temperature. This fact is a very important characteristics to establish a heat equilibrium process of such massive body as the Earth and other Planets. To carry out this exercise general mechanism has been provided, which makes a bridge between classical physics and quantum theory, and specific dependence of heat conductivity coefficient in wide region is also calculated.
average of the convective heat flux nT sv thus gives rise to the critical heat conduction. WithinMolecular dynamics simulation of heat conduction in near-critical fluids Toshiyuki Hamanaka fluids near the gas-liquid critical point under heat flow in two dimensions. We calculate the steady
R. S. Kwok; S. E. Brown
1990-01-01
A fully automated system which is capable of measuring specific heat and thermal conductivity simultaneously from liquid helium to room temperature is presented. Thermal conductivity is measured by a steady-state longitudinal heat flow technique, and specific heat by a thermal relaxation method. A numerical simulation of the one-dimensional heat flow equation is used to examine the basic operational principle. The
ERIC Educational Resources Information Center
Chiou, Guo-Li; Anderson, O. Roger
2010-01-01
This study proposes a multi-dimensional approach to investigate, represent, and categorize students' in-depth understanding of complex physics concepts. Clinical interviews were conducted with 30 undergraduate physics students to probe their understanding of heat conduction. Based on the data analysis, six aspects of the participants' responses…
Thermal conduction and heating by nonthermal electrons in the X-ray halo of M87
NASA Technical Reports Server (NTRS)
Tucker, W. H.; Rosner, R.
1983-01-01
A hydrostatic model for the X-ray halo around the giant elliptical galaxy M87 is presented. It is shown that by taking into account the processes of thermal conduction, and nonthermal heating by relativistic electrons in the radio lobes, a self-consistent hydrostatic model can be constructed. There is no need to invoke radiative accretion or the suppression of thermal conductivity.
-transfer process involves a combination of conduction, convection, and radiation. To fully describe heat transfer Dynamics (CFD) modeling to assess the accuracy of the simplified frame cavity conduction/convection models the convection effects and to use either view-factors or ray- tracing techniques to determine the radiation
Convection under a lid of finite conductivity: Heat flux scaling and application to continents
Paris-Sud XI, Université de
Convection under a lid of finite conductivity: Heat flux scaling and application to continents C of the dichotomy between oceans and continents, which imposes heterogeneous thermal boundary conditions and continents represented by nondeformable lids of finite thermal conductivity set above the surface
Thermal conductivity and specific heat of pure and iodine doped polyacetylene (CH)x
Paris-Sud XI, Université de
1453 Thermal conductivity and specific heat of pure and iodine doped polyacetylene (CH)x N and iodine doped samples of polyacetylene (CH)x are presented here. The thermal conductivity of pure (CH)x is about 75 mW/cm . K at room temperature and decreases monotonically to 1.6 mW/cm . K at 25 K
Heat Conduction through Surface Structures and Mixtures using Electric Circuits as Analogs
W. F. Huebner; D. C. Boice; J. R. Green
1998-01-01
We present a mathematical model using electric analogs to simulate vertical and lateral conductive heat flow in surface layers of planetary bodies with topography. The model can also be used to determine average electric and thermal conductivities of small-scale granular mixtures (as opposed to molecular mixtures). The algorithm is general and applicable to complex compositions. Analogies between thermal and electric
Kumar, Suhas; Pickett, Matthew D; Strachan, John Paul; Gibson, Gary; Nishi, Yoshio; Williams, R Stanley
2013-11-13
Joule-heating induced conductance-switching is studied in VO2 , a Mott insulator. Complementary in situ techniques including optical characterization, blackbody microscopy, scanning transmission X-ray microscopy (STXM) and numerical simulations are used. Abrupt redistribution in local temperature is shown to occur upon conductance-switching along with a structural phase transition, at the same current. PMID:23868142
Thermal conductivity of cementitious grouts for geothermal heat pumps. Progress report FY 1997
Allan, M.L.
1997-11-01
Grout is used to seal the annulus between the borehole and heat exchanger loops in vertical geothermal (ground coupled, ground source, GeoExchange) heat pump systems. The grout provides a heat transfer medium between the heat exchanger and surrounding formation, controls groundwater movement and prevents contamination of water supply. Enhanced heat pump coefficient of performance (COP) and reduced up-front loop installation costs can be achieved through optimization of the grout thermal conductivity. The objective of the work reported was to characterize thermal conductivity and other pertinent properties of conventional and filled cementitious grouts. Cost analysis and calculations of the reduction in heat exchanger length that could be achieved with such grouts were performed by the University of Alabama. Two strategies to enhance the thermal conductivity of cementitious grouts were used simultaneously. The first of these was to incorporate high thermal conductivity filler in the grout formulations. Based on previous tests (Allan and Kavanaugh, in preparation), silica sand was selected as a suitable filler. The second strategy was to reduce the water content of the grout mix. By lowering the water/cement ratio, the porosity of the hardened grout is decreased. This results in higher thermal conductivity. Lowering the water/cement ratio also improves such properties as permeability, strength, and durability. The addition of a liquid superplasticizer (high range water reducer) to the grout mixes enabled reduction of water/cement ratio while retaining pumpability. Superplasticizers are commonly used in the concrete and grouting industry to improve rheological properties.
RELAP5-3D multidimensional heat conduction enclosure model for RBMK reactor application
Paik, S.
1999-10-01
A heat conduction enclosure model is conceived and implemented by RELAP5-3D between heat structures. The suggested model uses a lumped parameter model that is generally applicable to multidimensional calculational domain. This new model is applied to calculation of RBMK reactor core graphite blocks and is compared to the commercially available Fluid Dynamics Analysis Package (FIDAP) finite element code. Reasonably good agreement between the results of RELAP5-3D and FIDAP is obtained. The new heat conduction enclosure model gives RELAP5-3D a general multidimensional heat conduction capability. It also provides new routes for temperature cooloff of the RBMK graphite blocks from the ruptured channel to the surrounding ones. This ability to predict graphite temperature cooloff is very important during accidents or for transient simulation, especially concerning long-term coolability of the RBMK reactor core.
Variable thermal properties and thermal relaxation time in hyperbolic heat conduction
NASA Technical Reports Server (NTRS)
Glass, David E.; Mcrae, D. Scott
1989-01-01
Numerical solutions were obtained for a finite slab with an applied surface heat flux at one boundary using both the hyperbolic (MacCormack's method) and parabolic (Crank-Nicolson method) heat conduction equations. The effects on the temperature distributions of varying density, specific heat, and thermal relaxation time were calculated. Each of these properties had an effect on the thermal front velocity (in the hyperbolic solution) as well as the temperatures in the medium. In the hyperbolic solutions, as the density or specific heat decreased with temperature, both the temperatures within the medium and the thermal front velocity increased. The value taken for the thermal relaxation time was found to determine the 'hyperbolicity' of the heat conduction model. The use of a time dependent relaxation time allowed for solutions where the thermal energy propagated as a high temperature wave initially, but approached a diffusion process more rapidly than was possible with a constant large relaxation time.
Artificial Ionospheric Heating Experiments Conducted by a Magnetosphere-Ionosphere Coupling Model
NASA Astrophysics Data System (ADS)
Stevens, R. J.; Otto, A.; Krzykowski, M.; Solie, D.
2007-12-01
This presentation discusses computational dynamics and results of artificial heating in the ionosphere. The results are then compared to experiments including a geophysical experiment conducted at the Polar Aeronomy and Radio Science Summer School (PARS) in conjunction with the High Frequency Active Auroral Research Program (HAARP) The computational model includes the following terms: ion inertia, Ohm's law (Hall term, electron pressure term, electron neutral and electron ion collisions), ionization, recombination, electron energy (heat advection, conduction, heating through ionization, ohmic heating, gravity, energy loss to neutrals and ions), as well as parameterized collisions frequencies, and a height resolved neutral atmosphere. Atmospheric conditions for the time of the experiment (plasma density, temperature, etc) are used as initial conditions. The power and frequency of the heater facility are then used to compute the heating of the ionosphere. Data processing for the experiment and model are ongoing.
Heat conduction: hyperbolic self-similar shock-waves in solids
Imre Ferenc Barna; Robert Kersner
2012-04-19
Analytic solutions for cylindrical thermal waves in solid medium is given based on the nonlinear hyperbolic system of heat flux relaxation and energy conservation equations. The Fourier-Cattaneo phenomenological law is generalized where the relaxation time and heat propagation coefficient have a general power law temperature dependence. From such laws one cannot form a second order parabolic or telegraph-type equation. We consider the original non-linear hyperbolic system itself with the self-similar Ansatz for the temperature distribution and for the heat flux. As results continuous and shock-wave solutions are presented. For physical establishment numerous materials with various temperature dependent heat conduction coefficients are mentioned.
Coupled conductive radiative heat transfer problem for two-layer slab
NASA Astrophysics Data System (ADS)
Elghazaly, A.
2006-12-01
The coupled conductive radiative transfer problem in two homogeneous layers slab of anisotropic scattering with specularly reflecting boundaries has been considered. A Galerkin-iterative technique is used to solve the coupled conductive radiative heat equations in integral forms for the two layers. Numerical results are obtained for the temperature, the conductive, radiative and the total heat fluxes for the two homogeneous layers with isotropic and anisotropic scattering. The calculations are also carried out for homogeneous plane parallel medium with anisotropic scattering which show good agreement with the published calculations.
B. I. Olajuwon
2010-01-01
This paper investigates convection heat and mass transfer flow in an electrically conducting power law fluid past a vertical porous plate in presence of a transverse magnetic field, thermal radiation, and thermal diffusion. The non–linear partial differential equations governing the flow are transformed into ordinary differential equations using the usual similarity method and the resulting similarity equations are solved numerically
Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties
Hansen, B.J.; White, M.J.; Klebaner, A.; /Fermilab
2011-06-10
Future superconducting radio frequency (SRF) cavities, as part of Project X at Fermilab, will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule-Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchangers will be utilized. Due to their compact size and ease of fabrication, plate-fin heat exchangers are an effective option. However, the design of compact and high-effectiveness cryogenic heat exchangers operating at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger. The model is used to guide design decisions on heat exchanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger to analyze the effect of heat load and cryogenic supply parameters. A numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger was developed and the effect of various design parameters on overall heat exchanger size was investigated. It was found that highly conductive metals should be avoided in the design of compact JT heat exchangers. For the geometry considered, the optimal conductivity is around 3.5 W/m-K and can range from 0.3-10 W/m-K without a large loss in performance. The model was implemented with an isenthalpic expansion process. Increasing the cold side inlet temperature from 2K to 2.2 K decreased the liquid fraction from 0.856 to 0.839 which corresponds to a 0.12 g/s increase in supercritical helium supply needed to maintain liquid level in the cooling bath. Lastly, it was found that the effectiveness increased when the heat load was below the design value. Therefore, the heat exchanger should be sized on the high end of the required heat load.
Conductivity heating a subterranean oil shale to create permeability and subsequently produce oil
Van Meurs, P.; DeRouffignac, E.P.; Vinegar, H.J.; Lucid, M.F.
1989-12-12
This patent describes an improvement in a process in which oil is produced from a subterranean oil shale deposit by extending at least one each of heat-injecting and fluid-producing wells into the deposit, establishing a heat-conductive fluid-impermeable barrier between the interior of each heat-injecting well and the adjacent deposit, and then heating the interior of each heat-injecting well at a temperature sufficient to conductively heat oil shale kerogen and cause pyrolysis products to form fractures within the oil shale deposit through which the pyrolysis products are displaced into at least one production well. The improvement is for enhancing the uniformity of the heat fronts moving through the oil shale deposit. Also described is a process for exploiting a target oil shale interval, by progressively expanding a heated treatment zone band from about a geometric center of the target oil shale interval outward, such that the formation or extension of vertical fractures from the heated treatment zone band to the periphery of the target oil shale interval is minimized.
Hilde Monika Zimmermann; Klaus Hartmann; Lukas Schreiber; Ernst Steudle
2000-01-01
. The hydraulic conductivity of roots (Lpr) of 6- to 8-d-old maize seedlings has been related to the chemical composition of apoplastic transport barriers in the endodermis\\u000a and hypodermis (exodermis), and to the hydraulic conductivity of root cortical cells. Roots were cultivated in two different\\u000a ways. When grown in aeroponic culture, they developed an exodermis (Casparian band in the hypodermal
Wang, Hsin [ORNL; Porter, Wallace D [ORNL; Bottner, Harold [Fraunhofer-Institute, Freiburg, Germany; Konig, Jan [Fraunhofer-Institute, Freiburg, Germany; Chen, Lidong [Chinese Academy of Sciences; Bai, Shengqiang [Chinese Academy of Sciences; Tritt, Terry M. [Clemson University; Mayolett, Alex [Corning, Inc; Senawiratne, Jayantha [Corning, Inc; Smith, Charlene [Corning, Inc; Harris, Fred [ZT-Plus; Gilbert, Partricia [Marlow Industries, Inc; Sharp, J [Marlow Industries, Inc; Lo, Jason [CANMET - Materials Technology Laboratory, Natural Resources of Canada; Keinke, Holger [University of Waterloo, Canada; Kiss, Laszlo I. [University of Quebec at Chicoutimi
2013-01-01
For bulk thermoelectrics, figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In recent years, the most significant improvements in ZT were mainly due to successful reduction of thermal conductivity. However, thermal conductivity cannot be measured directly at high temperatures. The combined measurements of thermal diffusivity and specific heat and density are required. It has been shown that thermal conductivity is the property with the greatest uncertainty and has a direct influence on the accuracy of the figure of merit. The International Energy Agency (IEA) group under the implementing agreement for Advanced Materials for Transportation (AMT) has conducted two international round-robins since 2009. This paper is Part II of the international round-robin testing of transport properties of bulk bismuth telluride. The main focuses in Part II are on thermal diffusivity, specific heat and thermal conductivity.
NASA Astrophysics Data System (ADS)
Hartung, M.; Köhler, W.
2005-06-01
We present a two-dimensional model to account for the role of heat-conducting walls in the measurement of heat transport and Soret-effect-driven mass transport in transient holographic grating experiments. Heat diffusion into the walls leads to non-exponential decay of the temperature grating. Under certain experimental conditions it can be approximated by an exponential function and assigned an apparent thermal diffusivity Dth, app < Dth, s, where Dth,s is the true thermal diffusivity of the sample. The ratio Dth, app/Dth, s depends on only three dimensionless parameters, d /ls, ?s/?w, and Dth, s/Dth, w. d is the grating period, ls the sample thickness, ?s and ?w the thermal conductivities of sample and wall, respectively, and Dth,w the thermal diffusivity of the wall. If at least two measurements are performed at different d /ls, both Dth,s and ?s can be determined. Instead of costly solving PDEs, Dth,s can be obtained by finding the zero of an analytic function. For thin samples and large grating periods, heat conduction into the walls plays a predominant role and the concentration grating in binary mixtures is no longer one-dimensional. Nevertheless, the normalized heterodyne diffraction efficiency of the concentration grating remains unaffected and the true thermal and collective diffusion coefficient and the correct Soret coefficient are still obtained from a simple one-dimensional model.
NASA Astrophysics Data System (ADS)
Vishwakarma, J. P.; Nath, G.
2012-01-01
The propagation of shock waves in a rotational axisymmetric dusty gas with heat conduction and radiation heat flux, which has a variable azimuthally fluid velocity together with a variable axial fluid velocity, is investigated. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-condition is maintained and variable energy input is continuously supplied by the piston (or inner expanding surface). The fluid velocities in the ambient medium are assume to be vary and obey power laws. The density of the ambient medium is assumed to be constant, the heat conduction is express in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient ?R are assumed to vary with temperature and density. In order to obtain the similarity solutions the angular velocity of the ambient medium is assume to be decreasing as the distance from the axis increases. The effects of the variation of the heat transfer parameter and non-idealness of the gas in the mixture are investigated. The effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are also investigated.
S. Colle; R. C. de Abreu; M. B. Halal
1981-01-01
The main purpose of this paper is to present a nonlinear integral equation formulation to numerically solve composite boundary value problems encountered in the physical problem of radiative heat transfer between solids of arbitrary shape. The main difficulty in solving these types of boundary value problems is due to the nonlinear boundary conditions, which impose additional difficulties on the use
Radiative heat exchange of a meteor body in the approximation of radiant heat conduction
Pilyugin, N.N.; Chernova, T.A.
1986-07-01
The problem of the thermal and dynamic destruction of large meteor bodies moving in planetary atmospheres is fundamental for the clarification of optical observations and anomalous phenomena in the atmosphere, the determination of the physicochemical properties of meteoroids, and the explanation of the fall of remnants of large meteorites. Therefore, it is important to calculate the coefficient of radiant heat exchange (which is the determining factor under these conditions) for large meteor bodies as they move with hypersonic velocities in an atmosphere. The solution of this problem enables one to find the ablation of a meteorite during its aerodynamic heating and to determine the initial conditions for the solution of problems of the breakup of large bodies and their subsequent motion and ablation. Hypersonic flow of an inviscid gas stream over an axisymmetric blunt body is analyzed with allowance for radiative transfer in a thick-thin approximation. The gas-dynamic problem of the flow of an optically thick gas over a large body is solved by the method of asymptotic joined expansions, using a hypersonic approximation and local self-similarity. An equation is obtained for the coefficient of radiant heat exchange and the peculiarities of such heat exchange for meteor bodies of large size are noted.
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.
Thermodynamically compatible conservation laws in the model of heat conducting radiating gas
NASA Astrophysics Data System (ADS)
Ivanov, M. Ya.
2011-01-01
Thermodynamic compatibility of the mass, momentum, and energy conservation laws that describe the motion of heat conducting gas in the presence of radiation heat exchange is considered. The study is based on the one-velocity two-component mathematical model of continuous compressible medium with the gas and radiation components. The work uses experimental data for radiation and other experimental data of modern physics.
Basic Inquiry: Radiation and Heat Transfer by Conduction (title provided or enhanced by cataloger)
NSDL National Science Digital Library
David Robison
This activity consists of two parts in which students investigate heat transfer by radiation and by conduction. In the first part, students design and conduct an experiment to test the effect of color on an object's ability to radiate energy (heat). In the second part, they investigate the transfer of energy from a hotter object to a cooler one, in this case, containers of hot and cold water. In both experiments, they are required to state a hypothesis, make a list of materials and procedures needed for the experiment, collect and graph data, and state a conclusion. Each experiment is accompanied by a set of analysis and conclusion questions.
NASA Astrophysics Data System (ADS)
Xu, K. Q.; Zeng, H. R.; Yu, H. Z.; Zhao, K. Y.; Li, G. R.; Song, J. Q.; Shi, X.; Chen, L. D.
2015-01-01
An ultrahigh resolution probe technique for charactering nanoscale Seebeck coefficient was developed based on a modified conductive AFM probe with local heating function. The heated AFM conductive tip realizes nanoscale thermal contact between the AFM tip and the thermoelectric samples and successfully excites nanoscale thermoelectric signal. Excellent agreement was found between nanoscale Seebeck coefficient values and their corresponding macroscopy measurements in thermoelectric bulk and thin films. Such AFM-based thermoelectric probe technique provides a very convenient and promising tool for measuring nanoscale thermoelectric parameters with ultrahigh resolution up to 15 nm.
NASA Astrophysics Data System (ADS)
Shabanova, M. R.; Meilanov, R. P.; Meilanov, R. R.; Akhmedov, E. N.
2015-01-01
Based on the heat conduction equation with fractional-order derivatives and the experimental measurements of temperature distribution in the upper layers of the Earth, the depth dependence of thermal diffusivity is studied at different values of the parameters of nonlocality in time and along the coordinates. It is shown that thermal diffusivity increases with depth, and the values of thermal diffusivity observed in the experiments coincide with the theoretical predictions provided by the solution of the nonlocal heat-conduction equation that allows for the memory effects in fractional-order time derivatives.
NASA Astrophysics Data System (ADS)
Sarman, Sten; Laaksonen, Aatto
2010-01-01
The temperature dependence of the heat conductivity has been obtained for a liquid crystal model based on the Gay-Berne fluid, from the isotropic phase at high temperatures through the nematic phase to the smectic A phase at low temperatures. The ratio of the parallel and the perpendicular components of the heat conductivity is about 2.5:1 in the nematic phase, which is similar to that of real systems. Both Green-Kubo methods and nonequilibrium molecular dynamics methods have been applied and the results agree within in a relative error of a couple of percent, but the latter method is much more efficient.
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.
LDEF (Prelaunch), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09
NASA Technical Reports Server (NTRS)
1983-01-01
LDEF (Prelaunch), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 EL-1994-00302 LDEF (Prelaunch), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 The prelaunch photograph was taken in SAEF II at KSC prior to installation of the Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) on the LDEF. The Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) occupies a 6 inch deep LDEF peripheral experiment tray and consist of two series connected variable conductance heatpipes, a black chrome solar collector panel and a silvered TEFLON® radiator panel, a power source to support six thermistor-type temperature monitoring sensors and actuations of two valves. Fiberglass standoffs and internal insulation blankets thermally isolated the experiment from the experiment tray and the LDEF interior. The outside of the CVCHPE, except the collector and radiator panels, was covered with an aluminumized Kapton multilayer insulation (MLI) blanket with an outer layer of 0.076 mm thick Kapton. The two patches of thin film materials, part of Experiment S1001 by NASA GSFC, were attached to the cover of the external thermal blanket with Kapton tape. The experiment was assembled and mounted in the experiment tray with non-magnetic stainless steel fasteners.
California at Santa Cruz, University of
to conductivity would predict that if the temperature gradient "T in a material is small, the heat current flowing in the system conserve momentum, the con- ductivity is singular, due to advection of heat in long wave- lengthOne-dimensional heat conductivity exponent from a random collision model J. M. Deutsch and Onuttom
Gustavsen, Arild; Arasteh, Dariush; Jelle, Bjorn Petter; Curcija, Charlie; Kohler, Christian
2008-09-11
While window frames typically represent 20-30% of the overall window area, their impact on the total window heat transfer rates may be much larger. This effect is even greater in low-conductance (highly insulating) windows that incorporate very low-conductance glazing. Developing low-conductance window frames requires accurate simulation tools for product research and development. Based on a literature review and an evaluation of current methods of modeling heat transfer through window frames, we conclude that current procedures specified in ISO standards are not sufficiently adequate for accurately evaluating heat transfer through the low-conductance frames. We conclude that the near-term priorities for improving the modeling of heat transfer through low-conductance frames are: (1) Add 2D view-factor radiation to standard modeling and examine the current practice of averaging surface emissivity based on area weighting and the process of making an equivalent rectangular frame cavity. (2) Asses 3D radiation effects in frame cavities and develop recommendation for inclusion into the design fenestration tools. (3) Assess existing correlations for convection in vertical cavities using CFD. (4) Study 2D and 3D natural convection heat transfer in frame cavities for cavities that are proven to be deficient from item 3 above. Recommend improved correlations or full CFD modeling into ISO standards and design fenestration tools, if appropriate. (5) Study 3D hardware short-circuits and propose methods to ensure that these effects are incorporated into ratings. (6) Study the heat transfer effects of ventilated frame cavities and propose updated correlations.
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.
Lee, Haw-Long; Chen, Wen-Lih; Chang, Win-Jin; Yang, Yu-Ching
2015-01-01
In this study, an inverse algorithm based on the conjugate gradient method and the discrepancy principle is applied to solve the inverse hyperbolic heat conduction problem in estimating the unknown time-dependent surface heat flux in a skin tissue, which is stratified into epidermis, dermis, and subcutaneous layers, from the temperature measurements taken within the medium. Subsequently, the temperature distributions in the tissue can be calculated as well. The concept of finite heat propagation velocity is applied to the modeling of the bioheat transfer problem. The inverse solutions will be justified based on the numerical experiments in which two different heat flux distributions are to be determined. The temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of measurement errors on the precision of the estimated results is also investigated. Results show that an excellent estimation on the time-dependent surface heat flux can be obtained for the test cases considered in this study. PMID:24946013
Lattice thermal conductivity of lower mantle minerals and heat flux from Earth’s core
Manthilake, Geeth M.; de Koker, Nico; Frost, Dan J.; McCammon, Catherine A.
2011-01-01
The amount of heat flowing from Earth’s core critically determines the thermo-chemical evolution of both the core and the lower mantle. Consisting primarily of a polycrystalline aggregate of silicate perovskite and ferropericlase, the thermal boundary layer at the very base of Earth’s lower mantle regulates the heat flow from the core, so that the thermal conductivity (k) of these mineral phases controls the amount of heat entering the lowermost mantle. Here we report measurements of the lattice thermal conductivity of pure, Al-, and Fe-bearing MgSiO3 perovskite at 26 GPa up to 1,073 K, and of ferropericlase containing 0, 5, and 20% Fe, at 8 and 14 GPa up to 1,273 K. We find the incorporation of these elements in silicate perovskite and ferropericlase to result in a ?50% decrease of lattice thermal conductivity relative to the end member compositions. A model of thermal conductivity constrained from our results indicates that a peridotitic mantle would have k = 9.1 ± 1.2 W/m K at the top of the thermal boundary layer and k = 8.4 ± 1.2 W/m K at its base. These values translate into a heat flux of 11.0 ± 1.4 terawatts (TW) from Earth’s core, a range of values consistent with a variety of geophysical estimates. PMID:22021444
Nonlinear thermal bending response of FGM plates due to heat conduction
Hui-Shen Shen
2007-01-01
Nonlinear thermal bending analysis is presented for a simply supported, shear deformable functionally graded plate without or with piezoelectric actuators subjected to the combined action of thermal and electrical loads. Heat conduction and temperature-dependent material properties are both taken into account. The temperature field considered is assumed to be a uniform distribution over the plate surface and varied in the
Heat Flow, Thermal Conductivity, and the Plausibility of the White Mars Hypothesis
NASA Technical Reports Server (NTRS)
Urquhart, M. L.; Gulick, V. C.
2002-01-01
Due to the low thermal conductivity of CO2 ice and clathrate vs. water ice, we find that liquid water reservoirs would not be confined to the deep subsurface as predicted by the controversial White Mars model, even assuming low global heat flow. Additional information is contained in the original extended abstract.
Heat conduction in simple networks: The effect of interchain coupling Zonghua Liu1,2
Li, Baowen
, and are attracting increasing attention in recent years from different fields such as biology, social sci- ence with the number of added bonds 3,4 . The whole electric resistance of a network can be figured out found that both the normal and anomalous heat conduction can be described by an effective phonon theory
TOPAZ - a finite element heat conduction code for analyzing 2-D solids
Shapiro, A.B.
1984-03-01
TOPAZ is a two-dimensional implicit finite element computer code for heat conduction analysis. This report provides a user's manual for TOPAZ and a description of the numerical algorithms used. Sample problems with analytical solutions are presented. TOPAZ has been implemented on the CRAY and VAX computers.
INSTABILITIES ASSOCIATED WITH HEAT CONDUCTION IN THE SOLAR WIND AND THEIR CONSEQUENCES
D. W. Forslund
1970-01-01
Associated with the large heat conduction in the solar wind is a skewing of the ion and electron distribution functions. It is shown that this collisional skewing of the electron distribution function can linearly excite collisionless ion-acoustic, electrostatic ion cyclotron, magnetoacoustic, and ion cyclotron waves in the steady-state solar wind even though the net equilibrium current parallel to B is
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…
Enhancement and reduction of one-dimensional heat conduction with correlated mass disorder
NASA Astrophysics Data System (ADS)
Ong, Zhun-Yong; Zhang, Gang
2014-10-01
Short-range order in strongly disordered structures plays an important role in their heat conduction property. Using numerical and analytical methods, we show that short-range spatial correlation (with a correlation length of ?m) in the mass distribution of the one-dimensional (1D) alloylike random binary lattice leads to a dramatic enhancement of the high-frequency phonon transmittance but also increases the low-frequency phonon opacity. High-frequency semiextended states are formed while low-frequency modes become more localized. This results in ballistic heat conduction at finite lengths but also paradoxically higher thermal resistance that scales as ?{?m} in the L ?? limit. We identify an emergent crossover length (Lc) below which the onset of thermal transparency appears. The crossover length is linearly dependent on but is two orders of magnitude larger than ?m. Our results suggest that the phonon transmittance spectrum and heat conduction in a disordered 1D lattice can be controlled via statistical clustering of the constituent component atoms into domains. They also imply that the detection of ballistic heat conduction in disordered 1D structures may be a signature of the intrinsic mass correlation at a much smaller length scale.
Coupled Conduction, Convection, Radiation Heat Transfer with Simultaneous Mass Transfer in Ice Rinks
O. Bellache; M. Ouzzane; N. Galanis
2005-01-01
This article presents numerical predictions of velocity, temperature, and absolute humidity distributions in an indoor ice rink with ventilation and heating. The computational fluid dynamics (CFD) simulation includes the effects of radiation between all inside surfaces of the building envelope, turbulent mixed convection, and vapor diffusion, as well as conduction through the walls and condensation on the ice. The net
Kumar K. Tamma; Sudhir B. Railkar
1988-01-01
This paper describes new and recent advances in the development of a hybrid transfinite element computational methodology for applicability to conduction\\/convection\\/radiation heat transfer problems. The transfinite element methodology, while retaining the modeling versatility of contemporary finite element formulations, is based on application of transform techniques in conjunction with classical Galerkin schemes and is a hybrid approach. The purpose of this
An analytical solution to the one-dimensional heat conduction-convection equation in soil
Technology Transfer Automated Retrieval System (TEKTRAN)
Heat transfer in soil occurs by conduction and convection. Infiltrating water affects soil temperature distributions, and measuring soil temperature distributions below infiltrating water can provide a signal for the flux of water. In earlier work a sine wave function (hereinafter referred to as the...
A note on stability in dual-phase-lag heat conduction
Ramón Quintanilla; Reinhard Racke
2006-01-01
In this note we compare two different mathematical hyperbolic models in dual-phase-lag heat conduction proposed by Tzou, and we ask for the parameter regions where stability can be expected. It is demonstrated that the parameter regions for the two lag-parameters ?q and ?? are different for the two models. That is, for certain parameters, in one model stability is expected
Spatial statistics models for stochastic inverse problems in heat conduction Jingbo Wanga
Zabaras, Nicholas J.
Spatial statistics models for stochastic inverse problems in heat conduction Jingbo Wanga due to the ill-posed nature of such problems. However, there is a rich statistical information) are computed in probabilistic spaces. A Bayesian statistical inference approach is presented here
Heat transfer in a gray tube with forced convection, internal radiation and axial wall conduction
NASA Technical Reports Server (NTRS)
Chung, B. T. F.; Thompson, J. E.
1983-01-01
A method of successive approximations is employed to solve the problem of heat transfer to a transparent gas flowing through a radiating-conducting tube with turbulent forced convection between the tube wall and the gas, and with energy generation in the wall. Emphasis is given to the effect of emissivity of the wall to the tube and gas temperature profiles.
Optimal modified method for a fractional-diffusion inverse heat conduction problem
Zhi Qian
2010-01-01
We consider the determination of the boundary temperature from one measured transient data temperature at some interior point of a one-dimensional semi-infinite conductor. Mathematically, it can be formulated as a fractional-diffusion inverse heat conduction problem where data are given at x = l and we want to determine a solution for 0 < x < l. This problem arises in
Stuart A. Henrys; Susan Ellis; Christopher Uruski
2003-01-01
Bottom simulating reflectors (BSRs) represent the base of a gas hydrate zone underlain by widespread free gas. The extent of BSRs (>40,000 km2) has been mapped on the continental slope of the Hikurangi margin using industry and research seismic data. A conductive model was used to calculate heat flow from the depth of the BSR to the surface. A regional
Conduction-dominated heat transport of the annual temperature signal in soil
Jason E. Smerdon; Henry N. Pollack; John W. Enz; Matthew J. Lewis
2003-01-01
(1) Conductive heat transport of temperature signals into the subsurface is a central assumption of ground surface temperature (GST) reconstructions derived from present- day temperatures in deep boreholes. Here we test this assumption and its implications for annual relationships between GST and surface air temperature (SAT) by analyzing two decades of shallow soil temperature (0.01-11.7 m) and SAT time series
Performance evaluation of a distributed algorithm for an inverse heat conduction problem
Lai, Choi-Hong
, subject to cutting, is vital in order to optimise the life time of the cutting tool and to guaranteePerformance evaluation of a distributed algorithm for an inverse heat conduction problem C for such problems becomes very important [10, 8]. One industrial problem, amongst many others, is the cutting
Application of the boundary element method to inverse heat conduction problems
D. Lesnic; L. Elliott; D. B. Ingham
1996-01-01
The solution of the one-dimensional, linear, inverse, unsteady heat conduction problem (IHCP) in a slab geometry is analysed. The initial temperature is known, together with a condition on an accessible part of the boundary of the body under investigation. Additional temperature measurements in time are taken with a sensor positioned at an arbitrary location within the solid material, and it
Soliton mechanism of the uranium nitride microdynamics and heat conductivity at high temperatures
Semenov, V. A.; Dubovsky, O. A., E-mail: dubov@ippe.ru; Orlov, A. V. [State Scientific Center of the Russian Federation Leipunsky Institute for Physics and Power Engineering (Russian Federation)
2011-12-15
The microdynamics of soliton waves and localized modes of nonlinear acoustic and optical oscillations in uranium nitride has been investigated. It is shown that, upon heating, the energies of solitons in the gap between the optical and acoustic phonon bands increase, while the energies of local modes decrease. The experimentally observed quasi-resonance features, which are shifted in the gap with a change in temperature, can be manifestations of the revealed soliton waves and local modes. The microdynamics of uranium nitride heat conductivity with the stochastic generation of the observed solitons and local modes at remote energy absorption have been investigated. The temperature dependence of the heat conductivity coefficient has been determined from the temperature gradient and energy flux within the standard approach (which is to be generalized).
Remediation of NAPL below the water table by steam-induced heat conduction
NASA Astrophysics Data System (ADS)
Gudbjerg, J.; Sonnenborg, T. O.; Jensen, K. H.
2004-08-01
Previous experimental studies have shown that NAPL will be removed when it is contacted by steam. However, in full-scale operations, steam may not contact the NAPL directly and this is the situation addressed in this study. A two-dimensional intermediate scale sand box experiment was performed where an organic contaminant was emplaced below the water table at the interface between a coarse and a fine sand layer. Steam was injected above the water table and after an initial heating period the contaminant was recovered at the outlet. The experiment was successfully modeled using the numerical code T2VOC and the dominant removal mechanism was identified to be heat conduction induced boiling of the separate phase contaminant. Subsequent numerical modeling showed that this mechanism was insensitive to the porous medium properties and that it could be evaluated by considering only one-dimensional heat conduction.
Effect of heat treatment time on microstructure and electrical conductivity in LATP glass ceramics
Sonigra, Dhiren, E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in; Soman, Swati, E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in; Kulkarni, Ajit R., E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in [Dept. of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai-400076 (India)
2014-04-24
Glass-ceramic is prepared by heat treatment of melt quenched 14Li{sub 2}O?9Al{sub 2}O{sub 3}?38TiO{sub 2}?39P{sub 2}O{sub 5} glass in the vicinity of crystallization temperature. Growth of ceramic phase is controlled by tuning heat treatment time at fixed temperature. Ceramic phase was identified to be LiTi{sub 2}(PO{sub 4}){sub 3} from X Ray Diffraction analysis. Microstructural evolution of this phase with hold time was observed under high resolution Scanning Electron Microscope. DC conductivity is observed to increase by 4-5 orders of magnitude in this glass-ceramic compared to parent glass. However, formation of pores and cracks with very large heat treatment time seem to hinder further increase of conductivity.
Guajardo-Cuéllar, Alejandro; Go, David B; Sen, Mihir
2010-03-14
Equilibrium molecular dynamics combined with the Green-Kubo formula can be used to calculate the thermal conductivity of materials such as germanium and carbon. The foundation of this calculation is extracting the heat current from the results and implementing it into the Green-Kubo formula. This work considers all formulations from the literature that calculate the heat current for the Tersoff potential, the interatomic potential most applicable to semiconductor materials. The formulations for the heat current are described, and results for germanium and carbon are presented. The formulations are compared with respect to how well they capture the physics of the Tersoff potential and how well the calculated value of the thermal conductivity reflects the experimentally measured value. PMID:20232951
A molecular dynamics study on heat conduction characteristics in DPPC lipid bilayer
NASA Astrophysics Data System (ADS)
Nakano, Takeo; Kikugawa, Gota; Ohara, Taku
2010-10-01
In this paper, nonequilibrium molecular dynamics simulations were performed on a single component 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine lipid bilayer in order to investigate the thermal conductivity and its anisotropy. To evaluate the thermal conductivity, we applied a constant heat flux to the lipid bilayer along and across the membrane with ambient water. The contribution of molecular interaction to the heat conduction was also evaluated. Along the bilayer plane, there is little transfer of thermal energy by the interaction between lipid molecules as compared with the interaction between water molecules. Across the bilayer plane, the local thermal conductivity depends on the constituents (i.e., water, head group, and tail group of lipid molecule) that occupy the domain. Although the intramolecular transfer of thermal energy in the tail groups of lipid molecules works efficiently to promote high local thermal conductivity in this region, the highest thermal resistance appears at the center of lipid bilayer where acyl chains of lipid molecules face each other due to a loss of covalent-bond and low number density. The overall thermal conductivities of the lipid bilayer in the directions parallel and perpendicular to the lipid membrane have been compared, and it was found that the thermal conductivity normal to the membrane is higher than that along the membrane, but it is still smaller than that of bulk water.
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
Armstrong, Jeff; Bresme, Fernando
2014-06-28
The coupling of mass and heat fluxes is responsible for the Soret effect in fluid mixtures containing particles of dissimilar mass and/or size. We investigate using equilibrium and non-equilibrium molecular dynamics simulations the relevance of these coupling effects in determining the thermal transport in fluids consisting of binary mixtures where the individual components feature significant mass, 1?:?8, or size, 1?:?3, asymmetries. We quantify the thermal transport by using both boundary driven molecular dynamics simulations (NEMD) and the equilibrium Green-Kubo (GK) approach and investigate the impact of different heat flux definitions, relevant in kinetic theory and experiments, in the quantification of the thermal conductivity. We find that the thermal conductivities obtained from the different definitions agree within numerical accuracy, suggesting that the Soret coefficient does not lead to significant changes in the thermal conduction, even for the large asymmetries considered here, which lead to significant Soret coefficients (?10(-2) K(-1)). The asymmetry in size and mass introduces large differences in the specific enthalpy of the individual components that must be carefully considered to compute accurate thermal conductivities using the GK approach. Neglecting the enthalpic contributions, results in large overestimations of the thermal conductivity, typically between 20% and 50%. Further, we quantify the time dependent behavior of the internal energy and mass flux correlation functions and propose a microscopic mechanism for the heat transport in these asymmetric mixtures. PMID:24818599
Naya, Daniel E; Spangenberg, Lucía; Naya, Hugo; Bozinovic, Francisco
2013-09-22
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. PMID:23902915
NASA Astrophysics Data System (ADS)
Kshirsagar, Jagdeep M.; Shrivastava, Ramakant
2015-03-01
Nanofluids, the fluid suspensions of nonmaterials, have shown many interesting properties and the unique features offer unprecedented potential for many applications. Research on nanofluids has progressed rapidly since its enhanced thermal conductivity was first noted, about a decade ago, though much debate and inconsistency have been reported. Insufficient understanding of the formulation, mechanism of nanofluids further limits their applications [1-34]. Inconsistent data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers [35-43] have noted an enhancement in the critical heat flux during nanofluid boiling. Some researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux augmentation. In the review, the future developments of these technologies are discussed. In order to be able to put the nanofluid heat transfer technologies into practice, fundamental of these studies are greatly needed to comprehend the physical mechanisms.
A Review on the Finite Element Methods for Heat Conduction in Functionally Graded Materials
NASA Astrophysics Data System (ADS)
Sharma, R.; Jadon, V. K.; Singh, B.
2015-01-01
The review presented in this paper focuses mainly on the application of finite element methods for investigating the effect of heat transfer, variation of temperature and other parameters in the functionally graded materials. Different methods have been investigated for thermal conduction in functionally graded materials. The use of FEM for steady state heat transfer has been addressed in this work. The authors have also discussed the utilization of FEM based shear deformation theories and FEM in combination with other methods for the problems involving complexity of the shape and geometry of functionally graded materials. Finite element methods proved to be effective for the solution of heat transfer problem in functionally graded materials. These methods can be used for steady state heat transfer and as well as for transient state.
Experimental and Theoretical Study of Heat Conduction for Air up to 5000 K
NASA Technical Reports Server (NTRS)
Peng, Tzy-Cheng; Ahtye, Warren F.
1961-01-01
The theoretical value of the integral of thermal conductivity is compared with the experimental values from shock-tube measurements. The particular case considered is the one-dimensional nonsteady flow of heat through air at constant pressure. This approach has been previously described in NASA TR R-27. experiment was uncertain because of the large scatter in the experimental data. In this paper, an attempt is made to improve the correlation by use of a more refined calculation of the integral of thermal conductivity, and by use of improved experimental techniques and instrumentation. As a result of these changes, a much closer correlation is shown between the experimental and theoretical heat-flux potentials. This indicates that the predicted values of the coefficient of thermal conductivity for high-temperature air may be suitably accurate for many engineering needs, up to the limits of the test (4600 K).
Fourier heat conduction as a phenomenon described within the scope of the second law
NASA Astrophysics Data System (ADS)
Jesudason, Christopher G.
2014-12-01
The historical development of the Carnot cycle necessitated the construction of isothermal and adiabatic pathways within the cycle that were also mechanically "reversible" which lead eventually to the Kelvin-Clausius development of the entropy function S where for any reversible closed path C, ?C dS = 0 based on an infinite number of concatenated Carnot engines that approximated the said path and where for each engine ?Q1/T1+?Q2/T2 = 0 where the Q's and T's are the heat absorption increments and temperature respectively with the subscripts indicating the isothermal paths (1;2) where for the Carnot engine, the heat absorption is for the diathermal (isothermal) paths of the cycle only. Since 'heat' has been defined as that form of energy that is transferred as a result of a temperature difference and a corollary of the Clausius statement of the Second law is that it is impossible for heat to be transferred from a cold to a hot reservoir with no other effect on the environment, these statements suggested that the local mode of transfer of 'heat' in the isothermal segments of the pathway does imply a Fourier heat conduction mechanism (to conform to the definition of 'heat') albeit of a "reversible" kind, but on the other hand, the Fourier mechanism is apparently irreversible, leading to an increase in entropy of the combined reservoirs at either end of the material involved in the conveyance of the heat energy. These and several other considerations lead Benofy and Quay (BQ) to postulate the Fourier heat conduction phenomenon to be an ancillary principle in thermodynamics, with this principle being strictly local in nature, where the global Second law statements could not be applied to this local process. Here we present equations that model heat conduction as a thermodynamically reversible but mechanically irreversible process where due to the belief in mechanical time reversible symmetry, thermodynamical reversibility has been unfortunately linked to mechanical reversibility, that has discouraged such an association. The modeling is based on an application of a "recoverable transition", defined and developed earlier on ideas derived from thermal desorption of particles from a surface where the Fourier heat conduction process is approximated as a series of such desorption processes. We recall that the original Carnot engine required both adiabatic and isothermal steps to complete the zero entropy cycle, and this construct lead to the consequent deduction that any Second law statement that refers to heat-work conversion processes are only globally relevant. Here, on the other hand, we examine Fourier heat conduction from MD simulation and model this process as a zero-entropy forward scattering process relative to each of the atoms in the lattice chain being treated as a system where the Carnot cycle can be applied individually. The equations developed predicts the "work" done to be equal to the energy transfer rate. The MD simulations conducted shows excellent agreement with the theory. Such views and results as these, if developed to a successful conclusion could imply that the Carnot cycle be viewed as describing a local process of energy-work conversion and that irreversible local processes might be brought within the scope of this cycle, implying a unified treatment of thermodynamically (i) irreversible, (ii) reversible, (iii) isothermal and (iv) adiabatic processes.
Miyagi, Lowell; Kanitpanyacharoen, Waruntorn; Raju, Selva Vennila; Kaercher, Pamela; Knight, Jason; MacDowell, Alastair; Wenk, Hans-Rudolf; Williams, Quentin; Alarcon, Eloisa Zepeda
2013-02-01
To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a Liermann-type diamond anvil cell with radial diffraction geometry (rDAC) was redesigned and developed for synchrotron X-ray diffraction experiments at beamline 12.2.2 of the Advanced Light Source. The rDAC, equipped with graphite heating arrays, allows simultaneous resistive and laser heating while the material is subjected to high pressure. The goals are both to extend the temperature range of external (resistive) heating and to produce environments with lower temperature gradients in a simultaneously resistive- and laser-heated rDAC. Three different geomaterials were used as pilot samples to calibrate and optimize conditions for combined resistive and laser heating. For example, in Run#1, FeO was loaded in a boron-mica gasket and compressed to 11 GPa then gradually resistively heated to 1007 K (1073 K at the diamond side). The laser heating was further applied to FeO to raise temperature to 2273 K. In Run#2, Fe-Ni alloy was compressed to 18 GPa and resistively heated to 1785 K (1973 K at the diamond side). The combined resistive and laser heating was successfully performed again on (Mg0.9Fe0.1)O in Run#3. In this instance, the sample was loaded in a boron-kapton gasket, compressed to 29 GPa, resistive-heated up to 1007 K (1073 K at the diamond side), and further simultaneously laser-heated to achieve a temperature in excess of 2273 K at the sample position. Diffraction patterns obtained from the experiments were deconvoluted using the Rietveld method and quantified for lattice preferred orientation of each material under extreme conditions and during phase transformation. PMID:23464262
NASA Astrophysics Data System (ADS)
Miyagi, Lowell; Kanitpanyacharoen, Waruntorn; Raju, Selva Vennila; Kaercher, Pamela; Knight, Jason; MacDowell, Alastair; Wenk, Hans-Rudolf; Williams, Quentin; Alarcon, Eloisa Zepeda
2013-02-01
To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a Liermann-type diamond anvil cell with radial diffraction geometry (rDAC) was redesigned and developed for synchrotron X-ray diffraction experiments at beamline 12.2.2 of the Advanced Light Source. The rDAC, equipped with graphite heating arrays, allows simultaneous resistive and laser heating while the material is subjected to high pressure. The goals are both to extend the temperature range of external (resistive) heating and to produce environments with lower temperature gradients in a simultaneously resistive- and laser-heated rDAC. Three different geomaterials were used as pilot samples to calibrate and optimize conditions for combined resistive and laser heating. For example, in Run#1, FeO was loaded in a boron-mica gasket and compressed to 11 GPa then gradually resistively heated to 1007 K (1073 K at the diamond side). The laser heating was further applied to FeO to raise temperature to 2273 K. In Run#2, Fe-Ni alloy was compressed to 18 GPa and resistively heated to 1785 K (1973 K at the diamond side). The combined resistive and laser heating was successfully performed again on (Mg0.9Fe0.1)O in Run#3. In this instance, the sample was loaded in a boron-kapton gasket, compressed to 29 GPa, resistive-heated up to 1007 K (1073 K at the diamond side), and further simultaneously laser-heated to achieve a temperature in excess of 2273 K at the sample position. Diffraction patterns obtained from the experiments were deconvoluted using the Rietveld method and quantified for lattice preferred orientation of each material under extreme conditions and during phase transformation.
Heat Conduction Analysis in a Tissue Phantom Calculated by FDTD and HCE Method
Endoh, Nobuyuki; Tsuchiya, Takenobu; Saito, Yoshikazu; Ishizeki, Takahiro [Department of Electronics, Electronics and Information Engineering, Kanagawa University, High-Tech Research Center, Kanagawa University, Yokohama (Japan)
2005-03-28
In order to study hyperthermia in tissue, it is important to predict accurately the heat distribution. This paper describes a preliminary study of the comparison between simulation and experiment for heat conduction in a simple tissue phantom. Since it is well known that the heat increase in tissue depends on the sound intensity and the absorption coefficient, the sound pressure distribution is calculated using a Finite Difference Time Domain (FDTD) method. The thermal diffusion profile in tissue generated by the energy of the sound pulse is also simulated using the Heat Conduction Equation (HCE) method. The calculation area is 100 x 40 [mm]. The simple tissue phantom is made of agar, water and graphite. The phantom whose attenuation coefficient is 1.1 dB/cm/MHz is placed in a temperature controlled water bath. This is kept at 37 deg. [C] while sound pulses of 1 MHz are emitted over 10 minutes. Temperatures at six points on the acoustic axis are measured in the phantom. The calculation and experiment results are compared to confirm the accuracy of the proposed method. As a result, the calculation results show the validity of the combined FDTD-HCE method for thermal conduction analysis.
Khine, Soe Minn; Houra, Tomoya; Tagawa, Masato
2013-04-01
In temperature measurement of non-isothermal fluid flows by a contact-type temperature sensor, heat conduction along the sensor body can cause significant measurement error which is called "heat-conduction error." The conventional formula for estimating the heat-conduction error was derived under the condition that the fluid temperature to be measured is uniform. Thus, if we apply the conventional formula to a thermal field with temperature gradient, the heat-conduction error will be underestimated. In the present study, we have newly introduced a universal physical model of a temperature-measurement system to estimate accurately the heat-conduction error even if a temperature gradient exists in non-isothermal fluid flows. Accordingly, we have been able to successfully derive a widely applicable estimation and/or evaluation formula of the heat-conduction error. Then, we have verified experimentally the effectiveness of the proposed formula using the two non-isothermal fields-a wake flow formed behind a heated cylinder and a candle flame-whose fluid-dynamical characteristics should be quite different. As a result, it is confirmed that the proposed formula can represent accurately the experimental behaviors of the heat-conduction error which cannot be explained appropriately by the existing formula. In addition, we have analyzed theoretically the effects of the heat-conduction error on the fluctuating temperature measurement of a non-isothermal unsteady fluid flow to derive the frequency response of the temperature sensor to be used. The analysis result shows that the heat-conduction error in temperature-fluctuation measurement appears only in a low-frequency range. Therefore, if the power-spectrum distribution of temperature fluctuations to be measured is sufficiently away from the low-frequency range, the heat-conduction error has virtually no effect on the temperature-fluctuation measurements even by the temperature sensor accompanying the heat-conduction error in the mean-temperature measurements. PMID:23635222
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.
NSDL National Science Digital Library
Integrated Teaching and Learning Program,
Students make a simple conductivity tester using a battery and light bulb. They learn the difference between conductors and insulators of electrical energy as they test a variety of materials for their ability to conduct electricity.
Garthwaite, Alaina J; Steudle, Ernst; Colmer, Timothy D
2006-01-01
The adventitious roots of Hordeum marinum grown in stagnant deoxygenated solution contain a barrier to radial O2 loss (ROL) in basal zones, whereas roots of plants grown in aerated solution do not. The present experiments assessed whether induction of the barrier to ROL influences root hydraulic conductivity (Lpr). Wheat (Triticum aestivum) was also studied since, like H. marinum, this species forms aerenchyma in stagnant conditions, but does not form a barrier to ROL. Plants were grown in either aerated or stagnant, deoxygenated nutrient solution for 21-28 d. Root-sleeving O2 electrodes were used to assess patterns of ROL along adventitious roots, and a root-pressure probe and a pressure chamber to measure Lpr for individual adventitious roots and whole root systems, respectively. Lpr, measured under a hydrostatic pressure gradient, was 1.8-fold higher for individual roots, and 5.6-fold higher for whole roots systems, in T. aestivum than H. marinum. However, there was no difference in Lpr between the two species when measured under an osmotic driving force, when water moved from cell to cell rather than apoplastically. Root-zone O2 treatments during growth had no effect on Lpr for either species (measured in aerobic solution). It is concluded that induction of the barrier to ROL in H. marinum did not significantly affect the hydraulic conductivity of either individual adventitious roots or of the whole root system. PMID:16410258
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.
M. Costea; M. Feidt
1998-01-01
This study aims to assess for a Stirling engine the influence of the overall heat transfer coefficient variation on the optimum state and on the optimum distribution of the heat transfer surface conductance or area among the machine heat exchangers. The analysis is based on a Stirling machine optimization method, previously elaborated, which is now applied to a cycle with
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.
Oceanic heat flow and thermal conductivity of sediments with lithology and depth
NASA Astrophysics Data System (ADS)
Engberts, Cynthia J.
The present study is three fold. The first part analyzes oceanic heat flow data for "pogo" (closely-spaced) measurements, to test if for regions where convection is the dominant mode of heat transfer, the measured heat flow values are more scattered and skewed to lower values, and for areas where conduction prevails, the values are normally (Gaussian) distributed and show less scatter, like previous studies suggest. Various descriptive statistics, test of the normality of the distribution, and the evolution of the scatter are used to this end and interpreted, for sites grouped according to geographic proximity. The second part uses many more data compared to previous studies from the Ocean Drilling Program (ODP), Legs 101-128, to determine how porosity decreases with depth, to about 1 km below the seafloor, in different sedimentary environments. The goal is to determine which trend, either linear or exponential, best fits these data over this depth range. Some spatial trends of rate of porosity decrease are examined, and an attempt to predict porosity at depth is made for various tectonic settings. Finally, the third part uses data from the Ocean Drilling Program, Legs 101-129, to determine how thermal conductivity increases with depth, to about 1 km below the seafloor, in different sedimentary environments. Again, the goal is to determine which trend, either linear or exponential, best fits these data over this depth range, and how it compares to the results of the geometric mean model of thermal conductivity as a function of porosity. The depth at which thermal conductivity starts to steadily increase is examined, and an attempt is made to predict thermal conductivity at depth for various tectonic settings. Finally, some spatial trends of rate of thermal conductivity increase in terms of lithologies and tectonic settings are observed as well.
Numerical solution of transient heat conduction in a cylindrical section during quenching
El-Genk, M.S.; Glebov, A. [Univ. of New Mexico, Albuquerque, NM (United States)
1995-11-01
A two-dimensional numerical solution is developed for transient heat conduction in a copper test section (20 mm thick and 50.8 mm in diameter) during quenching of its downward facing curved surface (surface radius 148 mm) in saturated water. The solution used the measured temperatures in the test section near the surface ({approximately}0.5 mm) to derive the transient pool boiling curves at different locations on the surface. The study investigated the effects of lateral conduction near the surface on local heat flux and local surface temperature in the different pool boiling regimes. The solution employed a fully implicit, alternating direction, control volume method to ensure numerical stability and reduce the storage and computation time. A parametric analysis is performed to assess the effect of the computation grid size and the value of the convergence coefficient on the accuracy of calculations as well as the computation time on a 50-MHz, 486 PC.
CTS-type variable conductance heat pipes for SEP FM/PPU
NASA Technical Reports Server (NTRS)
Antoniuk, D.; Luedke, E. E.
1978-01-01
The development effort for, and the fabrication and testing of, six CTS-type variable conductance heat pipes is described. The heat pipes are constructed of stainless steel, use methanol as a working fluid, and a nitrogen/helium mixture as the control gas. The wicking structure consists of interior wall grooves, a metal-felt diametral slab wick, and two wire-mesh arteries. The heat pipes are used to cool two Functional Model/Power Processing Units in a Solar Electric Propulsion prototype BIMOD thruster subsystem assembly. The Power Processing Units convert the electric power from a spacecraft solar array system to the voltages required to operate the electric thrusters which are part of the BIMOD assembly.
J. R. Creighton
1993-01-01
Radiative heat transfer across the gap between two coaxial cylinders can be approximated using an equivalent thermal conductivity that is a cubic polynomial in the temperatures T(sub 1) and T(sub 2) of the two surfaces (T(sub 1) greater than T(sub 2)). It is convenient to write the polynomial in terms of the average temperature, yielding T(sub avg(exp 3)) multiplied by
Two exact solutions of the DPL non-Fourier heat conduction equation with special conditions
Youtong Zhang; Changsong Zheng; Yongfeng Liu; Liang Shao; Chenhua Gou
2009-01-01
This paper presents two exact explicit solutions for the three dimensional dual-phase lag (DLP) heat conduction equation,\\u000a during the derivation of which the method of trial and error and the authors’ previous experiences are utilized. To the authors’\\u000a knowledge, most solutions of 2D or 3D DPL models available in the literature are obtained by numerical methods, and there\\u000a are few
NASA Astrophysics Data System (ADS)
Pourshaghaghy, A.; Kowsary, F.; Behbahaninia, A.
2007-01-01
In this study, four different versions of the variable metric method (VMM) are investigated in solving standard one-dimensional inverse heat conduction problems in order to evaluate their efficiency and accuracy. These versions include Davidon Fletcher Powell (DFP), Broydon Fletcher Goldfarb Shanno (BFGS), Symmetric Rank-one (SR1), and Biggs formula of the VMM. These investigations are carried out using temperature data obtained from numerical simulations.
Three-Dimensional Conduction Heat Transfer Model for Laser Cladding Process
S. Kumar; S. Roy; C. P. Paul; A. K. Nath
2008-01-01
Cladding is the process of depositing a superior built-up layer on a substrate by fusion. In the present study a three-dimensional conduction heat transfer model is developed and solved using the finite-volume method in a nonorthogonal grid system for a blown-powder laser cladding process. Comparisons with experimental data for deposition of copper powder on SS316 stainless steel show that the
Shock tube determination of the heat conductivity of non-ionized and partially ionized argon
A. Hirschberg
1981-01-01
A procedure to determine the heat conductivity of a monatomic gas, from measurements of the structure of the unsteady thermal boundary layer at the end-wall of a shock tube, is proposed. In the non-ionized case the structure of the boundary layer determined by means of laser schlieren measurements appears to be self-similar. Improved analysis of the schlieren data and accurate
N. S. Mera; L. Elliott; D. B. Ingham; D. Lesnic
2001-01-01
In this paper, the iterative algorithm proposed by V.A. Kozlov and V.G. Maz'ya [Leningrad Math. J. 5 (1990) 1207–1228] is numerically implemented using the boundary element method (BEM) in order to solve the backward heat conduction problem (BHCP). The convergence and the stability of the numerical method are investigated and a stopping criterion is proposed. The numerical results obtained confirm
Mixed Convection with Conduction and Surface Radiation from a Vertical Channel with Discrete Heating
NASA Astrophysics Data System (ADS)
Londhe, S. D.; Rao, C. G.
2013-10-01
A numerical investigation into fluid flow and heat transfer for the geometry of a vertical parallel plate channel subjected to conjugate mixed convection with radiation is attempted here. The channel considered has three identical flush-mounted discrete heat sources in its left wall, while the right wall that does not contain any heat source acts as a sink. Air, assumed to be a radiatively non-participating and having constant thermophysical properties subject to the Boussinesq approximation, is the cooling agent. The heat generated in the left wall gets conducted along it and is later dissipated by mixed convection and radiation. The governing equations, considered in their full strength sans the boundary layer approximations, are converted into vorticity-stream function form and are then normalized. These equations along with pertinent boundary conditions are solved through finite volume method coupled with Gauss-Seidel iterative technique. The effects of modified Richardson number, surface emissivity, thermal conductivity and aspect ratio on local temperature distribution along the channel, maximum channel temperature and relative contributions of mixed convection and radiation have been thoroughly studied. The prominence of radiation in the present problem has been highlighted.
Tree-shaped fluid flow and heat storage in a conducting solid
NASA Astrophysics Data System (ADS)
Combelles, L.; Lorente, S.; Anderson, R.; Bejan, A.
2012-01-01
This paper documents the time-dependent thermal interaction between a fluid stream configured as a plane tree of varying complexity embedded in a conducting solid with finite volume and insulated boundaries. The time scales of the convection-conduction phenomenon are identified. Two-dimensional and three-dimensional configurations are simulated numerically. The number of length scales of the tree architecture varies from one to four. The results show that the heat transfer density increases, and the time of approach to equilibrium decreases as the complexity of the tree designs increases. These results are then formulated in the classical notation of energy storage by sensible heating, which shows that the effective number of heat transfer units increases as the complexity of the tree design increases. The complexity of heat transfer designs in many applications is constrained by first cost and operating cost considerations. This work provides a fundamental basis for objective evaluation of cost and performance tradeoffs in thermal design of energy systems with complexity as an unconstrained parameter that can be actively varied over a broad range to determine the optimum system design.
Tree-Shaped Fluid Flow and Heat Storage in a Conducting Solid
Combelles, L.; Lorente, S.; Anderson, R.; Bejan, A.
2012-01-01
This paper documents the time-dependent thermal interaction between a fluid stream configured as a plane tree of varying complexity embedded in a conducting solid with finite volume and insulated boundaries. The time scales of the convection-conduction phenomenon are identified. Two-dimensional and three-dimensional configurations are simulated numerically. The number of length scales of the tree architecture varies from one to four. The results show that the heat transfer density increases, and the time of approach to equilibrium decreases as the complexity of the tree designs increases. These results are then formulated in the classical notation of energy storage by sensible heating, which shows that the effective number of heat transfer units increases as the complexity of the tree design increases. The complexity of heat transfer designs in many applications is constrained by first cost and operating cost considerations. This work provides a fundamental basis for objective evaluation of cost and performance tradeoffs in thermal design of energy systems with complexity as an unconstrained parameter that can be actively varied over a broad range to determine the optimum system design.
The effect of heat conduction on the realization of the primary standard for sound pressure
NASA Astrophysics Data System (ADS)
Jackett, Richard J.
2014-10-01
Pressure reciprocity calibration of microphones provides the basis for primary measurement standards for sound pressure in air. At low frequencies, reciprocity calibration requires that a heat conduction correction be employed to account for energy transfer to and from the bounding surfaces of the close-coupled microphone arrangement. The standard governing reciprocity calibration, IEC 61094-2?:?2009, provides two models for the heat conduction correction: the Low Frequency Solution, and the Broadband Solution. Analysis has revealed significant and unexplained differences in behaviour between the models at very low frequencies, leading to inconsistency in calibration results, which has been quantified. Additionally, both heat conduction solutions given in IEC 61094-2 are simplifications that strictly apply only above their respective lower limiting frequencies. An international comparison on microphone calibration is currently underway that includes measurements below the lower limiting frequencies of the models. In this paper, the origin and nature of the Broadband simplifications have been identified, and estimates of the error given. A flaw in the Broadband theory is identified and its effect quantified. Simplification error for the Low Frequency solution is evaluated, and the full spectrum solution is given. This paper urges caution in the application of the models at low frequency and provides data useful for assessing the contribution to the measurement uncertainty.
A direct approach to finding unknown boundary conditions in steady heat conduction
NASA Technical Reports Server (NTRS)
Martin, Thomas J.; Dulikravich, George S.
1993-01-01
The capability of the boundary element method (BEM) in determining thermal boundary conditions on surfaces of a conducting solid where such quantities are unknown was demonstrated. The method uses a non-iterative direct approach in solving what is usually called the inverse heat conduction problem (IHCP). Given any over-specified thermal boundary conditions such as a combination of temperature and heat flux on a surface where such data is readily available, the algorithm computes the temperature field within the object and any unknown thermal boundary conditions on surfaces where thermal boundary values are unavailable. A two-dimensional, steady-state BEM program was developed and was tested on several simple geometries where the analytic solution was known. Results obtained with the BEM were in excellent agreement with the analytic values. The algorithm is highly flexible in treating complex geometries, mixed thermal boundary conditions, and temperature-dependent material properties and is presently being extended to three-dimensional and unsteady heat conduction problems. The accuracy and reliability of this technique was very good but tended to deteriorate when the known surface conditions were only slightly over-specified and far from the inaccessible surface.
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.
Zhijie Xu
2012-07-01
We introduce a new method of solution for the convective heat transfer under forced laminar flow that is confined by two parallel plates with a distance of 2a or by a circular tube with a radius of a. The advection-conduction equation is first mapped onto the boundary. The original problem of solving the unknown field T(x,r,t) is reduced to seek the solutions of T at the boundary (r = a or r = 0, r is the distance from the centerline shown in Fig. 1), i.e., the boundary functions T{sub a}(x,t) {triple_bond} T(x,r=a,t) and/or T{sub 0}(x,t) {triple_bond} T(x,r=0,t). In this manner, the original problem is significantly simplified by reducing the problem dimensionality from 3 to 2. The unknown field T(x,r,t) can be eventually solved in terms of these boundary functions. The method is applied to the convective heat transfer with uniform wall temperature boundary condition and with heat exchange between flowing fluids and its surroundings that is relevant to the geothermal applications. Analytical solutions are presented and validated for the steady-state problem using the proposed method.
Xu, Zhijie
2012-07-01
We introduce a method of solution for the convective heat transfer under forced laminar flow that is confined by two parallel plates with a distance of 2a or by a circular tube with a radius of a. The advection-conduction equation is first mapped onto the boundary. The original problem of solving the unknown field is reduced to seek the solutions of T at the boundary (r=a or r=0, r is the distance from the centerline shown in Fig. 1), i.e. the boundary functions and/or . In this manner, the original problem is significantly simplified by reducing the problem dimensionality from 3 to 2. The unknown field can be eventually solved in terms of these boundary functions. The method is applied to the convective heat transfer with uniform wall temperature boundary condition and with heat exchange between flowing fluids and its surroundings that is relevant to the geothermal applications. Analytical solutions are presented and validated for the steady state problem using the proposed method.
M. B. Diop
2001-01-01
This paper presents both experimental and theoretical works concerning evaluation of the thermal conductivity, thermal diffusivity and heat capacity of wood composites. Moreover, the aim of this study is to show that the transient plane source technique originally used for measuring thermal properties of isotropic materials can be spread worthy of heat capacity, thermal conductivity and thermal diffusivity measurements of
Alok Sutradhar; Glaucio H. Paulino; L. J. Gray
2002-01-01
The Green's function for three-dimensional transient heat conduction (diffusion equation) for functionally graded materials (FGMs) is derived. The thermal conductivity and heat capacitance both vary exponentially in one coordinate. In the process of solving this diffusion problem numerically, a Laplace transform (LT) approach is used to eliminate the dependence on time. The fundamental solution in Laplace space is derived and
Heat, chloride, and specific conductance as ground water tracers near streams
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.
R. Karvinen
1976-01-01
The problem of heat exchange between a flat plate and a fluid is considered. An analysis applicable to laminar and turbulent flow is presented in order to determine the distribution of surface temperature along a plate undergoing simultaneous convective heat transfer, radiative transfer with the environment, conduction in a plate and internal heat sources. Both steady and unsteady cases are
C.-K. Chen; J. W. Cleaver; F.-S. Lien
1985-01-01
In the present consideration of the transfer of heat by fins to a surrounding fluid by forced convection and radiation, the heat transfer coefficient along the fin is not prescribed, but solved in advance on the basis of the boundary layer convection flow. The modified local heat transfer coefficient is accordingly determined by a highly coupled interaction among fin conduction,
Heat conduction in disordered harmonic lattices with energy-conserving noise
NASA Astrophysics Data System (ADS)
Dhar, Abhishek; Venkateshan, K.; Lebowitz, J. L.
2011-02-01
We study heat conduction in a harmonic crystal whose bulk dynamics is supplemented by random reversals (flips) of the velocity of each particle at a rate ?. The system is maintained in a nonequilibrium stationary state (NESS) by contacts with white-noise Langevin reservoirs at different temperatures. We show that the one-body and pair correlations in this system are the same (after an appropriate mapping of parameters) as those obtained for a model with self-consistent reservoirs. This is true both for the case of equal and random (quenched) masses. While the heat conductivity in the NESS of the ordered system is known explicitly, much less is known about the random mass case. Here we investigate the random system with velocity flips. We improve the bounds on the Green-Kubo conductivity obtained by Bernardin [J. Stat. Phys.JSTPBS0022-471510.1007/s10955-008-9620-1 133, 417 (2008)]. The conductivity of the one-dimensional system is then studied both numerically and analytically. This sheds some light on the effect of noise on the transport properties of systems with localized states caused by quenched disorder.
NASA Technical Reports Server (NTRS)
2005-01-01
[figure removed for brevity, see original site]
The ejecta surrounding the crater (off image to the left) in this image has undergone significant erosion by the wind. The wind has stripped the surface features from the ejecta and has started to winnow away the ejecta blanket. Near the margin of the ejecta the wind is eroding along a radial pattern -- taking advantage of radial emplacement. Note the steep margin of the ejecta blanket. Most, if not all, of the fine ejecta material has been removed and the wind in now working on the more massive continuous ejecta blanket.
Image information: VIS instrument. Latitude 12.5, Longitude 197.4 East (162.6 West). 37 meter/pixel resolution.
Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.
NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
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.
A. Mohammadian Pourtalari; M. A. Jafarizadeh; M. Ghoranneviss
2011-11-23
Electron heat conduction is one of the ways that energy transports in laser heating of fusible target material. The aim of Inertial Confinement Fusion (ICF) is to show that the thermal conductivity is strongly dependent on temperature and the equation of electron heat conduction is a nonlinear equation. In this article, we solve the one-dimensional (1-D) nonlinear electron heat conduction equation with a self-similar method (SSM). This solution has been used to investigate the propagation of 1-D thermal wave from a deuterium-tritium (DT) plane source which occurs when a giant laser pulse impinges onto a DT solid target. It corresponds to the physical problem of rapid heating of a boundary layer of material in which the energy of laser pulse is released in a finite initial thickness.
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.
NASA Astrophysics Data System (ADS)
Lakhal, E. K.; Hasnaoui, M.; Bilgen, E.; Vasseur, P.
The natural convection heat transfer in inclined rectangular enclosures with perfectly conducting fins attached to the heated wall is numerically studied. The parameters governing this problem are the Rayleigh number (102<=Ra<=2×105), the aspect ratio of the enclosures (2.5<=A=H'/L'<=?), the dimensionless lengths of the partitions (0<=B=l'/L'<=1), the aspect ratio of micro-cavities (A<=C=h'/L'<=0.33), the inclination angle (0<=?<=60?) and the Prandtl number (Pr=0.72). The results indicate that the heat transfer through the cover is considerably affected by the presence of the fins. At low Rayleigh numbers, the heat transfer regime is dominated by conduction. When B 0.75 and C 0.33, the heat transfer through the cold wall decreases considerably. This trend is enhanced when the enclosure is inclined. Useful engineering correlations are derived for practical applications. Zusammenfassung In einer numerischen Studie wird der Wärmeübergang bei natürlicher Konvektion in geneigten, rechteckigen Behältern mit ideal leitenden Rippen an der beheizten Wand untersucht. Die das Problem beschreibenden Parameter sind: die Rayleigh-Zahl (102<=Ra<=2.105), das Seitenverhältnis des Behälters (2,5<=A =H'/L'<=?), die dimensionslose Rippenhöhe (0<=B =l'/L'<=1), das Seitenverhältnis der Teilkammern (A<=C=h'/L'<=0,33), der Neigungswinkel (0<=?<=60?) und die Prandtl-Zahl (Pr=0,72). Die Ergebnisse zeigen, daß der Wärmeübergang durch Anbringung von Rippen ganz wesentlich beeinflußt werden kann. Für B 0,75 und C 0,33 erniedrigt sich der Wärmestrom durch die Kaltwand erheblich, insbesondere bei geneigtem Behälter. Bei niedrigen Rayleigh-Zahlen erfolgt der Wärmetransport hauptsächlich durch Leitung. Für praktische Anwendungen werden leicht handhabbare Gebrauchsformeln angegeben.
Volman, Vladimir; Zhu, Yu; Raji, Abdul-Rahman O; Genorio, Bostjan; Lu, Wei; Xiang, Changsheng; Kittrell, Carter; Tour, James M
2014-01-01
Deicing heating layers are frequently used in covers of large radio-frequency (RF) equipment, such as radar, to remove ice that could damage the structures or make them unstable. Typically, the deicers are made using a metal framework and inorganic insulator; commercial resistive heating materials are often nontransparent to RF waves. The preparation of a sub-skin-depth thin film, whose thickness is very small relative to the RF skin (or penetration) depth, is the key to minimizing the RF absorption. The skin depth of typical metals is on the order of a micrometer at the gigahertz frequency range. As a result, it is very difficult for conventional conductive materials (such as metals) to form large-area sub-skin-depth films. In this report, we disclose a new deicing heating layer composite made using graphene nanoribbons (GNRs). We demonstrate that the GNR film is thin enough to permit RF transmission. This metal-free, ultralight, robust, and scalable graphene-based RF-transparent conductive coating could significantly reduce the size and cost of deicing coatings for RF equipment covers. This is important in many aviation and marine applications. This is a demonstration of the efficacy and applicability of GNRs to afford performances unattainable by conventional materials. PMID:24328320
Two exact solutions of the DPL non-Fourier heat conduction equation with special conditions
NASA Astrophysics Data System (ADS)
Zhang, Youtong; Zheng, Changsong; Liu, Yongfeng; Shao, Liang; Gou, Chenhua
2009-04-01
This paper presents two exact explicit solutions for the three dimensional dual-phase lag (DLP) heat conduction equation, during the derivation of which the method of trial and error and the authors’ previous experiences are utilized. To the authors’ knowledge, most solutions of 2D or 3D DPL models available in the literature are obtained by numerical methods, and there are few exact solutions up to now. The exact solutions in this paper can be used as benchmarks to validate numerical solutions and to develop numerical schemes, grid generation methods and so forth. In addition, they are of theoretical significance since they correspond to physically possible situations. The main goal of this paper is to obtain some possible exact explicit solutions of the dual-phase lag heat conduction equation as the benchmark solutions for computational heat transfer, rather than specific solutions for some given initial and boundary conditions. Therefore, the initial and boundary conditions are indeterminate before derivation and can be deduced from the solutions afterwards. Actually, all solutions given in this paper can be easily proven by substituting them into the governing equation.
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.
ORMDIN: a finite element program for two-dimensional nonlinear inverse heat conduction analysis
Bass, B.R.; Drake, J.B.; Ott, L.J.
1980-12-01
The calculation of the surface temperature and surface heat flux from measured temperature transients at one or more interior points of a body is identified in the literature as the inverse heat conduction problem. Heretofore, analytical and computational methods of treating this problem have been limited to one-dimensional nonlinear or two-dimensional linear material models. This report presents, to the authors' knowledge, the first inverse solution technique applicable to the two-dimensional nonlinear model with temperature-dependent thermophysical properties. This technique, representing an extension of the one-dimensional formulation previously developed by one of the authors, utilizes a finite element heat conduction model and a generalization of Beck's one-dimensional nonlinear estimation procedure. A digital computer program ORMDIN (Oak Ridge Multi-Dimensional INverse) is developed from the formulation and applied to the cross section of a composite cylinder with temperature-dependent material properties. Results are presented to demonstrate that the inverse formulation is capable of successfully treating experimental data. An important feature of the method is that small time steps are permitted while avoiding severe oscillations or numerical instabilities due to experimental errors in measured data.
GRABER: The Duct Tape of Space and JIMO Heat Conducting Foam
NASA Technical Reports Server (NTRS)
Gamble, Eleanor A.
2004-01-01
Crack formation in the space shuttle's heat shield during flight poses a major safety concern to everyone on board. Cracking weakens the structure of the shield and lessens the protection it offers against the high temperatures and forces encountered during re-entry. Astronauts need a way to mend these cracks while in space. This is GRABER s function; it can be spackled into the cracks by an astronaut. The material then hardens, or cures, due to being in a vacuum and the heat encountered when it faces the sun. A great deal of work and testing is necessary to create a material that will be workable in a vacuum over a wide range of temperatures, will cure without cracking, will adhere to the sides of the crack, and that can withstand the extreme temperatures of re-entry. A Brookfield PVS Rheometer is being used to characterize GRABER's viscosity at various temperatures and stirring rates. Various compositions of GRABER are being heat treated in a vacuum to determine probably curing times in space. The microstructures of cured samples of each composition are being examined using both optical and electron microscopy. Jupiter s Icy Moon Orbiter (JIMO) will be lifting off sometime around 2013. JIMO will have more power than its predecessor, Galileo, allowing it to change orbits to circle three of Jupiter s moons. Both of the engine types being considered require large heat dissipation systems. These systems will be comprised of heat conductive tubing and plates with a liquid flowing through them. In order to maximize the speed of heat transfer between the tubes and the panels, the in-between areas will be filled with heat conductive silicon carbide foam. Two different foam systems are being considered for this foam. Currently, experimentation is underway with adding Sic, carbon, and carbon fibers to a two part fuel retardant foam. The foam is them pyrolized and its mass and dimensional changes are measured. The structure of the foam will be examined using optical and electron microscopy as well. Work is also planned with a foam system developed by an Italian team.
Cooling performance of a nanofluid flow in a heat sink microchannel with axial conduction effect
NASA Astrophysics Data System (ADS)
Izadi, M.; Shahmardan, M. M.; Norouzi, M.; Rashidi, A. M.; Behzadmehr, A.
2014-09-01
In this work, the forced convection of a nanofluid flow in a microscale duct has been investigated numerically. The governing equations have been solved utilizing the finite volume method. Two different conjugated domains for both flow field and substrate have been considered in order to solve the hydrodynamic and thermal fields. The results of the present study are compared to those of analytical and experimental ones, and a good agreement has been observed. The effects of Reynolds number, thermal conductivity and thickness of substrate on the thermal and hydrodynamic indexes have been studied. In general, considering the wall affected the thermal parameter while it had no impact on the hydrodynamics behavior. The results show that the effect of nanoparticle volume fraction on the increasing of normalized local heat transfer coefficient is more efficient in thick walls. For higher Reynolds number, the effect of nanoparticle inclusion on axial distribution of heat flux at solid-fluid interface declines. Also, less end losses and further uniformity of axial heat flux lead to an increase in the local normalized heat transfer coefficient.
Cooling performance of a nanofluid flow in a heat sink microchannel with axial conduction effect
NASA Astrophysics Data System (ADS)
Izadi, M.; Shahmardan, M. M.; Norouzi, M.; Rashidi, A. M.; Behzadmehr, A.
2014-12-01
In this work, the forced convection of a nanofluid flow in a microscale duct has been investigated numerically. The governing equations have been solved utilizing the finite volume method. Two different conjugated domains for both flow field and substrate have been considered in order to solve the hydrodynamic and thermal fields. The results of the present study are compared to those of analytical and experimental ones, and a good agreement has been observed. The effects of Reynolds number, thermal conductivity and thickness of substrate on the thermal and hydrodynamic indexes have been studied. In general, considering the wall affected the thermal parameter while it had no impact on the hydrodynamics behavior. The results show that the effect of nanoparticle volume fraction on the increasing of normalized local heat transfer coefficient is more efficient in thick walls. For higher Reynolds number, the effect of nanoparticle inclusion on axial distribution of heat flux at solid-fluid interface declines. Also, less end losses and further uniformity of axial heat flux lead to an increase in the local normalized heat transfer coefficient.
Thermally conductive cementitious grouts for geothermal heat pumps. Progress report FY 1998
Allan, M.L.; Philippacopoulos, A.J.
1998-11-01
Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98. The developed thermally conductive grout consists of cement, water, a particular grade of silica sand, superplasticizer and a small amount of bentonite. While the primary function of the grout is to facilitate heat transfer between the U-loop and surrounding formation, it is also essential that the grout act as an effective borehole sealant. Two types of permeability (hydraulic conductivity) tests was conducted to evaluate the sealing performance of the cement-sand grout. Additional properties of the proposed grout that were investigated include bleeding, shrinkage, bond strength, freeze-thaw durability, compressive, flexural and tensile strengths, elastic modulus, Poisson`s ratio and ultrasonic pulse velocity.
The gravitational heat conduction and the hierarchical structure in solar interior
NASA Astrophysics Data System (ADS)
Yahui, Zheng; Jiulin, Du
2014-03-01
With the assumption of local Tsallis equilibrium, the newly defined gravitational temperature is calculated in the solar interior, whose distribution curve can be divided into three parts: the solar core region, the radiation region and the convection region, in excellent agreement with the solar hierarchical structure. By generalizing Fourier's law, one new mechanism of heat conduction, based on the gradient of the gravitational temperature, is introduced into the astrophysical system. This mechanism is related to the self-gravity of such self-gravitating system whose characteristic scale is large enough. It perhaps plays an important role in the astrophysical system which, in the solar interior, leads to the heat accumulation at the bottom of the convection layer and then motivates the convection motion.
Wave transmission, phonon localization and heat conduction of 1D Frenkel-Kontorova chain
Peiqing Tong; Baowen Li; Bambi Hu
1999-01-20
We study the transmission coefficient of a plane wave through a 1D finite quasi-periodic system -- the Frenkel-Kontorova (FK) model -- embedding in an infinite uniform harmonic chain. By varying the mass of atoms in the infinite uniform chain, we obtain the transmission coefficients for {\\it all} eigenfrequencies. The phonon localization of the incommensurated FK chain is also studied in terms of the transmission coefficients and the Thouless exponents. Moreover, the heat conduction of Rubin-Greer-like model for FK chain at low temperature is calculated. It is found that the stationary heat flux $J(N)\\sim N^{\\alpha}$, and $\\alpha$ depends on the strength of the external potential.
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.
A Beale-Kato-Majda Criterion for Three Dimensional Compressible Viscous Heat-Conductive Flows
NASA Astrophysics Data System (ADS)
Sun, Yongzhong; Wang, Chao; Zhang, Zhifei
2011-08-01
We prove a blow-up criterion in terms of the upper bound of ( ?, ? -1, ?) for a strong solution to three dimensional compressible viscous heat-conductive flows. The main ingredient of the proof is an a priori estimate for a quantity independently introduced in Haspot (Regularity of weak solutions of the compressible isentropic Navier-Stokes equation, arXiv:1001.1581, 2010) and Sun et al. (J Math Pure Appl 95:36-47, 2011), whose divergence can be viewed as the effective viscous flux.
Heat conductivity from molecular chaos hypothesis in locally confined billiard systems.
Gilbert, Thomas; Lefevere, Raphaël
2008-11-14
We study the transport properties of a large class of locally confined Hamiltonian systems, in which neighboring particles interact through hard-core elastic collisions. When these collisions become rare and the systems large, we derive a Boltzmann-like equation for the evolution of the probability densities. We solve this equation in the linear regime and compute the heat conductivity from a Green-Kubo formula. The validity of our approach is demonstrated by comparing our predictions with the results of numerical simulations performed on a new class of high-dimensional defocusing chaotic billiards. PMID:19113325
Subsurface Temperature, Moisture, Thermal Conductivity and Heat Flux, Barrow, Area A, B, C, D
Cable, William; Romanovsky, Vladimir
2014-03-31
Subsurface temperature data are being collected along a transect from the center of the polygon through the trough (and to the center of the adjacent polygon for Area D). Each transect has five 1.5m vertical array thermistor probes with 16 thermistors each. This dataset also includes soil pits that have been instrumented for temperature, water content, thermal conductivity, and heat flux at the permafrost table. Area C has a shallow borehole of 2.5 meters depth is instrumented in the center of the polygon.
Subsurface Temperature, Moisture, Thermal Conductivity and Heat Flux, Barrow, Area A, B, C, D
Cable, William; Romanovsky, Vladimir
Subsurface temperature data are being collected along a transect from the center of the polygon through the trough (and to the center of the adjacent polygon for Area D). Each transect has five 1.5m vertical array thermistor probes with 16 thermistors each. This dataset also includes soil pits that have been instrumented for temperature, water content, thermal conductivity, and heat flux at the permafrost table. Area C has a shallow borehole of 2.5 meters depth is instrumented in the center of the polygon.
Analytical evaluation of thermal conductance and heat capacities of one-dimensional material systems
Saygi, Salih [Department of Physics, Gaziosmanpasa University, Tokat, 60200 Turkey (Turkey)] [Department of Physics, Gaziosmanpasa University, Tokat, 60200 Turkey (Turkey)
2014-02-15
We theoretically predict some thermal properties versus temperature dependence of one dimensional (1D) material nanowire systems. A known method is used to provide an efficient and reliable analytical procedure for wide temperature range. Predicted formulas are expressed in terms of Bloch-Grüneisen functions and Debye functions. Computing results has proved that the expressions are in excellent agreement with the results reported in the literature even if it is in very low dimension limits of nanowire systems. Therefore the calculation method is a fully predictive approach to calculate thermal conductivity and heat capacities of nanowire material systems.
Effects of friction and heat conduction on sound propagation in ducts
NASA Technical Reports Server (NTRS)
Huerre, P.; Karamcheti, K.
1975-01-01
A theoretical formulation of the propagation of sound in a viscous and heat conducting medium is presented. The problem is reduced to the determination of two scalar potentials related to pressure and entropy fluctuations respectively, and a vector potential related to vorticity fluctuations. The particular case of a two-dimensional duct of constant width is thoroughly investigated in the low, high, and very high frequency ranges. It is shown that three distinct families of modes may propagate along the duct axis, namely, pressure, entropy, and vorticity dominated modes. Perturbation methods are used to study the variations of attenuation rates, phase velocities, and mode shapes, as a function of frequency and duct width.
NASA Astrophysics Data System (ADS)
Kwok, R. S.; Brown, S. E.
1990-02-01
A fully automated system which is capable of measuring specific heat and thermal conductivity simultaneously from liquid helium to room temperature is presented. Thermal conductivity is measured by a steady-state longitudinal heat flow technique, and specific heat by a thermal relaxation method. A numerical simulation of the one-dimensional heat flow equation is used to examine the basic operational principle. The method is tested using GE 214 fused quartz and AISI 304 stainless-steel rods, and the results compare favorably with values quoted in the literature.
Laser heating of an absorbing and conducting media applied to laser flash property measurements
Gritzo, L.A. [Sandia National Labs., Albuquerque, NM (United States); Anderson, E.E. [Texas Tech Univ., Lubbock, TX (United States). Dept. of Mechanical Engineering
1993-12-31
The laser flash technique is widely used for determining the thermal diffusivity of a sample. In this work, the temperature distribution throughout the sample is investigated, identifying localized, highly-heated regions near the front surface of the sample as a function of: (1) pulse duration, (2) incident beam uniformity, and (3) sample opacity. These high-temperature regions result in an increase in the uncertainty due to temperature-dependent properties, an increase in the heat loss from the sample, and an increased risk of sample damage. The temperature within a semi-transparent media is also investigated in order to establish a regime for which the media can reasonably be considered as opaque. This analysis illustrates that, for same total energy deposition, treatment of the incident energy as a continuous heat source, as opposed to an infinitesimal pulse of energy, results in a factor of 2 increase in the front surface temperature during heating. Also, for the same total energy deposition and approximate beam size, use of a Gaussian intensity distribution increases the front surface temperature during heating by more than a factor of 2 as compared to the use of a uniform temperature distribution. By analyzing the front surface temperature of an absorbing and conducting semi-transparent sample subjected to a Gaussian intensity distribution, it is concluded that the media can be treated as opaque, (i.e. the energy can be applied as a boundary condition) for {var_epsilon} = kd > 50, where k is the extinction coefficient and d is the beam diameter. For materials with a sufficiently small absorption coefficient and thermal diffusivity, a closed-form solution suitable for design use is presented for the front-surface temperature at a location coincident with the beam centerline.
NASA Technical Reports Server (NTRS)
Tamma, Kumar K.; Railkar, Sudhir B.
1988-01-01
This paper describes new and recent advances in the development of a hybrid transfinite element computational methodology for applicability to conduction/convection/radiation heat transfer problems. The transfinite element methodology, while retaining the modeling versatility of contemporary finite element formulations, is based on application of transform techniques in conjunction with classical Galerkin schemes and is a hybrid approach. The purpose of this paper is to provide a viable hybrid computational methodology for applicability to general transient thermal analysis. Highlights and features of the methodology are described and developed via generalized formulations and applications to several test problems. The proposed transfinite element methodology successfully provides a viable computational approach and numerical test problems validate the proposed developments for conduction/convection/radiation thermal analysis.
NASA Technical Reports Server (NTRS)
Perkins, R. A.; Cieszkiewicz, M. T.
1991-01-01
Experimental measurements of thermal conductivity and thermal diffusivity obtained with a transient hot-wire apparatus are reported for three mixtures of nitrogen, oxygen, and argon. Values of the specific heat, Cp, are calculated from these measured values and the density calculated with an equation of state. The measurements were made at temperatures between 65 and 303 K with pressures between 0.1 and 70 MPa. The data cover the vapor, liquid, and supercritical gas phases for the three mixtures. The total reported points are 1066 for the air mixture (78.11 percent nitrogen, 20.97 percent oxygen, and 0.92 percent argon), 1058 for the 50 percent nitrogen, 50 percent oxygen mixture, and 864 for the 25 percent nitrogen, 75 oxygen mixture. Empirical thermal conductivity correlations are provided for the three mixtures.
NASA Astrophysics Data System (ADS)
Eldrup, M.; Singh, B. N.
1998-10-01
The electrical conductivity of three different types of copper alloys, viz. CuNiBe, CuCrZr and Cu-Al 2O 3 as well as of pure copper are reported. The alloys have undergone different pre-irradiation heat treatments and have been fission-neutron irradiated up to 0.3 dpa. In some cases post-irradiation annealing has been carried out. The results are discussed with reference to equivalent Transmission Electron Microscopy results on the microstructure of the materials. The CuNiBe has the lowest conductivity (?55% of that of pure Cu), and Cu-Al 2O 3 the highest (75-90% of pure Cu).
Effects of preheating and highly heat-conductive brick on coke quality
Fukuda, K.; Arima, T. [Nippon Steel Corp., Chiba (Japan). Process Technology, Research Labs.
1995-12-31
In replacing the coke ovens available currently, the introduction of a combined technique of a preheated coal charging method (preheating temperature:175 C) and the use of highly heat-conductive brick is under examination for raising the productivity of coke ovens. With such background, a study of the effects of this combined technique on the coke quality, especially the coke size was conducted. The experimental results revealed that the primary size of coke produced by the combined technique is noticeably larger than that of the coke made from wet coal and after five revolutions of drum (equivalent to mechanical impact given at a time of dropping from coke oven chamber to wharf), the coke size reduces even compared with an ordinary coke. This may be due to the fact that the coke produced by the combined technique includes a lot of fissures inside the coke lump.
Heat transfer in rotating serpentine passages with trips skewed to the flow
B. V. Johnson; J. H. Wagner; G. D. Steuber; F. C. Yeh
1994-01-01
Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips, skewed at 45 deg to the flow direction, were machined on the leading and trailing surfaces of the radial
NASA Astrophysics Data System (ADS)
Nath, G.; Vishwakarma, J. P.
2014-05-01
The propagation of a spherical (or cylindrical) shock wave in a non-ideal gas with heat conduction and radiation heat-flux, in the presence of a spacially decreasing azimuthal magnetic field, driven out by a moving piston is investigated. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient ?R are assumed to vary with temperature and density. The gas is assumed to have infinite electrical conductivity and to obey a simplified van der Waals equation of state. The shock wave moves with variable velocity and the total energy of the wave is non-constant. Similarity solutions are obtained for the flow-field behind the shock and the effects of variation of the heat transfer parameters, the parameter of the non-idealness of the gas, both, decreases the compressibility of the gas and hence there is a decrease in the shock strength. Further, it is investigated that with an increase in the parameters of radiative and conductive heat transfer the tendency of formation of maxima in the distributions of heat flux, density and isothermal speed of sound decreases. The pressure and density vanish at the inner surface (piston) and hence a vacuum is form at the center of symmetry. The shock waves in conducting non-ideal gas with conductive and radiative heat fluxes can be important for description of shocks in supernova explosions, in the study of central part of star burst galaxies, nuclear explosion, chemical detonation, rupture of a pressurized vessels, in the analysis of data from exploding wire experiments, and cylindrically symmetric hypersonic flow problems associated with meteors or reentry vehicles, etc. The findings of the present works provided a clear picture of whether and how the non-idealness parameter, conductive and radiative heat transfer parameters and the magnetic field affect the flow behind the shock front.
NASA Technical Reports Server (NTRS)
Zhu, Dongming; Miller, Robert A.
1999-01-01
Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings (TBCs) under near-realistic temperature and thermal gradients that may he encountered in advanced engine systems. Thermal conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures. A significant thermal conductivity increase was observed during the laser simulated engine heat flux tests. For a 0.25 mm thick ZrO2-8%Y2O3 coating system, the overall thermal conductivity increased from the initial value of 1.0 W/m-K to 1. 15 W/m-K, 1. 19 W/m-K and 1.5 W/m-K after 30 hour testing at surface temperatures of 990C, 1100C, and 1320C. respectively. Hardness and modulus gradients across a 1.5 mm thick TBC system were also determined as a function of laser testing time using the laser sintering/creep and micro-indentation techniques. The coating Knoop hardness values increased from the initial hardness value of 4 GPa to 5 GPa near the ceramic/bond coat interface, and to 7.5 GPa at the ceramic coating surface after 120 hour testing. The ceramic surface modulus increased from an initial value of about 70 GPa to a final value of 125 GPa. The increase in thermal conductivity and the evolution of significant hardness and modulus gradients in the TBC systems are attributed to sintering-induced micro-porosity gradients under the laser-imposed high thermal gradient conditions. The test techniques provide a viable means for obtaining coating data for use in design, development, stress modeling, and life prediction for various thermal barrier coating applications.
NASA Astrophysics Data System (ADS)
Vishwakarma, V.; Jain, A.
2014-12-01
The separator is a critical, multi-functional component of a Li-ion cell that plays a key role in performance and safety during energy conversion and storage processes. Heat flow through the separator is important for minimizing cell temperature and avoiding thermal runaway. Despite the critical nature of thermal conduction through the separator, very little research has been reported on understanding and measuring the thermal conductivity and heat capacity of the separator. This paper presents first-ever measurements of thermal conductivity and heat capacity of the separator material. These measurements are based on thermal response to an imposed DC heating within a time period during which an assumption of a thermally semi-infinite domain is valid. Experimental data are in excellent agreement with the analytical model. Comparison between the two results in measurement of the in-plane thermal conductivity and heat capacity of the separator. Results indicate very low thermal conductivity of the separator. Measurements at an elevated temperature indicate that thermal conductivity and heat capacity do not change much with increasing temperature. Experimental measurements of previously unavailable thermal properties reported here may facilitate a better fundamental understanding of thermal transport in a Li-ion cell, and enhanced safety due to more accurate thermal prediction.
NASA Technical Reports Server (NTRS)
Lang, Christapher G.; Bey, Kim S. (Technical Monitor)
2002-01-01
This research investigates residual-based a posteriori error estimates for finite element approximations of heat conduction in single-layer and multi-layered materials. The finite element approximation, based upon hierarchical modelling combined with p-version finite elements, is described with specific application to a two-dimensional, steady state, heat-conduction problem. Element error indicators are determined by solving an element equation for the error with the element residual as a source, and a global error estimate in the energy norm is computed by collecting the element contributions. Numerical results of the performance of the error estimate are presented by comparisons to the actual error. Two methods are discussed and compared for approximating the element boundary flux. The equilibrated flux method provides more accurate results for estimating the error than the average flux method. The error estimation is applied to multi-layered materials with a modification to the equilibrated flux method to approximate the discontinuous flux along a boundary at the material interfaces. A directional error indicator is developed which distinguishes between the hierarchical modeling error and the finite element error. Numerical results are presented for single-layered materials which show that the directional indicators accurately determine which contribution to the total error dominates.
NASA Astrophysics Data System (ADS)
Gan, Yanbiao; Xu, Aiguo; Zhang, Guangcai; Zhang, Ping; Li, Yingjun
2012-02-01
We investigate the effects of heat conduction, viscosity, and Prandtl number on thermal liquid-vapor separation via a lattice Boltzmann model for van der Waals fluids. The set of Minkowski measures on the density field enables to divide exactly the stages of the spinodal decomposition (SD) and domain growth. The duration tSD of the SD stage decreases with increasing the heat conductivity ?T but increases with increasing the viscosity ?. The two relations can be fitted by tSD=a+b/?T and tSD=c+d?+(e?)3, respectively, where a, b, c, d and e are fitting parameters. For fixed Prandtl number Pr, when ? is less than a critical value ?c, tSD shows an inverse power-law relationship with ?. However, when ?>?c, tSD for Pr>1 shows qualitatively different behavior. From the evolution of the Péclet number Pe, the separation procedure can also be divided into two stages. During the first stage, the convection effects become more dominant with time over those of the diffusivity, while they are reverse in the second stage.
Advanced development of the boundary element method for steady-state heat conduction
NASA Technical Reports Server (NTRS)
Dargush, G. F.; Banerjee, Prasanta K.
1989-01-01
Considerable progress has been made in recent years toward advancing the state-of-the-art in solid mechanics boundary element technology. In the present work, much of this new technology is applied in the development of a general-purpose boundary element method (BEM) for steady-state heat conduction. In particular, the BEM implementation involves the use of higher-order conforming elements, self-adaptive integration and multi-region capability. Two- and three-dimensional, as well as axisymmetric analysis, are incorporated within a unified framework. In addition, techniques are introduced for the calculation of boundary flux, and for the inclusion of thermal resistance across interfaces. As a final extension, an efficient formulation is developed for the analysis of solid three-dimensional bodies with embedded holes. For this last class of problems, the new BEM formulation is particularly attractive, since use of the alternatives (i.e. finite element or finite difference methods) is not practical. A number of detailed examples illustrate the suitability and robustness of the present approach for steady-state heat conduction.
NASA Astrophysics Data System (ADS)
Vermeersch, Bjorn; Mohammed, Amr M. S.; Pernot, Gilles; Koh, Yee Rui; Shakouri, Ali
2015-02-01
Nearly all experimental observations of quasiballistic heat flow are interpreted using Fourier theory with modified thermal conductivity. Detailed Boltzmann transport equation (BTE) analysis, however, reveals that the quasi-ballistic motion of thermal energy in semiconductor alloys is no longer Brownian but instead exhibits Lévy dynamics with fractal dimension ? <2 . Here, we present a framework that enables full three-dimensional experimental analysis by retaining all essential physics of the quasiballistic BTE dynamics phenomenologically. A stochastic process with just two fitting parameters describes the transition from pure Lévy superdiffusion as short length and time scales to regular Fourier diffusion. The model provides accurate fits to time domain thermoreflectance raw experimental data over the full modulation frequency range without requiring any "effective" thermal parameters and without any a priori knowledge of microscopic phonon scattering mechanisms. Identified ? values for InGaAs and SiGe match ab initio BTE predictions within a few percent. Our results provide experimental evidence of fractal Lévy heat conduction in semiconductor alloys. The formalism additionally indicates that the transient temperature inside the material differs significantly from Fourier theory and can lead to improved thermal characterization of nanoscale devices and material interfaces.
The specific heat capacity and thermal conductivity of normal liquid /sup 3/He
Mitchell, R.; Eastop, A.D.; Faraj, E.; Hook, J.R.
1986-07-01
By observing the diffusion of a heat pulse along a 10-cm column of normal liquid /sup 3/He with the aid of two vibrating wire thermometers, it has been possible to measure the heat capacity C and thermal conductivity K of the liquid in the temperature range from T /sub c/ to 10 mK and at pressures of 0.21, 4.39, 9.97, 20.01, and 29.32 bar. By using a Pt NMR thermometer, an LCMN thermometer, and a /sup 3/He melting curve thermometer calibrated using the melting curve given by Greywall in 1983, a temperature scale has been established and (1) it has been shown that this melting curve is consistent in the temperature range 5-22 mK with the Korringa law for the Pt thermometer with a Korringa constant of 29.8 +/- 0.2 sec mK, (2) departures have been observed from the Curie-Weiss law for LCMN at low temperatures, and (3) values of the superfluid transition temperature have been obtained that are about 4% lower than the Helsinki values. The measured heat capacities agree well with those of Greywall, but values of KT are higher than those of Greywall and show more temperature dependence below 10mK. The implications for the present results of the very different melting curve given by Greywall in 1985 are discussed in an Appendix.
Insulation with low thermal conductivity
G. L. Copeland; D. L. McElroy; R. S. Graves; F. J. Weaver; H. A. Fine; T. W. Tong
1983-01-01
In an effort to identify candidate materials, the thermal conductivity (lambda) was measured from 300 to 335 K for unevacuated and evacuated systems of angstrom and micron-size particles. A radial heat flow apparatus provided lambda-values for unevacuated systems as a function of density, particle size, and composition. For nominally 100 A diameter particles in air the lambda at 300 K
Song, Y.; Yao, Y.; Na, W.
2006-01-01
In this paper the composition and thermal property of soil are discussed. The main factors that impact the soil thermal conductivity and several commonly-used pipe materials are studied. A model of heat exchanger with horizontal pipes of ground...
NASA Astrophysics Data System (ADS)
Al-Odat, Mohammed Qassim; Al-Nimr, Moh'd Ahmad
2003-11-01
Three-dimensional simulation was used to study the thermal stability behavior of the anisotropic thick superconducting wire/cylinder under the effect of a dual-phase-lag heat conduction (DPL) model. The mathematical model developed considers the two lagging times for the heat flux vector and for the temperature gradient, the finite duration and finite length of the external heat disturbances and anisotropic thermal conductivity of the wire. It was found that the DPL model predicts a wider stable region as compared to the predictions of the parabolic and the wave heat conduction models. Additionally, it was shown that the thermal conductivity ratio is one of the most important factors affecting the thermal stability of the wire.
Schramm, Wolfgang; Yang, Deshan; Wood, Bradford J; Rattay, Frank; Haemmerich, Dieter
2007-01-01
Both radiofrequency (RF) and microwave (MW) ablation devices are clinically used for tumor ablation. Several studies report less dependence on vascular mediated cooling of MW compared to RF ablation. We created computer models of a cooled RF needle electrode, and a dipole MW antenna to determine differences in tissue heat transfer. We created Finite Element computer models of a RF electrode (Cooled needle, 17 gauge), and a MW antenna (Dipole, 13 gauge). We simulated RF ablation for 12 min with power controlled to keep maximum tissue temperature at 100 ºC, and MW ablation for 6 min with 75 W of power applied. For both models we considered change in electric and thermal tissue properties as well as perfusion depending on tissue temperature. We determined tissue temperature profile at the end of the ablation procedure and calculated effect of perfusion on both RF and MW ablation. Maximum tissue temperature was 100 ºC for RF ablation, and 177 ºC for MW ablation. Lesion shape was ellipsoid for RF, and tear-drop shaped for MW ablation. MW ablation is less affected by tissue perfusion mainly due to the shorter ablation time and higher tissue temperature, but not due to MW providing deeper heating than RF. Both MW and RF applicators only produce significant direct heating within mm of the applicator, with most of the ablation zone created by thermal conduction. Both RF and MW applicators only directly heat tissue in close proximity of the applicators. MW ablation allows for higher tissue temperatures than RF since MW propagation is not limited by tissue desiccation and charring. Higher temperatures coupled with lower treatment times result in reduced effects of perfusion on MW ablation. PMID:19662127
Clifford K. Ho; N. D. Francis
1996-01-01
The thermodynamic environment surrounding a heat-generating waste package can play an important role in the performance of a high-level radioactive waste repository. However, rigorous models of heat transfer are often compromised in near-drift simulations. Convection and radiation are usually ignored or approximated so that simpler conduction models can be used. This paper presents numerical simulations that explicitly model conduction, convection,
Heat capacity, enthalpy of mixing, and thermal conductivity of Hg(1-x)Cd(x)Te pseudobinary melts
NASA Technical Reports Server (NTRS)
Su, Ching-Hua
1986-01-01
Heat capacity and enthalpy of mixing of Hg(1-x)Cd(x)Te pseudobinary melts were calculated assuming an associated solution model for the liquid phase. The thermal conductivity of the pseudobinary melts for x = 0, 0.05, 0.1, and 0.2 was then calculated from the heat capacity values and the experimental values of thermal diffusivity and density for these melts. The thermal conductivity for the pseudobinary solid solution is also discussed.
Joaquín Zueco; O. Anwar Bég; L. M. López-Ochoa
2011-01-01
Network simulation method (NSM) is used to solve the laminar heat and mass transfer of an electrically-conducting, heat generating\\/absorbing fluid past a perforated horizontal surface in the presence of viscous and Joule heating problem. The governing partial differential equations are non-dimensionalized and transformed into a system of nonlinear ordinary differential similarity equations, in a single independent variable, eta. The resulting
Joaquín Zueco; O. Anwar Bég; L. M. López-Ochoa
2011-01-01
Network simulation method (NSM) is used to solve the laminar heat and mass transfer of an electrically-conducting, heat generating\\/absorbing\\u000a fluid past a perforated horizontal surface in the presence of viscous and Joule heating problem. The governing partial differential\\u000a equations are non-dimensionalized and transformed into a system of nonlinear ordinary differential similarity equations, in\\u000a a single independent variable, ?. The resulting
H. F. Nouanegue; A. Muftuoglu; E. Bilgen
2009-01-01
We study in this paper conjugate heat transfer by natural convection, conduction and radiation in an inclined square enclosure bounded by a solid wall with its outer boundary at constant temperature while the opposing active wall is with a constant heat flux. We solved two-dimensional coupled equations of conservation of mass, momentum and energy, with the Boussinesq approximation using finite
Bittagopal Mondal; Subhash C. Mishra
2007-01-01
This article deals with the use of the discrete ordinates method (DOM) to compute radiative information about an energy equation for a combined-mode heat transfer problem to be solved using the lattice Boltzmann method (LBM). For this study, transient conduction and radiation heat transfer in 1-D planar and 2-D rectangular geometries have been considered. To study the performance of the
Subhash C. Mishra; A. Lankadasu
2005-01-01
The lattice Boltzmann method (LBM) is used to solve the energy equation of a problem involving conduction and radiation heat transfer with and without heat generation. Both steady and transient situations are considered. To demonstrate that the two different kinds of methods can be coupled, the radiative information for the governing energy equation is computed using the discrete transfer method
R. C. Batra; M. Porfiri; D. Spinello
2004-01-01
SUMMARY We use two meshless local Petrov-Galerkin (MLPG) formulations to analyse heat conduction in a bimetallic circular disk. The continuity of the normal component of the heat flux at the interface between two materials is satisfied either by the method of Lagrange multipliers or by using a jump function. The convergence of the H 0 and H 1 error norms
John Townend
1997-01-01
Bottom-simulating reflectors (BSRs) represent the base of the stability field for gas hydrates in shallow oceanic sediments. A simple conductive model is used to calculate surface heat flow through the Hikurangi and southwest Fiordland continental margins of New Zealand, based on the depths of BSRs. The results indicate mean uncorrected heat flows through the two regions of 37 ± 8
A. G. Eliseev
1980-01-01
A numerical analysis of heat transfer between an air plasma and a semiinfinite body is presented; the plasma is formed in the wake of a shock wave that is reflected from the body. The radiative-conductive heat transfer process is described by an energy equation that is characterized by the nonlinear dependence of plasma properties on temperature and pressure and by
Zhijie Xu
2014-07-01
We present a new stochastic analysis for steady and transient one-dimensional heat conduction problem based on the homogenization approach. Thermal conductivity is assumed to be a random field K consisting of random variables of a total number N. Both steady and transient solutions T are expressed in terms of the homogenized solution (symbol) and its spatial derivatives (equation), where homogenized solution (symbol) is obtained by solving the homogenized equation with effective thermal conductivity. Both mean and variance of stochastic solutions can be obtained analytically for K field consisting of independent identically distributed (i.i.d) random variables. The mean and variance of T are shown to be dependent only on the mean and variance of these i.i.d variables, not the particular form of probability distribution function of i.i.d variables. Variance of temperature field T can be separated into two contributions: the ensemble contribution (through the homogenized temperature (symbol)); and the configurational contribution (through the random variable Ln(x)Ln(x)). The configurational contribution is shown to be proportional to the local gradient of (symbol). Large uncertainty of T field was found at locations with large gradient of (symbol) due to the significant configurational contributions at these locations. Numerical simulations were implemented based on a direct Monte Carlo method and good agreement is obtained between numerical Monte Carlo results and the proposed stochastic analysis.
LDEF (Flight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09
NASA Technical Reports Server (NTRS)
1990-01-01
LDEF (Flight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 EL-1994-00020 LDEF (Flight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 The flight photograph of the Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) was taken while the LDEF was attached to the Orbiter's RMS arm prior to berthing in the Orbiter's cargo bay. The white paint dots on the center clamp blocks of the experiment trays right flange and lower flange appear to be slightly discolored. The LDEF structure, top intercostal, has a dark brown discoloration adjacent to the black thermal panel. Aluminum particles from the degraded CVCHPE thermal blanket are also visible in this area. The Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) occupies a 6 inch deep LDEF peripheral experiment tray and consist of two series connected variable conductance heatpipes, a black chrome solar collector panel and a silvered TEFLON® radiator panel, a power source to support six thermistor-type temperature monitoring sensors and actuations of two valves. Fiberglass standoffs and internal insulation blankets thermally isolated the experiment from the experiment tray and the LDEF interior. The outside of the CVCHPE, except the collector and radiator panels, was covered with an aluminumized Kapton multilayer insulation (MLI) blanket with an outer layer of 0.076 mm thick Kapton. The two patches of thin film materials, part of an atomic oxygen experiment (see S1001) by NASA GSFC, were attached to the cover of the external thermal blanket with Kapton tape. The experiment was assembled and mounted in the experiment tray with non-magnetic stainless steel fasteners. The external CVCHPE materials have changed significantly. The Kapton on the thermal blanket aluminized Kapton cover appears to be completely eroded, except under Kel-F buttons used to secure the blanket, leaving only the very thin vapor deposited aluminum coating as a cover. Parts of the aluminum coating residue has moved to cover a portion of the black solar absorber panel and also areas of the trays upper and lower flanges. The shadow on the tray lower flange would indicate that the aluminum extends several inches out of the tray envelope. One of the two thin film atomic oxygen experiment patches is gone and the other does not appear to be securely attached. The layer of Kapton tape over the thin film strips appears to be eroded with only the adhesive remaining. The remaining atomic oxygen experiment materials have changed colors and most appear to be severely degraded. The silvered TEFLON® coating of the radiator panel appears diffuse with a light brown discoloration over most of the surface. The white, evenly spaced, discolorations along the vertical centerline and across the top of the panel appear to be above counter sunk flat head screws used to assemble the experiment. The black spots on the radiator panel appear to be impact craters where the impact penetrated the TEFLON® material and exposed the silver beneath to the atomic oxygen flux. Particles of the degraded thermal blanket material appear to be adhered to the surface of the radiator panel.
NASA Technical Reports Server (NTRS)
Cleveland, Paul E.; Buchko, Matthew T.; Stavely, Richard A.; Simpson, Alda (Technical Monitor)
2002-01-01
The Hubble Space Telescope (HST) is one of NASA s premier astronomical observatories. A unique design feature of the spacecraft is its capacity to be serviced and refurbished on-orbit. Repairs to the HST are made during events called Servicing Missions (SM). The SM consists of several phases that include: shuttle launch, ascent, rendezvous with HST, grapple, Extra Vehicular Activity (EVA) servicing, redeployment of the HST, shuttle entry and landing. The purpose of a SM is to upgrade the HST scientific capabilities and to repair or replace failed equipment. The benefit of the SM is to enhance the scientific capability of the HST and to extend its operational lifetime to a decade or more. Extra Vehicular Activity (EVA) days, the crew will replace the Wide Field Planetary Camera II (WFPCII) with the Wide Field Camera 3 (WFC3). The HST slot for these instruments is the "-V3 Radial Instrument" position. Servicing Mission 4 (SM-4) is currently scheduled for Spring 2005. During one of the five The WFC3 contains both Ultraviolet and Infrared detectors. Due to the differing thermal requirements for these items and their associated assemblies, the WFC3 contains several thermal subsystems within the instrument enclosure. One of these subsystems is the Variable Conductance Heat Pipe (VCHP) assembly. contains an integral constant conductance heat pipe (CCHP); a variable conductance heat pipe (VCHP); and a VCHP reservoir radiator (offset from the main WFC3 external radiator). The VCHP condenser utilizes the main WFC3 external radiator to reject its heat to space. The WFC3 VCHP assembly consists of the Optical Bench Cold Plate (OBCP), which The primary challenge for the VCHP assembly is to maintain the OBCP at -5 C +/- 2 C for various heat loads while subject to a 90-minute orbit cycling environment which ranges from 0 C to -143 C. Key components that provide active control include a 10 W heater system, the reservoir, and a proportional controller. This paper summarizes the overall thermal vacuum test program for the VCHP assembly. This includes performance during the 90-minute orbit cycling case, maximum capacity case, and cold system shut down case. The test was conducted in Building 7, Chamber #237 at the NASA/Goddard Space Flight Center. It lasted approximately fourteen days, from 5-28-02 to 6-10-02. Included in this paper is a comparison of the results with thermal model temperature predictions.
Hosseini Koupaie, E; Eskicioglu, C
2015-07-01
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. PMID:25863200
Passive amplification of the pyroelectric current in thin films on a heat-conducting substrate
Yablonskii, S. V., E-mail: yablonskii2005@yandex.r [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Soto-Bustamante, E. A., E-mail: esotobrasil2005@gmail.co [Universidad de Chile 1058 (Chile)
2010-11-15
We show both theoretically and experimentally that passive amplification of the pyroelectric current takes place when modulated radiation is recorded by a pyroelectric detector in some range of modulation frequencies. The amplification effect manifests itself in the fact that the current generated by a thin pyroelectric film lying on a massive heat-conducting substrate exceeds that in a freely suspended film. We use a ferroelectric 70:30 P(VDF-TrFE) copolymer, a crystalline guanidine pyroelectric, and a 70:30 composition of an achiral liquid-crystal polymer and its monomer PM6R14n-M6R14n to illustrate the frequency dependence of the pyroelectric current.
A complex variable meshless local Petrov—Galerkin method for transient heat conduction problems
NASA Astrophysics Data System (ADS)
Wang, Qi-Fang; Dai, Bao-Dong; Li, Zhen-Feng
2013-08-01
On the basis of the complex variable moving least-square (CVMLS) approximation, a complex variable meshless local Petrov—Galerkin (CVMLPG) method is presented for transient heat conduction problems. The method is developed based on the CVMLS approximation for constructing shape functions at scattered points, and the Heaviside step function is used as a test function in each sub-domain to avoid the need for a domain integral in symmetric weak form. In the construction of the well-performed shape function, the trial function of a two-dimensional (2D) problem is formed with a one-dimensional (1D) basis function, thus improving computational efficiency. The numerical results are compared with the exact solutions of the problems and the finite element method (FEM). This comparison illustrates the accuracy as well as the capability of the CVMLPG method.
NASA Astrophysics Data System (ADS)
Yang, Ruizhen; He, Yunze
2014-11-01
Longitudinal heat conduction from surface to inside of solid material could be used to evaluate the subsurface defects. Considering that the skin depth of high frequency eddy current in metal is quite small, this paper proposed logarithmic analysis of eddy current thermography (ECT) to quantify the depth of subsurface defects. The proposed method was verified through numerical and experimental studies. In numerical study, ferromagnetic material and non-ferromagnetic material were both considered. Results showed that the temperature-time curve in the logarithm domain could be used to detect subsurface defects. Separation time was defined as the characteristic feature to measure the defect's depth based on their linear relationships. The thermograms reconstructed by logarithm of temperature can improve defect detectability.
High Conductivity Carbon-Carbon Heat Pipes for Light Weight Space Power System Radiators
NASA Technical Reports Server (NTRS)
Juhasz, Albert J.
2008-01-01
Based on prior successful fabrication and demonstration testing of a carbon-carbon heat pipe radiator element with integral fins this paper examines the hypothetical extension of the technology via substitution of high thermal conductivity composites which would permit increasing fin length while still maintaining high fin effectiveness. As a result the specific radiator mass could approach an ultimate asymptotic minimum value near 1.0 kg/m2, which is less than one fourth the value of present day satellite radiators. The implied mass savings would be even greater for high capacity space and planetary surface power systems, which may require radiator areas ranging from hundreds to thousands of square meters, depending on system power level.
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.
F. Kazeminezhad; M. L. Goodman
2008-01-01
A complete anisotropic, inhomogeneous electrical conductivity tensor, which includes Spitzer, Pedersen, and Hall conductivities is included in an MHD simulation to describe how MHD shock waves may form, propagate, and resistively heat the atmosphere from the photosphere through the chromosphere. The MHD model includes an energy equation. The initial state is defined by FAL density, pressure, and temperature profiles, and
NASA Astrophysics Data System (ADS)
Wang, Hsin; Porter, Wallace D.; Böttner, Harald; König, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolet, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Patricia; Sharp, Jeff; Lo, Jason; Kleinke, Holger; Kiss, Laszlo
2013-06-01
For bulk thermoelectrics, improvement of the figure of merit ZT to above 2 from the current values of 1.0 to 1.5 would enhance their competitiveness with alternative technologies. In recent years, the most significant improvements in ZT have mainly been due to successful reduction of thermal conductivity. However, thermal conductivity is difficult to measure directly at high temperatures. Combined measurements of thermal diffusivity, specific heat, and mass density are a widely used alternative to direct measurement of thermal conductivity. In this work, thermal conductivity is shown to be the factor in the calculation of ZT with the greatest measurement uncertainty. The International Energy Agency (IEA) group, under the implementing agreement for Advanced Materials for Transportation (AMT), has conducted two international round-robins since 2009. This paper, part II of our report on the international round-robin testing of transport properties of bulk bismuth telluride, focuses on thermal diffusivity, specific heat, and thermal conductivity measurements.
Heat transport along an oscillating flat plate
U. H. Kurzweg; J. Chen
1988-01-01
Several recent papers have examined the transport of heat between a hot and cold fluid reservoir when the two reservoirs are connected to each other by an array of open-ended pipes and when the fluid within these pipes is set into sinusoidal axial oscillations. This new heat transfer mode involves the periodic interaction of axial convection with radial heat conduction
A. Aziz; V. J. Lunardini
1995-01-01
This article reviews the literature on multidimensional heat conduction in single fins and fin assemblies. The surface heat dissipation mechanisms include pure convection, pure radiation, and simultaneous convection and radiation. Two-dimensional heat transfer results are presented for longitudinal, radial, and cylindrical fins. The discussion also covers square and polygonal fins on round tubes and composite fins. These heat transfer results
NASA Technical Reports Server (NTRS)
Zhu, Dongming; Miller, Robert A.; Nagaraj, Ben A.; Bruce, Robert W.
2000-01-01
The thermal conductivity of electron beam-physical vapor deposited (EB-PVD) Zr02-8wt%Y2O3 thermal barrier coatings was determined by a steady-state heat flux laser technique. Thermal conductivity change kinetics of the EB-PVD ceramic coatings were also obtained in real time, at high temperatures, under the laser high heat flux, long term test conditions. The thermal conductivity increase due to micro-pore sintering and the decrease due to coating micro-delaminations in the EB-PVD coatings were evaluated for grooved and non-grooved EB-PVD coating systems under isothermal and thermal cycling conditions. The coating failure modes under the high heat flux test conditions were also investigated. The test technique provides a viable means for obtaining coating thermal conductivity data for use in design, development, and life prediction for engine applications.
Ogata, R.; Liu, H. Q.; Ishiguro, M.; Ikeda, T. [Interdisciplinary Graduate School of Engineering Science, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Hanada, K.; Zushi, H.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A. [Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Nishino, N. [Department of Mechanical System Engineering, Graduate School of Engineering, Hiroshima University (Japan); Collaboration: QUEST Group
2011-09-15
A study of radial propagation and electric fields induced by charge separation in blob-like structures has been performed in a non-confined cylindrical electron cyclotron resonance heating plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak using a fast-speed camera and a Langmuir probe. The radial propagation of the blob-like structures is found to be driven by E x B drift. Moreover, these blob-like structures were found to have been accelerated, and the property of the measured radial velocities agrees with the previously proposed model [C. Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)]. Although the dependence of the radial velocity on the connection length of the magnetic field appeared to be different, a plausible explanation based on enhanced short-circuiting of the current path can be proposed.
NASA Astrophysics Data System (ADS)
Shojaeefard, M. H.; Goudarzi, K.; Mazidi, M. Sh.
2009-06-01
The problems involving periodic contacting surfaces have different practical applications. An inverse heat conduction problem for estimating the periodic Thermal Contact Conductance (TCC) between one-dimensional, constant property contacting solids has been investigated with conjugate gradient method (CGM) of function estimation. This method converges very rapidly and is not so sensitive to the measurement errors. The advantage of the present method is that no a priori information is needed on the variation of the unknown quantities, since the solution automatically determines the functional form over the specified domain. A simple, straight forward technique is utilized to solve the direct, sensitivity and adjoint problems, in order to overcome the difficulties associated with numerical methods. Two general classes of results, the results obtained by applying inexact simulated measured data and the results obtained by using data taken from an actual experiment are presented. In addition, extrapolation method is applied to obtain actual results. Generally, the present method effectively improves the exact TCC when exact and inexact simulated measurements input to the analysis. Furthermore, the results obtained with CGM and the extrapolation results are in agreement and the little deviations can be negligible.
NASA Technical Reports Server (NTRS)
Jackson, H. W.; Watkins, J. L.; Chung, S.; Wagner, P.
1996-01-01
An electrically conductive spherical sample located in an electromagnetic field excited by rf (radio frequency) current in a system of coaxial coils is treated theoretically. Maxwell's equations are solved exactly and all integrals in the formulas for the fields are evaluated analytically for the case where the sphere is on the axis and the coil system is modeled by a stack of filamentary circular loops. Formulas are also derived for electromagnetic force exerted on the sphere, excess impedance in the coil system due to the presence of the sphere, and power absorbed by the sphere. All integrals in those formulas have been evaluated analytically. Force measurements are presented and they are in excellent agreement with the new theory. A low-power electromagnetic levitator that is accurately described by the theory has been demonstrated and is discussed. Experimental measurements of excess impedance are presented and compared with theory, and those results are used to demonstrate an accurate noncontact method for determining electrical conductivity. Theoretical formulas for power absorption are evaluated numerically and their usefulness in both rf heating and in making noncontact measurements of a number of thermophysical properties of materials is discussed.
Nanoparticle synergies in modifying thermal conductivity for heat exchanger in condensing boilers
NASA Astrophysics Data System (ADS)
Yang, Kai; He, Shan; Butcher, Thomas; Trojanowski, Rebecca; Sun, Ning; Gersappe, Dilip; Rafailovich, Miriam
2013-03-01
The heat exchanger we are using for condensing boilers is mainly made from aluminum alloys and stainless steel. However, the metal is relatively expensive and corrosion together with maintenance is also a big problem. Therefore, we have developed a new design and material which contain carbon black, carbon nanotube, aluminum oxide and graphene as additives in polypropylene. When multiple types of particles can be melt blended simultaneously and synergies can be achieved, imparting particles to the nanocomposite, achieved much higher thermal conductivity rather than single additive. Here we show the flame retardant nanocomposite which can pass the UL-94-V0 vertical burning test, perform nice in Cone Calorimetry Test and has relatively good mechanical properties. SEM images of the blend show that the Carbon nanobute and other additives well dispersed within the polymer matrix which match our computational calculation for getting the percolation to achieve thermal conductivity around 1.5W/m.K rather than 0.23W/m.K as pure polypropylene.
Keller, David M; Davis, Scott L; Low, David A; Shibasaki, Manabu; Raven, Peter B; Crandall, Craig G
2006-01-01
Prior studies investigating carotid baroreflex control of the cutaneous vasculature have yielded mixed findings. However, previously used methodological and analytical techniques may limit the ability to detect carotid baroreflex-mediated changes in cutaneous vascular conductance (CVC). The aim of this study was to test the hypothesis that dynamic carotid baroreceptor stimulation (i.e. 5 s trials) using neck pressure (NP, simulated carotid hypotension) and neck suction (NS, simulated carotid hypertension) will decrease and increase CVC, respectively, during normothermic and whole-body heating conditions in resting humans. Data were obtained from nine subjects (age, 31 ± 2 year). The ratio of forearm skin blood flux (laser-Doppler flowmetry) and arterial blood pressure (Finapres) was used as an index of CVC. Multiple 5 s trials of NP (+40Torr) and NS (?60Torr), as well as breath-hold/airflow control trials, were applied during end-expiratory breath-holds while subjects were normotheric and heat stressed (change in core temperature ?0.75°C). CVC responses to each NP and NS trial were averaged into 1 s intervals during the following periods: 3 s prestimulus, 5 s during stimulus, and 5 s poststimulus. Peak CVC responses (3 s average) to NP and NS were compared to prestimulus values using paired t test. During normothermia, NP decreased CVC by 0.032 ± 0.007 arbitrary units (a.u.) mmHg?1; (P < 0.05); however, breath-hold/airflow control trials resulted in similar decreases in CVC. NS did not change CVC (? = 0.002 ± 0.005 a.u. mmHg?1; P = 0.63). During whole-body heating, NP decreased CVC (by 0.16 ± 0.04 a.u. mmHg?1; (P < 0.05), whereas NS increased CVC by 0.07 ± 0.03 a.u. mmHg?1; (P < 0.05). Furthermore, these changes were greater than, or directionally different from, the breath-hold/airflow control trials. These findings indicate that carotid baroreceptor stimulation elicits dynamic changes in CVC and that these changes are more apparent during whole-body heating. PMID:17008379
LDEF (Postflight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09
NASA Technical Reports Server (NTRS)
1990-01-01
LDEF (Postflight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 EL-1994-00354 LDEF (Postflight), AO076 : Cascade Variable-Conductance Heat Pipe, Tray F09 The postflight photograph was taken in the SAEF II at KSC prior to removal of the experiment from the LDEF. The color of the white paint dots on the exper- iment tray clamp blocks appear to be unchanged. The LDEF structure, the intercostal on the right, has a dark brown discoloration adjacent to the black Earth end thermal panel. Aluminum pieces of the degraded CVCHPE thermal cover that were shown lodged in the vent area between the intercostal and the black thermal panel in the flight photograph are gone. The Cascade Variable Conductance Heat Pipe Experiment (CVCHPE) occupies a 6 inch deep LDEF peripheral experiment tray and consist of two series connected variable conductance heatpipes, a black chrome solar collector panel and a silvered TEFLON® radiator panel, a power source to support six thermistor-type temperature monitoring sensors and actuations of two valves. Fiberglass standoffs and internal insulation blankets thermally isolated the experiment from the experiment tray and the LDEF interior. The outside of the CVCHPE, except the collector and radiator panels, was covered with an aluminized Kapton multilayer insulation (MLI) blanket with an outer layer of 0.076 mm thick Kapton. The two patches of thin film materials, part of Experiment S1001 by NASA GSFC, were attached to the cover of the external thermal blanket with Kapton tape. The experiment was assembled and mounted in the experiment tray with non-magnetic stainless steel fasteners. The external surface of the CVCHPE has changed from that observed in the flight photograph. The thin vapor deposited aluminum coating, left after the Kapton eroded, is essentially gone with only fragments left near the edges of the thermal blanket. Pieces of a layer of Dacron mesh (bridle vail) material, used to separate the thermal cover from the thermal blanket and between thermal blanket sheets of aluminized Kapton, are visible along the edges of the blanket and near Kel-F buttons used to secure the blanket. A large fragment of the material is folded over the left side of the radiator panel. The large area of discoloration on the right side of the black solar absorber panel appears to be approximately the same shape as the aluminum coating that covered the area in the flight photograph. The orientation of the remaining thin film atomic oxygen experiment patch would indicate that the patch is attached to the Dacron mesh and that the attachment is very fragile. The layer of Kapton tape that covered the ends of the thin film strips appears to be eroded with only the adhesive remaining. The remaining strips of the atomic oxygen experiment materials have changed colors and most appear to be severely degraded. The silvered TEFLON® coating of the radiator panel appears diffuse with a light brown discoloration over most of the surface. The white, evenly spaced, discolorations along the horizontal centerline and along the edges of the panel appear to be above counter sunk flat head screws used to assemble the experiment. The black spots on the radiator panel appear to be impact craters that penetrated the TEFLON® material and exposed the silver beneath to the atomic oxygen flux. Particles of the degraded thermal blanket material that appeared to adhere to the surface of the radiator panel in the flight photograph are gone.
Ahmet Sar?; Ali Karaipekli
2007-01-01
This study aimed determination of proper amount of paraffin (n-docosane) absorbed into expanded graphite (EG) to obtain form-stable composite as phase change material (PCM), examination of the influence of EG addition on the thermal conductivity using transient hot-wire method and investigation of latent heat thermal energy storage (LHTES) characteristics of paraffin such as melting time, melting temperature and latent heat
Stacey, W. M. [Georgia Tech Fusion Research Center, Atlanta, Georgia 30332 (United States)] [Georgia Tech Fusion Research Center, Atlanta, Georgia 30332 (United States)
2014-04-15
A moments equation formalism for the interpretation of the experimental ion thermal diffusivity from experimental data is used to determine the radial ion thermal conduction flux that must be used to interpret the measured data. It is shown that the total ion energy flux must be corrected for thermal and rotational energy convection, for the work done by the flowing plasma against the pressure and viscosity, and for ion orbit loss of particles and energy, and expressions are presented for these corrections. Each of these factors is shown to have a significant effect on the interpreted ion thermal diffusivity in a representative DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] discharge.
NASA Technical Reports Server (NTRS)
Zhu, Dongming; Miller, Robert A.
1990-01-01
The development of low conductivity, robust thermal and environmental barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity and cyclic resistance at very high surface temperatures (up to 17OOOC) under large thermal gradients. In this study, a laser high-heat-flux test approach is established for evaluating advanced low conductivity, ultra-high temperature ceramic thermal and environmental barrier coatings under the NASA Ultra Efficient Engine Technology (UEET) program. The test approach emphasizes the real-time monitoring and assessment of the coating thermal conductivity: the initial conductivity rise under a steady-state high temperature thermal gradient test due to coating sintering, and the later coating conductivity reduction under a subsequent cyclic thermal gradient test due to coating cracking/delamination. The coating system is then evaluated based on the damage accumulations and failure after the combined steady-state and cyclic thermal gradient tests. The lattice and radiation thermal conductivity of advanced ceramic coatings can also be evaluated using laser heat-flux techniques. The coating external radiation resistance is assessed based on the measured specimen temperature response under a laser heated intense radiation flux source. The coating internal radiation contribution is investigated based on the measured apparent coating conductivity increases with the coating surface test temperature under large thermal gradient test conditions. Since an increased radiation contribution is observed at these very high surface test temperatures, by varying the laser heat-flux and coating average test temperature, the complex relation between the lattice and radiation conductivity as a function of surface and interface test temperature is derived.
Kollár, J; Uhrík, J; Hejj, F
1991-01-01
Forty one patients with ischaemic heart disease (IHD) of the age 60 +/- 12.3 years were hospitalized and treated two weeks with Curantyl (Dipyridamol) which was applied per os in a dose of 75 mg 3 times, and after another two weeks 34 of them wass applied Isoptin (Verapamil) in a dose of 40 mg 3 times daily. The heat conductivity (J.m-1, sec-1.degree C.10(-2), HC) and skin temperature (degree C, ST) were examined at the isothermic level 2 cm above the inner ankle by the apparatus Fluvograph 2 of Hartmann and Braun A. G. (BRD). The HC after Isoptin application above the left and right ankle was in 34 patients increased significantly (p less than 0.001). In patients with IHD after Curantyl application the HC and ST was significantly decreased above the left and right ankle in 9 (21.9%) and in 12 (30.0%), respectively. Curantyl could deteriorate HC and so to worsen legs ulceration healing and to point ap ischemia in patients with associated chronic postphlebitic syndrome with ulcera crurium. PMID:2071972
Verification of combined thermal-hydraulic and heat conduction analysis code FLOWNET/TRUMP
NASA Astrophysics Data System (ADS)
Maruyama, Soh; Fujimoto, Nozomu; Kiso, Yoshihiro; Murakami, Tomoyuki; Sudo, Yukio
1988-09-01
This report presents the verification results of the combined thermal-hydraulic and heat conduction analysis code, FLOWNET/TRUMP which has been utilized for the core thermal hydraulic design, especially for the analysis of flow distribution among fuel block coolant channels, the determination of thermal boundary conditions for fuel block stress analysis and the estimation of fuel temperature in the case of fuel block coolant channel blockage accident in the design of the High Temperature Engineering Test Reactor(HTTR), which the Japan Atomic Energy Research Institute has been planning to construct in order to establish basic technologies for future advanced very high temperature gas-cooled reactors and to be served as an irradiation test reactor for promotion of innovative high temperature new frontier technologies. The verification of the code was done through the comparison between the analytical results and experimental results of the Helium Engineering Demonstration Loop Multi-channel Test Section(HENDEL T(sub 1-M)) with simulated fuel rods and fuel blocks.
Steady-State and Transient Boundary Element Methods for Coupled Heat Conduction
NASA Technical Reports Server (NTRS)
Kontinos, Dean A.
1997-01-01
Boundary element algorithms for the solution of steady-state and transient heat conduction are presented. The algorithms are designed for efficient coupling with computational fluid dynamic discretizations and feature piecewise linear elements with offset nodal points. The steady-state algorithm employs the fundamental solution approach; the integration kernels are computed analytically based on linear shape functions, linear elements, and variably offset nodal points. The analytic expressions for both singular and nonsingular integrands are presented. The transient algorithm employs the transient fundamental solution; the temporal integration is performed analytically and the nonsingular spatial integration is performed numerically using Gaussian quadrature. A series solution to the integration is derived for the instance of a singular integrand. The boundary-only character of the algorithm is maintained by integrating the influence coefficients from initial time. Numerical results are compared to analytical solutions to verify the current boundary element algorithms. The steady-state and transient algorithms are numerically shown to be second-order accurate in space and time, respectively.
Zhi-Jie Xu
2012-03-01
We present a general homogenization method for diffusion, heat conduction, and wave propagation in a periodic heterogeneous material with piecewise constants. The method is relevant to the frequently encountered upscaling issues for heterogeneous materials. The dispersion relation for each problem is first expressed in the general form where the frequency w (or wavenumber k) is expanded in terms of the wavenumber k (or frequency w). A general homogenization model can be directly obtained with any given dispersion relation. Next step we study the unit cell of the heterogeneous material and derive the exact dispersion relation. The final homogenized equations include both leading order terms (effective properties) and high order contributions that represent the effect of the microscopic heterogeneity on the macroscopic behavior. That effect can be lumped into a single dimensionless heterogeneity parameter, which is bounded between -1/12 less than or equal to less than or equal to 0 and has a universal expression for all three problems. Numerical examples validate the proposed method and demonstrate a significant computational saving.
T. Hadgu; S. Webb; M. Itamura
2004-02-12
Yucca Mountain, Nevada has been designated as the nation's high-level radioactive waste repository and the U.S. Department of Energy has been approved to apply to the U.S. Nuclear Regulatory Commission for a license to construct a repository. Heat transfer in the Yucca Mountain Project (YMP) drift enclosures is an important aspect of repository waste emplacement. Canisters containing radioactive waste are to be emplaced in tunnels drilled 500 m below the ground surface. After repository closure, decaying heat is transferred from waste packages to the host rock by a combination of thermal radiation, natural convection and conduction heat transfer mechanism?. Current YMP mountain-scale and drift-scale numerical models often use a simplified porous medium code to model fluid and heat flow in the drift openings. To account for natural convection heat transfer, the thermal conductivity of the air was increased in the porous medium model. The equivalent thermal conductivity, defined as the ratio of total heat flow to conductive heat flow, used in the porous media models was based on horizontal concentric cylinders. Such modeling does not effectively capture turbulent natural convection in the open spaces as discussed by Webb et al. (2003) yet the approach is still widely used on the YMP project. In order to mechanistically model natural convection conditions in YMP drifts, the computational fluid dynamics (CFD) code FLUENT (Fluent, Incorporated, 2001) has been used to model natural convection heat transfer in the YMP emplacement drifts. A two-dimensional (2D) model representative of YMP geometry (e.g., includes waste package, drip shield, invert and drift wall) has been developed and numerical simulations made (Francis et al., 2003). Using CFD simulation results for both natural convection and conduction-only heat transfer in a single phase, single component fluid, equivalent thermal conductivities have been calculated for different Rayleigh numbers. Correlation equations for equivalent thermal conductivity as a function of Rayleigh number were developed for the Yucca Mountain geometry and comparisons were made to experimental data and correlations found in the literature on natural convection in horizontal concentric cylinders, a geometry similar to YMP. The objective of this work is to compare the results of CFD natural convection simulations and conduction-only calculations that used the equivalent thermal conductivity to represent heat transfer by turbulent natural convection. The FLUENT code was used for both simulations with heat generation boundary condition at the waste package and constant temperature boundary condition 5 meters into the host rock formation. Comparisons are made of temperature contours in the drift air and temperature profiles at surfaces of the different engineered components using the two approaches. The results show that for the two-dimensional YMP geometry considered, the average surface temperatures of the CFD natural convection and conduction-only using the equivalent thermal conductivity are similar and the maximum local temperature differences for the different surfaces were within two 2 C. The differences in temperature profiles reflect the use of a constant equivalent thermal conductivity. The effect of the differences is discussed.
Aamir, Muhammad; Liao, Qiang; Zhu, Xun; Aqeel-ur-Rehman; Wang, Hong
2014-01-01
An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27?mm and thickness (mm) 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2?MPa to 1.8?MPa, while sample initial temperature varied from 600°C to 900°C. Beck's sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF) within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024?MW/m2 was estimated for a thickness of 8.5?mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8?MPa. PMID:24977219
Aamir, Muhammad; Liao, Qiang; Zhu, Xun; Aqeel-ur-Rehman; Wang, Hong; Zubair, Muhammad
2014-01-01
An experimental study was carried out to investigate the effects of inlet pressure, sample thickness, initial sample temperature, and temperature sensor location on the surface heat flux, surface temperature, and surface ultrafast cooling rate using stainless steel samples of diameter 27 mm and thickness (mm) 8.5, 13, 17.5, and 22, respectively. Inlet pressure was varied from 0.2 MPa to 1.8 MPa, while sample initial temperature varied from 600°C to 900°C. Beck's sequential function specification method was utilized to estimate surface heat flux and surface temperature. Inlet pressure has a positive effect on surface heat flux (SHF) within a critical value of pressure. Thickness of the sample affects the maximum achieved SHF negatively. Surface heat flux as high as 0.4024 MW/m(2) was estimated for a thickness of 8.5 mm. Insulation effects of vapor film become apparent in the sample initial temperature range of 900°C causing reduction in surface heat flux and cooling rate of the sample. A sensor location near to quenched surface is found to be a better choice to visualize the effects of spray parameters on surface heat flux and surface temperature. Cooling rate showed a profound increase for an inlet pressure of 0.8 MPa. PMID:24977219
NASA Astrophysics Data System (ADS)
Christensen, W.; Kamai, T.; Fogg, G. E.
2012-12-01
The presence of metal piezometers (thermal conductivity 16.0 W m-1 K-1) in peat (thermal conductivity 0.5 W m-1 K-1) can significantly influence temperatures recorded in the subsurface. Radially symmetrical 2D numerical models of heat conduction and convection that use a transient specified temperature boundary condition (Dirichlet) and explicitly account for the difference in thermal properties differ from the commonly used 1D analytical solution by as much as 2°C at 0.15m below ground surface. Field data from temperature loggers located inside and outside piezometers show similar differences, supporting the use of the more complex numerical model. In order to better simulate field data, an energy balance approach is used to calculate the temperature along the upper boundary using hourly radiation and air temperature data, along with daily average wind velocity and cloud cover data. Normally distributed random noise is added to recorded field data to address potential natural variation between conditions at the instrument site and the field site (piezometer). Five influential parameters are considered: albedo, crop coefficient, hydraulic conductivity, thermal diffusivity, and surface water depth. Ten sets of these five parameters are generated from a uniform random distribution and constrained by values reported in the literature or measured in the field. The ten parameter sets and noise are used to generate synthetic subsurface data in the numerical model. The synthetic temperature data is offset by a constant value determined from a uniform random distribution to represent potential offset in instrument accuracy (+/- 0.1 °C). The original parameter values are satisfactorily recovered by indirect inversion of the noise-free model using UCODE. Comparison of the parameter estimates from the homogeneous numerical model (equivalent to the analytical model) and the numerical model that explicitly models the metal piezometer are compared. The same inversion scheme is used to estimate parameters from subsurface temperature records from Grass Lake, a large montane peatland located on Luther Pass, California.
Alok Sutradhar; Glaucio H. Paulino; L. J. Gray
2005-01-01
SUMMARY A symmetric Galerkin formulation and implementation for heat conduction in a three-dimensional functionally graded material is presented. The Green's function of the graded problem, in which the thermal conductivity varies exponentially in one co-ordinate, is used to develop a boundary-only formulation without any domain discretization. The main task is the evaluation of hypersingular and singular integrals, which is carried
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.
On the stability of the exact solutions of the dual-phase lagging model of heat conduction.
Ordonez-Miranda, Jose; Alvarado-Gil, Juan Jose
2011-01-01
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. PMID:21711850
On the stability of the exact solutions of the dual-phase lagging model of heat conduction
NASA Astrophysics Data System (ADS)
Ordonez-Miranda, Jose; Alvarado-Gil, Juan Jose
2011-12-01
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.
Virginia Tech
Heat Transfer - 1 You are given the following information for a fluid with thermal conductivity the flow is laminar near the wall. a) (30 points) Determine the corresponding heat transfer coefficient the heat transfer coefficient as a function of x. c) (25 points) Determine the average heat transfer
M. Thompson; C. Segatto; M. T. de Vilhena
2004-01-01
In this work we show that a stationary nonlinear coupled radiative?conductive heat?transfer problem in a convex bounded region with piecewise differentiable boundary in three dimensions under fairly general boundary conditions has a unique solution in a segment of a positive cone in a certain function space.
), the Himalaya (e.g. Bolch and others, 2008; Shukla and others, 2009) and the Southern Alps of New Zealand (eAn energy-balance model for debris-covered glaciers including heat conduction through the debris are often present in glacier ablation areas, and it is essential to assess exactly how the debris affects
J. Argyris; L. Tenek; F. Öberg
1995-01-01
Our latest study presents the theoretical formulation and computer implementation of a three-node six degrees of freedom multilayer flat triangular element intended for the study of the temperature fields in complex multilayer composite shells. Inherent in the formulation, in this first introductory and self-consistent systematic study, are the three modes of heat transfer, namely conduction, convection and radiation, the latter
R. D. Hyndman; E. E. Davis; J. A. Wright
1979-01-01
The design and use of a marine heat probe with capability for measuring thermal conductivity insitu with high accuracy, and providing digital acoustic transmission of data to the ship, is described. The instrument employs the ‘violin bow’ strength member and parallel sensor string configuration suggested by C. R. B. Lister. Several hundred measurements have been made in the deep ocean
NASA Technical Reports Server (NTRS)
Conel, J. E.
1975-01-01
A computer program (Program SPHERE) solving the inhomogeneous equation of heat conduction with radiation boundary condition on a thermally homogeneous sphere is described. The source terms are taken to be exponential functions of the time. Thermal properties are independent of temperature. The solutions are appropriate to studying certain classes of planetary thermal history. Special application to the moon is discussed.
Sk Mahapatra; P. Nanda; A. Sarkar
2005-01-01
The current study addresses the mathematical modeling aspects of coupled conductive and radiative heat transfer in presence of absorbing, emitting and isotropic scattering gray medium within two-dimensional square enclosure. The walls of the enclosure are considered to be opaque, diffuse and gray. The enclosure comprised of isothermal vertical walls and insulated horizontal walls. A new hybrid method where the concepts
Li, Baowen
and dielectric materials. In analogy to Ohm's law of electrical conduction, Fourier's law is the fundamental law of heat conduction in solids. Although Fourier's law has received great success in describing macroscopic, Fourier's law is not applicable in low dimensional structures. 1 Introduction The conduction of heat
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.
NASA Astrophysics Data System (ADS)
Yguel, F.; Peube, J.-L.
1981-03-01
Consideration is given to the problem of heat conduction in a thick wall exposed to a constant radiative flux density on one face with convective and radiative boundary conditions. The equation of heat conduction within the wall with the appropriate boundary conditions taking into account the three most common regimes of convective flow is solved numerically using a second-order implicit finite difference scheme and an alternating direction method. It is found that the effects of longitudinal convection remain constant for wall height/thickness ratios greater than 3, allowing the problem to be reduced one depending on five parameters. Results may be used in the optimization of vertical solar heat collection and storage walls.
ELECTRON HEAT CONDUCTION IN THE SOLAR WIND: TRANSITION FROM SPITZER-HAeRM TO THE COLLISIONLESS LIMIT
Bale, S. D.; Quataert, E. [Physics Department, University of California, Berkeley (United States); Pulupa, M.; Salem, C.; Chen, C. H. K. [Space Sciences Laboratory, University of California, Berkeley (United States)
2013-06-01
We use a statistically significant set of measurements to show that the field-aligned electron heat flux q{sub Parallel-To} in the solar wind at 1 AU is consistent with the Spitzer-Haerm collisional heat flux q{sub sh} for temperature gradient scales larger than a few mean free paths L{sub T} {approx}> 3.5{lambda}{sub fp}. This represents about 65% of the measured data and corresponds primarily to high {beta}, weakly collisional plasma ({sup s}low solar wind{sup )}. In the more collisionless regime {lambda}{sub fp}/L{sub T} {approx}> 0.28, the electron heat flux is limited to q{sub Parallel-To }/q{sub 0} {approx} 0.3, independent of mean free path, where q{sub 0} is the ''free-streaming'' value; the measured q{sub Parallel-To} does not achieve the full q{sub 0}. This constraint q{sub Parallel-To }/q{sub 0} {approx} 0.3 might be attributed to wave-particle interactions, effects of an interplanetary electric potential, or inherent flux limitation. We also show a {beta}{sub e} dependence to these results that is consistent with a local radial electron temperature profile T{sub e} {approx} r {sup -{alpha}} that is a function of the thermal electron beta {alpha} = {alpha}({beta}{sub e}) and that the {beta} dependence of the collisionless regulation constraint is not obviously consistent with a whistler heat flux instability. It may be that the observed saturation of the measured heat flux is a simply a feature of collisional transport. We discuss the results in a broader astrophysical context.
NASA Astrophysics Data System (ADS)
Zheng, D.; Tanaka, S.; Miyazaki, K.; Takashiri, M.
2014-11-01
To investigate the effect of strain on specific heat, sound velocity and lattice thermal conductivity of nanocrystalline bismuth antimony telluride thin films, we performed both experimental study and modeling. The nanocrystalline thin films had mostly preferred crystal orientation along c-axis, and strains in the both directions of c-axis and a-b-axis. It was found that the thermal conductivity of nanocrystalline thin films decreased greatly as compared with that of bulk alloys. To gain insight into the thermal transport in the strained nanocrystalline thin films, we estimated the lattice thermal conductivity based on the phonon transport model of full distribution of mean free paths accounting for the effects of grain size and strain which was influenced to both the sound velocity and the specific heat. As a result, the lattice thermal conductivity was increased when the strain was shifted from compressive to tensile direction. We also confirmed that the strain was influenced by the lattice thermal conductivity but the reduction of the lattice thermal conductivity of thin films can be mainly attributed to the nano-size effect rather than the strain effect. Finally, it was found that the measured lattice thermal conductivities were in good agreement with modeling.
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.
NASA Technical Reports Server (NTRS)
Gedeon, L.
1979-01-01
A variable-conductance heat-pipe system (VCHPS) with methanol as the working fluid and a nitrogen and helium mixture as the control gas was used for the thermal control of a 200 W RF traveling wave tube of the Communication Technology Satellite. Three stainless steel heat pipes (one redundant) and an aluminum radiator were designed to transfer 196 watts for an evaporator temperature of 50 C. The system has operated for three years with no noticeable change in performance. On four occasions the heat pipes apparently deprimed. A short time after reducing the tube power, the heat pipes reprimed and the system continued to operate normally. The description, qualification testing, and orbit data of the VCHPS are presented.
NASA Astrophysics Data System (ADS)
Lin, Weiren; Fulton, Patrick M.; Harris, Robert N.; Tadai, Osamu; Matsubayashi, Osamu; Tanikawa, Wataru; Kinoshita, Masataka
2014-12-01
We report thermal conductivities, thermal diffusivities, and volumetric heat capacities determined by a transient plane heat source method for four whole-round core samples obtained by the Japan Trench Fast Drilling Project/Integrated Ocean Drilling Program Expedition 343. These thermal properties are necessary for the interpretation of a temperature anomaly detected in the vicinity of the plate boundary fault that ruptured during the 2011 Tohoku-Oki earthquake and other thermal processes observed within the Japan Trench Fast Drilling Project temperature observatory. Results of measured thermal conductivities are consistent with those independently measured using a transient line source method and a divided bar technique. Our measurements indicate no significant anisotropy in either thermal conductivity or thermal diffusivity.
A local BIEM for analysis of transient heat conduction with nonlinear source terms in FGMs
Jan Sladek; Vladimir Sladek; Ch. Zhang
2004-01-01
The diffusion equation with nonlinear heat source intensity in functionally graded materials (FGMs) is considered. In FGMs the thermal material properties are dependent on spatial coordinates. For transient or steady-state heat problems in FGMs the conventional boundary integral equation method or boundary element method cannot be applied due to the lack of a fundamental solution. In this paper, a local
Daniel R. Rousse; Guillaume Gautier; Jean-Francois Sacadura
2000-01-01
This paper presents several test problems that were used to validate the formulation and implementation of a CVFEM for combined-mode heat transfer in participating media. The objective here is to demonstrate that the proposed CVFEM can be used to solve combined modes of heat transfer in media that emit, absorb, and scatter radiant energy in regularly- and irregularly-shaped geometries. The
Geothermal setting and simple heat conduction models for the Long Valley caldera
Arthur H. Lachenbruch; J. H. Sass; Robert J. Munroe; T. H. Jr. Moses
1976-01-01
Heat flow and heat production measurements have been made in the vicinity of Long Valley from 0-30 km from the rim of the caldera and up to 30 km on either side of the boundary of the Basin and Range province at the eastern scarp of the Sierra Nevada. The data show no conspicuous effect of the province transition, possibly
ERIC Educational Resources Information Center
Clough, Elizabeth Engel; Driver, Rosalind
1985-01-01
Describes main features of students' thinking about heat and temperature (developed before formal science teaching) and results of a study that shows that many notions about heat/temperature used by younger children are still apparent in the thinking of older students. The study involved interviews with 84 students in three age groups. (JN)
Design and testing of a passive, feedback-controlled, variable conductance heat pipe
NASA Technical Reports Server (NTRS)
Schlitt, K. R.
1973-01-01
A passive feedback system, which stabilizes the heat source temperature (T sub s) of a gas loaded heat pipe, was designed and tested. The control of T sub s is accomplished by an auxiliary liquid that senses the heat source and actuates a metal bellows system due to the liquid's thermal expansion. The movement of the bellows varies the gas reservoir volume and leads to a corresponding change of the condensation area of the heat pipe. With methanol as the heat pipe working fluid and perfluoro-n-pentane as the auxiliary liquid, the control capability was found to be T sub s = 31.5 + or - 1.5 C in a power range from 3 to 30 W, compared to T sub s = 33 + or - 3 C with methanol as auxiliary liquid. The change in T sub s was 35 + or - 5.5 C with the bellows held in the closed position.
Construction and testing of a gas-loaded, passive-control, variable-conductance heat pipe
NASA Technical Reports Server (NTRS)
Depew, C. A.; Sauerbrey, W. J.; Benson, B. A.
1973-01-01
A methanol heat pipe using nitrogen gas for temperature control has been constructed and tested. The system was run over a power ratio of 15 (2 to 30 watts) with the heat source near ambient temperature and with the heat sink at a nominal value of 32 F. Control was obtained with a metal bellows gas reservoir which was actuated by an internal liquid-filled bellows. The liquid bellows was pressurized by expanding liquid methanol which was contained in an auxiliary reservoir in the evaporator heater block. It was demonstrated that the temperature variation of the heat source was reduced from 36 F for the heat pipe with no control to 7 F with the actuated bellows control.
Boyer, Edmond
4-6, 2007 ET81- 1 HEAT TRANSFER BY SIMULTANEOUS RADIATION-CONDUCTION AND CONVECTION IN A HIGH be neglected compared with other exchange modes (conduction, radiation and forced convection). Fig. 1. Packed for the packed bed. The comparison between the radiative heat transfer and the exchanges by conduction and forced
Effects of microreactor wall heat conduction on the reforming process of methane
Michael J. Stutz; Dimos Poulikakos
2005-01-01
In this paper, the effect of wall conduction of an autothermal tubular methane microreformer is investigated numerically. It is found that the axial wall conduction can strongly influence the performance of the microreactor and should not be neglected without a careful a priori investigation of its impact. By increasing the wall thermal conductivity, the maximum wall surface temperature is decreased.
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.
A I Shestakov; M J Matthews; R M Vignes; J S Stolken
2010-01-01
Localized, transient heating of materials using micro-scale, highly absorbing laser light has been used in many industries to anneal, melt and ablate material with high precision. Accurate modeling of the relative contributions of conductive, convective and radiative losses as a function of laser parameters is essential to optimizing micro-scale laser processing of materials. In bulk semi-transparent materials such as silicate
NASA Technical Reports Server (NTRS)
Kim, J.; Bae, S. W.; Whitten, M. W.; Mullen, J. D.; Quine, R. W.; Kalkur, T. S.
1999-01-01
Two systems have been developed to study boiling heat transfer on the microscale. The first system utilizes a 32 x 32 array of diodes to measure the local temperature fluctuations during boiling on a silicon wafer heated from below. The second system utilizes an array of 96 microscale heaters each maintained at constant surface temperature using electronic feedback loops. The power required to keep each heater at constant temperature is measured, enabling the local heat transfer coefficient to be determined. Both of these systems as well as some preliminary results are discussed.
NASA Astrophysics Data System (ADS)
Megahed, Ahmed M.
2015-03-01
An analysis was carried out to describe the problem of flow and heat transfer of Powell-Eyring fluid in boundary layers on an exponentially stretching continuous permeable surface with an exponential temperature distribution in the presence of heat flux and variable thermal conductivity. The governing partial differential equations describing the problem were transformed into a set of coupled non-linear ordinary differential equations and then solved with a numerical technique using appropriate boundary conditions for various physical parameters. The numerical solution for the governing non-linear boundary value problem is based on applying the shooting method over the entire range of physical parameters. The effects of various parameters like the thermal conductivity parameter, suction parameter, dimensionless Powell-Eyring parameters and the Prandtl number on the flow and temperature profiles as well as on the local skin-friction coefficient and the local Nusselt number are presented and discussed. In this work, special attention was given to investigate the effect of the thermal conductivity parameter on the velocity and temperature fields above the sheet in the presence of heat flux. The numerical results were also validated with results from a previously published work on various special cases of the problem, and good agreements were seen.
Eryou, N. Dennis
1969-01-01
One dimensional temperature profiles and heat fluxes within a slab of molten glass were measured experimentally. The glass slab was contained in a platinum foil lined ceramic tray inside a high temperature furnace. An ...
Some aspects of the computer simulation of conduction heat transfer and phase change processes
Solomon, A. D.
1982-04-01
Various aspects of phase change processes in materials are discussd including computer modeling, validation of results and sensitivity. In addition, the possible incorporation of cognitive activities in computational heat transfer is examined.
Constantz, Jim; Su, Grace; Hatch, Christine
2004-08-01
Both the measurement of temperature and the simulation of heat and water transport have benefited from significant recent advances in data acquisition and computer resources. This has afforded the opportunity for routine use of heat as a tracer in a variety of hydrological regimes. Heat is particularly well suited for investigations of stream/groundwater exchanges. Dynamic temperature patterns between the stream and underlying sediments are typical, due to large stream surface area to volume ratios relative to other surface water bodies. Heat is a naturally occurring tracer, free from (real or perceived) issues of contamination associated with use of chemical tracers in stream environments. The use of heat as a tracer relies on the measurement of temperature gradients, and temperature is an extremely robust parameter to monitor. Temperature data is immediately available as opposed to chemical tracers, which often require significant laboratory analysis. In this work, we report on the progress in the use of heat as a tracer to determine the hydraulic conductance of the streambed along the middle reaches of the Russian River, located west of Santa Rosa, CA. The general hydrological setting is described and the unique matter in which the water resources are managed in an environment of increasing population, a rapid shift to agricultural crops requiring more irrigation, and a series of fishery related mandates.
Sass, J.H.; Morgan, P.
1988-01-01
Over 5% of heat in the western USA is lost through Quaternary silicic volcanic centers, including the Valles caldera in N central New Mexico. These centers are the sites of major hydrothermal activity and upper crustal metamorphism, metasomatism, and mineralization, producing associated geothermal resources. Presents new heat flow data from Valles caldera core hole 1 (VC-1), drilled in the SW margin of the Valles caldera. Thermal conductivities were measured on 55 segments of core from VC-1, waxed and wrapped to preserve fluids. These values were combined with temperature gradient data to calculate heat flow. Above 335 m, which is probably unsaturated, heat flow is 247 + or - 16 mW m-2. Inteprets the shallow thermal gradient data and the thermal regime at VC-1 to indicate a long-lived hydrothermal (and magmatic) system in the southwestern Valles caldera that has been maintained through the generation of shallow magma bodies during the long postcollapse history of the caldera. High heat flow at the VC-1 site is interpreted to result from hot water circulating below the base of the core hole, and we attribute the lower heat flow in the unsaturated zone is attributed to hydrologic recharge. -from Authors
H. F. Nouanégué; E. Bilgen
2009-01-01
Numerical study by conjugate heat transfer is carried out of solar chimney systems for heating and ventilation of dwellings. Conservation equations are solved by finite difference-control volume numerical method. The governing parameters were: the Rayleigh numbers from 5×108 to 1011, the Prandtl number, Pr=0.7, constant for air, the chimney aspect ratio, A=H\\/L from 6 to 15, the air channel width
Flight data analysis and further development of variable-conductance heat pipes
NASA Technical Reports Server (NTRS)
Eninger, J. E.; Edwards, D. K.; Luedke, E. E.
1976-01-01
The work focuses on the mathematical modeling of three critical mechanisms of heat-pipe operation: (1) the effect that excess liquid has on heat-pipe performance; (2) the calculation of the dryout limit of circumferential grooves; (3) an efficient mathematical model for the calculation of the viscous-inertial interaction in the vapor flow. These mathematical models are incorporated in the computer program GRADE II, which is described.
NASA Technical Reports Server (NTRS)
Eninger, J. E.; Fleischman, G. L.; Luedke, E. E.
1975-01-01
The design and testing of a heat pipe for spacecraft application is presented. The application in mind calls for heat loads up to 20 watts, a set-point temperature of 294K, and a sink that varies from -220K to nearly as high as the set-point. The overall heat pipe length is 137 cm. Two basically different mechanisms of achieving variable conductance in the pipe by vapor-flow throttling were studied. In one, the thermal resistance between the heat source and sink is due to a saturation-temperature drop corresponding to the vapor-pressure drop developed across the valve. In the other, the pressure difference across the valve induces capillary groove and wick dry out in an evaporation region, and thus results in an increased thermal resistance. This mechanism was selected for fabrication and testing. The pipe is a stainless-steel/methanol two-heat-pipe system. Results are presented and discussed. Engineering drawings and specifications of the pipe are shown.
Watanabe, Hiromichi; Yamashita, Yuichiro
2012-01-01
A modified pulse-heating method is proposed to improve the accuracy of measurement of the hemispherical total emissivity, specific heat capacity, and electrical resistivity of electrically conductive materials at high temperatures. The proposed method is based on the analysis of a series of rapid resistive self-heating experiments on a sample heated at different temperature rates. The method is used to measure the three properties of the IG-110 grade of isotropic graphite at temperatures from 850 to 1800 K. The problem of the extrinsic heating-rate effect, which reduces the accuracy of the measurements, is successfully mitigated by compensating for the generally neglected experimental error associated with the electrical measurands (current and voltage). The results obtained by the proposed method can be validated by the linearity of measured quantities used in the property determinations. The results are in reasonably good agreement with previously published data, which demonstrate the suitability of the proposed method, in particular, to the resistivity and total emissivity measurements. An interesting result is the existence of a minimum in the emissivity of the isotropic graphite at around 1120 K, consistent with the electrical resistivity results. PMID:22299976
Radial-radial single rotor turbine
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.
J. Sladek; V. Sladek; Ch. Hellmich; J. Eberhardsteiner
2007-01-01
The meshless local Petrov–Galerkin method is used to analyze transient heat conduction in 3-D axisymmetric solids with continuously inhomogeneous and anisotropic material properties. A 3-D axisymmetric body is created by rotation of a cross section around an axis of symmetry. Axial symmetry of geometry and boundary conditions reduces the original 3-D boundary value problem into a 2-D problem. The cross
a Meshless Method Based on Least-Squares Approach for - and Unsteady-State Heat Conduction Problems
Y. Liu; X. Zhang; M.-W. Lu
2005-01-01
The meshless method based on the least-squares approach, the meshless weighted least- squares (MWLS) method, is extended to solve conduction heat transfer problems. The MWLS formulation is first established for steady-state problems and then extended to unsteady-state problems with time-stepping schemes. Theoretical analysis and numerical examples indicate that larger time steps can be used in the present method than in
NASA Astrophysics Data System (ADS)
Yu, Junchun; Tonpheng, Bounphanh; Andersson, Ove
2010-06-01
The thermal conductivity, ?, of nylon-6 increased 22% whereas the heat capacity per unit volume, ?cp, decreased 10% by adding 2.1 wt% Multi-Wall Carbon Nanotubes MWCNTs. Simultaneously, the glass transition temperature, Tg, which was detected as a weak sigmoidal increase in ?cp and a decrease in d?/dT, increased 11 K. These results show that the MWCNTs-nylon-6 interaction restricts the segmental mobility of nylon-6 and decreases cp of nylon-6.
NASA Astrophysics Data System (ADS)
Brociek, R.; Hetmaniok, E.; S?ota, D.
2014-11-01
In this paper we propose an application of the homotopy analysis method for solving the two-dimensional steady-state heat conduction problem. Discussed method is based on the concept of creating the function series. The paper presents the sufficient condition for convergence of this series and the error estimation of approximate solution obtained by using the partial sum of received series. Examples illustrating the usage of investigated method are also presented in the paper.
NASA Technical Reports Server (NTRS)
Cox, D. P.; Edgar, R. J.
1982-01-01
Accurate approximations are presented for the self-similar structures of nonradiating blast waves with adiabatic ions, isothermal electrons, and equation ion and electron temperatures at the shock. The cases considered evolve in cavities with power law ambient densities (including the uniform density case) and have negligible external pressure. The results provide the early time asymptote for systems with shock heating of electrons and strong thermal conduction. In addition, they provide analytical results against which two fluid numerical hydrodynamic codes can be checked.
Hui-Shen Shen; N. Noda
2005-01-01
A postbuckling analysis is presented for a shear deformable functionally graded cylindrical shell of finite length subjected to combined axial and radial loads in thermal environments. Heat conduction and temperature-dependent material properties are both taken into account. The temperature field considered is assumed to be a uniform distribution over the shell surface and varied in the thickness direction only. Material
A. Amrollahi; A. M. Rashidi; M. Emami Meibodi; K. Kashefi
2009-01-01
Thermal conductivity enhancements in aqueous media in the presence of carbon nanotubes (SWNTs) are investigated. The SWNTs nanofluids are prepared using a two-step method. The concentration of SWNTs suspensions is below 1 wt%. The thermal conductivities of the SWNTs suspensions are measured by a modified transient hot wire method (KD2 thermal property meter). Zeta potential, turbidity measurements and sedimentation photographs
Julien Clinton Sprott; William Graham Hoover; Carol Griswold Hoover
2014-04-13
We use nonequilibrium molecular dynamics to analyze and illustrate the qualitative differences between the one-thermostat and two-thermostat versions of equilibrium and nonequilibrium (heat-conducting) harmonic oscillators. Conservative nonconducting regions can coexist with dissipative heat conducting regions in phase space with exactly the same imposed temperature field.
NASA Astrophysics Data System (ADS)
Sprott, Julien Clinton; Hoover, William Graham; Hoover, Carol Griswold
2014-04-01
We use nonequilibrium molecular dynamics to analyze and illustrate the qualitative differences between the one-thermostat and two-thermostat versions of equilibrium and nonequilibrium (heat-conducting) harmonic oscillators. Conservative nonconducting regions can coexist with dissipative heat conducting regions in phase space with exactly the same imposed temperature field.
Effect of wall conduction on melting in an enclosure heated at constant rate
NASA Astrophysics Data System (ADS)
Zhang, Yuwen; Chen, Zhongqi
1994-01-01
Solid-liquid phase change phenomena exist widely in nature and industrial processes such as freezing of water and melting of ice, thermal energy storage, casting and metallurgical process, cryogenic preservation of blood and bio-materials, etc. Many typical applications of heat transfer in phase change involve convection in the liquid phase. Recently, boundary layer theory has been adopted to solve the process of natural convection dominated melting. For example, the analytical solution for the melting process in a rectangular enclosure isothermally heated from one of its vertical wall was obtained by Bejan. This paper presents an analysis of work by Zhang and Bejan (1989).
Tzanos, C. P.; Dionne, B. (Nuclear Engineering Division)
2011-05-23
To support the analyses related to the conversion of the BR2 core from highly-enriched (HEU) to low-enriched (LEU) fuel, the thermal-hydraulics codes PLTEMP and RELAP-3D are used to evaluate the safety margins during steady-state operation (PLTEMP), as well as after a loss-of-flow, loss-of-pressure, or a loss of coolant event (RELAP). In the 1-D PLTEMP and RELAP simulations, conduction in the azimuthal and axial directions is not accounted. The very good thermal conductivity of the cladding and the fuel meat and significant temperature gradients in the lateral directions (axial and azimuthal directions) could lead to a heat flux distribution that is significantly different than the power distribution. To evaluate the significance of the lateral heat conduction, 3-D computational fluid dynamics (CFD) simulations, using the CFD code STAR-CD, were performed. Safety margin calculations are typically performed for a hot stripe, i.e., an azimuthal region of the fuel plates/coolant channel containing the power peak. In a RELAP model, for example, a channel between two plates could be divided into a number of RELAP channels (stripes) in the azimuthal direction. In a PLTEMP model, the effect of azimuthal power peaking could be taken into account by using engineering factors. However, if the thermal mixing in the azimuthal direction of a coolant channel is significant, a stripping approach could be overly conservative by not taking into account this mixing. STAR-CD simulations were also performed to study the thermal mixing in the coolant. Section II of this document presents the results of the analyses of the lateral heat conduction and azimuthal thermal mixing in a coolant channel. Finally, PLTEMP and RELAP simulations rely on the use of correlations to determine heat transfer coefficients. Previous analyses showed that the Dittus-Boelter correlation gives significantly more conservative (lower) predictions than the correlations of Sieder-Tate and Petukhov. STAR-CD 3-D simulations were performed to compare heat transfer predictions from CFD and the correlations. Section III of this document presents the results of this analysis.
Huang, Hai; Plummer, Mitchell; Podgorney, Robert
2013-02-01
Advancement of EGS requires improved prediction of fracture development and growth during reservoir stimulation and long-term operation. This, in turn, requires better understanding of the dynamics of the strongly coupled thermo-hydro-mechanical (THM) processes within fractured rocks. We have developed a physically based rock deformation and fracture propagation simulator by using a quasi-static discrete element model (DEM) to model mechanical rock deformation and fracture propagation induced by thermal stress and fluid pressure changes. We also developed a network model to simulate fluid flow and heat transport in both fractures and porous rock. In this paper, we describe results of simulations in which the DEM model and network flow & heat transport model are coupled together to provide realistic simulation of the changes of apertures and permeability of fractures and fracture networks induced by thermal cooling and fluid pressure changes within fractures. Various processes, such as Stokes flow in low velocity pores, convection-dominated heat transport in fractures, heat exchange between fluid-filled fractures and solid rock, heat conduction through low-permeability matrices and associated mechanical deformations are all incorporated into the coupled model. The effects of confining stresses, developing thermal stress and injection pressure on the permeability evolution of fracture and fracture networks are systematically investigated. Results are summarized in terms of implications for the development and evolution of fracture distribution during hydrofracturing and thermal stimulation for EGS.
Georgoudis, K; Stoforos, N G
2009-03-01
In the present study, a set of quality equivalent points, that is, points where the retention of a particular quality attribute at the end of a thermal process is equal to the volume average quality retention, was determined for conduction heating products in cylindrical containers. For this, initially, the temperature distribution inside the product during the thermal process was numerically calculated, assuming uniform initial product temperature, constant heating and cooling medium temperatures, and infinite heat transfer coefficient between the cylinder walls and the heating or cooling medium. Next, remaining concentration data at the end of the process were obtained at various points within the container for a heat labile quality factor following 1st-order degradation kinetics. Thereafter, the volume average remaining concentration for the quality parameter under consideration was calculated and the quality equivalent points were identified. The influence of product, quality factor, and process characteristics on the location of the quality equivalent points, was examined. For every case investigated, the entirety of quality equivalent points was modeled by the use of a single parameter, the empirical j value. For most cases of common practice, a j value between 0.34 and 0.40 was found appropriate for volume average quality retention calculations. Thus, by collecting temperature data during processing at a quality equivalent point, product quality at the end of the process can be assessed. PMID:19323741
Students' Design of Experiments: An Inquiry Module on the Conduction of Heat
ERIC Educational Resources Information Center
Hatzikraniotis, E.; Kallery, M.; Molohidis, A.; Psillos, D.
2010-01-01
This article examines secondary students' design of experiments after engagement in an innovative and inquiry-oriented module on heat transfer. The module consists of an integration of hands-on experiments, simulated experiments and microscopic model simulations, includes a structured series of guided investigative tasks and was implemented for a…
Olaf Klein; Peter Philip
2003-01-01
This article presents a finite volume scheme for transient nonlinear heat transport equations coupled by nonlocal interface conditions modeling diuse- gray radiation between the surfaces of (both open and closed) cavities. The model is considered in three space dimensions; modifications for the axisym- metric case are indicated. Proving a maximum principle as well as existence and uniqueness for roots to
Ahmad M. Mahmoud; Abdullatif Ben-Nakhi; Ammar Ben-Nakhi; Rashed Alajmi
2012-01-01
A computational fluid dynamics (CFD) model is developed to study thermal performance of hollow autoclaved aerated concrete (AAC) blocks in wall constructions of buildings under hot summer conditions. The goal is to determine size and distribution of cavities (within building blocks) that reduce heat flow through the walls and thereby lead to energy savings in air conditioning. The model couples
Ahmad M. Mahmoud; Abdullatif Ben-Nakhi; Ammar Ben-Nakhi; Rashed Alajmi
2011-01-01
A computational fluid dynamics (CFD) model is developed to study thermal performance of hollow autoclaved aerated concrete (AAC) blocks in wall constructions of buildings under hot summer conditions. The goal is to determine size and distribution of cavities (within building blocks) that reduce heat flow through the walls and thereby lead to energy savings in air conditioning. The model couples
R. C. Mehta; P. Kumar
1985-01-01
A simple numerical solution using the Runge-Kutta method in conjunction with an iterative scheme is developed for a nonlinear integrodifferential equation, and the results are compared with the results of the finite-difference solution of Siegel and Keshock (1964). The effects of the internal radiation exchange within the tube wall, and the variation of the convective heat transfer coefficient in the
March. 1968 RisB Report No. 175 On the Viscosity and Heat Conductivity
(A. 6) and (A. 7) differ from the formulas of Simon and Thompson ((27)), and they reduce exactly Commission Research Establishment Riso Physics Department Abstract The viscous stress tensor and the heat- ments method. No contradictionis found between the expressions of the vis- cous stress tensor obtained
THERMALLY CONDUCTIVE CEMENTITIOUS GROUTS FOR GEOTHERMAL HEAT PUMPS. PROGRESS REPORT BY 1998
ALLAN,M.L.; PHILIPPACOPOULOS,A.J.
1998-11-01
Research commenced in FY 97 to determine the suitability of superplasticized cement-sand grouts for backfilling vertical boreholes used with geothermal heat pump (GHP) systems. The overall objectives were to develop, evaluate and demonstrate cementitious grouts that could reduce the required bore length and improve the performance of GHPs. This report summarizes the accomplishments in FY 98.
Anomalous Heat Conduction in One-Dimensional Momentum-Conserving Systems Onuttom Narayan1,2
California at Santa Cruz, University of
temperature difference is applied across a system, it is expected that in steady state the heat current j the two ends of a system of length L are kept (with T1 T2), the steady state current should be j T1 ÿ T2,2 and Sriram Ramaswamy1 1 Centre for Condensed Matter Theory, Department of Physics, Indian Institute
Francisco DEL CERRO; Antonio CAMPO; Francisco ALHAMA
Differential and finite equations of lineal electric and heat transfer processes are equivalent and many textbooks devote long paragraphs to this important aspect for the education of mechanical engineers. Nevertheless, no reference alludes to nonlineal differential equations which, in practice, better simulate the real processes. In this paper, the basic electrical devises incorporated in most of the educational software simulation
Zhigilei, Leonid V.
Temperature dependences of the electronÂphonon coupling, electron heat capacity and thermal Available online 23 January 2007 Abstract The electron temperature dependences of the electron of temperatures typically realized in femtosecond laser material processing applications, from room temperature up
Effect of structural heat conduction on the performance of micro-combustors and micro-thrusters
NASA Astrophysics Data System (ADS)
Leach, Timothy Thierry
This thesis investigates the effect of gas-structure interaction on the design and performance of miniaturized combustors with characteristic dimensions less than a few millimeters. These are termed 'micro-combustors' and are intended for use in devices ranging from micro-scale rocket motors for micro, nano, and pico-satellite propulsion, to micro-scale engines for micro-Unmanned Air Vehicle (UAV) propulsion and compact power generation. Analytical models for the propagation of a premixed laminar flame in a micro-channel are developed. The models' predictions are compared to the results of more detailed numerical simulations that incorporate multi-step chemistry, distributed heat transfer between the reacting gas and the combustor structure, heat transfer between the combustor and the environment, and heat transfer within the combustor structure. The results of the modeling and simulation efforts are found to be in good qualitative agreement and demonstrate that the behavior of premixed laminar flames in micro-channels is governed by heat transfer within the combustor structure and heat loss to the environment. The key findings of this work are as follows: First, heat transfer through the micro-combustor's structure tends to increase the flame speed and flame thickness. The increase in flame thickness with decreasing passage height suggests that micro-scale combustors will need to be longer than their conventional-scale counterparts. However, the increase in flame speed more than compensates for this effect and the net effect is that miniaturizing a combustor can increase its power density substantially. Second, miniaturizing chemical rocket thrusters can substantially increase thrust/weight ratio but comes at the price of reduced specific impulse (i.e. overall efficiency). Third, heat transfer through the combustor's structure increases steady-state and transient flame stability. This means that micro-scale combustors will be more stable than their conventional-scale counterparts. Fourth and finally, the extended temperature profile associated with the broadened flame causes a different set of elementary reactions to dominate the operation of the overall reaction mechanism at the micro-scale. This suggests that new chemical mechanisms may need to be developed in order to accurately simulate combustion at small-scales. It also calls into question the efficacy of single-step mechanisms presently used by other researchers.
Anomalous heat conduction in polyethylene chains: Theory and molecular dynamics simulations
Henry, Asegun
In 1955 Fermi, Pasta, and Ulam showed that a simple model for a nonlinear one-dimensional chain of particles can be nonergodic, which implied infinite thermal conductivity. A more recent investigation of a realistic model ...
NASA Astrophysics Data System (ADS)
Zianni, Xanthippi; Jean, Valentin; Termentzidis, Konstantinos; Lacroix, David
2014-11-01
We report on scaling behavior of the thermal conductivity of width-modulated nanowires and nanofilms that have been studied with the phonon Monte Carlo technique. It has been found that the reduction of the thermal conductivity scales with the nanostructure transmissivity, a property entirely determined by the modulation geometry, irrespectively of the material choice. Tuning of the thermal conductivity is possible by the nanostructure width-modulation without strict limitations for the modulation profile. In addition, a very significant constriction thermal resistance due to width-discontinuity has been identified, in analogy to the contact thermal resistance between two dissimilar materials. The constriction thermal resistance also scales with the modulated nanostructure transmissivity. Our conclusions are generic indicating that a wide range of materials can be used for the modulated nanostructures. Direct heat flow control can be provided by designing the nanostructure width-modulation.
Daniel R. Rousse
2000-01-01
The research presented in this paper involves the detailed formulation of a Control-Volume Finite Element Method (CVFEM) for the solution of combined-mode heat transfer in participating media. The proposed numerical method accounts for emitting, absorbing, and scattering media in regularly- and irregularly-shaped geometries. In the proposed CVFEM, the calculation domain is divided into three-node triangular finite elements: the geometrical flexibility
Input Estimation Method Including Finite-Element Scheme for Solving Inverse Heat Conduction Problems
Tsung-Chien Chen; Pan-Chio Tuan
2005-01-01
This work presents an inverse method based on the input estimation method including the finite-element scheme to estimate unknown heat flux. The input estimation method is comprised of the Kalman filtering technique and a recursive least-squares estimator. This recursive least-squares estimator is weighted by the forgetting factor ?. It is derived using the residual innovation sequence to compute the magnitude
Spacelab experiments on convection in a rotating spherical shell with radial gravity
NASA Astrophysics Data System (ADS)
Toomre, J.; Hart, J. E.; Glatzmaier, G. A.
Experiments on thermal convection in a rotating, differentially-heated hemispherical shell of fluid with a radial gravity field were carried out in the microgravity environment of Spacelab 3 which was flown on the space shuttle Challenger in May 1985. Schlieren visualizations of these laboratory flows are compared briefly to three-dimensional nonlinear simulations that can be conducted at the more modest heating rates.
Electron heat conduction under non-Maxwellian distribution in hohlraum simulation
Wen Yihuo; Ke Lan; Pei Jungu; Heng Yong; Qing Hongzeng [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)
2012-01-15
An electron transport model based on the non-Maxwellian distribution f{sub 0}{proportional_to}e{sup -{nu}{sup m}} (NM model), caused by the inverse bremsstrahlung heating, is used in 1-D plane target and 2-D hohlraum simulations. In the NM model, the electron heat flux depends not only on the gradient of electron temperature T{sub e} but also on the gradients of electron number density and the index m. From 1-D simulations, the spatial distribution of T{sub e} is dune-like and T{sub e} decreases obviously in the flux-heated region, which is very different from the flat profile obtained by using the flux limit model (FL model) but similar to the experimental observations [Gregori et al., Phys. Rev. Lett. 92, 205006 (2004)] and the nonlocal results [Rosen et al., High Energy Density Phys. 7, 180 (2011)]. The reason which causes the dune-like profile of T{sub e} is discussed in the paper. From 2-D hohlraum simulations, the NM results of the plasma status, the emission peak and profile inside hohlraum are very different from the FL model results. Finally, it is hard to use an average flux limiter in the FL model to obtain the same hohlraum plasma status and emission with those under the NM model.
Electron heat conduction under non-Maxwellian distribution in hohlraum simulation
NASA Astrophysics Data System (ADS)
Yi Huo, Wen; Lan, Ke; Jun Gu, Pei; Yong, Heng; Hong Zeng, Qing
2012-01-01
An electron transport model based on the non-Maxwellian distribution f0?e-?m (NM model), caused by the inverse bremsstrahlung heating, is used in 1-D plane target and 2-D hohlraum simulations. In the NM model, the electron heat flux depends not only on the gradient of electron temperature Te but also on the gradients of electron number density and the index m. From 1-D simulations, the spatial distribution of Te is dune-like and Te decreases obviously in the flux-heated region, which is very different from the flat profile obtained by using the flux limit model (FL model) but similar to the experimental observations [Gregori et al., Phys. Rev. Lett. 92, 205006 (2004)] and the nonlocal results [Rosen et al., High Energy Density Phys. 7, 180 (2011)]. The reason which causes the dune-like profile of Te is discussed in the paper. From 2-D hohlraum simulations, the NM results of the plasma status, the emission peak and profile inside hohlraum are very different from the FL model results. Finally, it is hard to use an average flux limiter in the FL model to obtain the same hohlraum plasma status and emission with those under the NM model.
NASA Astrophysics Data System (ADS)
Grott, Matthias; Knollenberg, Joerg; Sohl, Frank; Krause, Christian
With landed lunar missions like the International Lunar Network ILN on the agenda of major space agencies, new opportunities for the in-situ geophysical exploration of the Moon are arising. In preparation for these missions, it is due time to re-evaluate earlier measurements and to identify open science questions and lessons learned from the Apollo Lunar Surface Experiment Package. Here we focus on the heat flow experiment conducted during the Apollo 15 and 17 missions, which provided the first extraterrestrial heat flow measurements in history. The lunar heat flow values measured at the two sites carry some uncertainty connected to am-biguities considering the in-situ determination of the thermal conductivity. Disparate thermal conductivity values were deduced using two different methods, (i) a modified line heat source (LHS) method and (ii) a transient method involving the analysis of transient thermal waves. This led to a downward correction of the estimated lunar heat flow by 30 to 50 % relative to first published results. It was concluded at that time that the discrepancy between the both methods must be attributed to regolith disruption close to the borestem and that transient methods would yield more reliable results. We have re-evaluated the influence of regolith disruption caused by probe emplacement on the measurements. We find that disturbed regolith probably extended across many cm from the drill stem into the surrounding soil. This finding poses significant challenges to future in-situ experiments, as the volume sampled by LHS methods is usually fairly restricted. On the other hand, as a direct method, the measurement accuracy of the LHS methods is much higher than that expected from transient methods. We therefore propose to use a combination of methods to gain confidence in the obtained results. Our results suggest that the influence of probe emplacement on the surroundings needs to be carefully analyzed and we will present a model for regolith disruption due to probe emplacement. Furthermore, we will show that the inversion of transients in terms of thermal conductivity would benefit from the simultaneous determination of the in-situ density by, e.g., measuring the electrical permittivity of the regolith at a working frequency around 1 MHz.
NASA Astrophysics Data System (ADS)
Li, W.; Zhang, Z.; Tong, P.
2012-02-01
The effect of the Dzyaloshinskii-Moriya (DM) interaction on the heat conduction in the quantum Ising chain has been studied by solving the Lindblad master equation. The chain is subject to a uniform transverse field h, while the exchange couplings { J m } between the nearest-neighbor spins are either uniform, random or quasi-periodic. The average energy-density profile and the average energy current in the non-equilibrium steady state have been numerically calculated. The ballistic transport is observed in the uniform Ising chain with DM interaction. For the random Ising chain with DM interaction, the energy gradient is observed in the bulk of the spin chain whose energy current appears to scale as the system size ? Q? ˜ exp( ?N) with ? < 0. For the quasi-periodic Ising chain with DM interaction, the J m takes the two values J A and J B arranged in the Fibonacci sequence. The energy gradient also exists in the spin chain and the energy current behaves as ? Q? ˜ N ? with ? < 0. By increasing the strength of the DM interaction D, a non-trivial transition from the thermal insulator heat transport to anomalous heat conduction is found in the Fibonacci Ising chain with large ratio of couplings ? = J A / J B . A rough phase diagram of ? vs. D is given in this paper as well.
Dry-out characteristics of heat pipes
NASA Astrophysics Data System (ADS)
Kuramae, M.; Matsumoto, M.
1985-09-01
Dryout characteristics of heat pipes having capillary wicks were analyzed by a simple model on the basis of the effect of axial heat conduction. It was found that the profiles of axial temperature distribution in the wall for heat transfer rates over the critical point were dependent upon the value of a dimensionless parameter Y-asterisk representing the degree of axial heat conduction compared to radial heat conduction. Namely, for heat pipes of larger Y-asterisk (greater than 10,000), the temperature increases at the end point of the heating section. But, for heat pipes of small Y-asterisk (less than 100), the temperature at the point does not rise so highly if dryout proceeds. From that viewpoint, the significance of a critical heat flux by capillary pumping limit was investigated.
eXtremes of heat conduction: Pushing the boundaries of the thermal
Braun, Paul
-called "nanofluids" (suspensions in liquids) polymer composites and coatings Fischer (2007) Lehman (2005) #12/m-K #12;High throughput measurements of polymer fibers by time-domain thermoreflectance · Dyneema, and polyethelene Ultralow conductivity disordered layered crystals High pressures: ice VII at 20 GPa High
A note on stability in three-phase-lag heat conduction Ramon Quintanilla1
Racke, Reinhard
the exponential stability of solutions. The spectral analysis complements the results and we show conduction, stability 1 Supported by the project "Qualitative study of thermomechanical problems " (MTM2006 also consider the spectral analysis of these equations. Both analysis aspects characterize suitable
Long-Wave Instability of Advective Flows in Inclined Layer with Solid Heat Conductive Boundaries
R. V. Sagitov; A. N. Sharifulin
2011-01-07
We investigate the stability of the steady convective flow in a plane tilted layer with ideal thermal conductivity of solid boundaries in the presence of uniform longitudinal temperature gradient. Analytically found the stability boundary with respect to the long-wave perturbations, find the critical Grashof number for the most dangerous among them of even spiral perturbation.
to bring down the largest single cost associated with tapping geothermal heat,and conducting
Gildor, Hezi
resource assessments of geothermal potential in the U.S. While the U.S.Geological Survey conducted an assessment of national geothermal resources in the 1970s,the project ran short of funding, according to Karl Gawell,president of the Geothermal Energy Association.Gawell said the assessment also did not look
NASA Astrophysics Data System (ADS)
Li, Jing; Feng, Yanhui; Zhang, Xinxin; Huang, Congliang; Wang, Ge
2015-01-01
Mesoporous silica substrate consists of uniformly distributed, unconnected cylindrical or spherical pores. Since the diameters of the pores are less than the wavelength, near-field radiative heat transfer across a cylindrical or spherical pore was simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material were analyzed. It turned out that when the diameter is greater than 1 nm and less than 50 nm, the radiative heat flux at the mesoscale is 2-6 orders higher than the value at the macroscale, and decreases exponentially with the pore radius increasing for both cylindrical and spherical pore. The thermal conductivity of the mesoporous silica was modified with consideration of near-field radiation. It was concluded that the combined thermal conductivities of mesoporous silica which considering near-field radiation can agree with the experimental results more properly than non-considering near-field radiation. The smaller the pore diameter, the more significant the near-field radiation effect. The combined thermal conductivities of mesoporous silica decrease gradually with the pore diameter increasing, while increase smoothly with the temperature increasing.
NASA Astrophysics Data System (ADS)
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 ? 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 ? 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.
Samet Y. Kadioglu; Robert R. Nourgaliev; Vincent A. Mousseau
2008-03-01
We perform a comparative study for the harmonic versus arithmetic averaging of the heat conduction coefficient when solving non-linear heat transfer problems. In literature, the harmonic average is the method of choice, because it is widely believed that the harmonic average is more accurate model. However, our analysis reveals that this is not necessarily true. For instance, we show a case in which the harmonic average is less accurate when a coarser mesh is used. More importantly, we demonstrated that if the boundary layers are finely resolved, then the harmonic and arithmetic averaging techniques are identical in the truncation error sense. Our analysis further reveals that the accuracy of these two techniques depends on how the physical problem is modeled.
NASA Astrophysics Data System (ADS)
Mittal, Arpit; Mazumder, Sandip
2011-08-01
The Boltzmann Transport Equation (BTE) for phonons has found prolific use for the prediction of non-equilibrium heat conduction phenomena in semiconductor materials. This article presents a new hybrid formulation and associated numerical procedures for solution of the BTE for phonons. In this formulation, the phonon intensity is first split into two components: ballistic and diffusive. The governing equation for the ballistic component is solved using two different established methods that are appropriate for use in complex geometries, namely the discrete ordinates method (DOM), and the control angle discrete ordinates method (CADOM). The diffusive component, on the other hand, is determined by invoking the first-order spherical harmonics (or P1) approximation, which results in a Helmholtz equation with Robin boundary conditions. Both governing equations, referred to commonly as the ballistic-diffusive equations (BDE), are solved using the unstructured finite-volume procedure. Results of the hybrid method are compared against benchmark Monte Carlo results, as well as solutions of the BTE using standalone DOM and CADOM for two two-dimensional transient heat conduction problems at various Knudsen numbers. Subsequently, the method is explored for a large-scale three-dimensional geometry in order to assess convergence and computational cost. It is found that the proposed hybrid method is accurate at all Knudsen numbers. From an efficiency standpoint, the hybrid method is found to be superior to direct solution of the BTE both for steady state as well as for unsteady non-equilibrium heat conduction calculations with the computational gains increasing with increase in problem size.
F. Tsuchiya; H. Misawa; K. Imai; A. Morioka
2011-01-01
Evidence of short-term changes in Jupiter's synchrotron radiaion at 325 MHzRadial diffusion rate of 3 × 10?8 L3 \\/s is suitable in Jupiter's radiation beltThe synchrotron emission does not contribute electron loss in the radiation belt
OHKUNI Kotaro; OGAWA Yuichi; MORIKAWA Junji; HORI Dan; YAMAKOSHI Shigeo; GOTO Takuya; YANAGI Nagato
2004-01-01
The relaxation state under the condition of a strong plasma flow is represented by the double Beltrami field. The generalized Bernoulli condition gives a simple relation between the flow velocity and the static pressure. An internal coil device is suitable for exploring this new relaxation state experimentally, because an appropriate radial electric field induces a strong toroidal flow. An internal
NASA Astrophysics Data System (ADS)
Zhuang, Qiao; Yu, Bo; Jiang, Xiaoyun
2015-01-01
In this paper, a time-fractional heat conduction problem is mathematically proposed for an experimental heat conduction process in a 3-layer composite medium. A numerical solution to the direct problem is obtained with finite difference method. In regard to the inverse problem, the optimal order of Caputo fractional derivative is estimated with Levenberg-Marquardt method. Comparing with the carbon-carbon experimental data, the results show that the time-fractional heat conduction model provides an effective and accurate simulation of the experimental data. The rationality of the proposed time-fractional model and validity of Levenberg-Marquardt method in solving the time-fractional inverse heat conduction problem are also manifested according to the results. By conducting the sensitivity analysis, the feasibility of the parameter estimation is further discussed.
Electron-muon heat conduction in neutron star cores via the exchange of transverse plasmons
P. S. Shternin; D. G. Yakovlev
2007-05-14
We calculate the thermal conductivity of electrons and muons kappa_{e-mu} produced owing to electromagnetic interactions of charged particles in neutron star cores and show that these interactions are dominated by the exchange of transverse plasmons (via the Landau damping of these plasmons in nonsuperconducting matter and via a specific plasma screening in the presence of proton superconductivity). For normal protons, the Landau damping strongly reduces kappa_{e-mu} and makes it temperature independent. Proton superconductivity suppresses the reduction and restores the Fermi-liquid behavior kappa_{e-mu} ~ 1/T. Comparing with the thermal conductivity of neutrons kappa_n, we obtain kappa_{e-mu}> kappa_n for T>2 GK in normal matter and for any T in superconducting matter with proton critical temperatures T_c>3e9 K. The results are described by simple analytic formulae.
Conductive and Radiative Heat Transfer in Ceramic and Metal Foams at Fire Temperatures
Rémi Coquard; Denis Rochais; Dominique Baillis
In addition to the multiple actual or possible applications of metal and ceramic foams in various technological fields, their\\u000a thermal properties make them a good candidate for utilization as fire barriers. Several studies have shown experimentally\\u000a their exceptional fire retardance due to their low apparent thermal conductivity. However, while the thermal properties of\\u000a this porous material have been widely studied
Control of differential strain during heating and cooling of mixed conducting metal oxide membranes
Carolan, Michael Francis (Allentown, PA)
2007-12-25
Method of operating an oxygen-permeable mixed conducting membrane having an oxidant feed side and a permeate side, which method comprises controlling the differential strain between the oxidant feed side and the permeate side by varying either or both of the oxygen partial pressure and the total gas pressure on either or both of the oxidant feed side and the permeate side of the membrane while changing the temperature of the membrane from a first temperature to a second temperature.
Shehzad, Sabir Ali; Alsaedi, Ahmed; Hayat, Tasawar; Alhuthali, M. Shahab
2013-01-01
This paper looks at the series solutions of three dimensional boundary layer flow. An Oldroyd-B fluid with variable thermal conductivity is considered. The flow is induced due to stretching of a surface. Analysis has been carried out in the presence of heat generation/absorption. Homotopy analysis is implemented in developing the series solutions to the governing flow and energy equations. Graphs are presented and discussed for various parameters of interest. Comparison of present study with the existing limiting solution is shown and examined. PMID:24223780
Ali Shehzad, Sabir; Alsaedi, Ahmed; Hayat, Tasawar; Alhuthali, M Shahab
2013-01-01
This paper looks at the series solutions of three dimensional boundary layer flow. An Oldroyd-B fluid with variable thermal conductivity is considered. The flow is induced due to stretching of a surface. Analysis has been carried out in the presence of heat generation/absorption. Homotopy analysis is implemented in developing the series solutions to the governing flow and energy equations. Graphs are presented and discussed for various parameters of interest. Comparison of present study with the existing limiting solution is shown and examined. PMID:24223780
Heat transfer in liquid metals with electric currents and magnetic fields: the conduction case
NASA Astrophysics Data System (ADS)
Kalkan, Ali Kaan; Talmage, Gita
1995-02-01
There are two volumetric heat sources in a liquid-metal sliding electric contact for a homopolar device; the viscous dissipation results from the motion of the liqiud metal and is enhanced by magnetohydrodynamic (MHD) effects. In a homopolar device, the liquid metal is confined to a small gap between the perimeter of a rotating disk and the surrounding static surface. The maximum temperature achieved within the liquid metal is significantly larger for an MHD flow than for an ordinary hydrodynamic flow, a flow in the absence of a magnetic field. Information concerning the temperature distribution within the liquid metal and solid parts of a homopolar device will result in the design of efficient and operational sliding electrical contacts.
Strong Evidence of Normal Heat Conduction in a one-Dimensional Quantum System
Keiji Saito
2002-12-11
We investigate how the normal energy transport is realized in one-dimensional quantum systems using a quantum spin system. The direct investigation of local energy distribution under thermal gradient is made using the quantum master equation, and the mixing properties and the convergence of the Green-Kubo formula are investigated when the number of spin increases. We find that the autocorrelation function in the Green-Kubo formula decays as $\\sim t^{-1.5}$ to a finite value which vanishes rapidly with the increase of the system size. As a result, the Green-Kubo formula converges to a finite value in the thermodynamic limit. These facts strongly support the realization of Fourier heat law in a quantum system.
Pern, J.; Noufi, R.; Li, X.; DeHart, C.; To, B.
2008-05-01
The objectives are: (1) To achieve a high long-term performance reliability for the thin-film CIGS PV modules with more stable materials, device structure designs, and moisture-resistant encapsulation materials and schemes; (2) to evaluate the DH stability of various transparent conducting oxides (TCOs); (3) to identify the degradation mechanisms and quantify degradation rates; (4) to seek chemical and/or physical mitigation methods, and explore new materials. It's important to note that direct exposure to DH represents an extreme condition that a well-encapsulated thin film PV module may never experience.
NASA Astrophysics Data System (ADS)
Kazeminezhad, F.; Goodman, M. L.
2008-12-01
A complete anisotropic, inhomogeneous electrical conductivity tensor, which includes Spitzer, Pedersen, and Hall conductivities is included in an MHD simulation to describe how MHD shock waves may form, propagate, and resistively heat the atmosphere from the photosphere through the chromosphere. The MHD model includes an energy equation. The initial state is defined by FAL density, pressure, and temperature profiles, and by a magnetic field that decreases with height z. The initial magnetic field strength at the photosphere is 500 G. A harmonic magnetic field perturbation with amplitude 250 G and period 30 seconds is applied at the photosphere. Smooth waves are generated at the photosphere that propagate upward and begin to form shock waves near z=350 km. This is the height near which electrons first become magnetized. The shocks become fully formed near the FAL temperature minimum at z=500 km. This is the height where the product of the electron and proton magnetizations first exceeds unity, causing the Pedersen resistivity to begin to rapidly exceed the Spitzer resistivity by orders of magnitude with increasing height. This is also the height at which heating by proton Pedersen current dissipation rapidly increases with height, and rapidly becomes large enough to balance the radiative losses from the chromosphere. The onset of this strong heating is triggered by the onset of electron and proton magnetization near the temperature minimum. The shock thicknesses are ~ ~ 5 km. The shocks are the sites of resistive heating rates as large as 3-10 ergs-cm-3-sec-1 in the chromosphere. The time averaged heating rate over an interval of 162 seconds corresponds to a chromospheric heating flux ~ 2-3 × 106 ergs-cm-2-sec-1. The heating rate increases with driving frequency, and is ? B2. These results support the proposition of Goodman (e.g. Goodman 2000, ApJ, 533, 501; Goodman 2004, A&A, 424,691; Kazeminezhad & Goodman 2006, ApJ, 166, 613) that the onset of electron and proton magnetization near the local temperature minimum, and their rapid increase with height causes the rate of proton Pedersen current dissipation to rapidly increase by orders of magnitude with height, creating and maintaining the solar chromosphere, and the chromospheres of solar type stars. This mechanism is not restricted to shock waves. It operates on any current generating MHD process. Such a process must involve currents driven by a combination of induction and convection generated electric fields. Examples are linear waves, and steady convection across magnetic field lines. It is the weakly ionized, strongly magnetized nature of the chromosphere that allows this heating mechanism to be so effective, and that distinguishes the chromosphere from the weakly ionized, weakly magnetized photosphere, and the strongly ionized, strongly magnetized corona. The dominance of proton-neutral H collisions in determining the proton collision frequency is necessary for this Pedersen current dissipation mechanism to be an effective heating mechanism in the chromosphere. This work was supported by Grant ATM 0650443 from the National Science Foundation to the West Virginia High Technology Consortium Foundation. class="ab'>
Manipulator having thermally conductive rotary joint for transferring heat from a test specimen
Haney, Steven J. (Tracy, CA); Stulen, Richard H. (Livermore, CA); Toly, Norman F. (Livermore, CA)
1985-01-01
A manipulator for rotatably moving a test specimen in an ultra-high vacuum chamber includes a translational unit movable in three mutually perpendicular directions. A manipulator frame is rigidly secured to the translational unit for rotatably supporting a rotary shaft. A first copper disc is rigidly secured to an end of the rotary shaft for rotary movement within the vacuum chamber. A second copper disc is supported upon the first disc. The second disc receives a cryogenic cold head and does not rotate with the first disc. A sapphire plate is interposed between the first and second discs to prevent galling of the copper material while maintaining high thermal conductivity between the first and second discs. A spring is disposed on the shaft to urge the second disc toward the first disc and compressingly engage the interposed sapphire plate. A specimen mount is secured to the first disc for rotation within the vacuum chamber. The specimen maintains high thermal conductivity with the second disc receiving the cryogenic transfer line.
Manipulator having thermally conductive rotary joint for transferring heat from a test specimen
Haney, S.J.; Stulen, R.H.; Toly, N.F.
1983-05-03
A manipulator for rotatably moving a test specimen in an ultra-high vacuum chamber includes a translational unit movable in three mutually perpendicular directions. A manipulator frame is rigidly secured to the translational unit for rotatably supporting a rotary shaft. A first copper disc is rigidly secured to an end of the rotary shaft for rotary movement within the vacuum chamber. A second copper disc is supported upon the first disc. The second disc receives a cryogenic cold head and does not rotate with the first disc. The second disc receives a cryogenic cold head and does not rotate with the first disc. A sapphire plate is interposed between the first and second discs to prevent galling of the copper material while maintaining high thermal conductivity between the first and second discs. A spring is disposed on the shaft to urge the second disc toward the first disc and compressingly engage the interposed sapphire plate. A specimen mount is secured to the first disc for rotation within the vacuum chamber. The specimen maintains high thermal conductivity with the second disc receiving the cryogenic transfer line.
The role of condensation and heat conduction in the formation of prominences - An MHD simulation
NASA Technical Reports Server (NTRS)
Wu, S. T.; Bao, J. J.; An, C. H.; Tandberg-Hanssen, E.
1990-01-01
The effects of condensation and thermal conduction on the formation of Kippenhahn-Schlueter (K-S) type prominences in quiet regions (QP) due to symmetric mass injection are investigated. To implement this investigation a self-consistent, two-dimensional, nonplanar, time-dependent MHD simulation model is developed. In the model, various values of the injection velocity, density, and magnetic field strength are used to determine the most favorable conditions for the QP formation. Based on these simulation results, it is found that the formation of a K-S type field configuration should be considered as a dynamic process which needs both condensation amd mass injection to supply enough mass to maintain such a configuration to complete the quiescent prominence formation process.
Modeling Heat Conduction and Radiation Transport with the Diffusion Equation in NIF ALE-AMR
Fisher, A C; Bailey, D S; Kaiser, T B; Gunney, B N; Masters, N D; Koniges, A E; Eder, D C; Anderson, R W
2009-10-06
The ALE-AMR code developed for NIF is a multi-material hydro-code that models target assembly fragmentation in the aftermath of a shot. The combination of ALE (Arbitrary Lagrangian Eulerian) hydro with AMR (Adaptive Mesh Refinement) allows the code to model a wide range of physical conditions and spatial scales. The large range of temperatures encountered in the NIF target chamber can lead to significant fluxes of energy due to thermal conduction and radiative transport. These physical effects can be modeled approximately with the aid of the diffusion equation. We present a novel method for the solution of the diffusion equation on a composite mesh in order to capture these physical effects.
NASA Technical Reports Server (NTRS)
Seyed-Yagoobi, J.; Didion, J.; Ochterbeck, J. M.; Allen, J.
2000-01-01
There are three kinds of electrohydrodynamics (EHD) pumping based on Coulomb force: induction pumping, ion-drag pumping, and pure conduction pumping. EHD induction pumping relies on the generation of induced charges. This charge induction in the presence of an electric field takes place due to a non-uniformity in the electrical conductivity of the fluid which can be caused by a non-uniform temperature distribution and/or an inhomogeneity of the fluid (e.g. a two-phase fluid). Therefore, induction pumping cannot be utilized in an isothermal homogeneous liquid. In order to generate Coulomb force, a space charge must be generated. There are two main mechanisms for generating a space charge in an isothermal liquid. The first one is associated with the ion injection at a metal/liquid interface and the related pumping is referred to as ion-drag pumping. Ion-drag pumping is not desirable because it can deteriorate the electrical properties of the working fluid. The second space charge generation mechanism is associated with the heterocharge layers of finite thickness in the vicinity of the electrodes. Heterocharge layers result from dissociation of the neutral electrolytic species and recombination of the generated ions. This type of pumping is referred to as pure conduction pumping. This project investigates the EHD pumping through pure conduction phenomenon. Very limited work has been conducted in this field and the majority of the published papers in this area have mistakenly assumed that the electrostriction force was responsible for the net flow generated in an isothermal liquid. The main motivation behind this study is to investigate an EHD conduction pump for a two-phase loop to be operated in the microgravity environment. The pump is installed in the liquid return passage (isothermal liquid) from the condenser section to the evaporator section. Unique high voltage and ground electrodes have been designed that generate sufficient pressure heads with very low electric power requirements making the EHD conduction pumping attractive to applications such as two-phase systems (e.g. capillary pumped loops and heat pipes). Currently, the EHD conduction pump performance is being tested on a two-phase loop under various operating conditions in the laboratory environment. The simple non-mechanical and lightweight design of the EHD pump combined with the rapid control of performance by varying the applied electric field, low power consumption, and reliability offer significant advantages over other pumping mechanisms; particularly in reduced gravity applications.
G. Ganesh Kumar; C. Gururaja Rao
2011-01-01
The present paper reports the parametric studies and correlations for the problem of combined conduction-mixed convection-radiation from a non-identically and discretely heated vertical plate. Three discrete heat sources of non-identical heights but with identical volumetric rate of heat generation are assumed to be flush-mounted in a thin vertical plate. The longest and the shortest heaters are provided at the leading
T. J. Chung; J. Y. Kim
1984-01-01
This paper is concerned with a two-dimensional analysis of combined mode heat transfer using finite elements. Conduction, convection, and radiation are coupled in the emitting, absorbing, and scattering medium. The standard Galerkin finite elements can be used if the product of Reynolds number and Prandtl number is equal to or less than 1000. It is shown that the two-dimensional heat
C. Gururaja Rao
2004-01-01
This article presents the results of a comprehensive fundamental numerical study of the problem of buoyancy-aided mixed convection with conduction and surface radiation from a vertical electronic board provided with a traversable, flush-mounted, discrete heat source. Air, a radiatively transparent medium, is considered to be the cooling agent. The governing equations in primitive variables for fluid flow and heat transfer
High thermally conductive green polymeric composites in electronic packaging The goal of electronic packaging is to provide mechanical support and also manage heat dissipation of electronics components such as Laptops, cell phones etc. As electronic devices become smaller and more powerful, it results in more heat
G. Nath
A self-similar solution is obtained for one dimensional adiabatic flow behind a cylindrical shock wave propagating in a rotating dusty gas in presence of heat conduction and radiation heat flux with increasing energy. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is
Gus'kov, Sergei Yu; Doskach, I Ya [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)
1999-10-31
An analytical solution is obtained to the problem of propagation of a 2-D nonlinear heat conduction wave from a cylindrical energy source, which acts in a planar layer of a material surrounded by a medium with different mass density and degree of ionisation. A theoretical justification is given of several interesting phenomena of 2-D thermal wave propagation through an inhomogeneous medium. These phenomena are related to the difference between the thermal wave velocities in the media with different thermal diffusivities. When the mass density in a layer experiencing the action of an energy source exceeds the density of the surrounding medium, the thermal wave front is shown to glide along the layer boundaries with a spatial velocity exceeding the velocity of the wave inside the layer. Moreover, there is a possibility of 'themal flow' of a layer across the boundaries between the layer and the surrounding medium in front of a thermal wave propagating inside the layer. The problems of heat transfer in multilayer targets for laser thermonuclear fusion are considered as an application. (interaction of laser radiation with matter. laser plasma)
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.
HEAT TRANSFER IN PACKED BED REACTORS WITH ONE PHASE FLOW
V. SPECCHIA; G. BALDI; S. SICARDI
1980-01-01
An extensive array of literature data on the heat transfer from a reactor wall to a fluid flowing through a packed bed and those obtained from some experimental runs were interpreted with a model containing two parameters: ke, (effective radial thermal conductivity within the bed) and hw (heat transfer coefficient at the wall).Both parameters were considered in terms of a
Shestakov, A I; Matthews, M J; Vignes, R M; Stolken, J S
2010-10-28
Localized, transient heating of materials using micro-scale, highly absorbing laser light has been used in many industries to anneal, melt and ablate material with high precision. Accurate modeling of the relative contributions of conductive, convective and radiative losses as a function of laser parameters is essential to optimizing micro-scale laser processing of materials. In bulk semi-transparent materials such as silicate glass melts, radiation transport is known to play a significantly larger role as the temperature increases. Conventionally, radiation is treated in the frequency-averaged diffusive limit (Rosseland approximation). However, the role and proper treatment of radiative processes under rapidly heated, high thermal gradient conditions, often created through laser-matter interactions, is at present not clear. Starting from the radiation transport equation for homogeneous, refractive lossy media, they derive the corresponding time-dependent multi-frequency diffusion equations. Zeroth and first moments of the transport equation couple the energy density, flux and pressure tensor. The system is closed by neglecting the temporal derivative of the flux and replacing the pressure tensor by its diagonal analogue. The radiation equations are coupled to a diffusion equation for the matter temperature. They are interested in modeling infrared laser heating of silica over sub-millimeter length scales, and at possibly rapid rates. Hence, in contrast to related work, they retain the temporal derivative of the radiation field. They derive boundary conditions at a planar air-silica interface taking account of reflectivities obtained from the Fresnel relations that include absorption. The effect of a temperature-dependent absorption index is explored through construction of a multi-phonon dielectric function that includes mode dispersion. The spectral dimension is discretized into a finite number of intervals yielding a system of multigroup diffusion equations. Simulations are presented. To demonstrate the bulk heat loss due to radiation and the effect of the radiation's temporal derivative, they model cooling of a silica slab, initially at 2500 K, for 10 s. Retaining the derivative enables correctly modeling the loss of photons initially present in the slab. Other simulations model irradiating silica discs (of approximately 5 mm radii and thickness) with a CO2 laser: {lambda} = 10.59 and 4.6 um, Gaussian profile, r{sub 0} = 0.5 mm for 1/e decay. By surrounding the disks in room-temperature air, they make use of the boundary conditions described above.
NASA Astrophysics Data System (ADS)
Sadoun, Nacer; Si-Ahmed, El-Khider; Colinet, Pierre; Legrand, Jack
Explicit numerical schemes obtained using variable space grid (VSGM) and boundary immobilization (BIM) methods are considered for the solution of the transient heat conduction problem with phase change. This article briefly reviews different approaches developed to track the phase change front with a particular interest to those tracking explicitly the moving boundary. The analysis shows that both methods lead to identical computational algorithm, then considers the modified numerical scheme developed by Kutluay et al. (J. Comput. Appl. Math. 81 (1997) 135-144) and proposes a refinement procedure for the scheme without any additional CPU time. Two Stefan-like problems, having exact solutions, are studied and numerical results are assessed with respect to their performances.