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.
Radial heat transfer from a moving plasma
Johnson, James Randall
1966-01-01
. The radiative heat flux from shock heat argor. to the stagr ation point of a blunt body has beer, investigated by Brown and Ross (13). Free ? free and free-bound electron-ion recombination in addition to tie characteristic line radiatior were the processes...RADIAL HEAT TRANSFER FROM A MOVING PLASMA A Thesis By JAMES RANDALL JOHNSON Submitted to the Graduate College of the Texas A!&I University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 1966 Major...
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.
Multi-scale Numerical Modeling of Radial Heat Transfer in Grooved Heat Pipe Evaporators
Séverine Rossomme; Cécile Goffaux; Koen Hillewaert; Pierre Colinet
2008-01-01
It is well known that small-scale effects near contact lines have a crucial importance on the radial heat transfer within\\u000a a grooved heat pipe evaporator. This paper studies this problem using a multi-scale model which is composed of two parts,\\u000a macroscopic and microscopic. At the macroscopic scale, we solve the heat conduction problem for the solid and the liquid phases,
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. PMID:25851897
Variable conductance heat pipe technology
NASA Technical Reports Server (NTRS)
Marcus, B. D.; Edwards, D. K.; Anderson, W. T.
1973-01-01
Research and development programs in variable conductance heat pipe technology were conducted. The treatment has been comprehensive, involving theoretical and/or experimental studies in hydrostatics, hydrodynamics, heat transfer into and out of the pipe, fluid selection, and materials compatibility, in addition to the principal subject of variable conductance control techniques. Efforts were not limited to analytical work and laboratory experimentation, but extended to the development, fabrication and test of spacecraft hardware, culminating in the successful flight of the Ames Heat Pipe Experiment on the OAO-C spacecraft.
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. Nitrogen, hydrogen, ard argon were the three gases used, The gererating unit was a dc-plasma jet capable of covering a range of 5 to 100 KW with 50 to &0% of this power absorbed by the gas. Test sections of I/2? 1, and 2 inc. , es in diameter...
Analysis of radial fin assembly heat transfer with dehumidification
Rosario, L.; Rahman, M.M. [Univ. of South Florida, Tampa, FL (United States). Dept. of Mechanical Engineering
1996-12-31
The aim of this paper is the analysis of heat transfer in a radial fin assembly during the process of dehumidification. An individual finned tube geometry is a reasonable representation of heat exchangers used in air conditioning. The condensation process involves both heat and mass transfer and the cooling takes place by the removal of sensible as well as latent heat. The ratio of sensible to total heat is an important quantity that defines the heat transfer process during a dehumidifier operation. A one-dimensional model for heat transfer in the fin and the heat exchanger block is developed to study the effects of condensation on the fin surface. The combined heat and mass transfer process is modeled by incorporating the ratio of sensible to total heat in the formulation. The augmentation of heat transfer due to fin was established by comparing heat transfer rate with and without fins under the same operating conditions. Numerical calculations were carried out to study the effects of relative humidity and dry bulb temperature of the incoming air, and cold fluid temperature inside the coil on the performance of the heat exchanger. Results were compared to those published for rectangular fin under humid condition showed excellent agreement when the present model was used to compute that limiting condition. It was found that the heat transfer rate increased with increment in both dry bulb temperature and relative humidity of the air. The augmentation factor, however, decreased with increment in relative humidity and the dry bulb temperature.
Optimization of a Radial Flow Heat Sink Under Natural Convection
NASA Astrophysics Data System (ADS)
Bhowmik, Himangshu
2014-01-01
A steady-state three-dimensional numerical model is developed to predict natural convection heat transfer from a radial flow heat sink. The considered medium is air. The effect of several design parameters, such as the fin length and height, number of fins, and the heat sink base radius, on heat transfer is investigated. The Taguchi method, known to be a very useful tool for selecting the best levels of control factors, is employed. Five factors and four levels for each factor are chosen. Sixteen kinds of models are analyzed, and the total heat transfer for each model is obtained. The results are used to estimate the optimum design values of the parameters affecting the heat sink performance. The reliability of these values is verified. The average heat transfer rate of the optimum model is shown to increase by 60% as compared to the reference model. Finally, the heat transfer data at different outer radii of the radial flow heat sink are correlated.
Microwave heating of conductive powder materials
K. I. Rybakov; V. E. Semenov; S. V. Egorov; A. G. Eremeev; I. V. Plotnikov; Yu. V. Bykov
2006-01-01
In recent years, a considerable interest has been drawn to microwave heating of powder metals and other electrically conductive materials. In this paper a consistent formulation describing the absorption of microwaves in electrically conductive materials under different microwave heating conditions is developed. A special case when conductive powder particles are surrounded by insulating oxide layers is investigated in detail using
Microwave heating of electrically conductive materials
NASA Astrophysics Data System (ADS)
Rybakov, K. I.; Semenov, V. E.
2005-10-01
In recent years, considerable interest has been drawn to microwave heating of powder metals and other electrically conductive materials. In this paper, we consider absorption of electromagnetic waves in materials with different effective conductivities for different microwave heating conditions. Specific features of microwave heating at the maxima of electric and magnetic fields in a standing-wave applicator are discussed. Absorption in materials containing conductive particles with dielectric shells are studied in detail using the effective-medium approximation.
Variable boundary II heat conduction
NASA Technical Reports Server (NTRS)
Gramer, J.; Oneill, R. F.
1972-01-01
Computer program for solving both transient and steady-state heat transfer problems is presented. Specific applications of computer program are described. Formulation for individual nodes of solid medium for heat balance is presented. Diffusion equation is solved for all nodes simultaneously at finite increments of time.
Heat Transfer Derivation of differential equations for heat transfer conduction
Veress, Alexander
Heat Transfer Derivation of differential equations for heat transfer conduction without convection/(hftF). T is the temperature, in C or F. dT=dx is the temperature gradient, in C/m or F/ft. This equation states that the heat sign in the above equation states heat flow is positive in the direction opposite the direction
Microwave heating of conductive powder materials
NASA Astrophysics Data System (ADS)
Rybakov, K. I.; Semenov, V. E.; Egorov, S. V.; Eremeev, A. G.; Plotnikov, I. V.; Bykov, Yu. V.
2006-01-01
In recent years, a considerable interest has been drawn to microwave heating of powder metals and other electrically conductive materials. In this paper a consistent formulation describing the absorption of microwaves in electrically conductive materials under different microwave heating conditions is developed. A special case when conductive powder particles are surrounded by insulating oxide layers is investigated in detail using the effective-medium approximation. The conditions giving rise to skin effect governed, volumetric, and localized microwave heating are analyzed. Experimental observations of different microwave heating regimes in silicon, iron, and copper powder compacts are in general agreement with the theoretical model.
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,
Heat conduction in heterogeneous materials
J. Baker-Jarvis; R. Inguva
1985-01-01
A new solution to the heat equation in composite media is derived using a variational principle developed by Ben-Amoz. The model microstructure is fed into the equations via a term for the polar moment of the inclusions in a representative volume. The general solution is presented as an integral in terms of sources and a Green function. The problem of
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.
Information filtering via biased heat conduction.
Liu, Jian-Guo; Zhou, Tao; Guo, Qiang
2011-09-01
The process of heat conduction has recently found application in personalized recommendation [Zhou et al., Proc. Natl. Acad. Sci. USA 107, 4511 (2010)], which is of high diversity but low accuracy. By decreasing the temperatures of small-degree objects, we present an improved algorithm, called biased heat conduction, which could simultaneously enhance the accuracy and diversity. Extensive experimental analyses demonstrate that the accuracy on MovieLens, Netflix, and Delicious datasets could be improved by 43.5%, 55.4% and 19.2%, respectively, compared with the standard heat conduction algorithm and also the diversity is increased or approximately unchanged. Further statistical analyses suggest that the present algorithm could simultaneously identify users' mainstream and special tastes, resulting in better performance than the standard heat conduction algorithm. This work provides a creditable way for highly efficient information filtering. PMID:22060533
Information filtering via biased heat conduction
NASA Astrophysics Data System (ADS)
Liu, Jian-Guo; Zhou, Tao; Guo, Qiang
2011-09-01
The process of heat conduction has recently found application in personalized recommendation [Zhou , Proc. Natl. Acad. Sci. USA PNASA60027-842410.1073/pnas.1000488107107, 4511 (2010)], which is of high diversity but low accuracy. By decreasing the temperatures of small-degree objects, we present an improved algorithm, called biased heat conduction, which could simultaneously enhance the accuracy and diversity. Extensive experimental analyses demonstrate that the accuracy on MovieLens, Netflix, and Delicious datasets could be improved by 43.5%, 55.4% and 19.2%, respectively, compared with the standard heat conduction algorithm and also the diversity is increased or approximately unchanged. Further statistical analyses suggest that the present algorithm could simultaneously identify users' mainstream and special tastes, resulting in better performance than the standard heat conduction algorithm. This work provides a creditable way for highly efficient information filtering.
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.
Determination of the heat transfer coefficients in transient heat conduction
NASA Astrophysics Data System (ADS)
Nho Hào, Dinh; Thanh, Phan Xuan; Lesnic, D.
2013-09-01
The determination of the space- or time-dependent heat transfer coefficient which links the boundary temperature to the heat flux through a third-kind Robin boundary condition in transient heat conduction is investigated. The reconstruction uses average surface temperature measurements. In both cases of the space- or time-dependent unknown heat transfer coefficient the inverse problems are nonlinear and ill posed. Least-squares penalized variational formulations are proposed and new formulae for the gradients are derived. Numerical results obtained using the nonlinear conjugate gradient method combined with a boundary element direct solver are presented and discussed.
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-Conducting Anchors for Thermocouples
NASA Technical Reports Server (NTRS)
Macdavid, Kenton S.
1987-01-01
Metal particles in adhesive aid heat transfer. Aluminum caps containing silver-filled epoxy used as high-thermal-conductance anchors for thermocouples, epoxy providing thermal path between mounting surfaces and thermocouple measuring junctions. Normally, epoxy-filled aluminum caps used when measuring steady-state temperatures. Silver-filled epoxy used when thermocouple not isolated electrically from surface measured.
High conductive heat-resistant aluminium alloy
Sato, K.; Hanaki, Y.; Kondo, T.; Yamauchi, K.; Yokota, M.
1983-09-06
A heat-resistant aluminum alloy is disclosed for electrical use, having high heat resistance and conductivity, obtained by subjecting an Al-Zr alloy comprising 0.23-0.35% Zr, the balance consisting of ordinary impurities and aluminum, to melting, casting, hot rolling in the state of high temperature or continuous heating, cold working to a predetermined size, ageing at a temperature within the range of 310/sup 0/ C.-390/sup 0/ C. for 50-400 hours so that Al/sub 3/Zr is dispersed uniformly and in fine particles, and, optionally, further cold working to a degree not exceeding 30% of reduction of area. The resultant aluminum alloy has conductivity in excess of 58% IACS, same strength as 1350 aluminum wire, and 10% softening temperature higher than 400/sup 0/ C. at one hour annealing.
North, Gretchen B; Lynch, Frank H; Maharaj, Franklin D R; Phillips, Carly A; Woodside, Walter T
2013-01-01
Epiphytic plants in the Bromeliaceae known as tank bromeliads essentially lack stems and absorptive roots and instead take up water from reservoirs formed by their overlapping leaf bases. For such plants, leaf hydraulic conductance is plant hydraulic conductance. Their simple strap-shaped leaves and parallel venation make them suitable for modeling leaf hydraulic conductance based on vasculature and other anatomical and morphological traits. Plants of the tank bromeliad Guzmania lingulata were investigated in a lowland tropical forest in Costa Rica and a shaded glasshouse in Los Angeles, CA, USA. Stomatal conductance to water vapor and leaf anatomical variables related to hydraulic conductance were measured for both groups. Tracheid diameters and numbers of vascular bundles (veins) were used with the Hagen-Poiseuille equation to calculate axial hydraulic conductance. Measurements of leaf hydraulic conductance using the evaporative flux method were also made for glasshouse plants. Values for axial conductance and leaf hydraulic conductance were used in a model based on leaky cable theory to estimate the conductance of the radial pathway from the vein to the leaf surface and to assess the relative contributions of both axial and radial pathways. In keeping with low stomatal conductance, low stomatal density, low vein density, and narrow tracheid diameters, leaf hydraulic conductance for G. lingulata was quite low in comparison with most other angiosperms. Using the predicted axial conductance in the leaky cable model, the radial resistance across the leaf mesophyll was predicted to predominate; lower, more realistic values of axial conductance resulted in predicted radial resistances that were closer to axial resistance in their impact on total leaf resistance. Tracer dyes suggested that water uptake through the tank region of the leaf was not limiting. Both dye movement and the leaky cable model indicated that the leaf blade of G. lingulata was structurally and hydraulically well-suited to conserve water. PMID:23596446
North, Gretchen B.; Lynch, Frank H.; Maharaj, Franklin D. R.; Phillips, Carly A.; Woodside, Walter T.
2013-01-01
Epiphytic plants in the Bromeliaceae known as tank bromeliads essentially lack stems and absorptive roots and instead take up water from reservoirs formed by their overlapping leaf bases. For such plants, leaf hydraulic conductance is plant hydraulic conductance. Their simple strap-shaped leaves and parallel venation make them suitable for modeling leaf hydraulic conductance based on vasculature and other anatomical and morphological traits. Plants of the tank bromeliad Guzmania lingulata were investigated in a lowland tropical forest in Costa Rica and a shaded glasshouse in Los Angeles, CA, USA. Stomatal conductance to water vapor and leaf anatomical variables related to hydraulic conductance were measured for both groups. Tracheid diameters and numbers of vascular bundles (veins) were used with the Hagen–Poiseuille equation to calculate axial hydraulic conductance. Measurements of leaf hydraulic conductance using the evaporative flux method were also made for glasshouse plants. Values for axial conductance and leaf hydraulic conductance were used in a model based on leaky cable theory to estimate the conductance of the radial pathway from the vein to the leaf surface and to assess the relative contributions of both axial and radial pathways. In keeping with low stomatal conductance, low stomatal density, low vein density, and narrow tracheid diameters, leaf hydraulic conductance for G. lingulata was quite low in comparison with most other angiosperms. Using the predicted axial conductance in the leaky cable model, the radial resistance across the leaf mesophyll was predicted to predominate; lower, more realistic values of axial conductance resulted in predicted radial resistances that were closer to axial resistance in their impact on total leaf resistance. Tracer dyes suggested that water uptake through the tank region of the leaf was not limiting. Both dye movement and the leaky cable model indicated that the leaf blade of G. lingulata was structurally and hydraulically well-suited to conserve water. PMID:23596446
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.
Coupled heat conduction and deformation in a viscoelastic composite cylinder
NASA Astrophysics Data System (ADS)
Shah, Sneha; Muliana, Anastasia; Rajagopal, K. R.
2009-05-01
We study the coupled problem of deformation due to mechanical and thermal loading of a composite cylinder made up of two layers of linear isotropic viscoelastic materials. The effect of a time-varying temperature field due to unsteady heat conduction on the short term and long term material response is examined in terms of the stress, displacement, and strain fields. The material properties of the two layers of the composite cylinder at any given location and time are assumed to depend on the temperature at that location at that given instant of time. Sequentially coupled analyses of heat conduction and deformation of the viscoelastic composite cylinder are carried out. Analytical solutions for the stress, strain and displacement fields of the viscoelastic composite cylinder are obtained from the corresponding solution of the linear elasticity problem by applying the Correspondence Principle. We examine the discontinuity in the hoop stress and the radial strain at the interface of the two layers caused by mismatches in material properties, during transient heat conduction. We find that the discontinuities change over time as the mismatch in the moduli of the two layers changes due to the material properties which are time-dependent. We also investigate the effect of the thermal field on the time-dependent field variables in the composite body.
Heat conduction of laser vanadate crystals
Zagumennyi, A I; Zavartsev, Yu D; Kutovoi, S A; Shcherbakov, I A [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Popov, P A [Acad. I. G. Petrovskii Bryansk State University, Bryansk (Russian Federation); Zerouk, F [Zecotek Medical Systems Ltd (Singapore)
2008-03-31
The heat conduction of laser vanadate crystals GdVO{sub 4} and YVO{sub 4} and their solid solutions is measured in the temperature interval from 50 to 350 K. Mixed rare-earth vanadates have the common chemical formula Re'{sub 1-x}Re''{sub x}VO{sub 4}, where Re' and Re'' are two or more types of ions from a series La{sup 3+}, Pr{sup 3+}, Nd{sup 3+}, Sm{sup 3+}, Eu{sup 3+}, Gd{sup 3+}, Tb{sup 3+}, Dy{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+}, Yb{sup 3+}, Lu{sup 3+}, Sc{sup 3+}, Y{sup 3+}. The heat conduction of Nd:YVO{sub 4} measured at room temperature proved to be more than twice higher than that reported in the literature and in certificate characteristics of laser Nd:YVO{sub 4} elements manufactured by numerous commercial companies. The empirical dependences of the heat conduction along the crystallographic axes <100> and <001> on the composition of rare-earth vanadates Re'{sub 1-x}Re''{sub x}VO{sub 4}, are obtained in the temperature interval from 200 to 350 K. (active media)
NASA Astrophysics Data System (ADS)
Ruiz, Maritza
Thermal management of systems under high heat fluxes on the order of hundreds of W/cm2 is important for the safety, performance and lifetime of devices, with innovative cooling technologies leading to improved performance of electronics or concentrating solar photovoltaics. A novel, spiraling radial inflow microchannel heat sink for high flux cooling applications, using a single phase or vaporizing coolant, has demonstrated enhanced heat transfer capabilities. The design of the heat sink provides an inward swirl flow between parallel, coaxial disks that form a microchannel of 1 cm radius and 300 micron channel height with a single inlet and a single outlet. The channel is heated on one side through a conducting copper surface, and is essentially adiabatic on the opposite side to simulate a heat sink scenario for electronics or concentrated photovoltaics cooling. Experimental results on the heat transfer and pressure drop characteristics in the heat sink, using single phase water as a working fluid, revealed heat transfer enhancements due to flow acceleration and induced secondary flows when compared to unidirectional laminar fully developed flow between parallel plates. Additionally, thermal gradients on the surface are small relative to the bulk fluid temperature gain, a beneficial feature for high heat flux cooling applications. Heat flux levels of 113 W/cm2 at a surface temperature of 77 deg C were reached with a ratio of pumping power to heat rate of 0.03%. Analytical models on single phase flow are used to explore the parametric trends of the flow rate and passage geometry on the streamlines and pressure drop through the device. Flow boiling heat transfer and pressure drop characteristics were obtained for this heat sink using water at near atmospheric pressure as the working fluid for inlet subcooling levels ranging from 20 to 80 deg C and mean mass flux levels ranging from 184-716 kg/m. 2s. Flow enhancements similar to singlephase flow were expected, as well as enhancements due to increased buoyant forces on vapor bubbles resulting from centripetal acceleration in the flow which will tend to draw the vapor towards the outlet. This can also aid in the reduction of vapor obstruction of the flow. The flow was identified as transitioning through three regimes as the heat rate was increased: partial subcooled flow boiling, oscillating boiling and fully developed flow boiling. During partial subcooled flow boiling, both forced convective and nucleate boiling effects are important. During oscillating boiling, the system fluctuated between partial subcooled flow boiling and fully developed nucleate boiling. Temperature and pressure oscillations were significant in this regime and are likely due to bubble constriction of flow in the microchannel. This regime of boiling is generally undesirable due to the large oscillations in temperatures and pressure and design constraints should be established to avoid large oscillations from occurring. During fully developed flow boiling, water vapor rapidly leaves the surface and the flow does not sustain large oscillations. Reducing inlet subcooling levels was found to reduce the magnitude of oscillations in the oscillating boiling regime. Additionally, reduced inlet subcooling levels reduced the average surface temperature at the highest heat flux levels tested when heat transfer was dominated by nucleate boiling, yet increased the average surface temperatures at low heat flux levels when heat transfer was dominated by forced convection. Experiments demonstrated heat fluxes up to 301 W/cm. 2at an average surface temperature of 134 deg C under partial subcooled flow boiling conditions. At this peak heat flux, the system required a pumping power to heat rate ratio of 0.01%. This heat flux is 2.4 times the typical values for critical heat flux in pool boiling under similar conditions.
High conductivity carbon nanotube wires from radial densification and ionic doping
NASA Astrophysics Data System (ADS)
Alvarenga, Jack; Jarosz, Paul R.; Schauerman, Chris M.; Moses, Brian T.; Landi, Brian J.; Cress, Cory D.; Raffaelle, Ryne P.
2010-11-01
Application of drawing dies to radially densify sheets of carbon nanotubes (CNTs) into bulk wires has shown the ability to control electrical conductivity and wire density. Simultaneous use of KAuBr4 doping solution, during wire drawing, has led to an electrical conductivity in the CNT wire of 1.3×106 S/m. Temperature-dependent electrical measurements show that conduction is dominated by fluctuation-assisted tunneling, and introduction of KAuBr4 significantly reduces the tunneling barrier between individual nanotubes. Ultimately, the concomitant doping and densification process leads to closer packed CNTs and a reduced charge transfer barrier, resulting in enhanced bulk electrical conductivity.
Shape factors in conductive heat transfer
Faulkner, Richard Campbell
1954-01-01
Vs L 2/9, ; Ll/9, O. 166V. . . . . 54 XL Vs L 2/Do, L /D 0. 250Q. L Vs L. /9; L /9 0. 5555. . . . . 56 LX Vs L /9 ; Ll/9 0. 3. 667. . . . . 5V LXI Vs L 2/9, ; Ll/9 O. 25OO. . . . . 52 XXII Pactox 1-2 Vs L 2/9 ; L /9 0, 5555, LXV abactor 1-2 Vs Ll/9...: q e -k(~)ZT hT q = Heat flow, Btu/Hr k = Thexmal conductivity, -Btu Jk ~ Lrea, ZtB I ~ length of. heat flow path& Jt 6 T = Temperatux e di f f er ence, dp. R Resistance, (op Zt)pt. ln othex simple cases, such as the cylinder and, the sphex...
Information filtering via weighted heat conduction algorithm
NASA Astrophysics Data System (ADS)
Liu, Jian-Guo; Guo, Qiang; Zhang, Yi-Cheng
2011-06-01
In this paper, by taking into account effects of the user and object correlations on a heat conduction (HC) algorithm, a weighted heat conduction (WHC) algorithm is presented. We argue that the edge weight of the user-object bipartite network should be embedded into the HC algorithm to measure the object similarity. The numerical results indicate that both the accuracy and diversity could be improved greatly compared with the standard HC algorithm and the optimal values reached simultaneously. On the Movielens and Netflix datasets, the algorithmic accuracy, measured by the average ranking score, can be improved by 39.7% and 56.1% in the optimal case, respectively, and the diversity could reach 0.9587 and 0.9317 when the recommendation list equals to 5. Further statistical analysis indicates that, in the optimal case, the distributions of the edge weight are changed to the Poisson form, which may be the reason why HC algorithm performance could be improved. This work highlights the effect of edge weight on a personalized recommendation study, which maybe an important factor affecting personalized recommendation performance.
Radially rotating miniature heat pipes for turbine blade cooling applications
Jian Ling
1999-01-01
Aerospace turboengines present a demanding challenge to many heat transfer scientists and engineers. Designers in this field are seeking the best design to transform the chemical energy of the fuel into the useful work of propulsive thrust at maximum efficiency. To this aim, aerospace turboengines must operate at very high temperatures and pressures with very little heat losses. These requirements
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
NASA Astrophysics Data System (ADS)
Gan, K. F.; Ahn, J.-W.; Park, J.-W.; Maingi, R.; McLean, A. G.; Gray, T. K.; Gong, X.; Zhang, X. D.
2013-02-01
The divertor heat flux footprint in tokamaks is often observed to be non-axisymmetric due to intrinsic error fields, applied 3D magnetic fields or during transients such as edge localized modes. Typically, only 1D radial heat flux profiles are analyzed; however, analysis of the full 2D divertor measurements provides opportunities to study the asymmetric nature of the deposited heat flux. To accomplish this an improved 3D Fourier analysis method has been successfully applied in a heat conduction solver (TACO) to determine the 2D heat flux distribution at the lower divertor surface in the National Spherical Torus Experiment (NSTX) tokamak. This advance enables study of helical heat deposition onto the divertor. In order to account for heat transmission through poorly adhered surface layers on the divertor plate, a heat transmission coefficient, defined as the surface layer thermal conductivity divided by the thickness of the layer, was introduced to the solution of heat conduction equation. This coefficient is denoted as ? and a range of values were tested in the model to ensure a reliable heat flux calculation until a specific value of ? led to the constant total deposited energy in the numerical solution after the end of discharge. A comparison between 1D heat flux profiles from TACO and from a 2D heat flux calculation code, THEODOR, shows good agreement. Advantages of 2D heat flux distribution over the conventional 1D heat flux profile are also discussed, and examples of 2D data analysis in the study of striated heat deposition pattern as well as the toroidal degree of asymmetry of peak heat flux and heat flux width are demonstrated.
Gan, K F; Ahn, J-W; Park, J-W; Maingi, R; McLean, A G; Gray, T K; Gong, X; Zhang, X D
2013-02-01
The divertor heat flux footprint in tokamaks is often observed to be non-axisymmetric due to intrinsic error fields, applied 3D magnetic fields or during transients such as edge localized modes. Typically, only 1D radial heat flux profiles are analyzed; however, analysis of the full 2D divertor measurements provides opportunities to study the asymmetric nature of the deposited heat flux. To accomplish this an improved 3D Fourier analysis method has been successfully applied in a heat conduction solver (TACO) to determine the 2D heat flux distribution at the lower divertor surface in the National Spherical Torus Experiment (NSTX) tokamak. This advance enables study of helical heat deposition onto the divertor. In order to account for heat transmission through poorly adhered surface layers on the divertor plate, a heat transmission coefficient, defined as the surface layer thermal conductivity divided by the thickness of the layer, was introduced to the solution of heat conduction equation. This coefficient is denoted as ? and a range of values were tested in the model to ensure a reliable heat flux calculation until a specific value of ? led to the constant total deposited energy in the numerical solution after the end of discharge. A comparison between 1D heat flux profiles from TACO and from a 2D heat flux calculation code, THEODOR, shows good agreement. Advantages of 2D heat flux distribution over the conventional 1D heat flux profile are also discussed, and examples of 2D data analysis in the study of striated heat deposition pattern as well as the toroidal degree of asymmetry of peak heat flux and heat flux width are demonstrated. PMID:23464209
Nonintegrability and the Fourier heat conduction law
NASA Astrophysics Data System (ADS)
Chen, Shunda; Wang, Jiao; Casati, Giulio; Benenti, Giuliano
2014-09-01
We study in momentum-conserving systems, how nonintegrable dynamics may affect thermal transport properties. As illustrating examples, two one-dimensional (1D) diatomic chains, representing 1D fluids and lattices, respectively, are numerically investigated. In both models, the two species of atoms are assigned two different masses and are arranged alternatively. The systems are nonintegrable unless the mass ratio is one. We find that when the mass ratio is slightly different from one, the heat conductivity may keep significantly unchanged over a certain range of the system size and as the mass ratio tends to one, this range may expand rapidly. These results establish a new connection between the macroscopic thermal transport properties and the underlying dynamics.
Electrohydrodynamic instability in an annular liquid layer with radial conductivity gradients.
Ding, Zijing; Wong, Teck Neng
2014-03-01
In this paper, the electrohydrodynamic stability in an annular liquid layer with a radial electrical conductivity gradient is investigated. A weak shear flow arises from a constant pressure gradient in the axial direction. In the radial direction, an electric field is applied. The three-dimensional linear instability analysis is implemented to study the influence of the inner radius, electrical conductivity gradient, shear flow, and ionic diffusion on the dynamics of the fluid layer. It is found that the critical unstable mode may either be oscillatory or stationary. The system becomes more unstable as the dimensionless inner radius a increases. When the inner radius a is small, the critical unstable mode is stationary, while it is given by three-dimensional oblique waves when a is large. When the conductivity gradient is small, the critical unstable mode is the three-dimensional oblique wave, while when the conductivity gradient is large, it would switch to the stationary mode rather than the oscillatory mode. The system becomes more unstable when the Reynolds number is slightly increased from zero. Additionally, it is found that the electrical Schmidt number has dual effects. The liquid layer becomes either more unstable or stable as the electric Schmidt number increases. PMID:24730940
Variable-Conductance Heat-Transfer Module
NASA Technical Reports Server (NTRS)
Hewitt, D. R.
1984-01-01
Working lengths of heat pipes electronically controlled. Rate of heat transfer controlled by electrical heaters shorten effective working lengths of heat pipes. Concept not limited to right circular cylindrical shape. Concept adaptable to terrestrial instruments or processes in which atmospheres or fluids must be cooled and returned to instruments or processes at fixed lower temperatures.
Phonon wave heat conduction in thin films and superlattices
G. Chen
1999-01-01
Heat conduction in thin films and superlattices is important for many engineering applications such as thin-film based microelectronic, photonic, thermoelectric, and thermionic divides. Past modeling efforts on the thermal conductivity of thin films were based on solving the Boltzmann transport equation that treats phonons as particles. The effects of phonon interference and tunneling on the heat conduction and the thermal
Measurements of radial heat wave propagation in laser-produced exploding-foil plasmas
Montgomery, D.S.; Landen, O.L.; Drake, R.P.; Estabrook, K.G.; Baldis, H.A.; Batha, S.H.; Bradley, K.S.; Procassini, R.J. (Lawrence Livermore National Laboratory, Livermore, California 94551 (United States) Plasma Physics Research Institute, University of California Davis, Lawrence Livermore National Laboratory, Livermore, California 94551 (United States) Department of Applied Science, University of California Davis, Davis, California 95616 (United States))
1994-10-10
Time-resolved, 2D images of x-ray emission from thin, laser-irradiated titanium foils are presented. The foils are irradiated with 0.35 [mu]m light at intensities of 1[times]10[sup 15] W/cm[sup 2] which produces a plasma with electron densities [le]10[sup 22] cm[sup [minus]3] and electron temperature of 3--4 keV. X-ray emission that is characteristic of the thermal heat front is observed to propagate radially outward from the heated region. Comparison of these measurements with 2D hydrodynamic simulations of the experiment suggests the radial heat flux to be about 3% of the free-streaming heat flux.
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.
Measurements of radial heat wave propagation in laser-produced exploding-foil plasmas
D. S. Montgomery; O. L. Landen; R. P. Drake; K. G. Estabrook; H. A. Baldis; S. H. Batha; K. S. Bradley; R. J. Procassini
1994-01-01
Time-resolved, 2D images of x-ray emission from thin, laser-irradiated titanium foils are presented. The foils are irradiated with 0.35 mum light at intensities of 1×1015 W\\/cm2 which produces a plasma with electron densities <=1022 cm-3 and electron temperature of 3-4 keV. X-ray emission that is characteristic of the thermal heat front is observed to propagate radially outward from the heated
Thermal conductivity and specific heat of sorghum grain
Miller, Clinton Frank
1963-01-01
of Melting Equations and the Quantity of Heat Contained in Grain Sample. . . 78 LIST OF FIGURES Figures Page 1. Thermal Conductivity Apparatus. 2. Cylinder in Test Position and Voltmeter Used to Determine Thermal Conductivity of Sorghum Grain. . . 12 3.... 20 8. Relationship of Moisture Content to the Thermal Conductivity of Sorghum Grain Hybrid RS 610 . 9. Apparatus Used for the Determination of Specific 31 Heat 37 10. Apparatus Used for Specific Heat Tests. . . . . . 11. Test Canister Used...
Extended Development of Variable Conductance Heat Pipes
NASA Technical Reports Server (NTRS)
Antoniuk, D.; Edwards, D. K.; Luedke, E. E.
1978-01-01
A high-capacity vapor-modulated heat pipe was designed and tested. In 1977, a program was undertaken to use the aforementioned heat pipe to study protection from freezing-point failure, increase control sensitivity, and transient behavior under a wide range of operating conditions in order to determine the full performance potential of the heat pipe. A new concept, based on the vapor-induced-dry-out principle, was developed for passive feedback temperature control as a heat pipe diode. This report documents this work and describes: (1) the experimental and theoretical investigation of the performance of the vapor-modulated heat pipe; and (2) the design, fabrication and test of the heat pipe diode.
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
Deborah N. Aguilera; Vincenzo Cirigliano; José A. Pons; Sanjay Reddy; Rishi Sharma
2008-07-29
We report on a new mechanism for heat conduction in the neutron star crust. We find that collective modes of superfluid neutron matter, called superfluid phonons (sPhs), can influence heat conduction in magnetized neutron stars. They can dominate the heat conduction transverse to magnetic field when the magnetic field $B \\gsim 10^{13}$ G. At density $\\rho \\simeq 10^{12}-10^{14} $ g/cm$^3$ the conductivity due to sPhs is significantly larger than that due to lattice phonons and is comparable to electron conductivity when temperature $\\simeq 10^8$ K. This new mode of heat conduction can limit the surface anisotropy in highly magnetized neutron stars. Cooling curves of magnetized neutron stars with and without superfluid heat conduction could show observationally discernible differences.
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.
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.
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.
Anelastic Dynamo Models with Radially Varying Conductivity - an Application to the Gas Giants
NASA Astrophysics Data System (ADS)
Duarte, L.; Wicht, J.; Gastine, T.
2011-12-01
The gas envelopes of Jupiter and Saturn are separated into an outer molecular and an inner metallic region by a hydrogen phase transition. While the dynamo action takes part in the inner region, the observed zonal jets are presumably restricted to the outer. Typical numerical models deal with either the outer region for modeling the observed zonal jets, or the metallic region for modeling the dynamo effect. Here we present a holistic approach, simulating both layers together by assuming a radially varying electrical conductivity. An anelastic approximation allows to incorporate effects of density stratification. The results show that the dynamos tend to create dipole-dominated magnetic fields when density stratification is neglected and the electrical conductivity is homogeneous. The dipole dominance is lost, however, when the conductivity is decreased in the very outer layer which confirms the results by Gómez-Pérez et. al (2010). Anelastic simulations with homogeneous electrical conductivities typically yield non-dipolar magnetic field, even for rather small density scale heights. The local Rossby number criterion developed by Christensen and Aubert (2006), which successfully predicts whether a dynamo produces a dipole-dominated field in non-compressible Boussinesq simulations, does not apply any more in the anelastic case. The Lorentz forces associated with the magnetic field suppress the strong zonal jets found in comparable non-magnetic cases. Decreasing the electrical conductivity in the outer layer has now two effects: the magnetic field becomes once more dipole-dominated and strong zonal jets develop where the electrical conductivity is low. We therefore conclude that a combination of anelastic effects and varying electrical conductivity is important for appropriately modeling the interior dynamics of the gas giants. So far, we have not succeeded in simulating multiple jets as our simulation shows only the prograde equatorial and the two flanking retrograde jets.
Thermal conductivity of iron\\/potassium perchlorate heat powder
C. M. Love; D. E. Etter; J. E. Glaub
1984-01-01
The thermal conductivity of unburned and burned Fe\\/KC10â heat powder pellets, of two different weight ratios, was determined as a function of pellet density and temperature. Thermal diffusivities as a function of temperature were measured by a laser flash diffusivity method and these data were combined with density and specific heat data to obtain the thermal conductivity results. The thermal
Compressible Navier–Stokes Equations with Zero Heat Conductivity
Tai-Ping Liu; Yanni Zeng
1999-01-01
We study the large-time behavior of solutions of the compressible Navier–Stokes equations without heat conductivity. Acoustic waves are dissipative due to the viscosity. Entropy waves are nondissipative due to lack of heat conductivity. Thus the system is of composite type, the simplest prototype of this class of nonlinear partial differential equations. We study the nonlinear interactions of waves using a
Entropy and temperature gradients thermomechanics: dissipation, heat conduction
Boyer, Edmond
, assuming that the heat flux, the specific internal energy and entropy are functions of the temperatureEntropy and temperature gradients thermomechanics: dissipation, heat conduction inequality and heat or entropy gradients, in thermomechanics of materials. Using the balance of energy, an analysis
Efficient numerical solution of the nonlinear inverse heat conduction problem
J. V. Beck; B. Litkouhi; C. R. Saint Clair Jr.
1980-01-01
The nonlinear inverse heat conduction problem is the calculation of surface heat fluxes and temperatures utilizing measured interior temperatures in opaque solids possessing temperature-variable thermal properties. The most widely used numerical method for this problem was developed by Beck. The new procedure presented herein reduces the number of computer calculations by a factor of three or four. The general heat
High Conductance Loop Heat Pipes for Space Application
Sergey Y. Semenov; Wei-Lin Cho; Scott M. Jensen
2006-01-01
Three high conductance Loop Heat Pipes (LHPs) for the Geostationary Imaging Fourier Transform Spectrometer (GIFTS) were designed, fabricated and thermal vacuum tested. One LHP with ammonia working fluid was designed for heat removal from a cryocooler cold head. Two ethane LHPs were designed to reject heat from the aft and fore optics to space. Thermal performance tests were performed in
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.
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.
Analysis and application of variable conductance heat pipe air preheater
Chengming Shi; Yang Wang; Quan Liao; Ying Yang
2011-01-01
The heat transfer analysis of variable conductance heat pipe air preheater was carried out. The temperature transfer matrix\\u000a was obtained for the air preheater that comprises several discrete heat transfer units with same or different heat transfer\\u000a surface area in a parallel or counter flow mode. By using the temperature transfer matrix, the outlet fluid temperatures could\\u000a be easily calculated
Molecular dynamics study of heat conduction in silicon nanowires
NASA Astrophysics Data System (ADS)
Volz, Sebastian; Chen, Gang
1998-03-01
With the advancement of nanofabrication technologies, nanowires may be produced for both fundamental studies and practical applications. While many former works have been carried out to characterize the electronic and optical properties of nanowires, little attention has been paid to the heat conduction mechanisms occurring in these structures. However, a fundamental understanding of heat conduction in these nanodevices is important for a number of technological areas such as electronics and thermoelectrics. In this works, we performed numerical studies based on molecular dynamics technique to simulate heat conduction in silicon nanowires lying in the vacuum. The device cells are arranged according to a diamond single crystal structure and interatomic forces are derived from the Stillinger-Weber potential currently assumed in solid silicon. By computing the time dependent heat flux and temperature field, the effective thermal conductivity of the wire was derived. The dependence of thermal conductivity on transverse dimensions and temperature is also probed.
Making Conductive, Compliant Heat-Transfer Pads
NASA Technical Reports Server (NTRS)
Douglas, Lawrence E.
1992-01-01
Composite copper/tungsten pads developed for use in thermoelectric generators. Pads thermally and electrically conductive and compliant enough to accommodate large mismatches in thermal expansion between different parts. Each pad consists of tungsten fibers in copper matrix interconnecting pair of tungsten face sheets.
GRETCHEN B. NORTH; PARK S. NOBEL
1996-01-01
The constraints on water uptake imposed by individual root tissues were examined forOpuntia ficus-indicaunder wet, drying, and rewetted soil conditions. Root hydraulic conductivity (LP) and axial conductance (Kh) were measured for intact root segments from the distal region with an endodermis and from midroot with a periderm;LPwas then measured for each segment with successive tissues removed by dissection. Radial conductivity
Electrical conductivity of rocks in the heating and cooling cycle
Marcela Lastovicková; F. Janák
1978-01-01
Summary The values of the electrical conductivity, recorded during the heating and cooling cycle, of eclogites and basalts are compared. The observed difference in the values is explained by reversible and irreversible changes which take place in the samples.
Zhigilei, Leonid V.
Heat conduction in carbon nanotube materials: Strong effect of intrinsic thermal conductivity conductivity of interconnected networks of bundles in carbon nanotube (CNT) films reveals a strong effect to the thermal resistance of a CNT segment with Leq ¼ 59 lm. At first sight, this estimation appears to support
Modeling Earth's Outer Radiation Belt Electron Dynamics---Radial Diffusion, Heating, and Loss
NASA Astrophysics Data System (ADS)
Tu, Weichao
Earth's outer radiation belt is a relativistic electron environment that is hazardous to space systems. It is characterized by large variations in the electron flux, which are controlled by the competition between source, transport, and loss processes. One of the central questions in outer radiation belt research is to resolve the relative contribution of radial diffusion, wave heating, and loss to the enhancement and decay of the radiation belt electrons. This thesis studies them together and separately. Firstly, we develop an empirical Fokker-Planck model that includes radial diffusion, an internal source, and finite electron lifetimes parameterized as functions of geomagnetic indices. By simulating the observed electron variations, the model suggests that the required magnitudes of radial diffusion and internal heating for the enhancement of energetic electrons in the outer radiation belt vary from storm to storm, and generally internal heating contributes more to the enhancements of MeV energy electrons at L=4 (L is approximately the radial distance in Earth radii at the equator). However, since the source, transport, and loss terms in the model are empirical, the model results have uncertainties. To eliminate the uncertainty in the loss rate, both the precipitation and the adiabatic loss of radiation belt electrons are quantitatively studied. Based on the observations from Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX), a Drift-Diffusion model is applied to quantify electron precipitation loss, which is the dominant non-adiabatic loss mechanism for electrons in the heart of the outer radiation belt. Model results for a small storm, a moderate storm, and an intense storm indicate that fast precipitation losses of relativistic electrons, on the time scale of hours, persistently occur in the storm main phases and with more efficient losses at higher energies over wide range of L regions. Additionally, calculations of adiabatic effects on radiation belt electrons at low altitudes demonstrate that the adiabatic flux drop of electrons during the storm main phase is both altitude and storm dependent. During the main phase of a moderate geomagnetic storm, due solely to adiabatic effects a satellite at low altitude sees either zero electron flux or a fractional flux drop depending on its altitude. To physically quantify the radial diffusion rate, we use power spectral density and global mode structure of the Ultra-Low-Frequency (ULF) waves, which are derived from the Lyon-Fedder-Mobarry (LFM) MHD simulation and validated by field data from real satellites. The calculated total diffusion rate is shown to be dominated by the contribution from magnetic field perturbations, and much less from the electric field. Fast diffusion generally occurs when solar wind dynamic pressure is high or nightside geomagnetic activity is strong and with higher diffusion rates at higher L regions. Work performed in this thesis provides realistic loss rate and radial diffusion rate of radiation belt electrons, as well as a comprehensive Fokker-Planck model that can take the loss and radial diffusion rates as inputs and then determine the internal heating rate with less uncertainty. By this approach, we will be able to quantitatively understand the relative contribution of radial diffusion, wave heating, and loss to the variations of radiation belt electrons.
Efficient Sequential Solution of the Nonlinear Inverse Heat Conduction Problem
J. V. Beck; B. Litkouhi; C. R. St. Clair Jr.
1982-01-01
The nonlinear inverse heat conduction problem is the calculation of surface heat fluxes and temperatures by utilizing measured interior temperatures in opaque solids possessing temperature-variable thermal properties. The most widely used numerical method for this problem was developed by Beck. The new sequential procedure presented here reduces the number of computer calculations by a factor of 3 or 4.The general
Efficient sequential solution of the nonlinear inverse heat conduction problem
J. V. Beck; B. Litkouhi; C. R. Saint Clair Jr.
1982-01-01
A solution to the nonlinear inverse heat conduction problem is offered which employs a sequential procedure for the calculation of surface heat fluxes and temperatures from measured interior temperatures in opaque solids having temperature-variable thermal properties. The nonlinear problem is linearized, and through the elimination of iteration, computation time can be reduced by a factor of 3 or 4. The
TRANSIENT HEAT CONDUCTION ANALYSIS OF LAMINATED COMPOSITE NOSE CONE
J. M. Mahishi; Ramesh Chandra; M. V. V. Murthy
This paper presents transient heat conduction analysis of composite nose cone subjected to aerodynamic heating by finite element technique in space domain and finite difference technique in time domain. An anisotropic rectangular ring element with four nodal circles, each having tempera- ture as degree of freedom is developed. Application of finite element technique is space domain results in a set
NASA Astrophysics Data System (ADS)
Meher, K. C.; Tiwari, N.; Ghorui, S.; Sahasrabudhe, S. N.; Das, A. K.
2014-12-01
Axial evolutions of radial heat flux profiles in argon and nitrogen plasma jets from an atmospheric pressure dc non-transferred arc plasma torch are determined using a double calorimetric technique. Results are presented for power levels suitable for the processing of high temperature ceramic oxides, where the heat flux data reported in the literature is rare. Variations of the profile widths and profile maxima are presented as a function of axial distance as well as power. Relatively uniform profile width over prolonged axial distance for nitrogen plasma compared to argon is an important observation which has the potential to offer a much longer dwell time of the injected particles inside the plasma, avoiding the problem of unmelts, especially for ceramics. A comparative study of the heat flux profiles for argon and nitrogen plasma is presented. The obtained results are compared with the data reported in literature.
Single-photon heat conduction in electrical circuits
P. J. Jones; J. A. M. Huhtamäki; K. Y. Tan; M. Möttönen
2011-07-14
We study photonic heat conduction between two resistors coupled weakly to a single superconducting microwave cavity. At low enough temperature, the dominating part of the heat exchanged between the resistors is transmitted by single-photon excitations of the fundamental mode of the cavity. This manifestation of single-photon heat conduction should be experimentally observable with the current state of the art. Our scheme can possibly be utilized in remote interference-free temperature control of electric components and environment engineering for superconducting qubits coupled to cavities.
Low-temperature specific heat and thermal conductivity of glasses
L. Gil; M. A. Ramos; A. Bringer; U. Buchenau
1993-01-01
The soft potential model (an extension of the tunneling model to include soft localized vibrations) is shown to describe the anomalous features of the specific heat CP and the thermal conductivity of glasses over the entire low-temperature range, up to an including the peak in CP\\/T3 and the second rise of the thermal conductivity above the plateau.
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
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.
Heat Pipe Embedded AlSiC Plates for High Conductivity - Low CTE Heat Spreaders
Johnson, Matthew (DOE/NNSA Kansas City Plant (United States)); Weyant, J.; Garner, S. (Advanced Cooling Technologies, Inc. (Lancaster, PA (United States)); Occhionero, M. (CPS Technologies Corporation, Norton, MA (United States))
2010-01-07
Heat pipe embedded aluminum silicon carbide (AlSiC) plates are innovative heat spreaders that provide high thermal conductivity and low coefficient of thermal expansion (CTE). Since heat pipes are two phase devices, they demonstrate effective thermal conductivities ranging between 50,000 and 200,000 W/m-K, depending on the heat pipe length. Installing heat pipes into an AlSiC plate dramatically increases the plate’s effective thermal conductivity. AlSiC plates alone have a thermal conductivity of roughly 200 W/m-K and a CTE ranging from 7-12 ppm/ deg C, similar to that of silicon. An equivalent sized heat pipe embedded AlSiC plate has effective thermal conductivity ranging from 400 to 500 W/m-K and retains the CTE of AlSiC.
Measurements of radial heat wave propagation in laser-produced exploding-foil plasmas
D. S. Montgomery; O. L. Landen; R. P. Drake; K. G. Estabrook; H. A. Baldis; S. H. Batha; K. S. Bradley; R. J. Procassini
1994-01-01
Time-resolved, 2D images of x-ray emission from thin, laser-irradiated titanium foils are presented. The foils are irradiated with 0.35 [mu]m light at intensities of 1[times]10[sup 15] W\\/cm[sup 2] which produces a plasma with electron densities [le]10[sup 22] cm[sup [minus]3] and electron temperature of 3--4 keV. X-ray emission that is characteristic of the thermal heat front is observed to propagate radially
Evolution of the radial electric field in high-Te ECH heated plasmas on LHD
NASA Astrophysics Data System (ADS)
Pablant, Novimir; Bitter, Manfred; Delgado Aparicio, Luis F.; Dinklage, Andreas; Gates, David; Goto, Motoshi; Ido, Takeshi; Hill, Kenneth H.; Kubo, Shin; Morita, Shigeru; Nagaoka, Kenichi; Oishi, Tetsutarou; Satake, Shinsuke; Takahashi, Hiromi; Yokoyama, Masayuki; LHD Experiment Group Team
2014-10-01
A detailed study is presented on the evolution of the radial electric field (Er) under a range of densities and injected ECH powers on the Large Helical Device (LHD). These plasmas focused on high-electron temperature ECH heated plasmas which exhibit a transition of Er from the ion-root to the electron-root when either the density is reduced or the ECH power is increased. Measurements of poloidal rotation were achieved using the X-Ray Imaging Crystal Spectrometer (XICS) and are compared with neo-classical predictions of the radial electric field using the GSRAKE and FORTEC-3D codes. This study is based on a series of experiments on LHD which used fast modulation of the gyrotrons on LHD to produce a detailed power scan with a constant power deposition profile. This is a novel application of this technique to LHD, and has provided the most detailed study to date on dependence of the radial electric field on the injected power. Detailed scans of the density at constant injected power were also made, allowing a separation of the power and density dependence.
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...
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...
Induction heating of mastic containing conductive fibers and fillers
Á. García; E. Schlangen; M. Van de Ven; D. Van Vliet
1995-01-01
The objective of this research is to examine the induction heating of mastic through the addition of electrically conductive fillers and fibers (graphite and steel wool), and to prove that this material can be healed with induction energy. The effect of fibers content, sand–bitumen ratio and the\\u000acombination of fillers and fibers on the induction heating of mastic was investigated.
Induction heating of mastic containing conductive fibers and fillers
Álvaro García; Erik Schlangen; Martin van de Ven; Dave van Vliet
2011-01-01
The objective of this research is to examine the induction heating of mastic through the addition of electrically conductive\\u000a fillers and fibers (graphite and steel wool), and to prove that this material can be healed with induction energy. The effect\\u000a of fibers content, sand–bitumen ratio and the combination of fillers and fibers on the induction heating of mastic was investigated.
Mechanical control of heat conductivity in molecular chains.
Savin, A V; Gendelman, O V
2014-01-01
We discuss a possibility to control heat conductivity in molecular chains by means of external mechanical loads. To illustrate such possibilities we consider first well-studied one-dimensional chain with degenerate double-well potential of the nearest-neighbor interaction. We consider varying lengths of the chain with fixed number of particles. Number of possible energetically degenerate ground states strongly depends on the overall length of the chain, or, in other terms, on average length of the link between neighboring particles. These degenerate states correspond to mechanical equilibria; therefore, one can say that formation of such structures mimics a process of plastic deformation. We demonstrate that such modification of the chain length can lead to quite profound (almost fivefold) reduction of the heat conduction coefficient. Even more profound effect is revealed for a model with a single-well nonconvex potential. It is demonstrated that in a certain range of constant external forcing, this model becomes effectively double-well and has a multitude of possible states of equilibrium for fixed value of the external load. Due to this degeneracy, the heat-conduction coefficient can be reduced by two orders of magnitude. We suggest a mechanical model of a chain with periodic double-well potential, which allows control of the heat transport. The models considered may be useful for description of heat transfer in biological macromolecules and for control of the heat transport in microsystems. The possibility of the heat transport control in more realistic three-dimensional systems is illustrated by simulation of a three-dimensional model of polymer ?-helix. In this model, the mechanical stretching also brings about the structural inhomogeneity and, in turn, to essential reduction of the heat conductivity. PMID:24580199
Heat conduction in one-dimensional aperiodic quantum Ising chains
NASA Astrophysics Data System (ADS)
Li, Wenjuan; Tong, Peiqing
2011-03-01
The heat conductivity of nonperiodic quantum Ising chains whose ends are connected with heat baths at different temperatures are studied numerically by solving the Lindblad master equation. The chains are subjected to a uniform transverse field h, while the exchange coupling Jm between the nearest-neighbor spins takes the two values JA and JB arranged in Fibonacci, generalized Fibonacci, Thue-Morse, and period-doubling sequences. We calculate the energy-density profile and energy current of the resulting nonequilibrium steady states to study the heat-conducting behavior of finite but large systems. Although these nonperiodic quantum Ising chains are integrable, it is clearly found that energy gradients exist in all chains and the energy currents appear to scale as the system size ~N?. By increasing the ratio of couplings, the exponent ? can be modulated from ?>-1 to ?<-1 corresponding to the nontrivial transition from the abnormal heat transport to the heat insulator. The influences of the temperature gradient and the magnetic field to heat conduction have also been discussed.
Heat conduction in one-dimensional aperiodic quantum Ising chains.
Li, Wenjuan; Tong, Peiqing
2011-03-01
The heat conductivity of nonperiodic quantum Ising chains whose ends are connected with heat baths at different temperatures are studied numerically by solving the Lindblad master equation. The chains are subjected to a uniform transverse field h, while the exchange coupling J{m} between the nearest-neighbor spins takes the two values J{A} and J{B} arranged in Fibonacci, generalized Fibonacci, Thue-Morse, and period-doubling sequences. We calculate the energy-density profile and energy current of the resulting nonequilibrium steady states to study the heat-conducting behavior of finite but large systems. Although these nonperiodic quantum Ising chains are integrable, it is clearly found that energy gradients exist in all chains and the energy currents appear to scale as the system size ~N{?}. By increasing the ratio of couplings, the exponent ? can be modulated from ? > -1 to ? < -1 corresponding to the nontrivial transition from the abnormal heat transport to the heat insulator. The influences of the temperature gradient and the magnetic field to heat conduction have also been discussed. PMID:21517475
Explosive crystallization in thin amorphous layers on heat conducting substratesa)
NASA Astrophysics Data System (ADS)
Buchner, Christoph; Schneider, Wilhelm
2015-06-01
A model for explosive crystallization in a thin amorphous layer on a heat conducting substrate is presented. For the thin layer, the energy equation is used in a one-dimensional approximation. Heat conduction into the substrate and thermal contact resistance at the interface between layer and substrate are taken into account. Four rate equations are used to describe the kinetics of the homogeneous amorphous-crystalline transition. The whole process is examined as a plane wave of invariant shape in a moving frame of reference. Heat conduction in the substrate is described by introducing a continuous distribution of moving heat sources at the interface. This gives an integral representation for the temperature in the substrate in terms of the unknown source distribution. The integral term implies that there is a non-local influence of the temperature distribution in the layer on the heat loss. A coupled system of an integro-differential equation and four ordinary differential equations is obtained and solved numerically. The propagation velocity of the wave is obtained as an eigenvalue of the system of equations. Varying a non-dimensional heat loss parameter, a critical value is found beyond which no crystallization wave of invariant shape is possible. This can also be interpreted as a certain minimum layer thickness. Temperature and crystallinity distributions are shown for some interesting configurations. Predictions of crystallization-wave velocities and minimum layer thicknesses are compared with experimental values for explosive crystallization in germanium.
Application of Genetic Algorithms in Nonlinear Heat Conduction Problems
Khan, Waqar A.
2014-01-01
Genetic algorithms are employed to optimize dimensionless temperature in nonlinear heat conduction problems. Three common geometries are selected for the analysis and the concept of minimum entropy generation is used to determine the optimum temperatures under the same constraints. The thermal conductivity is assumed to vary linearly with temperature while internal heat generation is assumed to be uniform. The dimensionless governing equations are obtained for each selected geometry and the dimensionless temperature distributions are obtained using MATLAB. It is observed that GA gives the minimum dimensionless temperature in each selected geometry. PMID:24695517
Application of genetic algorithms in nonlinear heat conduction problems.
Kadri, Muhammad Bilal; Khan, Waqar A
2014-01-01
Genetic algorithms are employed to optimize dimensionless temperature in nonlinear heat conduction problems. Three common geometries are selected for the analysis and the concept of minimum entropy generation is used to determine the optimum temperatures under the same constraints. The thermal conductivity is assumed to vary linearly with temperature while internal heat generation is assumed to be uniform. The dimensionless governing equations are obtained for each selected geometry and the dimensionless temperature distributions are obtained using MATLAB. It is observed that GA gives the minimum dimensionless temperature in each selected geometry. PMID:24695517
Neutrino Heat Conduction and Inhomogeneities in the Early Universe
NASA Technical Reports Server (NTRS)
Heckler, A.; Hogan, C. J.
1993-01-01
Constraints on parameters of inhomogeneous nucteosynthesis, namely, the overdensity and size of baryon lumps, are found by calculatig the blackbody neutrino heat conduction into the lumps, which tends to inflate them away. The scale size for efficient heat conduction is determined by the mean free path lambda of the neutrino, and so we compute lambda in our case of a high-temperature plasma with low chemical potential, and find a general result that many-body effects are unimportant, simplifying the calculation. We find that in the region of interest for nucleosynthesis, neutrino inflation is important for overdensities greater than 10(exp 4).
Tunable heat conduction through coupled Fermi-Pasta-Ulam chains.
Su, Ruixia; Yuan, Zongqiang; Wang, Jun; Zheng, Zhigang
2015-01-01
We conduct a study on heat conduction through coupled Fermi-Pasta-Ulam (FPU) chains by using classical molecular dynamics simulations. Our attention is dedicated to showing how the phonon transport is affected by the interchain coupling. It has been well accepted that the heat conduction could be impeded by the interchain interaction due to the interface phonon scattering. However, recent theoretical and experimental studies suggest that the thermal conductivity of nanoscale materials can be counterintuitively enhanced by the interaction with the substrate. In the present paper, by consecutively varying the interchain coupling intensity, we observed both enhancement and suppression of thermal transport through the coupled FPU chains. For weak interchain couplings, it is found that the heat flux increases with the coupling intensity, whereas in the case of strong interchain couplings, the energy transport is found to be suppressed by the interchain interaction. Based on the phonon spectral energy density method, we attribute the enhancement of the energy transport to the excited phonon modes (in addition to the intrinsic phonon modes), while the upward shift of the high-frequency phonon branch and the interface phonon-phonon scattering account for the suppressed heat conduction. PMID:25679599
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.
Genetic Algorithm in Solution of Inverse Heat Conduction Problems
Miroslav Raudenský; Keith A. Woodbury; J. Kral; T. Brezina
1995-01-01
This report demonstrates the use of a genetic algorithm search in the solution of an inverse problem. The genetic algorithm is used to solve the one-dimensional inverse heat conduction problem using numerical data generated by solution of the corresponding direct problem. Both “pure” and noisy data are considered. If used with regularization, the method is shown to yield reasonable results
Group classification of heat conductivity equations with a nonlinear source
R. Z. Zhdanov; V. I. Lahno
1999-01-01
We suggest a systematic procedure for classifying partial differential equations (PDEs) invariant with respect to low-dimensional Lie algebras. This procedure is a proper synthesis of the infinitesimal Lie method, the technique of equivalence transformations and the theory of classification of abstract low-dimensional Lie algebras. As an application, we consider the problem of classifying heat conductivity equations in one variable with
Disparate quasiballistic heat conduction regimes from periodic heat sources on a substrate
Zeng, Lingping
We report disparate quasiballistic heat conduction trends for periodic nanoscale line heaters deposited on a substrate, depending upon whether measurements are based on the peak temperature of the heaters or the temperature ...
Heat capacity, magnetic susceptibility, EPR, and dc conductivity of some conducting polymers
Pawan Kahol; James Ho; Stefania Deterich; Y. Y. Chen; C. R. Wang; S. Neeleshwar; C. B. Tsai; B. Wessling
2004-01-01
Polyaniline doped with polystyrene-sulfonic-acid (PAN-PSSA), such that y =[sulfonate]\\/[aniline] = 1, exhibits a dc conductivity of 0.1 S\\/cm. On increasing the dopant concentration to y = 6, the conductivity drops by four orders of magnitude. Poly(3,4-ethylenedioxythiophene) doped with polystyrene-sulfonic-acid (PEDOT-PSSA) also exhibits a similar behavior on doping. The results of a study involving heat capacity, magnetic susceptibility, EPR, and dc
The specific heat and the radial thermal expansion of bundles of single-walled carbon nanotubes
NASA Astrophysics Data System (ADS)
Bagatskii, M. I.; Barabashko, M. S.; Dolbin, A. V.; Sumarokov, V. V.; Sundqvist, B.
2012-06-01
The specific heat at constant pressure C(T) of bundles of single-walled carbon nanotubes (SWNTs) closed at their ends has been investigated in the temperature interval of 2-120 K. It is found that the curve C(T) has features near 5, 36, 80, and 100 K. The experimental results on the C(T) and the radial thermal expansion coefficient ?R(T) of bundles of SWNTs oriented perpendicular to the sample axis have been compared. It is found that the curves C(T) and ?R(T) exhibit a similar temperature behavior at T > 10 K. The temperature dependence of the Grüneisen coefficient ?(T) has been calculated. The curve ?(T) also has a feature near 36 K. Above 36 K the Grüneisen coefficient is practically independent of temperature (? ~ 4). Below 36 K, ?(T) decreases monotonically with lowering temperature and becomes negative at T < 6 K.
The specific heat and the radial thermal expansion of bundles of single-walled carbon nanotubes
NASA Astrophysics Data System (ADS)
Bagatskii, M. I.; Barabashko, M. S.; Dolbin, A. V.; Sumarokov, V. V.; Sundqvist, B.
2012-06-01
The specific heat at constant pressure C(T) of bundles of single-walled carbon nanotubes (SWNTs) closed at their ends has been investigated in the temperature interval of 2-120 K. It is found that the curve C(T) has features near 5, 36, 80, and 100 K. The experimental results on the C(T) and the radial thermal expansion coefficient ?R(T) of bundles of SWNTs oriented perpendicular to the sample axis have been compared. It is found that the curves C(T) and ?R(T) exhibit a similar temperature behavior at T > 10 K. The temperature dependence of the Grüneisen coefficient ?(T) has been calculated. The curve ?(T) also has a feature near 36 K. Above 36 K the Grüneisen coefficient is practically independent of temperature (? ? 4). Below 36 K, ?(T) decreases monotonically with lowering temperature and becomes negative at T < 6 K.
Heat, Light, and Videotapes: Experiments in Heat Conduction Using Liquid Crystal Film.
ERIC Educational Resources Information Center
Bacon, Michael E.; And Others
1995-01-01
Presents a range of experiments in heat conduction suitable for upper-level undergraduate laboratories that make use of heat sensitive liquid crystal film to measure temperature contours. Includes experiments mathematically described by Laplace's equation, experiments theoretically described by Poisson's equation, and experiments that involve…
Mechanical behavior of bolted joints under steady heat conduction
Kumano, H. (Tokyo Metropolitan Inst. of Tech., Hino (Japan). Dept. of Mechanical Engineering); Sawa, T.; Hirose, T. (Yamanashi Univ., Kofu (Japan). Dept. of Mechanical Engineering)
1994-02-01
Bolted joints in heat exchangers, cylinder heads in combustion engines, and so on are subjected in heat fluxes. It is necessary to examine the mechanical behavior of such bolted joints under thermal changes in order to establish an optimal design. This paper deals with mechanical behavior of bolted joints, in which two hollow cylinders and two rectangular thick plates made of aluminum are fastened at room temperature by a bolt and nut made of steel, and are subjected to thermal changes or steady heat conduction. Temperature distributions of the joints are analyzed using the finite difference method. Then, methods of estimating an increment in axial bolt force and a maximum stress produced in the bolts are proposed. In the experiments, the aforementioned bolted joints are put in a furnace. Furthermore, the rectangular thick plates fastened by a bolt and nut are heated by an electric heater. Then, the temperature on the surfaces of the clamped parts and the bolts are measured with thermocouples. The increase in axial bolt force and the maximum stress produced in the bolts under steady heat conduction for thermal changes are measured. The analytical results are in fairly good agreement with the experimental ones.
Estimating interfacial thermal conductivity in metamaterials through heat flux mapping
NASA Astrophysics Data System (ADS)
Canbazoglu, Fatih M.; Vemuri, Krishna P.; Bandaru, Prabhakar R.
2015-04-01
The variability of the thickness as well as the thermal conductivity of interfaces in composites may significantly influence thermal transport characteristics and the notion of a metamaterial as an effective medium. The consequent modulations of the heat flux passage are analytically and experimentally examined through a non-contact methodology using radiative imaging, on a model anisotropic thermal metamaterial. It was indicated that a lower Al layer/silver interfacial epoxy ratio of ˜25 compared to that of a Al layer/alumina interfacial epoxy (of ˜39) contributes to a smaller deviation of the heat flux bending angle.
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
Revealing the complex conduction heat transfer mechanism of nanofluids
NASA Astrophysics Data System (ADS)
Sergis, A.; Hardalupas, Y.
2015-06-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects
Revealing the complex conduction heat transfer mechanism of nanofluids.
Sergis, A; Hardalupas, Y
2015-12-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects. PMID:26058515
Collins, Kimberlee C. (Kimberlee Chiyoko)
2015-01-01
Studies of non-diffusive heat conduction provide insight into the fundamentals of heat transport in condensed matter. The mean free paths (MFPs) of phonons that are most important for conducting heat are well represented ...
NASA Astrophysics Data System (ADS)
Runov, A. M.; Reiter, D.; Kasilov, S. V.; Heyn, M. F.; Kernbichler, W.
2001-03-01
The heat balance equation is derived and solved for fusion edge plasma conditions with (partially developed) ergodic magnetic-field structures. For this purpose, a three-dimensional (3D) Monte Carlo code, "E3D," based upon the "multiple local magnetic coordinate system approach" has been developed. Parameters typical for the Dynamic Ergodic Divertor (DED) of TEXTOR-94 (Torus Experiment for the Technology Oriented Research) [K. H. Finken et al., Fusion Eng. Des. 37, 1 (1997)] are chosen in the applications. The plasma temperature fields and the profiles of the radial component of heat flux due to the classical parallel and anomalous perpendicular diffusion are calculated. Because of magnetic-field ergodization and diversion of field lines, parallel conduction also can contribute to this radial flux. The results are compared with theoretical predictions for two limiting cases: With the Rechester-Rosenbluth model of ergodization-induced transport and with a "laminar flow model" proposed in the present paper. This latter model describes the effects of field line diversion. The diversion effect is shown to be dominant for TEXTOR-DED conditions.
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.
Gilles Roy; Cong Tam Nguyen; Paul-René Lajoie
2004-01-01
Nanofluids, because of their enhanced heat transfer capability as compared to normal water\\/glycol\\/oil based fluids, offer the engineer opportunities for development in areas where high heat transfer, low temperature tolerance and small component size are required. In this present paper, the hydrodynamic and thermal fields of a water–?Al2O3 nanofluid in a radial laminar flow cooling system are considered. Results indicate
Fourier's heat conduction equation: History, influence, and connections
NASA Astrophysics Data System (ADS)
Narasimhan, T. N.
1999-02-01
The equation describing the conduction of heat in solids has, over the past two centuries, proved to be a powerful tool for analyzing the dynamic motion of heat as well as for solving an enormous array of diffusion-type problems in physical sciences, biological sciences, earth sciences, and social sciences. This equation was formulated at the beginning of the nineteenth century by one of the most gifted scholars of modern science, Joseph Fourier of France. A study of the historical context in which Fourier made his remarkable contribution and the subsequent impact his work has had on the development of modern science is as fascinating as it is educational. This paper is an attempt to present a picture of how certain ideas initially led to Fourier's development of the heat equation and how, subsequently, Fourier's work directly influenced and inspired others to use the heat diffusion model to describe other dynamic physical systems. Conversely, others concerned with the study of random processes found that the equations governing such random processes reduced, in the limit, to Fourier's equation of heat diffusion. In the process of developing the flow of ideas, the paper also presents, to the extent possible, an account of the history and personalities involved.
NASA Technical Reports Server (NTRS)
Kachanov, Mark
1998-01-01
Analysis of the effective thermal conductivity of ceramic coatings and its relation to the microstructure continued. Results (obtained in Task 1) for the three-dimensional problem of heat conduction in a solid containing an inclusion (or, in particular, cavity - thermal insulator) of the ellipsoidal shape, were further advanced in the following two directions: (1) closed form expressions of H tensor have been derived for special cases of ellipsoidal cavity geometry: spheroid, crack-like spheroidal cavity and needle shaped spheroidal cavity; (2) these results for one cavity have been incorporated to construct heat energy potential for a solid with many spheroidal cavities (in the approximation of non-interacting defects). This problem constitutes a basic building block for further analyses.
M. Slodi?ka; D. Lesnic; T. T. M. Onyango
2010-01-01
In this article, the determination of the time-dependent heat transfer coefficient, involving nonlinear boundary conditions of the third kind in the one-dimensional transient heat conduction from a non-standard boundary measurement is investigated. For this inverse, nonlinear, ill-posed problem, the existence and uniqueness of the solution are proved. Numerical results are obtained, using the boundary element method, and discussed.
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.
Numerical Model for Conduction-Cooled Current Lead Heat Loads
White, M.J.; Wang, X.L.; /Fermilab; Brueck, H.D.; /DESY
2011-06-10
Current leads are utilized to deliver electrical power from a room temperature junction mounted on the vacuum vessel to a superconducting magnet located within the vacuum space of a cryostat. There are many types of current leads used at laboratories throughout the world; however, conduction-cooled current leads are often chosen for their simplicity and reliability. Conduction-cooled leads have the advantage of using common materials, have no superconducting/normal state transition, and have no boil-off vapor to collect. This paper presents a numerical model for conduction-cooled current lead heat loads. This model takes into account varying material and fluid thermal properties, varying thicknesses along the length of the lead, heat transfer in the circumferential and longitudinal directions, electrical power dissipation, and the effect of thermal intercepts. The model is validated by comparing the numerical model results to ideal cases where analytical equations are valid. In addition, the XFEL (X-Ray Free Electron Laser) prototype current leads are modeled and compared to the experimental results from testing at DESY's XFEL Magnet Test Stand (XMTS) and Cryomodule Test Bench (CMTB).
NASA Astrophysics Data System (ADS)
Everett, Mark E.
2010-12-01
A new simulation tool is introduced for extracting Earth conductivity information from geomagnetic satellites in low Earth orbit (LEO) such as CHAMP, Swarm and potential follow-on missions. Theoretical reconstruction of spherical harmonic spectra of global universal time (UT) geomagnetic field maps is analysed. An idealized regular solar daily variation field is assumed, along with its induced counterpart from a radially stratified Earth. Solar-quiet (Sq) spectra can be reliably reconstructed from discrete time-series of measurements sampled daily within a fixed UT window. A single LEO satellite should be in orbit for at least 1 yr under quiet-time conditions to ensure accurate spectral reconstruction of an Sq geomagnetic spectrum. The length of the daily sampling window and random day-to-day variability in the Sq source strength have only minor effects on spectral reconstruction. The shape of the spectra, and spectral ratios, are independent of radial mantle conductivity. Further research employing 3-D forward modelling of induction in a laterally heterogeneous earth, with more realistic and complete external source descriptions, is advocated. The new simulation tool should prove valuable to planners of future multisatellite geomagnetic missions, as well as scientists interested in analysing and interpreting satellite induction signals.
Tunable single-photon heat conduction in electrical circuits
P. J. Jones; J. A. M. Huhtamäki; M. Partanen; K. Y. Tan; M. Möttönen
2012-05-21
We build on the study of single-photon heat conduction in electronic circuits taking into account the back-action of the superconductor--insulator--normal-metal thermometers. In addition, we show that placing capacitors, resistors, and superconducting quantum interference devices (SQUIDs) into a microwave cavity can severely distort the spatial current profile which, in general, should be accounted for in circuit design. The introduction of SQUIDs also allows for in situ tuning of the photonic power transfer which could be utilized in experiments on superconducting quantum bits.
Pseudo-updated constrained solution algorithm for nonlinear heat conduction
NASA Technical Reports Server (NTRS)
Tovichakchaikul, S.; Padovan, J.
1983-01-01
This paper develops efficiency and stability improvements in the incremental successive substitution (ISS) procedure commonly used to generate the solution to nonlinear heat conduction problems. This is achieved by employing the pseudo-update scheme of Broyden, Fletcher, Goldfarb and Shanno in conjunction with the constrained version of the ISS. The resulting algorithm retains the formulational simplicity associated with ISS schemes while incorporating the enhanced convergence properties of slope driven procedures as well as the stability of constrained approaches. To illustrate the enhanced operating characteristics of the new scheme, the results of several benchmark comparisons are presented.
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.
Anelastic dynamo models with radially varying conductivity applied to the gas giants
NASA Astrophysics Data System (ADS)
Duarte, L.; Gastine, T.; Wicht, J.
2012-12-01
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.
Application of inverse heat conduction problem on temperature measurement
NASA Astrophysics Data System (ADS)
Zhang, X.; Zhou, G.; Dong, B.; Li, Q.; Liu, L. Q.
2013-09-01
For regenerative cooling devices, such as G-M refrigerator, pulse tube cooler or thermoacoustic cooler, the gas oscillating bring about temperature fluctuations inevitably, which is harmful in many applications requiring high stable temperatures. To find out the oscillating mechanism of the cooling temperature and improve the temperature stability of cooler, the inner temperature of the cold head has to be measured. However, it is difficult to measure the inner oscillating temperature of the cold head directly because the invasive temperature detectors may disturb the oscillating flow. Fortunately, the outer surface temperature of the cold head can be measured accurately by invasive temperature measurement techniques. In this paper, a mathematical model of inverse heat conduction problem is presented to identify the inner surface oscillating temperature of cold head according to the measured temperature of the outer surface in a GM cryocooler. Inverse heat conduction problem will be solved using control volume approach. Outer surface oscillating temperature could be used as input conditions of inverse problem and the inner surface oscillating temperature of cold head can be inversely obtained. A simple uncertainty analysis of the oscillating temperature measurement also will be provided.
Underground heat conduction near a spherical inhomogeneity: theory and applications
NASA Astrophysics Data System (ADS)
Rabinovich, A.; Dagan, G.; Miloh, T.
2012-04-01
A large underground inhomogeneity, such as a salt dome or cavity, is known to disturb the subsurface temperature field. Such anomalies appear in many geophysical surveys. Detection and knowledge of the magnitude of these disturbances is the objective of both near surface and deep borehole temperature surveys aimed at delineating the inhomogeneities. It also impacts surface temperature history analysis which reconstructs past climate change in an effort to study the recent global warming. This work is aimed at quantifying these effects by solving, for the first time, a problem of heat conduction in Earth's subsurface in the presence of a spherical inhomogeneity. Both the steady state temperature field pertaining to the constant geothermal gradient and the time dependent field caused by a surface jump in temperature are solved. A solution is derived for both cases as an infinite series of spherical harmonics and Bessel functions (in the Laplace domain) for the steady and unsteady problems, respectively. It is found that an accurate solution can be achieved by a small number of terms. The results are illustrated and analyzed for a given accuracy and for a few values of the governing parameters. The general solution can be simplified considerably for asymptotic values of the parameters. Comparison with the exact solution shows that these approximations are accurate for a wide range of parameter values. Some examples of applying the solution to the geophysical methods stated above are discussed. In the case of ground surface temperature history reconstruction from borehole temperature profiles, all current methods assume one-dimensional heat conduction. We present calculations of the anomalies generated near inhomogeneities in the presence of a sudden change in surface temperature used to model climate change. Though the sphere is an idealized shape, the simplicity of the solution makes possible a general analysis toward gaining a better understanding of the process. Furthermore, it can be employed for preliminary assessment of the impact of a body and may serve as a benchmark for numerical solutions. Reference: A. Rabinovich, G. Dagan and T. Miloh, "Heat conduction in a semi-infinite medium with a spherical inhomogeneity and time-periodic boundary temperature", International Journal of Heat and Mass Transfer, 55 (2012) 618-628.
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.
NASA Astrophysics Data System (ADS)
Püthe, Christoph; Kuvshinov, Alexey; Olsen, Nils; Khan, Amir
2015-04-01
We present a new model of the radial (1-D) conductivity structure of Earth's mantle. This model was derived from more than ten years of magnetic measurements taken by the satellites Ørsted, CHAMP, SAC-C and the Swarm trio as well as the global network of geomagnetic observatories. After removal of core and crustal field as predicted by a recent field model we fit the data with spherical harmonic coefficients describing ring current activity and associated induction effects, and estimate global C-responses at periods between 1.5 days and 150 days. An iterative approach is used to correct the estimated C-responses for 3-D effects arising from induction in a heterogeneous surface shell that takes into account the distribution of oceans and continents. We invert the corrected C-responses for a 1-D model of mantle conductivity using both probabilistic and deterministic methods. The different methods yield very similar results, consisting of a highly resistive upper mantle, a conductive lower mantle, and an increase in conductivity in and beneath the transition zone. Analysis of the Hessian of the cost function reveals that the data are most sensitive to structures at depths between 700 km and 1200 km, in agreement with the results obtained from the probabilistic approach. The recovered models feature a marked kink in this well-resolved depth range.
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...
Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes
Maruyama, Shigeo
Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes-3-1 Hongo, Bunkyo-ku Tokyo 113-8656, Japan Diffusive-ballistic heat conduction of finite-length single. A gradual transition from nearly pure ballistic to diffusive-ballistic heat conduction was identified from
Maruyama, Shigeo
Diffusive-Ballistic Heat Conduction of Carbon Nanotubes and Nanographene Ribbons Junichiro Shiomi-3-5800-6983 Abstract Investigations of diffusive-ballistic heat conduction of finite-length single-walled carbon of the balance between ballistic and diffusive heat conduction. For both systems, the profile indicates
A Global Stability Analysis of Clusters of Galaxies with Conduction and AGN Feedback Heating
NASA Astrophysics Data System (ADS)
Guo, Fulai; Oh, S. Peng; Ruszkowski, M.
2008-12-01
We investigate a series of steady state models of galaxy clusters, in which the hot intracluster gas is efficiently heated by active galactic nucleus (AGN) feedback and thermal conduction, and in which the mass accretion rates are highly reduced compared to those predicted by the standard cooling flow models. We perform a global Lagrangian stability analysis. We show for the first time that the global radial instability in cool core clusters can be suppressed by the AGN feedback mechanism, provided that the feedback efficiency exceeds a critical lower limit. Furthermore, our analysis naturally shows that the clusters can exist in two distinct forms. Globally stable clusters are expected to have either (1) cool cores stabilized by both AGN feedback and conduction or (2) noncool cores stabilized primarily by conduction. Intermediate central temperatures typically lead to globally unstable solutions. This bimodality is consistent with the recent observation by Dunn & Fabian of anticorrelation between the flatness of the temperature profiles and the AGN activity and the observation by Rafferty et al. that the shorter central cooling times tend to correspond to significantly younger AGN X-ray cavities.
J. Sarkar; Souvik Bhattacharyya; M. Ram Gopal
2007-01-01
Minimization of heat exchanger area for a specified capacity is very important in the design of refrigeration and heat pump systems, yielding space, weight and cost benefits. In this study, minimization of overall conductance and total area per unit capacity of refrigeration and heat pump systems has been performed analytically. The analysis is performed for constant temperature heat sources and
Radiation and gas conduction heat transport across a helium dewar multilayer insulation system
Green, M.A.
1994-10-10
This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulate a 4 K liquid helium cryostat. The method described here permits one to estimate the insulation potential for a multilayer insulation system from first principles. The heat transfer regimes included are: radiation, conduction by free molecule gas conduction, and conduction through continuum gas conduction. Heat transfer in the transition region between the two gas conduction regimes is also included.
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.
Manipulating Steady Heat Conduction by Sensu-shaped Thermal Metamaterials.
Han, Tiancheng; Bai, Xue; Liu, Dan; Gao, Dongliang; Li, Baowen; Thong, John T L; Qiu, Cheng-Wei
2015-01-01
The ability to design the control of heat flow has innumerable benefits in the design of electronic systems such as thermoelectric energy harvesters, solid-state lighting, and thermal imagers, where the thermal design plays a key role in performance and device reliability. In this work, we employ one identical sensu-unit with facile natural composition to experimentally realize a new class of thermal metamaterials for controlling thermal conduction (e.g., thermal concentrator, focusing/resolving, uniform heating), only resorting to positioning and locating the same unit element of sensu-shape structure. The thermal metamaterial unit and the proper arrangement of multiple identical units are capable of transferring, redistributing and managing thermal energy in a versatile fashion. It is also shown that our sensu-shape unit elements can be used in manipulating dc currents without any change in the layout for the thermal counterpart. These could markedly enhance the capabilities in thermal sensing, thermal imaging, thermal-energy storage, thermal packaging, thermal therapy, and more domains beyond. PMID:25974383
Numerical heat conduction in hydrodynamical models of colliding hypersonic flows
Parkin, E R
2010-01-01
Hydrodynamical models of colliding hypersonic flows are presented which explore the dependence of the resulting dynamics and the characteristics of the derived X-ray emission on numerical conduction and viscosity. For the purpose of our investigation we present models of colliding flow with plane-parallel and cylindrical divergence. Numerical conduction causes erroneous heating of gas across the contact discontinuity which has implications for the rate at which the gas cools. We find that the dynamics of the shocked gas and the resulting X-ray emission are strongly dependent on the contrast in the density and temperature either side of the contact discontinuity, these effects being strongest where the postshock gas of one flow behaves quasi-adiabatically while the postshock gas of the other flow is strongly radiative. Introducing additional numerical viscosity into the simulations has the effect of damping the growth of instabilities, which in some cases act to increase the volume of shocked gas and can re-he...
Demko, Jonathan Alexander
1980-01-01
EFFECTS OF AXIAL PLATE HEAT CONDUCTION ON THE THERMAL PERFORMANCE QF A LAMINAR COUNTERFLON FLAT PLATE HEAT EXCHANGER A Thesis by JONATHAN ALZKVRER DEMKO Submitted to the Graduate College of Texas A&M University in partial fulfillment... of the requirement for the degree of MASTER OF SCIENCE December 1980 Major Subject: Mechanical Engineering EFFECTS OF AXIAL PLATE HEAT CONDUCTION ON THE THERMAL PERFORMANCE OF A SHINAR COUNTERFLOW FLAT PLATE HEAT EXCHANGER A Thesis by JONATHAN ALEXANDER DEMKO...
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.
T. P. Fredman
2004-01-01
A boundary identification problem in inverse heat conduction is studied, based on data from internal measurement of temperature and heat flux. Formulated as a sideways heat conduction equation, a spatial continuation technique is applied to extend the solution to a known boundary condition at the desired boundary position. Recording the positions traversed in the continuation for each time instant yields
B. R. Bass; L. J. Ott
1980-01-01
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 as the inverse heat conduction problem. An inverse solution technique applicable to the two dimensional nonlinear model with temperature dependent thermophysical properties is presented. The technique utilizes a finite element heat conduction model and a
Diffusive-Ballistic Heat Conduction along a Single-Walled Carbon Nanotube Shigeo Maruyama
Maruyama, Shigeo
Diffusive-Ballistic Heat Conduction along a Single-Walled Carbon Nanotube Shigeo Maruyama *E-mail address: maruyama@photon.t.u-tokyo.ac.jp The diffusive-ballistic heat conduction of finite at room temperature. A gradual transition from nearly pure ballistic to diffusive-ballistic heat
Thermal flywheel effects on the time varying conduction heat transfer through structural walls
P. T Tsilingiris
2003-01-01
Wall time varying conduction heat transfer investigations are very important for the prediction of heating and cooling loads in air conditioning practice and absolutely essential to the passive solar heating design. The walls store heat, absorb and dissipate a fraction of it and transmit the rest into the conditioned space at a later time, which depends on the wall thermal
Prediction of heat transfer to a thin liquid film in plane and radially spreading flows
M. M. Rahman; A. Faghri; W. L. Hankey; T. D. Swanson
1990-01-01
The energy equation is incorporated in the solution algorithm of Rahman et al. (1990) to compute the heat transfer to a thin film in the presence or absence of gravity. For a plane flow under zero gravity, it is found that, for both isothermal and uniformly heated walls, the heat transfer coefficient gradually decreases downstream, with Nu-asterisk (the Nusselt number
Maruyama, Shigeo
Isotope Effects on Heat Conduction of Carbon Nanotubes Shigeo Maruyama, Yuki Taniguchi and Yasushi that the inclusion of only 1 % of 13 C natural isotope dramatically reduces the thermal conductivity of diamond. However, isotope effects on heat conduction of SWNTs have not been elucidated. We estimated isotope
In vitro burn model illustrating heat conduction patterns using compressed thermal papers.
Lee, Jun Yong; Jung, Sung-No; Kwon, Ho
2015-01-01
To date, heat conduction from heat sources to tissue has been estimated by complex mathematical modeling. In the present study, we developed an intuitive in vitro skin burn model that illustrates heat conduction patterns inside the skin. This was composed of tightly compressed thermal papers with compression frames. Heat flow through the model left a trace by changing the color of thermal papers. These were digitized and three-dimensionally reconstituted to reproduce the heat conduction patterns in the skin. For standardization, we validated K91HG-CE thermal paper using a printout test and bivariate correlation analysis. We measured the papers' physical properties and calculated the estimated depth of heat conduction using Fourier's equation. Through contact burns of 5, 10, 15, 20, and 30 seconds on porcine skin and our burn model using a heated brass comb, and comparing the burn wound and heat conduction trace, we validated our model. The heat conduction pattern correlation analysis (intraclass correlation coefficient: 0.846, p?heat conduction depth correlation analysis (intraclass correlation coefficient: 0.93, p?heat conduction patterns. PMID:25421614
NASA Astrophysics Data System (ADS)
Han, J. C.; Zhang, Y. M.; Lee, C. P.
1992-06-01
The study investigates the effect of the surface heating condition on the local heat transfer coefficient in a rotating square channel with smooth walls and radial outward flow for Reynolds numbers from 2500 and 25,000 and rotation numbers from 0 to 0.352. Four surface heating conditions were tested: (1) four walls uniform temperature, (2) temperature ratio of leading surface to side wall and trailing surface to side wall is 1.05 and 1.10, respectively, (3) trailing surface hot and remaining three walls cold, and (4) leading surface hot and remaining three walls cold. It is shown that the heat transfer coefficients on the leading surface are much lower than that of the trailing surface due to rotation. It is suggested that the local wall heating condition creates the local buoyancy forces which reduce the effects of the bulk buoyancy and Coriolis forces. Therefore, the local heat transfer coefficients on the leading and trailing surfaces are altered by the surface local heating condition.
NASA Astrophysics Data System (ADS)
Belyaev, Alexander K.
1999-06-01
The heat conduction equation and the dynamic boundary value problem for simple piezothermoelastic materials with time- dependent properties are derived directly from the first and second laws of thermodynamics. It is also shown that the conventional form of the heat conduction equation for geometrically nonlinear anisotropic thermoelastic media does not satisfy the principle of material frame indifference. A consistent form of the heat conduction equation is suggested.
Alaina J. Garthwaite; Ernst Steudle; Timothy D. Colmer; Universitaet Bayreuth
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 experi- ments assessed whether induction of the barrier to ROL influences root hydraulic conductivity (Lpr). Wheat (Triti- cum aestivum) was also studied since, like H. marinum,
Analysis of heat conduction in a disk brake system
NASA Astrophysics Data System (ADS)
Talati, Faramarz; Jalalifar, Salman
2009-06-01
In this paper, the governing heat equations for the disk and the pad are extracted in the form of transient heat equations with heat generation that is dependant to time and space. In the derivation of the heat equations, parameters such as the duration of braking, vehicle velocity, geometries and the dimensions of the brake components, materials of the disk brake rotor and the pad and contact pressure distribution have been taken into account. The problem is solved analytically using Green’s function approach. It is concluded that the heat generated due to friction between the disk and the pad should be ideally dissipated to the environment to avoid decreasing the friction coefficient between the disk and the pad and to avoid the temperature rise of various brake components and brake fluid vaporization due to excessive heating.
Effective heat conductivity of fuel element bundles and steam generator tube bundles
NASA Astrophysics Data System (ADS)
Fedotovsky, V.; Orlov, A.
2008-06-01
Effective heat conductivity of rod and tube bundles is one of thermophysical properties necessary for calculation of thermo hydraulic characteristics of heat producing devices, heat exchange devices and steam generators. This report introduces results of mathematical modeling of effective heat conductivity of transversally anisotropic rod bundles in solid conductive medium. The considered bundles represented cylindrical rods fitted in corners of stretched and compressed in direction of heat transfer rectangular and triangular grids. The calculated results were compared to analytical solutions and previous numerical results.
High temperature electrically conducting ceramic heating element and control system
C. R. Halbach; R. J. Page
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,
Shrestha, R.; Lee, K. M.; Chang, W. S.; Kim, D. S.; Rhee, G. H.; Choi, T. Y.
2013-01-01
In this paper, we describe the thermal conductivity measurement of single-walled carbon nanotubes thin film using a laser point source-based steady state heat conduction method. A high precision micropipette thermal sensor fabricated with a sensing tip size varying from 2 ?m to 5 ?m and capable of measuring thermal fluctuation with resolution of ±0.01 K was used to measure the temperature gradient across the suspended carbon nanotubes (CNT) film with a thickness of 100 nm. We used a steady heat conduction model to correlate the temperature gradient to the thermal conductivity of the film. We measured the average thermal conductivity of CNT film as 74.3 ± 7.9 W m?1 K?1 at room temperature. PMID:23556837
NASA Astrophysics Data System (ADS)
Zou, Ling
Subcooled flow boiling is generally characterized by high heat transfer capacity and low wall superheat, which is essential for cooling applications requiring high heat transfer rate, such as nuclear reactors and fossil boilers. In this study, subcooled flow boiling on copper and stainless steel heating surfaces was experimentally investigated from both macroscopic and microscopic points of view. Flow boiling heat flux and heat transfer coefficient were experimentally measured on both surfaces under different conditions, such as pressure, flow rate and inlet subcooling. Significant boiling heat transfer coefficient differences were found between the copper and the stainless steel heating surfaces. To explain the different flow boiling behaviors on these two heating surfaces, nucleation site density and bubble dynamics were visually observed and measured at different experimental conditions utilizing a high-speed digital video camera. These two parameters are believed to be keys in determining flow boiling heat flux. Wall superheat, critical cavity size and wall heat flux were used to correlate with nucleation site density data. Among them, wall heat flux shows the best correlation for eliminating both pressure and surface property effects. The observed nucleation site distribution shows a random distribution. When compared to the spatial Poisson distribution, similarity between them was found, while the measured nucleation site distribution is more uniform. From experimental observations, for the two surface materials investigated, which have similar surface wettability but sharply different thermal properties, bubble dynamics displayed fairly similar behavior. The obtained experimental results indicate that thermal conductivity of heating surface material plays an important role in boiling heat transfer. This is due to thermal conductivity having a significant impact on the lateral heat conduction at the heating surface and consequently temperature uniformity of the heating surface. A model was then developed and solved numerically for heat conduction at the heating surface when bubbles are present. Several key parameters which impact lateral heat conduction and surface temperature profile were studied. These parameters include material thermal conductivity, bubble size, heating surface thickness, etc. Numerical results show that, temperature profile on the heating surface tends to be more uniform and have a lower average value on a heating surface with higher thermal conductivity, which agrees well with the experimental observation.
Maruyama, Shigeo
a significant contribution of the optical phonon modes to the observed wavelike heat conduction. The result suggests that, in carbon nanotubes with finite length where the long wavelength acoustic phonons behave ballistic, even optical phonons can play a major role in the non-Fourier heat conduction. PACS numbers: 61
Thermal conductance of pneumatic conveying preheater for air–gypsum and air–sand heat transfer
K. S. Rajan; S. N. Srivastava; B. Pitchumani; V. Surendiran
2010-01-01
The use of pneumatic conveying duct as gas–solid heat exchanger is in vogue in the form of preheater and dryer in cement and pharmaceutical industries, among several other industries. Experiments were conducted to study the effect of solids feed rate, particle size and air velocity on thermal conductance of a vertical pneumatic conveying heat exchanger for preheating of dry solids.
Cheng-Hung Huang; Yan Jan-Yuan
1995-01-01
An inverse analysis utilizing the conjugate gradient method of minimization and the adjoint equation is used for simultaneously estimating the temperature-dependent thermal conductivity and heat capacity per unit volume of a material. No prior information is used for the functional forms of the unknown thermal conductivity and heat capacity in the present study, thus, it is classified as the function
Alexander K. Belyaev
1999-01-01
The heat conduction equation and the dynamic boundary value problem for simple piezothermoelastic materials with time- dependent properties are derived directly from the first and second laws of thermodynamics. It is also shown that the conventional form of the heat conduction equation for geometrically nonlinear anisotropic thermoelastic media does not satisfy the principle of material frame indifference. A consistent form
A. K. Belyaev
2000-01-01
Summary It is shown that the dynamic boundary value problem and the heat conduction equation for simple piezoelectric materials with time-dependent properties result from the first and second law of thermodynamics. It is also shown that the conventional form of the heat conduction equation for geometrically nonlinear anisotropic thermoelastic media does not satisfy the principle of material frame indifference. A
An Input Estimation Approach to On-Line Two-Dimensional Inverse Heat Conduction Problems
Pan-Chio Tuan; Ching-China Ji; Li-Wei Fong; Wen-Tang Huang
1996-01-01
An on-line methodology to solve two-dimensional inverse heat conduction problems (IHCP) is presented. A new input estimation approach based on the Kalman filtering technique is developed to estimate the two separate unknown heat flux inputs on the two boundaries in real time. A recursive relation between the observed value of the residual sequence with unknown heat flux and the theoretical
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…
B. F. Blackwell; R. E. Hogan
1991-01-01
A finite control volume technique is developed to solve two-dimensional axisymmetric heat conduction problems using an arbitrary quadrilateral mesh. In this technique, the integral form of the conservation of energy equation is applied to control volumes of finite size. The boundary conditions considered include specified flux, aerodynamic heating, convection, and radiation. Two example problems involving a specified heat flux boundary
Some essential problems with ablation and heat-conduction in solid rocket nozzle
NASA Astrophysics Data System (ADS)
He, Hongqing
1993-06-01
The main problems connected with calculation of ablation and heat conductance in an integral solid-rocket nozzle are discussed. These include: (1) calculations of two-phase viscous transonic flow and heat-transfer between gas and wall in the nozzle, which are the foundation of the ablation and heat-conductance computations, (2) the need for aerodynamic thermochemical ablative models for various compounds used, (3) the need to account for particles' erosion, (4) the need to study the ablative control mechanism, (5) the need for treating moving multiboundaries in transient heat conductance, (6) the need to account for coupling between ablation and heat conductance, (7) the need for precise measurements, and (8) the need of programming ablation and heat transfer in CAD software. Taking into account the above considerations, the ablative rate and temperature distributions for an integral complexly structured solid-rocket nozzle are obtained.
Nonstationary heat conduction in one-dimensional chains with conserved momentum
NASA Astrophysics Data System (ADS)
Gendelman, Oleg V.; Savin, Alexander V.
2010-02-01
This Rapid Communication addresses the relationship between hyperbolic equations of heat conduction and microscopic models of dielectrics. Effects of the nonstationary heat conduction are investigated in two one-dimensional models with conserved momentum: Fermi-Pasta-Ulam (FPU) chain and chain of rotators (CR). These models belong to different universality classes with respect to stationary heat conduction. Direct numeric simulations reveal in both models a crossover from oscillatory decay of short-wave perturbations of the temperature field to smooth diffusive decay of the long-wave perturbations. Such behavior is inconsistent with parabolic Fourier equation of the heat conduction. The crossover wavelength decreases with increase in average temperature in both models. For the FPU model the lowest-order hyperbolic Cattaneo-Vernotte equation for the nonstationary heat conduction is not applicable, since no unique relaxation time can be determined.
B. A. Strukov; S. T. Davitadze; S. N. Kravchun; S. A. Taraskin; M. Goltzman; V. V. Lemanov; S. G. Shulman
2003-01-01
Thermal properties - specific heat and heat conductivity coefficient---of polycrystalline BaTiO3 films on massive substrates were studied as a function of the temperature and the film thickness by the ac-hot probe method. The anomalies of specific heat with the film thickness decreasing from 1100 to 20 nm revealed the reduction of Tc and excess entropy of the ferroelectric phase transition
J. E. Eninger; G. L. Fleischman; E. E. Luedke
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
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.
Glass-Like Heat Conduction in Crystalline Semiconductors
Nolas, G.S.; Cohn, J.L.; Chakoumakos, B.C.; Slack, G.A.
1999-06-13
The thermal conductivity and structural properties of polycrystalline and single crystal semiconductor type-1 germanium clathrates are reported. Germanium clathrates exhibit thermal conductivities that are typical of amorphous materials. This behavior occurs in spite of their well-defined crystalline structure. The authors employ temperature dependent neutron diffraction data in investigating the displacements of the caged strontium atoms in Sr{sub 8}Ga{sub 16}Ge{sub 30} and their interaction with the polyhedral cages that entrap them. Their aim is to investigate the correlation between the structural properties and the low, glass-like thermal conductivity observed in this compound.
Variable Conductance Heat Pipes for Radioisotope Stirling Systems
William G. Anderson; Calin Tarau
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
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
Paradoxical heat sensation in healthy subjects: peripherally conducted by A delta or C fibres?
Susser, E; Sprecher, E; Yarnitsky, D
1999-02-01
Paradoxical heat sensation upon cooling of the skin has been reported in central as well as in peripheral neurological conditions. In our study, we examined this phenomenon in 35 naive healthy test subjects, of whom 23 experienced paradoxical heat sensation under test conditions. We measured the peripheral conduction velocities of cold sensation, warm sensation and of paradoxical heat sensation by using a quantitative sensory testing model of indirect peripheral conduction velocity measurement. This was based on comparison of measurements at a proximal and a distal site using two measurement methods, one inclusive and the other exclusive of reaction time. We found that the conduction velocity of paradoxical heat sensation (0.70 m/s) was similar to that of warm sensation (0.68 m/s), and that the conduction velocity of cold sensation (7.74-8.01 m/s) was considerably faster. Thus, we conclude that paradoxical heat sensation in healthy subjects is conducted peripherally via slow unmyelinated C fibres and not via the faster A delta fibres. Consequently, we propose that paradoxical heat sensation is encoded via the heat sensing pathway, in accordance with the labelled-line code theory. The mechanisms proposed suggest a malfunctioning cold-sensing pathway disinhibiting the heat-sensing pathway, at peripheral, central or both levels, thus facilitating a paradoxical heat sensation. PMID:10071052
A MOLECULAR DYNAMICS SIMULATION OF HEAT CONDUCTION IN A CARBON NANOTUBE
Maruyama, Shigeo
A MOLECULAR DYNAMICS SIMULATION OF HEAT CONDUCTION IN A CARBON NANOTUBE Shigeo Maruyama conduction of finite length single walled carbon nanotubes (SWNTs) was simulated by the molecular dynamics experiments, several preliminary molecular dynamics simulations4-6 showed very high thermal conductivity
Non-linear vibrations of heated non-homogeneous circular plates with radially varying rigidity
Ohnabe, H. [Ishikawajima-Harima Heavy Industries, Tanashi (Japan); Mizuguchi, F. [Japan Maritime Safety Academy, Kure (Japan)
1994-12-31
The field equation of the vertical motion of heated non-homogeneous elastic circular plates with varying rigidity are derived by Berger approach. Assuming the non-homogeneous Young` s modulus, for a circular clamped plate due to a temperature distribution as seen in aerodynamic heating and prevented from inplane motions on the boundary, the governing time equation is derived by means of a Galerkin procedure applied to the field equation of the vertical motion. It is solved for free vibration and also for forced vibration by Ritz`s method. The influence of non-homogeneous Young`s modulus and temperature change on the period of free and forced vibration are shown in the graphs.
Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties
Hansen, B J; Klebaner, A; 10.1063/1.4706971
2012-01-01
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 ...
NASA Astrophysics Data System (ADS)
Dede, Ercan M.; Nomura, Tsuyoshi; Schmalenberg, Paul; Seung Lee, Jae
2013-08-01
Experimental results are presented for heat flux cloaking, focusing, and reversal in ultra-thin anisotropic composites. A two-material system is utilized in the device design, which features an annular region for heat flow control. The effective thermal conductivity layout of the composite is specified through logical combination of the base material constituents. Heat transfer considering conduction-convection is numerically predicted and experimentally verified via infrared thermography. A Biot number analysis reveals the significance of high rates of convection for large-area planar devices, while the experimental results indicate the feasibility of such heat flow control techniques for advanced electronics applications involving natural convection.
An approximate substitution principle for viscous heat conducting flows
NASA Astrophysics Data System (ADS)
Greitzer, E. M.; Paterson, R. W.; Tan, C. S.
1985-09-01
A new, approximate substitution principle is presented for a class of steady flows in which both heat transfer and momentum interchange by viscous stresses are significant. The principle, which has important implications for the design and scaling of mixing experiments, can be regarded as an extension of the Munk and Prim substitution principle (for steady isentropic flows) to nonisentropic flows (Munk and Prim, 1947). The concepts that are developed explain the scaling and distribution of various fluid dynamic properties observed in several different types of flow mixing experiments. Calculations are done to indicate the expected regimes of applicability of the approximate principle and comparison with experiment is made to show its utility in practical situations.
MOLECULAR DYNAMICS SIMULATION OF QUASI-BALLISTIC HEAT CONDUCTION IN CARBON NANOTUBES
Maruyama, Shigeo
characteristics of short wavelength phonons are strongly influence by the anharmonic effects. This aspect-tube interaction on the heat conduction is of an interest. In addition, we consider an SWNT confining an ice
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 ...
NASA Astrophysics Data System (ADS)
Kök, M.; Aydo?du, Y.
2007-04-01
The thermal conductivity of polyvinylchloride (PVC), polysytrene (PS) and polypropylene (PP) were measured by heat flux DSC. Our results are in good agreement with the results observed by different methods.
The importance of electron heat conduction in the energy balance of the F-region
NASA Technical Reports Server (NTRS)
Hoegy, W. R.; Brace, L. H.
1978-01-01
Taking into account heat conduction in the analysis of electron temperature data acquired by the AE-C satellite during the daytime at middle latitudes is shown to bring theoretical electron temperature profiles in good agreement with experimental ones. Middle latitude passes were chosen because in this region the horizontal electron temperature gradient is negligible and the height variation can be approximated by the satellite data. Inclusion of heat conduction is shown to have little effect on low-latitude data.
Pulsed RF heating simulations in normal-conducting L-band cavities.
Pulsed RF heating simulations in normal-conducting L-band cavities. V.V. Paramonov, A and results of pulsed heating effect simulations in L-band cavities, operating with high pulsed RF loss references. At L-band frequency the maximal electric and related magnetic fields are lower. Together
Measurement of the electronic thermal conductance channels and heat capacity of graphene at low opto-electronics, plasmonics, and ultra-sensitive bolometry. Here we present measurements of bipolar relation, Wiedemann- Franz ratio[3, 4], and electronic specific heat[5] . Thermal transport measurements
A Conduction Calorimeter for Measuring the Heat of Cement Hydration in the Initial Hydration Period
W. Zielenkiewicz; M. Kami?ski
2001-01-01
A new-design conduction microcalorimeter is described, which has been used to measure the heat of cement hydration evolved\\u000a in the initial period of hydration. The calorimeter is 30 cm3 in volume; the heat loss coefficient is 27.2700.015 W V–1, the time constant is 300 s.
Dennis, Brian
difficult or even impossible to place temperature probes, heat flux probes, or strain gauges on certain conditions on parts of a three-dimensional solid body surface by using FEM. It should be pointed out of inverse determination of unknown boundary conditions in two-dimensional steady heat conduction has been
Hyperbolic heat conduction equation for materials with a nonhomogeneous inner structure
W. Kaminski
1990-01-01
The physical meaning of the constant Ï in Cattaneo and Vernotte's equation for materials with a nonhomogeneous inner structure has been considered. An experimental determination of the constant Ï has been proposed and some values for selected products have been given. The range of differences in the description of heat transfer by parabolic and hyperbolic heat conduction equations has been
J. M. Zhao; L. H. Liu
2007-01-01
A spectral element method is presented to solve coupled radiative and conductive heat transfer problems in multidimensional semitransparent medium. The solution of radiative energy source is based on a second order radiative transfer equation. Both the second order radiative transfer equation and the heat diffusion equation are discretized by spec- tral element approach. Four various test problems are taken as
Fygenson, Deborah Kuchnir
-Be´nard convection Guenter Ahlers Department of Physics and iQUEST, University of California, Santa Barbara transport in Rayleigh-Be´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
Finite element formulation of the two-dimensional nonlinear inverse heat conduction problem
B. R. Bass; L. J. Ott
1980-01-01
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. An inverse solution technique applicable to
Heat conduction in anisotropic media: Nonlinear self-adjointness and conservation laws
Nail H. Ibragimov; Elena D. Avdonina
2012-02-27
Nonlinear self-adjointness of the anisotropic nonlinear heat equation is investigated. Mathematical models of heat conduction in anisotropic media with a source are considered and a class of self-adjoint models is identified. Conservation laws corresponding to the symmetries of the equations in question are computed.
Makarenko, A.S. [Kiev State Univ. (Russian Federation)
1994-06-01
Problems in the mathematical modeling of heat-distribution processes on the basis of more general equations than parabolic equations are considered. We study the general structure of the relations between solutions of various approximations to the generalized heat-conductivity equations. We introduce a notion of singularly perturbed dissipative structures and analyze singularly, perturbed blow-up regimes.
Communication Cement of high specific heat and high thermal conductivity, obtained by
Chung, Deborah D.L.
Received 21 December 1999; accepted 19 April 2000 Abstract Cement paste of high specific heat and high; Silica fume; Cement paste; Compressive strength; Silane 1. Introduction Concrete of low thermal of a structure. Cement paste exhibiting high specific heat and low thermal conductivity can be obtained by using
Y. Okamoto; R. Himeno; K. Ushida; A. Ahagon
2006-01-01
In order to reuse all waste plastics containing polyvinyl chloride (PVC) effectively, the removal of chlorine from PVC is required during the preprocess of feedback recycling. In this paper, we explain the detail of heated process in PVC, and a coupled analysis method was developed to investigate the correlation of high frequency electromagnetic wave propagation and heat conduction
Maruyama, Shigeo
Influence of interfaces on diffusive-ballistic heat conduction of carbon nanotubes Shiomi to significant ballistic phonon transport for realistic nanotube length in many applications even at room. In a system with significant ballistic heat transport, the intrinsic phonon distribution function and thus
V. A. Karkhin; A. Pittner; C. Schwenk; M. Rethmeier
2011-01-01
The paper presents bounded volume heat sources and the corresponding functional-analytical expressions for the temperature\\u000a field. The power density distributions considered here are normal, exponential and parabolic. The sources model real heat\\u000a sources like the welding arc, laser beam, electron beam, etc., the convection in the weld pool as well as the latent heat\\u000a due to fusion and solidification. The
NASA Astrophysics Data System (ADS)
Rushmer, T.; Beier, C.; Turner, S.
2007-12-01
Melting anomalies in the Earth's upper mantle have often been attributed to the presence of mantle plumes that may originate in the lower mantle, possibly from the core-mantle boundary. Globally, mantle plumes exhibit a large range in buoyancy flux that which is proportional to their temperature and volume. Plumes with higher buoyancy fluxes should have higher temperatures and experience higher degrees of partial melting. Excess heat in mantle plumes could reflect either a) an enrichment of the heat producing elements (HPE: U, Th, K) in their mantle source leading to an increase of heat production by radioactive decay or b) advective or conductive heat transport across the core-mantle boundary. The advective transport of heat may result in a physical contribution of material from the core to the lower mantle. If core material is incorporated into the lower mantle, mantle plumes with a higher buoyancy flux should have higher core tracers, e.g. increased 186Os and Fe concentrations. Geophysical and dynamic modelling indicate that at least Afar, Easter, Hawaii, Louisville and Samoa may all originate at the core-mantle boundary. These plumes encompass the whole range of known buoyancy fluxes from 1.2 Mgs -1(Afar) to 6.5 Mgs -1 (Hawaii) providing evidence that the buoyancy flux is largely independent of other geophysical parameters. In an effort to explore whether the heat producing elements are the cause of excess heat we looked for correlations between fractionation corrected concentrations of the HPE and buoyancy flux. Our results suggest that there is no correlation between HPE concentrations and buoyancy flux (with and without an additional correction for variable degrees of partial melting). As anticipated, K, Th and U are positively correlated with each other (e.g. Hawaii, Iceland and Galapagos have significantly lower concentrations than e.g. Tristan da Cunha, the Canary Islands and the Azores). We also find no correlation between currently available Fe concentration data and buoyancy flux. The apparent lack of correlation suggests that excess heat may be a result of conductive heat contribution from the core. Additional precise 186Os and Fe data are needed to further assess these conclusions.
On Thermo-viscoelasticity with Variable Thermal Conductivity and Fractional-Order Heat Transfer
NASA Astrophysics Data System (ADS)
Ezzat, M. A.; El-Karamany, A. S.; El-Bary, A. A.
2015-04-01
The equations of generalized thermo-viscoelasticity for an isotropic medium with variable thermal conductivity and fractional-order heat transfer are given. The resulting formulation is applied to a half-space subjected to arbitrary heating which is taken as a function of time and is traction free. The Laplace transform technique is used. A numerical method is employed for the inversion of the Laplace transforms. Numerical results for temperature, displacement, and stress distributions are given and illustrated graphically for the problem. The effects of the fractional order and the variable thermal conductivity for heat transfer on a viscoelastic material such as poly(methyl methacrylate) (Perspex) are discussed.
Phonon Heat Conduction in Corrugated Silicon Nanowires Below the Casimir Limit Christophe Blanc,1
, 2013) The thermal conductance of straight and corrugated monocrystalline silicon nanowires has beenPhonon Heat Conduction in Corrugated Silicon Nanowires Below the Casimir Limit Christophe Blanc,1. This result suggests an original approach to transforming a monocrystalline material into a phonon glass. PACS
Phonon Heat Conduction in Corrugated Silicon Nanowires Below the Casimir Limit Christophe Blanc,1
Paris-Sud XI, UniversitÃ© de
, 2013) The thermal conductance of straight and corrugated monocrystalline silicon nanowires has beenPhonon Heat Conduction in Corrugated Silicon Nanowires Below the Casimir Limit Christophe Blanc,1 an original approach to transforming a monocrystalline material into a phonon glass. PACS numbers: 63.22.-m
H. Q. Yang
1990-01-01
For extremely short durations oral very low temperatures (near absolute zero), the classical Fourier heat conduction equation fails and has to be replaced by a hyperbolic equation to account for finite thermal wave propagation. During the last few years, there has been a growing interest in numerical simulation of the hyperbolic heal conduction problem. The schemes used in previous studies
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.
The thermal conductivity of refractory fiber products
I. I. Vishnevskii; E. I. Akselrod; N. D. Talyanskaya; A. D. Melentev; D. B. Glushkova
1975-01-01
Conclusions A device is described for measuring the thermal conductivity of refractory-fiber products at temperatures up to 1200°C by a method based on a steady-state radial heat flow. The instrument error does not exceed ±15%.
Two-phase numerical model for thermal conductivity and convective heat transfer in nanofluids
2011-01-01
Due to the numerous applications of nanofluids, investigating and understanding of thermophysical properties of nanofluids has currently become one of the core issues. Although numerous theoretical and numerical models have been developed by previous researchers to understand the mechanism of enhanced heat transfer in nanofluids; to the best of our knowledge these models were limited to the study of either thermal conductivity or convective heat transfer of nanofluids. We have developed a numerical model which can estimate the enhancement in both the thermal conductivity and convective heat transfer in nanofluids. It also aids in understanding the mechanism of heat transfer enhancement. The study reveals that the nanoparticle dispersion in fluid medium and nanoparticle heat transport phenomenon are equally important in enhancement of thermal conductivity. However, the enhancement in convective heat transfer was caused mainly due to the nanoparticle heat transport mechanism. Ability of this model to be able to understand the mechanism of convective heat transfer enhancement distinguishes the model from rest of the available numerical models. PMID:21711746
Heat conduction: hyperbolic self-similar shock-waves in solids
Imre Ferenc Barna; Robert Kersner
2012-04-19
Analytic solutions for cylindrical thermal waves in solid medium is given based on the nonlinear hyperbolic system of heat flux relaxation and energy conservation equations. The Fourier-Cattaneo phenomenological law is generalized where the relaxation time and heat propagation coefficient have a general power law temperature dependence. From such laws one cannot form a second order parabolic or telegraph-type equation. We consider the original non-linear hyperbolic system itself with the self-similar Ansatz for the temperature distribution and for the heat flux. As results continuous and shock-wave solutions are presented. For physical establishment numerous materials with various temperature dependent heat conduction coefficients are mentioned.
NASA Astrophysics Data System (ADS)
Dhar, Purbarun; Sen Gupta, Soujit; Chakraborty, Saikat; Pattamatta, Arvind; Das, Sarit K.
2013-04-01
A thermal transport mechanism leading to the enhanced thermal conductivity of graphene nanofluids has been proposed. The graphene sheet size is postulated to be the key to the underlying mechanism. Based on a critical sheet size derived from Stokes-Einstein equation for the poly-dispersed nanofluid, sheet percolation and Brownian motion assisted sheet collisions are used to explain the heat conduction. A collision dependant dynamic conductivity considering Debye approximated volumetric specific heat due to phonon transport in graphene has been incorporated. The model has been found to be in good agreement with experimental data.
Allan, M.L.
1996-06-01
Preliminary studies were preformed to determine whether thermal conductivity of cementitious grouts used to backfill heat exchanger loops for geothermal heat pumps could be improved, thus improving efficiency. Grouts containing selected additives were compares with conventional bentonite and cement grouts. Significant enhancement of grout alumina grit, steel fibers, and silicon carbide increased the thermal conductivity when compared to unfilled, high solids bentonite grouts and conventional cement grouts. Furthermore, the developed grouts retained high thermal conductivity in the dry state, where as conventional bentonite and cement grouts tend to act as insulators if moisture is lost. The cementitious grouts studied can be mixed and placed using conventional grouting equipment.
Lijuan He; Shengbiao Hu; Shaopeng Huang; Wencai Yang; Jiyang Wang; Yusong Yuan; Shuchun Yang
2008-01-01
The Chinese Continental Scientific Drilling (CCSD) Project offers a unique opportunity for studying the thermal regime of the Dabie-Sulu ultrahigh-pressure metamorphic belt. In this paper, we report measurements of borehole temperature, thermal conductivity, and radiogenic heat production from the 5158 m deep main hole (CCSD MH). We have obtained six continuous temperature profiles from this borehole so far. The temperature
NASA Astrophysics Data System (ADS)
Fushimi, K.; Ono, A.; Matsushita, K.; Kumagai, H.; Konno, H.
2011-07-01
A simple heat treatment was used to fabricate carbonaceous layer-coated electrodes: micro-ring electrodes and conductive stainless steel. Substrates of sharpened quartz capillaries or type-316 stainless steel plates were put in an alumina boat with powder of petroleum pitch A240F separately and heated at 1073-1273 K in a flow of nitrogen or argon. By this treatment, both of the substrates were coated with a uniform carbonaceous layer of several hundred nano-meters in thickness. The electric conductivity of the layer was improved by increases in temperature and period of the heating. The quartz glass-capillary covered with the conductive layer was modified to a needle-type microelectrode by coating with an insulating polymer and baring the tip. At least a dozen carbon micro-ring electrodes with an outer radius of about 1 ?m were successfully prepared by the simple heat treatment. On the other hand, the carbonaceous layer formed on type-316 stainless steel showed relatively poor conductivity due to the formation of oxides in the layer. However, the conductivity was improved by electroplating of nickel on the substrate before the heating. The carbonaceous layer-coated stainless steel showed good corrosion resistance in sulphuric acid.
The radiant component of steam heat conductivity at high pressures and temperatures
NASA Astrophysics Data System (ADS)
Panchenko, S. V.; Dli, M. I.; Borisov, V. V.
2015-07-01
The problem of energy transfer by heat conduction and radiation is brought to a differential equation containing temperature derivatives at the boundaries and based on the selectively gray approximation of absorbing medium. A method for analytically solving the linearized problem radiant-conductive heat transfer in a flat layer of selectively absorbing medium is proposed, using which an unsymmetrical temperature profile more accurately approximating the experimental results can be obtained. The adequacy of the solution method is demonstrated by comparing the calculation results with the experimental and the results obtained using numerical methods. The effect the intermolecular interactions have on the optical properties of highly compressed media is analyzed. A dependence for determining the integral intensity of steam bands at pressures of up to 100 MPa is obtained. Quite satisfactory agreement is obtained between the calculated values of absorption intensities at increased pressures, including those for steam. The radiant component values obtained from steam heat conductivity measurements carried out in a wide range of temperatures taking into account the absorption selectivity and deviation of heat conductivity coefficients with absorption and for a transparent gas model are presented. The study results can be used for estimating the radiant component in heat conductivity measurements of absorbing fluids.
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)
Vasyliunas, Vytenis M.
1987-12-01
Heat produced at the surface of Mercury by the highly time-variable precipitation of charged particles need not be radiated away immediately but can also be conducted into the interior of the planet. For a given precipitated energy flux density, the rise of surface temperature can be computed taking both heat conduction and radiation into account. When the energy input varies on time scales shorter than a characteristic period, estimated to be one (terrestrial) day for conditions typical of Mercury's dark side, heat conduction dominates over radiation and the predicted surface temperature rise becomes negligibly small. Possible observable calorimetric effects are therefore confined to long time scales, and their magnitude is constrained by the average rate of energy input from the solar wind together with limits on the observable area of precipitation.
NASA Technical Reports Server (NTRS)
Tamma, Kumar K.; D'Costa, Joseph F.
1991-01-01
This paper describes the evaluation of mixed implicit-explicit finite element formulations for hyperbolic heat conduction problems involving non-Fourier effects. In particular, mixed implicit-explicit formulations employing the alpha method proposed by Hughes et al. (1987, 1990) are described for the numerical simulation of hyperbolic heat conduction models, which involves time-dependent relaxation effects. Existing analytical approaches for modeling/analysis of such models involve complex mathematical formulations for obtaining closed-form solutions, while in certain numerical formulations the difficulties include severe oscillatory solution behavior (which often disguises the true response) in the vicinity of the thermal disturbances, which propagate with finite velocities. In view of these factors, the alpha method is evaluated to assess the control of the amount of numerical dissipation for predicting the transient propagating thermal disturbances. Numerical test models are presented, and pertinent conclusions are drawn for the mixed-time integration simulation of hyperbolic heat conduction models involving non-Fourier effects.
R. G. Keanini; Xianwu Ling; H. P. Cherukuri
2005-01-01
A method for enhancing the stability of parabolic inverse heat conduction problems (IHCP) is presented. The investigation extends recent work on non-iterative finite element-based IHCP algorithms which, following Beck’s two-step approach, first derives a discretized standard form equation relating the instantaneous global temperature and surface heat flux vectors, and then formulates a least squares-based linear matrix normal equation in the
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 thermoelectric devices have been studied inten- sively. They make use of the Seebeck effect to convert a steady
Radiative heat exchange of a meteor body in the approximation of radiant heat conduction
N. N. Pilyugin; T. A. Chernova
1986-01-01
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
Naoki Asai; Naoya Fukuda; Ryoji Matsumoto
2004-04-07
Recent Chandra observations of clusters of galaxies revealed the existence of a sharp ridge in the X-ray surface brightness where the temperature drops across the front. This front is called the cold front. We present the results of two-dimensional magnetohydrodynamic simulations of the time evolution of a dense subcluster plasma moving in a cluster of galaxies. Anisotropic heat conduction along the magnetic field lines is included. In the models without magnetic fields, the numerical results indicate that the heat conduction from the hot ambient plasma heats the cold dense plasma of the subcluster and diffuses out the cold front. When magnetic fields exist in a cluster of galaxies, however, cold fronts can be maintained because the heat conduction across the magnetic field lines is suppressed. We found that, even when the magnetic fields in a cluster of galaxies are disordered, heat conduction across the front is restricted because the magnetic field lines are stretched along the front. Numerical results reproduced the X-ray intensity distribution observed in the A3667 cluster of galaxies.
Are X-ray Clusters Cooled by Heat Conduction to the Surrounding Intergalactic Medium?
Abraham Loeb
2002-04-29
We show that X-ray clusters would have cooled substantially over a Hubble time by transport of heat from their hot interior to the their envelope, if the heat conductivity had not been heavily suppressed relative to the Spitzer value due to magnetic fields. The suppression is required in order for the observed abundance of hot X-ray clusters to be consistent with predictions from popular cosmological models. If a similar or stronger suppression factor applies to cluster cores, then thermal conduction can not be the mechanism that prevents cooling flows there.
Heat capacities and electrical conductivities of 1-ethyl-3-methylimidazolium-based ionic liquids
Ya-Hung Yu; Allan N. Soriano; Meng-Hui Li
2009-01-01
We present the heat capacities and electrical conductivities of five [Emim] 1-ethyl-3-methylimidazolium-based ionic liquids: [Emim][BF4] (tetrafluoroborate), [Emim][CF3SO3] (trifluoromethanesulfonate), [Emim][C2N3] (dicyanamide), [Emim][C2H5SO4] (ethylsulfate), and [Emim][MDEGSO4] (2-(2-methoxyethoxy) ethylsulfate). The heat capacities were measured using a differential scanning calorimeter (DSC) over the temperature ranging from (303.2 to 358.2)K. The electrical conductivities were measured over the temperature ranging from (293.2 to 353.2)K using a
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 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.
Electrical conductivity of carbonaceous chondrites and electric heating of meteorite parent bodies
NASA Technical Reports Server (NTRS)
Duba, AL
1987-01-01
Electromagnetic heating of rock-forming materials most probably was an important process in the early history of the solar system. Electrical conductivity experiments of representative materials such as carbonaceous chondrites are necessary to obtain data for use in electromagnetic heating models. With the assumption that carbon was present at grain boundaries in the material that comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance using the T-Tauri model of Sonett and Herbert (1977). The results are discussed.
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.
B. R. Bass; L. J. Ott
1980-01-01
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. An inverse solution technique applicable to the two-dimensional nonlinear model with temperature dependent thermophysical properties is presented. The technique utilizes a finite element heat conduction model
Dongming Zhu; Robert A. Miller
2000-01-01
Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings\\u000a (TBCs) under near-realistic temperature and thermal gradients that may be encountered in advanced engine systems. Thermal\\u000a conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures.\\u000a A significant thermal conductivity increase was observed during
Sumin Kim; Lawrence T. Drzal
2009-01-01
Using exfoliated graphite nanoplatelets (xGnP), paraffin\\/xGnP composite phase change materials (PCMs) were prepared by the stirring of xGnP in liquid paraffin for high electric conductivity, thermal conductivity and latent heat storage. xGnP of 1, 2, 3, 5 and 7wt% was added to pure paraffin at 75°C. Scanning electron microscopy (SEM) morphology showed uniform dispersion of xGnP in the paraffin wax.
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.
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.
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
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
Tien-Chang Lee; A. D. Duchkov; S. G. Morozov
2003-01-01
The formation temperature below the sea or lake floor is frequently measured with a sensor probe that is inserted into the unconsolidated sediment, and the thermal conductivity of sediment is measured in situ with an independent heating experiment. Friction during the insertion raises the temperature of a probe. This paper presents the method and the test results of using the
Numerical study of conductive heat losses from a magmatic source at Phlegraean Fields
NASA Astrophysics Data System (ADS)
Di Maio, Rosa; Piegari, Ester; Mancini, Cecilia; Scandone, R.
2015-01-01
The thermal evolution of the Phlegraean magmatic system (southern Italy) is studied by analyzing the influence of the thermal property variations on the solution of the heat conduction equation. The aim of this paper is to verify if appropriate choices of thermal parameters can reproduce, at least to greater depths, the high temperatures measured in the geothermal wells, drilled inside the caldera, under the assumption of heat loss from a magma chamber by conduction. Since the main purpose is to verify the plausibility of such an assumption, rather simple models of the magmatic system are adopted and only major volcanic events (i.e., the Campanian Ignimbrite and the Neapolitan Yellow Tuff eruptions) are considered. The results of the simulated two-dimensional model scenarios show that by assuming an extended source region, whose emplacement time is longer than 40 ka, heat conduction mechanisms can provide temperatures as high as those measured at depths deeper than about 2000 m. On the other hand, the 1D simulations show that appropriate choices for the thermal conductivity depth profiles can reproduce the observed temperatures at depths deeper than about 1000 m. These findings question the apparent consensus that convection is the only dominant form of heat transfer at Phlegraean Fields and might motivate new research for reconstructing the thermal evolution of the Phlegraean magmatic system.
Global large solutions of magnetohydrodynamics with temperature-dependent heat conductivity
NASA Astrophysics Data System (ADS)
Hu, Yuxi; Ju, Qiangchang
2015-06-01
In this paper, we consider an initial boundary value problem for the magnetohydrodynamic compressible flows. By assuming that the heat conductivity depends on temperature with ? (?) = ? q , q > 0, we prove the existence and uniqueness of global strong solutions with large initial data and show that neither shock waves nor vacuum and concentration of mass in the solutions are developed in a finite time.
COYOTE: a finite-element computer program for nonlinear heat-conduction problems
Gartling, D.K.
1982-10-01
COYOTE is a finite element computer program designed for the solution of two-dimensional, nonlinear heat conduction problems. The theoretical and mathematical basis used to develop the code is described. Program capabilities and complete user instructions are presented. Several example problems are described in detail to demonstrate the use of the program.
Effect of Heat Treatment on Thermal Conductivity of U-Mo\\/Al Alloy Dispersion Fuel
S. H. Lee; J. C. Kim; J. M. Park; C. K. Kim; S. W. Kim
2003-01-01
The molybdenum content of fuel core whose matrix is aluminium 1060, was varied to be 7, 8, and 10 wt% and the volume fraction of U-Mo fuel powders was varied to be 10, 30, and 40 vol%. In this work, thermal conductivities were calculated from measured thermal diffusivities, specific heat capacities, and densities, which were determined using the laser flash,
Review and Comparison of Nanofluid Thermal Conductivity and Heat Transfer Enhancements
Wenhua Yu; David M. France; Jules L. Routbort
2008-01-01
This study provides a detailed literature review and an assessment of results of the research and development work forming the current status of nanofluid technology for heat transfer applications. Nanofluid technology is a relatively new field, and as such, the supporting studies are not extensive. Specifically, experimental results were reviewed in this study regarding the enhancement of the thermal conductivity
C. H. Huang; M. N. Özi?ik
1991-01-01
One of the difficulties in the solution of inverse heat conduction problems is that of making sufficiently accurate initial guesses for the unknowns in order to start the iterations. In this work a direct integration method is developed for determining good initial guesses for the unknown property coefficients within about 10% error. The Levenberg-Marquardt method is then applied to refine
Martin, Timothy
Summary Weusedthreemethodstomeasureboundarylayer conductance to heat transfer (gbH) and water vapor (rsV) measured with a porometer from the total branch vapor phase resistance were unusually small, water vapor transfer. Introduction Water loss from plant leaves is controlled by boundary layer
A chemical heat pump using carbon fibers as additive. Part I: enhancement of thermal conduction
T Dellero; D Sarmeo; Ph Touzain
1999-01-01
To use carbon fibers as additive in a chemical heat pump, based on a solid–gas reaction, three mixtures of carbon fibers with the reagent compounds are proposed: simple mixture, impregnation of the carbon fibers with reagent compounds and intercalation of the reagent compounds into graphite fibers. By adding carbon fibers, the thermal conductivity of the reagent bed is enhanced. While
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…
N. Daouas; M.-S. Radhouani
2007-01-01
A new approach combining the use of the Kalman filter with an extended version of a smoothing technique and introducing the use of future time measurements is developed in order to improve the solution of a nonlinear Inverse Heat Conduction Problem (IHCP). The behaviour of the proposed algorithm is analysed in presence of a real set of experimental noisy temperature
Identification methods in nonlinear heat conduction. Part II: inverse problem using a reduced model
Manuel Girault; Daniel Petit
2005-01-01
A method for solving nonlinear Inverse Heat Conduction Problems (IHCPs) using a Reduced Model (RM) is proposed in this numerical study. In a first step, RM is identified through a specific procedure using optimization techniques and a Detailed Model (DM). Compared to DM, RM allows drastic reduction of computing time without significant loss of accuracy. The second step is the
A simplified approach for heat conduction analysis of CNT-based nano-composites
Jianming Zhang; Masataka Tanaka; Toshiro Matsumoto
2004-01-01
The unique thermal properties of carbon nanotubes (CNT) may offer possibilities for the development of fundamentally new composite materials. Numerical simulation for such CNT-based composites usually demands extremely large and expensive computer resources. In preliminary computations, temperature distribution in the CNT has been turned out to be almost uniform, due to its exceptionally high heat conductivity in comparison with the
The form of Abstract Molecular dynamics simulations of diffusive-ballistic heat conduction
Maruyama, Shigeo
The form of Abstract Molecular dynamics simulations of diffusive-ballistic heat conduction carbon bonds and quasi-one-dimensional confinement of phonons. As a consequence, the ballistic phonon, phonon transport exhibits complex diffusive-ballistic feature, which gives rise to unique steady
Conductive heat loss in recent eruptions at mid-ocean ridges
NASA Astrophysics Data System (ADS)
Johnson, Paul; Hutnak, Michael
A new technique for measuring conductive heat flow from unsedimented volcanic rocks on the sea floor has been tested on two new eruption sites in the NE Pacific. This technique consists of isolating the surficial rocks from sea water using water-saturated urethane foam as an insulating thermal blanket. The thermal gradient transferred from the outcrop to the thermal blanket is a quantitative measurement of the conductive heat flow that takes place in unsedimented volcanic areas. We deployed two thermal blankets at 13 sites on the 1993 and 1996 Juan de Fuca/Gorda Ridge flows and found (1) a factor of 10 decrease in heat flow over a period of 12 months on the 1993 CoAxial flow, (2) a value of 6950 mW/m² on the 8 month old Gorda flow, and (3) measurements of heat flow versus age-since-eruption indicate that newly extruded volcanic units are quite permeable to fluid circulation and cool rapidly by convection in only a few years. These new heat flux data confirm that the extrusive volcanic layer is not the primary heat source for long-lived, high temperature hydrothermal systems, which must instead rely on a more isolated thermal reservoir within the lower crustal rocks.
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
Finite element formulation of the two-dimensional nonlinear inverse heat conduction problem
Bass, B.R.; Ott, L.J.
1980-01-01
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. An inverse solution technique applicable to the two-dimensional nonlinear model with temperature-dependent thermophysical properties is presented. This utilizes a finite element heat conduction model and a generalization of Beck's one-dimensional nonlinear estimation procedure. The formulation is 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.
NASA Astrophysics Data System (ADS)
Gong, Feng; Tam, Yong Siang; Nguyen, Son T.; Duong, Hai M.
2015-05-01
Heat conduction in single-walled carbon nanotube (SWNT) aerogels is investigated by an off-lattice Monte Carlo method. Thermal boundary resistances (TBRs) between the SWNT and four permeated gases of argon, nitrogen, neon and hydrogen are reported from fitting simulation results with experimental data. It is found that the TBRs between the SWNT and the permeated gases decrease with larger gas molecular masses. Effects of volume fractions and complex morphologies of SWNTs on thermal conductivities of SWNT aerogels are also quantified. The effective thermal conductivities of SWNT aerogels increase with the larger volume fraction, the greater length and the smaller diameter of the SWNTs.
NASA Astrophysics Data System (ADS)
Jiang, Xiaoyun; Xu, Mingyu
2010-09-01
In this paper a time fractional Fourier law is obtained from fractional calculus. According to the fractional Fourier law, a fractional heat conduction equation with a time fractional derivative in the general orthogonal curvilinear coordinate system is built. The fractional heat conduction equations in other orthogonal coordinate systems are readily obtainable as special cases. In addition, we obtain the solution of the fractional heat conduction equation in the cylindrical coordinate system in terms of the generalized H-function using integral transformation methods. The fractional heat conduction equation in the case 0heat conduction equation (?=1) and the Localized heat conduction equation (??0). Finally, numerical results are presented graphically for various values of order of fractional derivative.
NASA Technical Reports Server (NTRS)
Phillips, Wayne M.
1995-01-01
Heat radiators of proposed type feature thermally conductive fibers protruding from metallic surfaces to provide increased heat-dissipation surface areas. Free of leaks and more reliable than radiators incorporating heat pipes. Also lightweight and relatively inexpensive. Radial graphite fibers carry heat away from spherical shell and radiate heat into space. Radiators prove useful on Earth in special industrial and scientific applications involving dissipation of heat in vacuum or in relatively still air.
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
Heat conduction in double-walled carbon nanotubes with intertube additional carbon atoms.
Cui, Liu; Feng, Yanhui; Tan, Peng; Zhang, Xinxin
2015-07-01
Heat conduction of double-walled carbon nanotubes (DWCNTs) with intertube additional carbon atoms was investigated for the first time using a molecular dynamics method. By analyzing the phonon vibrational density of states (VDOS), we revealed that the intertube additional atoms weak the heat conduction along the tube axis. Moreover, the phonon participation ratio (PR) demonstrates that the heat transfer in DWCNTs is dominated by low frequency modes. The added atoms cause the mode weight factor (MWF) of the outer tube to decrease and that of the inner tube to increase, which implies a lower thermal conductivity. The effects of temperature, tube length, and the number and distribution of added atoms were studied. Furthermore, an orthogonal array testing strategy was designed to identify the most important structural factor. It is indicated that the tendencies of thermal conductivity of DWCNTs with added atoms change with temperature and length are similar to bare ones. In addition, thermal conductivity decreases with the increasing number of added atoms, more evidently for atom addition concentrated at some cross-sections rather than uniform addition along the tube length. Simultaneously, the number of added atoms at each cross-section has a considerably more remarkable impact, compared to the tube length and the density of chosen cross-sections to add atoms. PMID:26051798
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.
Mehdizadeh, Seyedeh Neda; Eskicioglu, Cigdem; Bobowski, Jake; Johnson, Thomas
2013-09-15
Microwave (2.45 GHz, 1200 W) and conventional heating (custom pressure vessel) pretreatments were applied to dewatered municipal waste sludge (18% total solids) using identical heating profiles that span a wide range of temperatures (80-160 °C). Fourteen lab-scale semi-continuous digesters were set up to optimize the energy (methane) output and sludge retention time (SRT) requirements of untreated (control) and thermally pretreated anaerobic digesters operated under mesophilic and thermophilic temperatures. Both pretreatment methods indicated that in the pretreatment range of 80-160 °C, temperature was a statistically significant factor (p-value < 0.05) for increasing solubilization of chemical oxygen demand and biopolymers (proteins, sugars, humic acids) of the waste sludge. However, the type of pretreatment method, i.e. microwave versus conventional heating, had no statistically significant effect (p-value >0.05) on sludge solubilization. With the exception of the control digesters at a 5-d SRT, all control and pretreated digesters achieved steady state at all three SRTs, corresponding to volumetric organic loading rates of 1.74-6.96 g chemical oxygen demand/L/d. At an SRT of 5 d, both mesophilic and thermophilic controls stopped producing biogas after 20 d of operation with total volatile fatty acids concentrations exceeding 1818 mg/L at pH <5.64 for mesophilic and 2853 mg/L at pH <7.02 for thermophilic controls, while the pretreated digesters continued producing biogas. Furthermore, relative (to control) organic removal efficiencies dramatically increased as SRT was shortened from 20 to 10 and then 5 d, indicating that the control digesters were challenged as the organic loading rate was increased. Energy analysis showed that, at an elevated temperature of 160 °C, the amount of methane recovered was not enough to compensate for the energy input. Among the digesters with positive net energy productions, control and pretreated digesters at 80 °C were more favorable at an SRT of 10 d. PMID:23866153
Fourier heat conduction as a phenomenon described within the scope of the second law
NASA Astrophysics Data System (ADS)
Jesudason, Christopher G.
2014-12-01
The historical development of the Carnot cycle necessitated the construction of isothermal and adiabatic pathways within the cycle that were also mechanically "reversible" which lead eventually to the Kelvin-Clausius development of the entropy function S where for any reversible closed path C, ?C dS = 0 based on an infinite number of concatenated Carnot engines that approximated the said path and where for each engine ?Q1/T1+?Q2/T2 = 0 where the Q's and T's are the heat absorption increments and temperature respectively with the subscripts indicating the isothermal paths (1;2) where for the Carnot engine, the heat absorption is for the diathermal (isothermal) paths of the cycle only. Since 'heat' has been defined as that form of energy that is transferred as a result of a temperature difference and a corollary of the Clausius statement of the Second law is that it is impossible for heat to be transferred from a cold to a hot reservoir with no other effect on the environment, these statements suggested that the local mode of transfer of 'heat' in the isothermal segments of the pathway does imply a Fourier heat conduction mechanism (to conform to the definition of 'heat') albeit of a "reversible" kind, but on the other hand, the Fourier mechanism is apparently irreversible, leading to an increase in entropy of the combined reservoirs at either end of the material involved in the conveyance of the heat energy. These and several other considerations lead Benofy and Quay (BQ) to postulate the Fourier heat conduction phenomenon to be an ancillary principle in thermodynamics, with this principle being strictly local in nature, where the global Second law statements could not be applied to this local process. Here we present equations that model heat conduction as a thermodynamically reversible but mechanically irreversible process where due to the belief in mechanical time reversible symmetry, thermodynamical reversibility has been unfortunately linked to mechanical reversibility, that has discouraged such an association. The modeling is based on an application of a "recoverable transition", defined and developed earlier on ideas derived from thermal desorption of particles from a surface where the Fourier heat conduction process is approximated as a series of such desorption processes. We recall that the original Carnot engine required both adiabatic and isothermal steps to complete the zero entropy cycle, and this construct lead to the consequent deduction that any Second law statement that refers to heat-work conversion processes are only globally relevant. Here, on the other hand, we examine Fourier heat conduction from MD simulation and model this process as a zero-entropy forward scattering process relative to each of the atoms in the lattice chain being treated as a system where the Carnot cycle can be applied individually. The equations developed predicts the "work" done to be equal to the energy transfer rate. The MD simulations conducted shows excellent agreement with the theory. Such views and results as these, if developed to a successful conclusion could imply that the Carnot cycle be viewed as describing a local process of energy-work conversion and that irreversible local processes might be brought within the scope of this cycle, implying a unified treatment of thermodynamically (i) irreversible, (ii) reversible, (iii) isothermal and (iv) adiabatic processes.
NASA Astrophysics Data System (ADS)
Imamura, K.; Tanaka, Y.; Nishiguchi, N.; Tamura, S.; Maris, H. J.
2003-12-01
We report on a molecular dynamics study of the cross-plane lattice thermal conductivity in GaAs/AlAs superlattices. The layers of the superlattice are modelled by a three-dimensional face centred cubic lattice with cubic anharmonicity, and with atomic scale roughness at the interfaces. We perform the simulation of heat flow for a section of a superlattice with high- and low-temperature thermal reservoirs attached to opposite ends. The calculation reproduces qualitatively the features observed experimentally, i.e., the dramatic reduction of the conductivity relative to the conductivity of the bulk constituent materials, and the variation of the thermal conductivity with the superlattice repeat distance. The results are also in agreement with those obtained previously by Daly et al (2002 Phys. Rev. B 66 024301) who determined the thermal conductivity from the time taken for an initially inhomogeneous temperature distribution to relax.
Miyagi, Lowell [Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112 (United States); Department of Earth Sciences, Montana State University, Bozeman, Montana 59717 (United States); Kanitpanyacharoen, Waruntorn; Kaercher, Pamela; Wenk, Hans-Rudolf; Alarcon, Eloisa Zepeda [Department of Earth and Planetary Science, University of California, Berkeley, California 94720 (United States); Raju, Selva Vennila [Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States); HiPSEC, Department of Physics, University of Nevada, Las Vegas, Nevada 89154 (United States); Knight, Jason; MacDowell, Alastair [Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States); Williams, Quentin [Department of Earth and Planetary Science, University of California, Santa Cruz, California 95064 (United States)
2013-02-15
To extend the range of high-temperature, high-pressure studies within the diamond anvil cell, a Liermann-type diamond anvil cell with radial diffraction geometry (rDAC) was redesigned and developed for synchrotron X-ray diffraction experiments at beamline 12.2.2 of the Advanced Light Source. The rDAC, equipped with graphite heating arrays, allows simultaneous resistive and laser heating while the material is subjected to high pressure. The goals are both to extend the temperature range of external (resistive) heating and to produce environments with lower temperature gradients in a simultaneously resistive- and laser-heated rDAC. Three different geomaterials were used as pilot samples to calibrate and optimize conditions for combined resistive and laser heating. For example, in Run1, FeO was loaded in a boron-mica gasket and compressed to 11 GPa then gradually resistively heated to 1007 K (1073 K at the diamond side). The laser heating was further applied to FeO to raise temperature to 2273 K. In Run2, Fe-Ni alloy was compressed to 18 GPa and resistively heated to 1785 K (1973 K at the diamond side). The combined resistive and laser heating was successfully performed again on (Mg{sub 0.9}Fe{sub 0.1})O in Run3. In this instance, the sample was loaded in a boron-kapton gasket, compressed to 29 GPa, resistive-heated up to 1007 K (1073 K at the diamond side), and further simultaneously laser-heated to achieve a temperature in excess of 2273 K at the sample position. Diffraction patterns obtained from the experiments were deconvoluted using the Rietveld method and quantified for lattice preferred orientation of each material under extreme conditions and during phase transformation.
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.
NASA Technical Reports Server (NTRS)
Parker, Hermon M
1953-01-01
An analysis is made of the transient heat-conduction effects in three simple semi-infinite bodies: the flat insulated plate, the conical shell, and the slender solid cone. The bodies are assumed to have constant initial temperatures and, at zero time, to begin to move at a constant speed and zero angle of attack through a homogeneous atmosphere. The heat input is taken as that through a laminar boundary layer. Radiation heat transfer and transverse temperature gradients are assumed to be zero. The appropriate heat-conduction equations are solved by an iteration method, the zeroeth-order terms describing the situation in the limit of small time. The method is presented and the solutions are calculated to three orders which are sufficient to give reasonably accurate results when the forward edge has attained one-half the total temperature rise (nose half-rise time). Flight Mach number and air properties occur as parameters in the result. Approximate expressions for the extent of the conduction region and nose half-rise times as functions of the parameters of the problem are presented. (author)
Wang, Wen-Jie; Cui, Song; Liu, Wei; Zu, Yuan-Gang; Sun, Wei; Wang, Hui-Min
2008-10-01
Based on a 3-year (2003-2005) observation of soil heat flux (SHF) in a larch (Larix gmelinii) plantation, the characteristics of soil heat conduction in the plantation and their relationships with environment factors were analyzed. The results showed that there was an obvious seasonal variation of SHF in different years and sampling sites. The SHF was positive from April to August and mostly negative from September to next March, with an almost balance between heat income and outcome at annual scale. Solar net radiation had significant effects on the SHF and soil heat conductance (k), and an obvious time-lag effect was found, with 4-5 hours' time-lag in winter and 2-3 hours' time-lag in summer. Based on the real-time measurement of SHF and soil temperature difference at the study sites, the k value was significantly higher in early spring (P < 0.05), but no significant difference was observed in other seasons (P > 0.05). Therefore, when we use the observation data of soil temperature from weather stations to estimate soil heat flux, the k value in spring (from March to May) could induce a bias estimation. PMID:19123344
Low conductivity water loop heat pump study at Lawrence Livermore National Laboratory
Chen, C.C.; Onu, C. [Southern Univ., Baton Rouge, LA (United States). College of Engineering; Smith, T.; Holda, M. [Lawrence Livermore National Lab., CA (United States)
1995-12-31
Based on results of the new Water Source Heat Pump (WSHP) systems operating in the US, these highly efficient heat pumps provide energy saving that will make them economically feasible to replace the inefficient, conventional HVAC systems. Additionally, an option to replace a centrifugal-compressor CFC chiller with a non-CFC chiller can be to replace the system with a highly efficient Water-Loop Heat Pump (WSHP) system. This replacement can result in a reduction of 20 to 30% in heating and air-conditioning energy costs. Low Conductivity Water (LCW) is purified water used for cooling in experimental laboratory, process, and air-conditioning equipment. It is one of several lab-wide mechanical utilities systems provided at Lawrence Livermore National Laboratory (LNL). The system is designed to maintain a supply temperature between 65 F and 85 F, with 100 psi at the inlet of the user building, 50--55 psi minimum differential pressures in the building, 35 psi maximum return pressure, and 0.4 umho/cm conductivity. However, this study is to utilize the existing LCW water loop to achieve the energy-efficiency improvement in a water resource heat pump (WRHP) system. The study will also utilize the life cycle costs as a tool to as the general selected criteria.
Statistical properties of Joule heating rate, electric field and conductances at high latitudes
NASA Astrophysics Data System (ADS)
Aikio, A. T.; Selkälä, A.
2009-07-01
Statistical properties of Joule heating rate, electric field and conductances in the high latitude ionosphere are studied by a unique one-month measurement made by the EISCAT incoherent scatter radar in Tromsø (66.6 cgmlat) from 6 March to 6 April 2006. The data are from the same season (close to vernal equinox) and from similar sunspot conditions (about 1.5 years before the sunspot minimum) providing an excellent set of data to study the MLT and Kp dependence of parameters with high temporal and spatial resolution. All the parameters show a clear MLT variation, which is different for low and high Kp conditions. Our results indicate that the response of morning sector conductances and conductance ratios to increased magnetic activity is stronger than that of the evening sector. The co-location of Pedersen conductance maximum and electric field maximum in the morning sector produces the largest Joule heating rates 03-05 MLT for Kp?3. In the evening sector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates in the nightside are statistically observed at 23 MLT, which is the location of the electric Harang discontinuity. An important outcome of the paper are the fitted functions for the Joule heating rate as a function of electric field magnitude, separately for four MLT sectors and two activity levels (Kp<3 and Kp?3). In addition to the squared electric field, the fit includes a linear term to study the possible anticorrelation or correlation between electric field and conductance. In the midday sector, positive correlation is found as well as in the morning sector for the high activity case. In the midnight and evening sectors, anticorrelation between electric field and conductance is obtained, i.e. high electric fields are associated with low conductances. This is expected to occur in the return current regions adjacent to auroral arcs as a result of ionosphere-magnetosphere coupling, as discussed by Aikio et al. (2004) In addition, a part of the anticorrelation may come from polarization effects inside high-conductance regions, e.g. auroral arcs. These observations confirm the speculated effect of small scale electrodynamics, which is not included in most of the global modeling efforts of Joule heating rate.
Variation of thermal conductivity and heat flux at the Earth's core mantle boundary
NASA Astrophysics Data System (ADS)
Ammann, Michael W.; Walker, Andrew M.; Stackhouse, Stephen; Wookey, James; Forte, Alessandro M.; Brodholt, John P.; Dobson, David P.
2014-03-01
The two convective systems that dominate Earth's internal dynamics meet at the boundary between the rocky mantle and metallic liquid core. Energy transfer between processes driving plate tectonics and the geodynamo is controlled by thermal conduction in the lowermost mantle (D?). We use atomic scale simulations to determine the thermal conductivity of MgSiO3 perovskite and post-perovskite under D? conditions and probe how these two convective systems interact. We show that the thermal conductivity of post-perovskite (?12 W/mK) is 50% larger than that of perovskite under the same conditions (?8.5 W/mK) and is anisotropic, with conductivity along the a-axis being 40% higher than conductivity along the c-axis. This enhances the high heat flux into cold regions of D? where post-perovskite is stable, strengthening the feedback between convection in the core and mantle. Reminiscent of the situation in the lithosphere, there is potential for deformation induced texturing associated with mantle convection to modify how the mantle is heated from below. We test this by coupling our atomic scale results to models of texture in D? and suggest that anisotropic thermal conductivity may help to stabilise the roots of mantle plumes over their protracted lifetime.
Hartenstine, J.R.
1991-08-01
Sodium-sulfur batteries can provide electrical power to satellite instrumentation operating in geosynchronous-earth-orbit (GEO) and low-earth-orbit (LEO) conditions. While on orbit, the sodium-sulfur battery requires thermal management as the battery is cycled between discharge in solar eclipse and recharge in sunlight. As the battery discharges in solar eclipses, waste heat is generated and the battery requires cooling. During recharge in sunlight, the battery temperature needs to be maintained above 320 C. In this Phase I program, Thermacore developed and demonstrated a dual titanium/cesium heat pipe to provide passive, lightweight management of the battery during orbital cycling. The dual heat pipe concept uses both constant and variable conductance heat pipes. Constant conductance heat pipes are inserted between sodium-sulfur cells. The cells radiate to the constant conductance heat pipes and this energy is transferred to a variable conductance heat pipe and radiated to deep space.
Pometescu, N.; Weyssow, B. [Department of Physics, University of Craiova, Association Euratom-MEdC, 13 A.I.Cuza Str., 200585 Craiova (Romania); Physique Statistique et Plasmas, Universite Libre de Bruxelles, Association Euratom-Etat Belge, Campus Plaine CP231, Bd. du Triomphe, 1050 Brussels (Belgium)
2007-02-15
The combined effect of the turbulence and of the external radio-frequency heating on the radial and poloidal components of the ion particle and energy fluxes in magnetically confined plasma is analyzed analytically from the drift kinetic equation. These two components of the transport are derived in terms of the thermodynamic forces and of correlations of fluctuating quantities using the methodology of neoclassical transport theory based on the tokamak standard model of confining magnetic field. The ion cyclotron heating is specifically considered since, to first order, the electron dynamics may be neglected. The formalism is applied to different types of instabilities in order to quantify the role of the heating versus turbulence on the transport.
Thermal conductance of and heat generation in tire-pavement interface and effect on aircraft braking
NASA Technical Reports Server (NTRS)
Miller, C. D.
1976-01-01
A finite-difference analysis was performed on temperature records obtained from a free rolling automotive tire and from pavement surface. A high thermal contact conductance between tire and asphalt was found on a statistical basis. Average slip due to squirming between tire and asphalt was about 1.5 mm. Consequent friction heat was estimated as 64 percent of total power absorbed by bias-ply, belted tire. Extrapolation of results to aircraft tire indicates potential braking improvement by even moderate increase of heat absorbing capacity of runway surface.
Self-gravitational instability of rotating anisotropic heat-conducting plasma
Prajapati, R. P.; Parihar, A. K.; Chhajlani, R. K. [School of Studies in Physics, Vikram University, Ujjain-456010 (India)
2008-01-15
The self-gravitational instability of rotating anisotropic heat-conducting plasma with modified Chew-Goldberger-Low equations is investigated. The general dispersion relation is obtained using normal mode analysis by constructing the linearized set of equations. This dispersion relation is further reduced for propagation parallel and perpendicular to the direction of magnetic field. These conditions are discussed for axis of rotation along and perpendicular to the magnetic field. It is found that the heat flux vector does not influence the transverse mode of propagation for both cases of rotation and Jeans condition remains unchanged. In case of propagation parallel to the magnetic field with axis of rotation perpendicular to the magnetic field, we get the dispersion relation, which shows the joint effect of rotation and heat flux vector. The two separate modes of propagation are obtained in terms of rotation and heat flux vector for rotation parallel to the magnetic field. It is demonstrated that the Alfven wave and the associated firehose instability are not affected by the presence of heat flux corrections and rotation also. The numerical analysis is performed to show the effect of rotation, pressure anisotropy, and heat flux parameter on the condition of instability in the spiral arms of galaxy. The Jeans condition of gravitational instability is obtained for both the cases of propagation.
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.
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
Self-similar ablative flow of nonstationary accelerating foil due to nonlinear heat conduction
Murakami, M.; Sakaiya, T.; Sanz, J. [Institute of Laser Engineering, Osaka University, Osaka (Japan)
2007-02-15
Ablating plasma flow of an accelerating foil driven by nonlinear heat conduction is investigated theoretically. It is shown that the hydrodynamic system admits a new self-similar solution describing the nonstationary ablation process, through which the payload mass decreases to burn out at the end. In contrast to previous analyses based on stationary flow, the present solution provides a practical physical picture with a finite peak density and a distinct vacuum boundary at the front. The system is solved as a novel eigenvalue problem such that the acceleration and the heat conductivity are restrictive with each other under the self-similar evolution. Scaling laws are obtained to describe the temporal evolution for the shell acceleration and such ablation performances as the mass ablation rate and the ablation pressure.
Two-Gradient Convection in a Vertical Slot with Maxwell-Cattaneo Heat Conduction
Papanicolaou, N. C. [Department of Computer Science, University of Nicosia, P.O. Box 24005, 1700 Nicosia (Cyprus); Christov, C. I. [Department of Mathematics, University of Louisiana at Lafayette, LA 70504-1010 (United States); Jordan, P. M. [Entropy Reversal Consultants (L.L.C), P. O. Box 691, Abita Springs, LA 70420 (United States); Code 7181, Naval Research Lab., Stennis Space Ctr., MS 39529 (United States)
2009-10-29
We study the effect of the Maxwell-Cattaneo law of heat conduction (MCHC) on the 1D flow in a vertical slot subject to both vertical and horizontal temperature gradients. The gravitational acceleration is allowed to oscillate, which provides an opportunity to investigate the quantitative contribution of thermal inertia as epitomized by MCHC. The addition of the time derivative in MCHC increases the order of the system. We use a spectral expansion with Rayleigh's beam functions as the basis set, which is especially suited to fourth order boundary value problems (BVP). We show that the time derivative (relaxation of the thermal flux) has a dissipative nature and leads to the appearance of purely real negative eigenvalues. Yet it also increases the absolute value of the imaginary part and decreases the absolute value of the real part of the complex eigenvalues. Thus, the system has a somewhat more oscillatory behavior than the one based on Fourier's heat conduction law (FHC)
A blow-up criterion for compressible viscous heat-conductive flows
Song Jiang; Yaobin Ou
2010-06-12
We study an initial boundary value problem for the Navier-Stokes equations of compressible viscous heat-conductive fluids in a 2-D periodic domain or the unit square domain. We establish a blow-up criterion for the local strong solutions in terms of the gradient of the velocity only, which coincides with the famous Beale-Kato-Majda criterion for ideal incompressible flows.
Cheng-Ying Lo; Bo-Yo Chen
2009-01-01
This article presents a hybrid differential transform\\/control-volume method to solve hyperbolic heat conduction problems. First, the governing equations are transformed using the differential transform technique. Second, the temperature spectra, given by predefined shape functions are calculated through a recursive formula after applying the control-volume method to each individual subinterval. Finally, the inverse differential transform technique is adopted to determine the
Specific heat and thermal conductivity of thin film amorphous magnetic semiconductors
Barry Lee Zink
2002-01-01
Amorphous Gd-Si is a spin glass which has many characteristics of classic spin glasses but displays as yet unexplained phenomena, including large magnetic entropy and enhanced effective magnetic moment near the metal-insulator transition. Specific heat and thermal conductivity measurements are important contributions to the understanding of amorphous solids, spin-glasses and the physics of the metal-insulator transition. This thesis presents specific
William J. Fisk; Woody Delp; Rick Diamond; Darryl Dickerhoff; Ronnen Levinson; Mark Modera; Matty Nematollahi; Duo Wang
2000-01-01
Through field studies in large commercial buildings and reviews of building plans, we investigated the effective leakage areas (ELAs), air-leakage rates, and conduction heat gains of duct systems. Different methods for measuring air-leakage rates were also compared. ELAs of supply ducts ranged from 0.4 to 2.0 cm2 per square meter of floor area served, and from 1.0 to 4.8 cm2
Second law analysis of coupled conduction–radiation heat transfer with phase change
D. Makhanlall; L. H. Liu
2010-01-01
This work considers an exergy-based analysis of two-dimensional solid-liquid phase change processes in a square cavity enclosure. The phase change material (PCM) concerns a semi-transparent absorbing, emitting and anisotropically scattering medium with constant thermodynamic properties. The enthalpy-based energy equation is solved numerically using computational fluid dynamics. Once the energy equation is solved, local exergy loss due to heat conduction and
Yong Liu; R. D. Reitz
1998-01-01
A two-dimensional (axisymmetric) transient heat conduction in components computer program (HCC) was successfully developed for predicting engine combustion chamber wall temperatures. The alternating direction explicit (ADE) Saul'yev method, an explicit, unconditionally stable finite difference method, was used in the code. Special treatments for the head gasket and the piston-liner air gap, the piston movement, and a grid transformation for describing
Meng-Bi Cheng; Verica Radisavljevic; Chung-Cheng Chang; Chia-Fu Lin; Wu-Chung Su
2009-01-01
This note presents a sampled-data strategy for a boundary control problem of a heat conduction system modeled by a parabolic partial differential equation (PDE). Using the zero-order-hold, the control law becomes a piecewise constant signal, in which a step change of value occurs at each sampling instant. Through the dasialiftingpsila technique, the PDE is converted into a sequence of constant
Siu N. Leung; Omer M. Khan; Ellen Chan; Hani E. Naguib; Francis Dawson; Vincent Adinkrah; Laszlo Lakatos-Hayward
2011-01-01
Today's smaller, more powerful electronic devices, communications equipment, and lighting apparatus required optimum heat dissipation solutions. Traditionally, metals are widely known for their superior thermal conductivity; however, their good electrical conductivity has limited their applications in heat management components for microelectronic applications. This prompts the requirement to develop novel plastic composites that satisfy multifunctional requirements thermally, electrically, and mechanically. Furthermore,
A. R. Zokayi; M. Hadizadeh; P. Darania; A. Rajabi
2006-01-01
The main objective of this article is to analyze the RF-pair approach for the relation between the Emden–Fowler equation and the nonlinear heat conduction problem with variable transfer coefficient. The nonlinear heat conduction equation, by means of appropriate series of operators and transformations is transformed into the classical Emden–Fowler equation.
A. K. Belyaev; V. A. Palmov
1996-01-01
Summary It is shown that the dynamic boundary value problem and the heat conduction equation for some simple materials are derivable from the first and second laws of thermodynamics. The dynamic boundary value problem, the heat conduction equation and two variational principles are derived for thermoelastic materials with time-dependent properties, for the case when the volume and surface forces are
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.
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.
Pradhan, N R; Duan, H; Liang, J; Iannacchione, G S
2008-12-01
We report simultaneous specific heat (c(p)) and thermal conductivity (?) measurements for anisotropic and random macroscopic composites of cobalt nanowires (Co NWs), from 300 to 400 K. Anisotropic composites of Co NW consist of nanowires grown within the highly ordered, densely packed array of parallel nanochannels in anodized aluminum oxide. Random composites are formed by drop-casting a thin film of randomly oriented Co NWs, removed from the anodized aluminum oxide host, within a calorimetric cell. The specific heat measured with the heat flow parallel to the Co NW alignment ([Formula: see text]) and that for the random sample (c(p)(R)) deviate strongly in temperature dependence from that measured for bulk, amorphous, powder cobalt under identical experimental conditions. The thermal conductivity for random composites (?(R)) follows a bulk-like behavior though it is greatly reduced in magnitude, exhibiting a broad maximum near 365 K indicating the onset of boundary-phonon scattering. The thermal conductivity in the anisotropic sample ([Formula: see text]) is equally reduced in magnitude but increases smoothly with increasing temperature and appears to be dominated by phonon-phonon scattering. PMID:21836319
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.
L. I. Tuchinskii; E. M. Veksler; V. G. Zatovskii
1992-01-01
The most important characteristic of materials used for development of heat exchangers is their thermal conductivity. Knowledge of it is necessary for making calculations andfor selection of the optimum design of equipment. In connection with this it is of interest to analyze the thermal conductivity of polycapillary composite materials (PCM) developed in the Institute of Materials Science of the Academy
Review and comparison of nanofluid thermal conductivity and heat transfer enhancements.
Yu, W.; France, D. M.; Routbort, J. L.; Choi, S. U.S.; Energy Systems; Univ. of Illinois at Chicago; Korea Inst. of Energy Research
2008-05-01
This study provides a detailed literature review and an assessment of results of the research and development work forming the current status of nanofluid technology for heat transfer applications. Nanofluid technology is a relatively new field, and as such, the supporting studies are not extensive. Specifically, experimental results were reviewed in this study regarding the enhancement of the thermal conductivity and convective heat transfer of nanofluids relative to conventional heat transfer fluids, and assessments were made as to the state-of-the-art of verified parametric trends and magnitudes. Pertinent parameters of particle volume concentration, particle material, particle size, particle shape, base fluid material, temperature, additive, and acidity were considered individually, and experimental results from multiple research groups were used together when assessing results. To this end, published research results from many studies were recast using a common parameter to facilitate comparisons of data among research groups and to identify thermal property and heat transfer trends. The current state of knowledge is presented as well as areas where the data are presently inconclusive or conflicting. Heat transfer enhancement for available nanofluids is shown to be in the 15-40% range, with a few situations resulting in orders of magnitude enhancement.
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.
On the equilibrium of heated self-gravitating masses - Cooling by conduction
NASA Technical Reports Server (NTRS)
Lerche, I.; Low, B. C.
1980-01-01
An investigation is given of the equilibrium states available to a self-gravitating mass of gas, cooling by conduction, and being heated at a rate proportional to the local gas density. The plane geometry situation is shown to be reducible to quadratures for the pressure, density, temperature, and gravitational potential. For a constant thermal conductivity it is shown that the gas density has either a central maximum or a central minimum, depending on the ratio of the thermal conductivity to a parameter taken to be a measure of the rate of heating. For a thermal conductivity which is a positive power of the temperature, it is shown that the gas density always has a central minimum and a maximum at the outer boundary of the configuration. For cylindrical and spherical geometrical configurations the same general properties are obtained. The physical origin of this behavior is discussed, and it is suggested that these exploratory calculations provide an effect which may not only aid in understanding thin filamentary structure observed in supernova remnants, but also help to assuage the difficulties of producing maser activity in the interior regions of 'cocoon' protostars.
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.
First Principles Modeling of Phonon Heat Conduction in Nanoscale Crystalline Structures
Sandip Mazumder; Ju Li
2010-06-30
The inability to remove heat efficiently is currently one of the stumbling blocks toward further miniaturization and advancement of electronic, optoelectronic, and micro-electro-mechanical devices. In order to formulate better heat removal strategies and designs, it is first necessary to understand the fundamental mechanisms of heat transport in semiconductor thin films. Modeling techniques, based on first principles, can play the crucial role of filling gaps in our understanding by revealing information that experiments are incapable of. Heat conduction in crystalline semiconductor films occurs by lattice vibrations that result in the propagation of quanta of energy called phonons. If the mean free path of the traveling phonons is larger than the film thickness, thermodynamic equilibrium ceases to exist, and thus, the Fourier law of heat conduction is invalid. In this scenario, bulk thermal conductivity values, which are experimentally determined by inversion of the Fourier law itself, cannot be used for analysis. The Boltzmann Transport Equation (BTE) is a powerful tool to treat non-equilibrium heat transport in thin films. The BTE describes the evolution of the number density (or energy) distribution for phonons as a result of transport (or drift) and inter-phonon collisions. Drift causes the phonon energy distribution to deviate from equilibrium, while collisions tend to restore equilibrium. Prior to solution of the BTE, it is necessary to compute the lifetimes (or scattering rates) for phonons of all wave-vector and polarization. The lifetime of a phonon is the net result of its collisions with other phonons, which in turn is governed by the conservation of energy and momentum during the underlying collision processes. This research project contributed to the state-of-the-art in two ways: (1) by developing and demonstrating a calibration-free simple methodology to compute intrinsic phonon scattering (Normal and Umklapp processes) time scales with the inclusion of optical phonons, and (2) by developing a suite of numerical algorithms for solution of the BTE for phonons. The suite of numerical algorithms includes Monte Carlo techniques and deterministic techniques based on the Discrete Ordinates Method and the Ballistic-Diffusive approximation of the BTE. These methods were applied to calculation of thermal conductivity of silicon thin films, and to simulate heat conduction in multi-dimensional structures. In addition, thermal transport in silicon nanowires was investigated using two different first principles methods. One was to apply the Green-Kubo formulation to an equilibrium system. The other was to use Non-Equilibrium Molecular Dynamics (NEMD). Results of MD simulations showed that the nanowire cross-sectional shape and size significantly affects the thermal conductivity, as has been found experimentally. In summary, the project clarified the role of various phonon modes - in particular, optical phonon - in non-equilibrium transport in silicon. It laid the foundation for the solution of the BTE in complex three-dimensional structures using deterministic techniques, paving the way for the development of robust numerical tools that could be coupled to existing device simulation tools to enable coupled electro-thermal modeling of practical electronic/optoelectronic devices. Finally, it shed light on why the thermal conductivity of silicon nanowires is so sensitive to its cross-sectional shape.
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 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.
Perano, Kristen M; Usack, Joseph G; Angenent, Largus T; Gebremedhin, Kifle G
2015-08-01
The objective of this research was to test the effectiveness of conductive cooling in alleviating heat stress of lactating dairy cows. A conductive cooling system was built with waterbeds (Dual Chamber Cow Waterbeds, Advanced Comfort Technology Inc., Reedsburg, WI) modified to circulate chilled water. The experiment lasted 7 wk. Eight first-lactation Holstein cows producing 34.4±3.7kg/d of milk at 166±28 d in milk were used in the study. Milk yield, dry matter intake (DMI), and rectal temperature were recorded twice daily, and respiration rate was recorded 5 times per day. During wk 1, the cows were not exposed to experimental heat stress or conductive cooling. For the remaining 6 wk, the cows were exposed to heat stress from 0900 to 1700h each day. During these 6 wk, 4 of the 8 cows were cooled with conductive cooling (experimental cows), and the other 4 were not cooled (control cows). The study consisted of 2 thermal environment exposures (temperature-humidity index mean ± standard deviation of 80.7±0.9 and 79.0±1.0) and 2 cooling water temperatures (circulating water through the water mattresses at temperatures of 4.5°C and 10°C). Thus, a total of 4 conductive cooling treatments were tested, with each treatment lasting 1 wk. During wk 6, the experimental and control cows were switched and the temperature-humidity index of 79.0±1.0 with 4.5°C cooling water treatment was repeated. During wk 7, waterbeds were placed directly on concrete stalls without actively cooling the water. Least squares means and P-values for the different treatments were calculated with multivariate mixed models. Conductively cooling the cows with 4.5°C water decreased rectal temperature by 1.0°C, decreased respiration rate by 18 breaths/min, increased milk yield by 5%, and increased DMI by 14% compared with the controls. When the results from the 2 cooling water temperatures (4.5°C and 10°C circulating water) were compared, we found that the rectal temperature from 4.5°C cooling water was 0.3°C lower than the rectal temperature with 10°C cooling water, but the other measurements (respiration rate, milk production, and DMI) did not show a statistically significant difference between the cooling water temperatures. Placing waterbeds on concrete stalls without additional cooling did not have a measurable effect in alleviating the heat stress of the cows. PMID:26074243
Dongming Zhu; Robert A. Miller; Ben A. Nagaraj; Robert W. Bruce
2001-01-01
The thermal conductivity of electron beam-physical vapor deposited (EB-PVD) ZrO2–8 wt.%Y2O3 thermal barrier coatings was determined by a steady-state laser heat flux technique. Thermal conductivity change kinetics of the EB-PVD ceramic coatings were also obtained in real time, at high temperatures, under the laser high heat flux, long-term test conditions. The thermal conductivity increase due to micro-pore sintering and the
X. Fu; D. D. L. Chung
1997-01-01
Due to their poor conductivity, latex (20–30% by weight of cement), methylcellulose (0.4–0.8% by weight of cement), and silica fume (15% by weight of cement) decreased the thermal conductivity of cement paste by up to 46%. In addition, these admixtures increased the specific heat of cement paste by up to 10%. The thermal conductivity decreased and the specific heat increased
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.
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
Surface roughness and three-dimensional heat conduction in thermophysical models
NASA Astrophysics Data System (ADS)
Davidsson, Björn J. R.; Rickman, Hans
2014-11-01
A thermophysical model is presented that considers surface roughness, cast shadows, multiple or single scattering of radiation, visual and thermal infrared self heating, as well as heat conduction in one or three dimensions. The code is suitable for calculating infrared spectral energy distributions for spatially resolved or unresolved minor Solar System bodies without significant atmospheres or sublimation, such as the Moon, Mercury, asteroids, irregular satellites or inactive regions on comet nuclei. It is here used to explore the effects of surface roughness on spatial scales small enough for heat conduction to erase lateral temperature gradients. Analytically derived corrections to one-dimensional models that reproduce the results of three-dimensional modeling are presented. We find that the temperature of terrains with such small-scale roughness is identical to that of smooth surfaces for certain types of topographies and non-scattering material. However, systematic differences between smooth and rough terrains are found for scattering materials, or topographies with prominent positive relief. Contrary to common beliefs, the roughness on small spatial scales may therefore affect the thermal emission of Solar System bodies.
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.
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.
Deposition of high photo-conductivity a-Si:H film using ICPs without substrate heating
Goto, M.; Toyoda, H.; Sugai, H. [Nagoya Univ. (Japan). Dept. of Electrical Engineering; Kitagawa, M. [Matsushita Electric Industrial Co., Kyoto (Japan). Central Research Lab.; Hirao, T. [Matsushita Technoresearch Inc., Moriguchi, Osaka (Japan)
1996-12-31
Hydrogenated amorphous silicon (a-Si:H) films have been commonly prepared by glow discharge decomposition of silane (SiH{sub 4}) using capacitively coupled plasmas (CCP). In course of the film deposition with CCP, however, substrates must be heated at moderate temperatures around 250 C to obtain high quality films. This fact makes it impossible to deposit films on materials with no heat resistance such as polymer sheets. To break through this problem, a-Si:H deposition by ECR plasmas has been proposed. Inductively coupled plasmas (ICPs) are also very attractive for a-Si:H film deposition because high density plasmas at low pressures can be produced with compact and simple configurations compared with ECR discharges. The authors in this paper, demonstrate deposition of high photo-conductivity a-Si:H films at low substrate temperature, using a SiH{sub 4} ICP. Photo- and dark-conductivities are measured as a function of rf power, SiH{sub 4} pressure and substrate position with respect to the gas feed position. It is found that, at proper discharge conditions, high photo-conductivity films (10{sup {minus}6} {approximately} 10{sup {minus}5} {Omega}{sup {minus}1} cm{sup {minus}1}) can be deposited even at a substrate temperature of 40 C. This result is very promising for the a-Si:H deposition using ICP near room temperatures.
NASA Astrophysics Data System (ADS)
Min, Dong; Shen, Jun; Lai, Shiqiang; Chen, Jie; Xu, Nan; Liu, Hui
2011-01-01
The effects of heat input on the low power Nd:YAG pulse laser conduction weldability of magnesium alloy AZ61 plates were investigated. The results show that for a hot-extruded AZ61 magnesium alloy plate laser conduction welding, the penetration depth and area of welds cross-section increased with an increase of the heat input. The microstructure of a band zone, which is located in the fusion zone (FZ) and close to the fusion boundary, evolved with an increase of the heat input. Moreover, an increase of the heat input increased the tendency of the formation of solidification cracking and liquation cracking. The porosities and average diameters of pores increased with an increase of the heat input but reduced sharply when a relatively large heat input was achieved. In addition, the degree of formation of craters increased linearly with an increase of the heat input.
The improved element-free Galerkin method for three-dimensional transient heat conduction problems
NASA Astrophysics Data System (ADS)
Zhang, Zan; Wang, JianFei; Cheng, YuMin; Liew, Kim Meow
2013-08-01
With the improved moving least-squares (IMLS) approximation, an orthogonal function system with a weight function is used as the basis function. The combination of the element-free Galerkin (EFG) method and the IMLS approximation leads to the development of the improved element-free Galerkin (IEFG) method. In this paper, the IEFG method is applied to study the partial differential equations that control the heat flow in three-dimensional space. With the IEFG technique, the Galerkin weak form is employed to develop the discretized system equations, and the penalty method is applied to impose the essential boundary conditions. The traditional difference method for two-point boundary value problems is selected for the time discretization. As the transient heat conduction equations and the boundary and initial conditions are time dependent, the scaling parameter, number of nodes and time step length are considered in a convergence study.
Layered thermal metamaterials for the directing and harvesting of conductive heat
NASA Astrophysics Data System (ADS)
Bandaru, P. R.; Vemuri, K. P.; Canbazoglu, F. M.; Kapadia, R. S.
2015-05-01
The utility of a metamaterial, assembled from two layers of nominally isotropic materials, for thermal energy re-orientation and harvesting is examined. A study of the underlying phenomena related to heat flux manipulation, exploiting the anisotropy of the thermal conductivity tensor, is a focus. The notion of the assembled metamaterial as an effective thermal medium forms the basis for many of these investigations and will be probed. An overarching aim is to implement in such thermal metamaterials, functionalities well known from light optics, such as reflection and refraction, which in turn may yield insights on efficient thermal lensing. Consequently, the harness and dissipation of heat, which are for example, of much importance in energy conservation and improving electrical device performance, may be accomplished. The possibilities of energy harvesting, through exploiting anisotropic thermopower in the metamaterials is also examined. The review concludes with a brief survey of the outstanding issues and insights needed for further progress.
Held, Markus; Steigmeir, Andreas
2015-01-01
We present and discuss three discontinuous Galerkin (dG) discretizations for the anisotropic heat conduction equation on non-aligned cylindrical grids. Our most favourable scheme relies on a self-adjoint local dG (LDG) discretization of the elliptic operator. It conserves the energy exactly and converges with arbitrary order. The pollution by numerical perpendicular heat fluxes degrades with superconvergence rates. We compare this scheme with aligned schemes that are based on the flux-coordinate independent approach for the discretization of parallel derivatives. Here, the dG method provides the necessary interpolation. The first aligned discretization can be used in an explicit time-integrator. However, the scheme violates conservation of energy and shows up stagnating convergence rates for very high resolutions. We overcome this partly by using the adjoint of the parallel derivative operator to construct a second self-adjoint aligned scheme. This scheme preserves energy, but reveals unphysical oscillations ...
An implicit-iterative solution of the heat conduction equation with a radiation boundary condition
NASA Technical Reports Server (NTRS)
Williams, S. D.; Curry, D. M.
1977-01-01
For the problem of predicting one-dimensional heat transfer between conducting and radiating mediums by an implicit finite difference method, four different formulations were used to approximate the surface radiation boundary condition while retaining an implicit formulation for the interior temperature nodes. These formulations are an explicit boundary condition, a linearized boundary condition, an iterative boundary condition, and a semi-iterative boundary method. The results of these methods in predicting surface temperature on the space shuttle orbiter thermal protection system model under a variety of heating rates were compared. The iterative technique caused the surface temperature to be bounded at each step. While the linearized and explicit methods were generally more efficient, the iterative and semi-iterative techniques provided a realistic surface temperature response without requiring step size control techniques.
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.
2011-01-01
An alternative insight is presented concerning heat propagation velocity scales in predicting the effective thermal conductivities of nanofluids. The widely applied Brownian particle velocities in published literature are often found too slow to describe the relatively higher nanofluid conductivities. In contrast, the present model proposes a faster heat transfer velocity at the same order as the speed of sound, rooted in a modified kinetic principle. In addition, this model accounts for both nanoparticle heat dissipation as well as coagulation effects. This novel model of effective thermal conductivities of nanofluids agrees well with an extended range of experimental data. PMID:21711892
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.
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.
Multiply scaled constrained nonlinear equation solvers. [for nonlinear heat conduction problems
NASA Technical Reports Server (NTRS)
Padovan, Joe; Krishna, Lala
1986-01-01
To improve the numerical stability of nonlinear equation solvers, a partitioned multiply scaled constraint scheme is developed. This scheme enables hierarchical levels of control for nonlinear equation solvers. To complement the procedure, partitioned convergence checks are established along with self-adaptive partitioning schemes. Overall, such procedures greatly enhance the numerical stability of the original solvers. To demonstrate and motivate the development of the scheme, the problem of nonlinear heat conduction is considered. In this context the main emphasis is given to successive substitution-type schemes. To verify the improved numerical characteristics associated with partitioned multiply scaled solvers, results are presented for several benchmark examples.
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.
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
Mathematical equations for heat conduction in the fins of air-cooled engines
NASA Technical Reports Server (NTRS)
Harper, R R; Brown, W B
1923-01-01
The problem considered in this report is that of reducing actual geometrical area of fin-cooling surface, which is, of course, not uniform in temperature, to equivalent cooling area at one definite temperature, namely, that prevailing on the cylinder wall at the point of attachment of the fin. This makes it possible to treat all the cooling surface as if it were part of the cylinder wall and 100 per cent effective. The quantities involved in the equations are the geometrical dimensions of the fin, thermal conductivity of the material composing it, and the coefficient of surface heat dissipation between the fin and the air streams.
Effects of fiber direction on heat conduction in unidirectionally aligned fiber composites
Havis, Clark Reagan
1987-01-01
distribution and measured temperatures, st = 60 qe = 0. 66 W/cm, kgf f = 0. 498 W/m K 38 sss gas A 341 3 K~ B ~ 388 ' 7 KI C 393 9 K D ~ 401 7 KI E = 412 ' 5 K, B ~ 429 ' 5 K, G = 458. 7 K Fig. 18 Predicted two-dimensional temperature distribution... of MASTER OF SCIENCE December 1987 Major Subject: Mechanical Engineering EFFECTS OF FIBER DIRECTION ON HEAT CONDUCTION IN UNIDIRECTIONALLY ALIGNED FIBER COMPOSITES A Thesis CLARK REAGAN HAVIS Approved as to style and content by: G. P. Peterson...
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.
B. A. Strukov; S. T. Davitadze; S. N. Kravchun; S. A. Taraskin; M Goltzman; V. V. Lemanov; S. G. Shulman
2003-01-01
Thermal properties - specific heat and heat conductivity coefficient—of polycrystalline BaTiO3 films on massive substrates were studied as a function of the temperature and the film thickness by the ac-hot probe method. The anomalies of specific heat with the film thickness decreasing from 1100 to 20 nm revealed the reduction of Tc and excess entropy of the ferroelectric phase transition
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)
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.
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...
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...
On the dynamical Rayleigh-Taylor instability in compressible viscous flows without heat conductivity
Fei Jiang; Song Jiang
2014-03-20
We investigate the instability of a smooth Rayleigh-Taylor steady-state solution to compressible viscous flows without heat conductivity in the presence of a uniform gravitational field in a bounded domain $\\Omega\\subset{\\mathbb R}^3$ with smooth boundary $\\partial\\Omega$. We show that the steady-state is linearly unstable by constructing a suitable energy functional and exploiting arguments of the modified variational method. Then, based on the constructed linearly unstable solutions and a local well-posedness result of classical solutions to the original nonlinear problem, we further reconstruct the initial data of linearly unstable solutions to be the one of the original nonlinear problem and establish an appropriate energy estimate of Gronwall-type. With the help of the established energy estimate, we show that the steady-state is nonlinearly unstable in the sense of Hadamard by a careful bootstrap argument. As a byproduct of our analysis, we find that the compressibility has no stabilizing effect in the linearized problem for compressible viscous flows without heat conductivity.
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.
Sarman, Sten; Laaksonen, Aatto
2013-03-14
The lack of a centre of inversion in a cholesteric liquid crystal allows linear cross couplings between thermodynamic forces and fluxes that are polar vectors and pseudovectors, respectively. This makes it possible for a temperature gradient parallel to the cholesteric axis to induce a torque that rotates the director, a phenomenon known as the Lehmann effect or thermomechanical coupling. The converse is also possible: a torque applied parallel to the cholesteric axis rotates the director and drives a heat flow. In order to study this phenomenon, nonequilibrium molecular dynamics simulation algorithms and Green-Kubo relations evaluated by equilibrium molecular dynamics simulation have been used to calculate the Leslie coefficient, i.e. the cross coupling coefficient between the temperature gradient and the director angular velocity, for a model system composed of soft prolate ellipsoids of revolution interacting via the Gay-Berne potential augmented by a chiral interaction potential causing the formation of a cholesteric phase. It is found that the Leslie coefficient is two orders of magnitudes smaller than other transport coefficients such as the heat conductivity and the twist viscosity, so that very long simulations are required to evaluate it. The Leslie coefficient decreases with the pitch but it has not been possible to determine the exact functional dependence of this coefficient on the pitch. Since very long simulations have been performed to evaluate the Leslie coefficient, very accurate values have been obtained for the twist viscosity and the heat conductivity as a by-product and it is found that they are very similar to the values of the corresponding quantities in the achiral nematic phase that arises when the pitch goes to infinity. PMID:23223192
Subhash C. Mishra; T. B. Pavan Kumar; Bittagopal Mondal
2008-01-01
This article concerns the application of the lattice Boltzmann method (LBM) to solve the energy equation of a combined radiation and non-Fourier conduction heat transfer problem. The finite propagation speed of the thermal wave front is accounted by non-Fourier heat conduction equation. The governing energy equation is solved using the LBM. The finite-volume method (FVM) is used to compute the
B. R. Bass
1978-01-01
The application is presented of a solution technique for the inverse problem that utilizes a finite element heat conduction model and Beck's nonlinear estimation procedure. The technique is applicable to the one-dimensional nonlinear model with temperature-dependent thermophysical properties. The formulation is applied first to a numerical example with a known solution. The example treated is that of a periodic heat
N. Daouas; M.-S. Radhouani
2004-01-01
An extended version of a smoothing technique applied to the Kalman filter estimates is developed in order to solve a nonlinear one-dimensional inverse heat conduction problem. This new algorithm introduces the use of future time measurements and so provides a best estimation of the surface conditions, involving heat flux density and temperature, in which time lag and sensitivity to measurement
Ibrahim A. Abdallah
In this work the uncopled thermoelastic model based on the Dual Phase Lag (DPL) heat conduction equation is used to investigate the thermoelastic properties of a semi-infinite medium induced by a homogeneously illuminating ultrashort pulsed laser heating. The exact solution for the temperature, the displacement and the stresses distributions ob- tained analytically using the separation of variables method (SVM) hybrid
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 masculineC, 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 masculineC for RF ablation, and 177 masculineC 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
Nathenson, Menuel; Tilling, Robert I.
1993-01-01
A steady-state solution for heat transfer from an isothermal, spherical magma chamber, with an imposed regional geothermal gradient far from the chamber, is developed. The extensive published heat-flow data set for Mount Hood, Oregon, is dominated by conductive heat transfer in the deeper parts of most drill holes and provides an ideal application of such a model. Magma-chamber volumes or depths needed to match the distribution of heat-flow data are larger or shallower than those inferred from geologic evidence.
Fu, X.; Chung, D.D.L. [State Univ. of New York, Buffalo, NY (United States). Composite Materials Research Lab.] [State Univ. of New York, Buffalo, NY (United States). Composite Materials Research Lab.
1997-12-01
Due to their poor conductivity, latex (20--30% by weight of cement), methylcellulose (0.4--0.8% by weight of cement), and silica fume (15% by weight of cement) decreased the thermal conductivity of cement paste by up to 46%. In addition, these admixtures increased the specific heat of cement paste by up to 10%. The thermal conductivity decreased and the specific heat increased with increasing latex or methylcellulose content. Short carbon fibers (0.5--1.0% by weight of cement) either did not change or decreased the thermal conductivity of cement paste, such that the thermal conductivity decreased with increasing fiber content due to the increase in air void content. The fibers increased the specific heat due to the contribution of the fiber-matrix interface to vibration.
NASA Astrophysics Data System (ADS)
Fong, Kin Chung; Wollman, Emma E.; Ravi, Harish; Chen, Wei; Clerk, Aashish A.; Shaw, M. D.; Leduc, H. G.; Schwab, K. C.
2013-10-01
The ability to transport energy is a fundamental property of the two-dimensional Dirac fermions in graphene. Electronic thermal transport in this system is relatively unexplored and is expected to show unique fundamental properties and to play an important role in future applications of graphene, including optoelectronics, plasmonics, and ultrasensitive bolometry. Here, we present measurements of bipolar thermal conductances due to electron diffusion and electron-phonon coupling and infer the electronic specific heat, with a minimum value of 10kB (10-22J/K) per square micron. We test the validity of the Wiedemann-Franz law and find that the Lorenz number equals 1.32×(?2/3)(kB/e)2. The electron-phonon thermal conductance has a temperature power law T2 at high doping levels, and the coupling parameter is consistent with recent theory, indicating its enhancement by impurity scattering. We demonstrate control of the thermal conductance by electrical gating and by suppressing the diffusion channel using NbTiN superconducting electrodes, which sets the stage for future graphene-based single-microwave photon detection.
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.
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.
Bass, B.R.; Ott, L.J.
1980-01-01
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. An inverse solution technique applicable to the two-dimensional nonlinear model with temperature dependent thermophysical properties is presented. The technique utilizes a finite element heat conduction model and a generalization of Beck's one-dimensional nonlinear estimation procedure. Results are presented to demonstrate that the inverse formulation is capable of successfully treating experimental data.
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.
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. 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. Haydale/Cheap Tubes
Response-coefficient method for heat-conduction transients with time-dependent inputs
NASA Technical Reports Server (NTRS)
Ceylan, Tamer
1993-01-01
A theoretical overview of the response coefficient method for heat conduction transients with time-dependent input forcing functions is presented with a number of illustrative applications. The method may be the most convenient and economical if the same problem is to be solved many times with different input-time histories or if the solution time is relatively long. The method is applicable to a wide variety of problems, including irregular geometries, position-dependent boundary conditions, position-dependent physical properties, and nonperiodic irregular input histories. Nonuniform internal energy generation rates within the structure can also be handled by the method. The area of interest is long-time solutions, in which initial condition is unimportant, and not the early transient period. The method can be applied to one dimensional problems in cartesian, cylindrical, and spherical coordinates as well as to two dimensional problems in cartesian and cylindrical coordinates.
A search for the dominant heat conducting phonon modes in graphene: An atomistic simulation study
NASA Astrophysics Data System (ADS)
Zhang, Hengji; Cho, Kyeongjae
2011-03-01
We have performed an equilibrium molecular dynamic (MD) simulation study to investigate phonon thermal transport in graphene at 300K with Green-Kubo method. Using a newly optimized reactive empirical bond order carbon potential (Lindsay, et al. Physical Review B 81, 205441, 2010), our calculated thermal conductivity (TC) of defect free graphene is about 3000 W/mK in good agreement with experiments(~ 3000-5000 W/mK). A maximum of ~ 1000 fold reduction in TC is possible to achieve for graphene with defects and surrounding viscous medium. As we decompose the in-plane and out-plane phonon vibration modes of graphene in MD simulations, the out of plane vibration modes (ZA phonon) contribute to about 50% of the overall TC. This large contribution from ZA modes is explained with density of states analysis. We have clarified a recent controversy on which polarization mode in graphene is the main heat carrier.
Effect of the time window on the heat-conduction information filtering model
NASA Astrophysics Data System (ADS)
Guo, Qiang; Song, Wen-Jun; Hou, Lei; Zhang, Yi-Lu; Liu, Jian-Guo
2014-05-01
Recommendation systems have been proposed to filter out the potential tastes and preferences of the normal users online, however, the physics of the time window effect on the performance is missing, which is critical for saving the memory and decreasing the computation complexity. In this paper, by gradually expanding the time window, we investigate the impact of the time window on the heat-conduction information filtering model with ten similarity measures. The experimental results on the benchmark dataset Netflix indicate that by only using approximately 11.11% recent rating records, the accuracy could be improved by an average of 33.16% and the diversity could be improved by 30.62%. In addition, the recommendation performance on the dataset MovieLens could be preserved by only considering approximately 10.91% recent records. Under the circumstance of improving the recommendation performance, our discoveries possess significant practical value by largely reducing the computational time and shortening the data storage space.
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.
Influence of heat conductivity on the performance of RTV SIR coatings with different fillers
NASA Astrophysics Data System (ADS)
Siderakis, K.; Agoris, D.; Gubanski, S.
2005-10-01
Room temperature vulcanized silicone rubber (RTV SIR) coatings are employed in order to improve the pollution performance of high voltage ceramic insulators by imparting surface hydrophobicity. In this paper, the performance of three RTV SIR coatings containing different fillers is investigated in a salt-fog test. Alumina trihydrate (ATH) and silica are the fillers included in the formulation, aiming to increase the material endurance to the energy supplied by the surface electrical activity during periods of hydrophobicity loss. The primary action of these fillers is to increase the material heat conductivity, i.e. the amount of energy conducted to the substrate. In addition, in the case of ATH relief is also achieved due to particle decomposition. The results indicate that for the compositions commercially available, where low amounts of fillers are used, and under the conditions of the test, ATH filled coatings performed better than the silica filled ones. This is attributed to ATH decomposition which further relieves the material structure and therefore decelerates material aging.
Ján Benacka
2008-01-01
The paper gives the analytical solution to the one dimensional hyperbolic heat conduction equation in an insulated slab-shaped\\u000a sample that is heated uniformly on the front face with ? or laser impulse. The solution results in a formula that enables\\u000a to estimate the minimum mean free path of energy carriers in the sample to detect the second sound (i.e. the
L. M. Sun; Y. Feng; M. Pons
1997-01-01
A numerical analysis of an adsorptive heat pump system with thermal wave heat regeneration is presented, using a two-dimensional model taking into account axial heat transfer in the circulating fluid and radial heat conduction in the adsorbent bed. The axial heat conduction in the adsorbent bed is neglected, allowing the two-dimensional model to be solved as a one-dimensional one. The
Radiative thermal conductivity in obsidian and estimates of heat transfer in magma bodies
Stein, J.; Shankland, T.J.; Nitsan, U.
1981-05-10
The optical transmission spectra of four ryholitic obsidian samples were measured in order to determine the importance of radiative heat transfer in granite magmas. The spectra, obtained in the temperature range 20-800/sup 0/C, show that the radiative spectral window in these samples is limited by a charge transfer band in the UV (400 nm) and Si-O stretching overtone in the IR (4500 nm). Within this window the main obstacles to radiative transfer, in order of decreasing importance, are background scattering, a water band centered at 2800 nm, and an Fe/sup 2 +/ crystal field band at 1100 nm. Unlike crystalline silicates the absorption bands in obsidian do not broaden significantly as temperature increases. As a result, the temperature dependence of the calculated radiative thermal conductivity K/sub R/ is dominated by the T/sup ..beta../ term. Actual values of K/sub R/ increase from 9 x 10/sup -5/ to 1 x 1/sup -3/ cal cm/sup -1/ s/sup -1/ deg/sup -1/ between 300/sup 0/ and 800/sup 0/C, the high-temperature value being comparable to the lattice thermal conductivity in obsidian and a lower limit for K/sub R/ in granitic melts. As the scattering coefficient in melts is probably significantly lower than in obsidian, the radiative conductivity in active plutons is likely to be much higher. As an example, if scattering and the water band are removed from the observed spectra of the obsidian samples, calculated values of K/sub R/ could increase by a factor of 5, to about 5 x 10/sup -3/ cal cm/sup -1/ s/sup -1/ deg/sup -1/ at 1000/sup 0/C.
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.
NASA Astrophysics Data System (ADS)
Su Na, Young; David Kihm, Kenneth; Sik Lee, Joon
2012-08-01
The dynamic thermal conductivities of nanofluids (Al2O3) in heating or cooling under fully developed laminar flow conditions show opposite dependence on Reynolds numbers, i.e., the dynamic conductivities under the heating conditions increase with increasing ReD but under the cooling conditions, the dynamic conductivities decrease with increasing ReD. Furthermore, the dynamic conductivities for cooling are higher than those for heating, and the thermal conductivities of stationary nanofluids with uniform distributions fall between these two values, for the entire tested ReD range from 300 to 800. We believe that the main reason for this distinction is because of the drastically different cross-sectional nanoparticle concentration distributions that are in turn attributed to the opposite thermophoretic behavior near the tube wall between heating and cooling. The near-wall nanoparticle concentrations for cooling are substantially higher than those for heating; however, the stationary nanofluid with no thermophoresis maintains its uniform concentration in the middle between the two concentrations.
Reza, Ahmed Wasif
2014-01-01
Non-Fourier heat conduction model with dual phase lag wave-diffusion model was analyzed by using well-conditioned asymptotic wave evaluation (WCAWE) and finite element method (FEM). The non-Fourier heat conduction has been investigated where the maximum likelihood (ML) and Tikhonov regularization technique were used successfully to predict the accurate and stable temperature responses without the loss of initial nonlinear/high frequency response. To reduce the increased computational time by Tikhonov WCAWE using ML (TWCAWE-ML), another well-conditioned scheme, called mass effect (ME) T-WCAWE, is introduced. TWCAWE with ME (TWCAWE-ME) showed more stable and accurate temperature spectrum in comparison to asymptotic wave evaluation (AWE) and also partial Pade AWE without sacrificing the computational time. However, the TWCAWE-ML remains as the most stable and hence accurate model to analyze the fast transient thermal analysis of non-Fourier heat conduction model. PMID:25019096
Conductive heat flux in VC-1 and the thermal regime of Valles caldera, Jemez Mountains, New Mexico
Sass, J.H.; Morgan, P.
1988-06-10
Over 5% of heat in the western United States is lost through Quaternary silicic volcanic centers, including the Valles caldera in north central New Mexico. These centers are the sites of major hydrothermal activity and upper crystal metamorphism, metasomatism, and mineralization, producing associated geothermal resources. We present new heat flow data from Valles caldera core hole 1 (VC-1), drilled in the southwestern 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 +- 16 mW m/sup -2/. The only deep temperature information available is from an uncalibrated commercial log made 19 months after drilling. Gradients, derived from uncalibrated temperature logs, and conductivities are inversely correlated between 335 and 737 m, indicating a conductive thermal regime, and component heat fluxes over three depth intervals (335--539 m, 549--628 m, and 628--737 m) are in excellent agreement with each other with an average of 504 +- 15 mW m/sup -2/. Temperature logs to 518 m depth with well-calibrated temperature sensors result in a revised heat flow of 463 +- 15 mW m. We use shallow thermal gradient data from 75 other sites in and around the caldera to interpret the thermal regime at the VC-1 site. A critical review of published thermal conductivity data from the Valles caldera yields an average thermal conductivity of greater than or equal to1 W m/sup -1/ K/sup -1/ for the near-surface tuffaceous material, and we assume that shallow gradient values (/sup 0/C km/sup -1/) are approximately numerically equal to heat flow (mW m/sup -2/).
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
Expansion of a radial jet from a guillotine tube breach in a shell-and-tube heat exchanger
Velasco, F.J.S.; del Pra, C. Lopez; Herranz, Luis E. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Nuclear fission division, Nuclear Safety Research Unit, Avda. Complutense, 22, P.O. Box 28040 Madrid (Spain)
2008-02-15
Aerodynamics of a particle-laden gas jet entering the secondary side of a shell-and-tube heat exchanger from a tube guillotine breach, determines to a large extent radioactive retention in the break stage of the steam generator (SG) during hypothetical SGTR accident sequences in pressurized nuclear water reactors (PWRs). These scenarios were shown to be risk-dominant in PWRs. The major insights gained from a set of experiments into such aerodynamics are summarized in this paper. A scaled-down mock-up with representative dimensions of a real SG was built. Two-dimensional (2D) PIV technique was used to characterize the flow field in the space between the breach and the neighbor tubes in the gas flow range investigated (Re{sub D} = 0.8-2.7 x 10{sup 5}). Pitot tube measurements and CFD simulations were used to discuss and complement PIV data. The results, reported mainly in terms of velocity and turbulent intensity profiles, show that jet penetration and gas entrainment are considerably enhanced when increasing Re{sub D}. The presence of tubes was observed to distort the jet shape and to foster gas entrainment with respect to a jet expansion free of tubes. Turbulence intensity level close to the breach increases linearly with Re{sub D}. Account of this information into aerosol modeling will enhance predictive capability of inertial impaction and turbulent deposition equations. (author)
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.
Self-heating of metallic carbon nanotube bundles in the regime of the Luttinger-liquid conductivity
NASA Astrophysics Data System (ADS)
Danilchenko, B. A.; Tripachko, N. A.; Voytsihovska, E. A.; Obukhov, I. A.; Yaskovets, I. I.; Sundqvist, B.
2011-08-01
The conductivity of bundles of carbon single-walled nanotubes with metallic conductivity (metallic nanotubes) is investigated over the wide temperature range 4.2-330 K and electrical fields up to 50 V. The usage of short electrical pulses of the duration of 10 ns allowed to avoid an influence of a self-heating of the investigated structures on current-voltage characteristics. It is shown that the temperature dependence of conductivity is described by the power function G?T?. At helium temperatures the asymptotic dependence of current on applied voltage is close to J?V1+? with ? = 0.45. From comparison of the obtained results of measurements with calculations, it is shown that the conductivity of nanotube bundles is well described within the theory of the Luttinger-liquid conductivity for one-dimensional conductors. The self-heating of the carbon nanotube bundles was observed in the case of measurements in the regime of dc current. A method for determination of the self-heating temperature of nanotube bundles as a function of an applied electrical field is proposed. The power dependence of the self-heating temperature on voltage T?Vp with the exponent p = 2.1 was observed above some threshold voltage in the temperature range 4.2-200 K. Above 200 K the exponent decreased down to p = 1.35.
A boundary-dispatch Monte Carlo (Exodus) method for analysis of conductive heat transfer problems
Naraghi, M.H.N. [Manhattan Coll., Riverdale, NY (United States); Shunchang Tsai [Harvard Univ., Cambridge, MA (United States)
1993-12-01
A boundary-dispatch Monte Carlo (Exodus) method, in which the particles are dispatched from the boundaries of a conductive medium or source of heat, is developed. A fixed number of particles are dispatched from a boundary node to the nearest internal node. These particles make random walks within the medium similar to that of the conventional Monte Carlo method. Once a particle visits an internal node, a number equal to the temperature of the boundary node from which particles are dispatched is added to a counter. Performing this procedure for all boundary nodes, the temperature of a node can be determined by dividing the flag, or the counter of this node by the total number of particle visits to this node. Two versions of the boundary-dispatch method (BDM) are presented, multispecies and bispecies BDM. The results of bispecies BDM based on the Exodus dispatching method compare well with the Gauss-Seidel method in both accuracy and computational time. Its computational time is much less than the shrinking-boundary Exodus method.
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.
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
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
Pradhan, N R; Duan, H; Liang, J; Iannacchione, G S
2009-06-17
We present a study of the specific heat and effective thermal conductivity in anisotropic and randomly oriented multi-wall carbon nanotube (MWCNT) and randomly oriented single-wall carbon nanotube (SWCNT) composites from 300 to 400 K. Measurements on randomly oriented MWCNTs and SWCNTs were made by depositing a thin film of CNTs within a calorimetric cell. Anisotropic measurements were made on MWCNTs grown inside the highly ordered, densely packed nanochannels of anodic aluminum oxide. The specific heat of randomly oriented MWCNTs and SWCNTs showed similar behavior to the specific heat of bulk graphite powder. However, the specific heat of aligned MWCNTs is smaller and has weaker temperature dependence than that of the bulk above room temperature. The effective thermal conductivity of randomly oriented MWCNTs and SWCNTs is similar to that of powder graphite, exhibiting a maximum value near 364 K indicating the onset of phonon-phonon scattering. The effective thermal conductivity of the anisotropic MWCNTs increased smoothly with increasing temperature and is indicative of the one-dimensional nature of the heat flow. PMID:19471077
Boyer, Edmond
Eurotherm Seminar N°81 Reactive Heat Transfer in Porous Media, Ecole des Mines d'Albi, France June 4-6, 2007 ET81- 1 HEAT TRANSFER BY SIMULTANEOUS RADIATION-CONDUCTION AND CONVECTION IN A HIGH for the packed bed. The comparison between the radiative heat transfer and the exchanges by conduction and forced
M. A. Alim
2008-01-01
In this paper, the effect of viscous dissipation and pressure stress work on free convection flow along a vertical flat plate has been investigated. Heat conduction due to wall thickness b is considered in this investigation. With a goal to attain similarity solutions of the problem posed, the developed equations are made dimensionless by using suitable transformations. The non-dimensional equations
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.
S. Rainieri; F. Bozzoli; G. Pagliarini
2008-01-01
An experimental analysis and a data processing procedure, aimed to the characterization of an uncooled microbolometric infrared camera, have been carried out. The instrument performance test is addressed to the application of infrared thermography to the parameter estimation problem based on the solution of the inverse heat conduction problem. With this regard, a new figure of merit, which enables to
The interaction between two radial jets
Gruber, Thomas Clifton
1993-01-01
on an impingement surface with high surface heat and mass transfer. The objective of this study was to characterize the flow, surface pressure, and heat transfer for two radial jets as a function of nozzle geometry, in order to be able to design arrays of radial...
AGN heating, thermal conduction and Sunyaev-Zeldovich effect in galaxy groups and clusters
S. Roychowdhury; M. Ruszkowski; B. B. Nath
2005-08-04
(abridged) We investigate in detail the role of active galactic nuclei on the physical state of the gas in galaxy groups and clusters, and the implications for anisotropy in the CMB from Sunyaev-Zeldovich effect. We include the effect of thermal conduction, and find that the resulting profiles of temperature and entropy are consistent with observations. Unlike previously proposed models, our model predicts that isentropic cores are not an inevitable consequence of preheating. The model also reproduces the observational trend for the density profiles to flatten in lower mass systems. We deduce the energy E_agn required to explain the entropy observations as a function of mass of groups and clusters M_cl and show that E_agn is proportional to M_cl^alpha with alpha~1.5. We demonstrate that the entropy measurements, in conjunction with our model, can be translated into constraints on the cluster--black hole mass relation. The inferred relation is nonlinear and has the form M_bh\\propto M_cl^alpha. This scaling is an analog and extension of a similar relation between the black hole mass and the galactic halo mass that holds on smaller scales. We show that the central decrement of the CMB temperature is reduced due to the enhanced entropy of the ICM, and that the decrement predicted from the plausible range of energy input from the AGN is consistent with available data of SZ decrement. We show that AGN heating, combined with the observational constraints on entropy, leads to suppression of higher multipole moments in the angular power spectrum and we find that this effect is stronger than previously thought.
NASA Astrophysics Data System (ADS)
Zheng, D.; Tanaka, S.; Miyazaki, K.; Takashiri, M.
2015-06-01
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.
Sayer, Robert A; Piekos, Edward S; Phinney, Leslie M
2012-12-01
Accurate knowledge of thermophysical properties is needed to predict and optimize the thermal performance of microsystems. Thermal conductivity is experimentally determined by measuring quantities such as voltage or temperature and then inferring a thermal conductivity from a thermal model. Thermal models used for data analysis contain inherent assumptions, and the resultant thermal conductivity value is sensitive to how well the actual experimental conditions match the model assumptions. In this paper, a modified data analysis procedure for the steady state Joule heating technique is presented that accounts for bond pad effects including thermal resistance, electrical resistance, and Joule heating. This new data analysis method is used to determine the thermal conductivity of polycrystalline silicon (polysilicon) microbridges fabricated using the Sandia National Laboratories SUMMiT V™ micromachining process over the temperature range of 77-350 K, with the value at 300 K being 71.7 ± 1.5 W/(m K). It is shown that making measurements on beams of multiple lengths is useful, if not essential, for inferring the correct thermal conductivity from steady state Joule heating measurements. PMID:23278015
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.
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.
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.
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)
Delaney, P.T.
1988-01-01
Temperature histories obtained from transient heat-conduction theory are applicable to most dikes despite potential complicating effects related to magma flow during emplacement, groundwater circulation, and metamorphic reaction during cooling. Here. machine-independent FORTRAN 77 programs are presented to calculate temperatures in and around dikes as they cool conductively. Analytical solutions can treat thermal-property contrasts between the dike and host rocks, but cannot address the release of magmatic heat of crystallization after the early stages of cooling or the appreciable temperature dependence of thermal conductivity and diffusivity displayed by most rock types. Numerical solutions can incorporate these additional factors. The heat of crystallization can raise the initial temperature at the dike contact, ??c1, about 100??C above that which would be estimated if it were neglected, and can decrease the rate at which the front of solidified magma moves to the dike center by a factor of as much as three. Thermal conductivity and diffusivity of rocks increase with decreasing temperature and, at low temperatures, these properties increase more if the rocks are saturated with water. Models that treat these temperature dependencies yield estimates of ??c1 that are as much as 75??C beneath those which would be predicted if they were neglected. ?? 1988.
Achanta, Vamsee Satish
2004-09-30
the following expression Tb;i = Tin + iQplateúmC P (5.5) where Tin is the average inlet temperature, CP is the specific heat capacity of air and i is the number of plate for which the bulk temperature is to be calculated. As we assumed that each of the two... AN EXPERIMENTAL STUDY OF ENDWALL HEAT TRANSFER ENHANCEMENT FOR FLOW PAST STAGGERED NON-CONDUCTING PIN FIN ARRAYS A Thesis by VAMSEE SATISH ACHANTA Submitted to the Office of Graduate Studies of Texas A&M University in partial...
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.
Zheng, Jingming; Martínez-Cabrera, Hugo I.
2013-01-01
Background and Aims In recent years considerable effort has focused on linking wood anatomy and key ecological traits. Studies analysing large databases have described how these ecological traits vary as a function of wood anatomical traits related to conduction and support, but have not considered how these functions interact with cells involved in storage of water and carbohydrates (i.e. parenchyma cells). Methods We analyzed, in a phylogenetic context, the functional relationship between cell types performing each of the three xylem functions (conduction, support and storage) and wood density and theoretical conductivity using a sample of approx. 800 tree species from China. Key Results Axial parenchyma and rays had distinct evolutionary correlation patterns. An evolutionary link was found between high conduction capacity and larger amounts of axial parenchyma that is probably related to water storage capacity and embolism repair, while larger amounts of ray tissue have evolved with increased mechanical support and reduced hydraulic capacity. In a phylogenetic principal component analysis this association of axial parenchyma with increased conduction capacity and rays with wood density represented orthogonal axes of variation. In multivariate space, however, the proportion of rays might be positively associated with conductance and negatively with wood density, indicating flexibility in these axes in species with wide rays. Conclusions The findings suggest that parenchyma types may differ in function. The functional axes represented by different cell types were conserved across lineages, suggesting a significant role in the ecological strategies of the angiosperms. PMID:23904446
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
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
NASA Astrophysics Data System (ADS)
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.
In-Situ Thermal Conductivity Testing Using a Portable Heat Flow Meter
Harr, K. S.; Hutto, F. B., Jr.
1979-01-01
A method has been developed for measuring heat losses from insulated systems in the field. While the measurements are not as precise as those made under laboratory conditions, they are more indicative of actual in service ...
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.
In-Situ Thermal Conductivity Testing Using a Portable Heat Flow Meter
Harr, K. S.; Hutto, F. B., Jr.
1979-01-01
A method has been developed for measuring heat losses from insulated systems in the field. While the measurements are not as precise as those made under laboratory conditions, they are more indicative of actual in service conditions. Extensive field...
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 ...
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.
Heat conductivity in small quantum systems: Kubo formula in Liouville space
Mathias Michel; Jochen Gemmer; Guenter Mahler
2004-01-01
. We consider chains consisting of several identical subsystems weakly coupled by various types of next neighbor interactions.\\u000aAt both ends the chain is coupled to a respective heat bath with different temperature modeled by a Lindblad formalism.\\u000aThe temperature gradient introduced by this environment is then treated as an external perturbation.\\u000aWe propose a method to evaluate the heat current
An experimental study of conductive heating using a concentric double-electrode applicator
Takashi Tanaka; Tadaoki Morimoto; Yohsuke Kinouchi; Tadamitsu Iritani; Yasumasa Monden
1995-01-01
With hyperthermia for treatment of superficial tumors in mind, a prototype applicator with two electrodes arranged concentrically\\u000a on a disk was designed for efficient local heating, and a basic heating test was carried out. Frequencies as low as 200 kHz\\u000a were used in order to simplify the configuration of the power device. The applicator consists of two electrodes, a circular
NASA Astrophysics Data System (ADS)
Kim, B.-W.; Park, S.-H.; Bandaru, P. R.
2014-12-01
We report an unusual specific heat variation in nanotube/polymer composites, related to a reduction in its value at the electrical and the thermal conductivity percolation threshold, with a concomitant increase in the crystallinity. The reduction has been interpreted in terms of the partition of the total number of nanostructures into isolated or clustered/connected entities, the numbers of which vary as a function of the nanotube filler fraction, and the consequent modulation of the entropic characteristics as well as the conductivity.
Kadioglu, Samet Y. [Multiphysics Methods Group, Reactor Physics Analysis and Design, Idaho National Laboratory, P.O. Box 1625, MS 3840, Idaho Falls, ID 83415 (United States)], E-mail: Samet.Kadioglu@inl.gov; Knoll, Dana A. [Multiphysics Methods Group, Reactor Physics Analysis and Design, Idaho National Laboratory, P.O. Box 1625, MS 3840, Idaho Falls, ID 83415 (United States)], E-mail: dana.knoll@inl.gov
2010-05-01
We present a fully second order implicit/explicit time integration technique for solving hydrodynamics coupled with nonlinear heat conduction problems. The idea is to hybridize an implicit and an explicit discretization in such a way to achieve second order time convergent calculations. In this scope, the hydrodynamics equations are discretized explicitly making use of the capability of well-understood explicit schemes. On the other hand, the nonlinear heat conduction is solved implicitly. Such methods are often referred to as IMEX methods. The Jacobian-Free Newton Krylov (JFNK) method (e.g. ) is applied to the problem in such a way as to render a nonlinearly iterated IMEX method. We solve three test problems in order to validate the numerical order of the scheme. For each test, we established second order time convergence. We support these numerical results with a modified equation analysis (MEA). The set of equations studied here constitute a base model for radiation hydrodynamics.
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. H. Sass; Arthur H. Lachenbruch; Robert J. Munroe
1971-01-01
A series of measurements indicates that the thermal conductivity of a rock generally can be estimated adequately for geophysical purposes from simple laboratory measurements on fragments of the rock. The solid-rock conductivity is deduced from a divided-bar measurement of the conductivity of a cylindrical cell containing water-saturated rock fragments. All determinations fall within about ten per cent of conventionally measured
Degradation mechanism of Ag-epoxy conductive adhesive joints by heat and humidity exposure
Sun Sik Kim; Keun Soo Kim; Katsuaki Suganuma; Hirokazu Tanaka
2008-01-01
Isotropic conductive adhesives (ICA), such as Ag-epoxy pastes, have been recognized as one of the ecological alternatives to lead-bearing solders in surface mount technology (SMT) applications. Although Ag-epoxy conductive adhesives possess many advantages as an alternative, they still have several drawbacks to be clarified. The present study shows the degradation mechanism of mounted chip components with Ag-epoxy conductive adhesives under
NASA Technical Reports Server (NTRS)
Hansen, C. Frederick; Early, Richard A.; Alzofon, Frederick E.; Witteborn, Fred C.
1959-01-01
Solutions are presented for the conduction of beat through a semi-infinite gas medium having a uniform initial temperature and a constant boundary temperature. The coefficients of thermal conductivity and diffusivity are treated as variables, and the solutions are extended to the case of air at temperatures where oxygen dissociation occurs. These solutions are used together with shock-tube measurements to evaluate the integral of thermal conductivity for air as a function of temperature.
NASA Astrophysics Data System (ADS)
Sleptsov, S. D.; Grishin, M. A.; Sharypov, O. V.
2015-05-01
Radiative-conductive heat exchange with the melting of a flat layer of gray semitransparent isotropically scattering medium has been analyzed by methods of mathematical simulation. A nonlinear initial boundary problem with a moving free phase-transition boundary is considered within a single-phase statement of the Stefan problem with allowance for the thermal radiation. The temperature distributions are obtained, and the influence of bulk and surface optical characteristics of the material on the layer melting is analyzed.
A. S. Usenko
2001-02-21
We obtained a new representation of a solution of the heat conduction equation with boundary condition of the third kind for a layer. The result is presented as a superposition of fundamental solutions for an unbounded system with variable coefficients, the explicit form of which is given. We consider the well-known problem of the evolution of the temperature field initially uniformly distributed in a layer. The distribution of the temperature field is represented in terms of the obtained functions.
A. D. Gadzhiev; V. N. Pisarev
1979-01-01
An implicit scheme is proposed for solving boundary value problems for the equations describing one-dimensional heat-conducting gas flows, written in Laplace variables. The scheme is conservative with respect to the laws of conservation of momentum, energy and matter. For calculating flows with shock waves, a hybrid structure of the scheme is proposed, where a monotonic first-order scheme is used in
Maruyama, Shigeo
Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes towards their thermal and electric device applications. In this study, diffusive-ballistic heat conduction-lengths up to a micrometer at room temperature. A gradual transition from nearly pure ballistic to diffusive-ballistic
NASA Astrophysics Data System (ADS)
Duong, Hai; Gong, Feng; Papavassiliou, Dimitrios
2015-03-01
For the first time, an Off-Lattice Monte Carlo method is developed successfully to predict thermal conductivities (Keff) of three-phase composites having carbon nanotubes (CNTs) and tungsten disulfide (WS2) nanoparticles more accurately and faster than previous methods such as effective medium theories, molecular dynamics and finite element methods. The Keff predicted by our model using a random walk algorithm and taking into account various thermal boundary resistances at each interface and inter-CNT contact has an excellent agreement with experimental data. Our model can comprehensively explain the mechanism of heat conduction in complex composite structures. Effects of WS2 and CNT morphologies (diameter, length, inter-contact, bundle), CNT concentrations, CNT orientations (parallel, random and perpendicular to heat flux) and thermal boundary resistances of CNT-polymer, WS2-polymer, CNT-CNT, CNT-WS2 on heat conduction limitation of the three-phase composites are also investigated systematically. Our model can be also applied to the biological and nanofluid systems.
H. S. Kit; O. P. Sushko
2011-01-01
We present solutions of axially symmetric problems of stationary heat conduction and thermoelasticity for a body with a thin\\u000a thermally active disk inclusion (where the temperature or heat flow is given) and also with a thermally insulated inclusion.\\u000a The heat conduction problems are reduced to integral equations, and exact solutions are obtained in the case where their right-hand\\u000a sides are
NASA Technical Reports Server (NTRS)
Van Hoven, G.; Mok, Y.
1984-01-01
The condensation-mode growth rate of the thermal instability in an empirically motivated sheared field is shown to depend upon the existence of perpendicular thermal conduction. This typically very small effect (perpendicular conductivity/parallel conductivity less than about 10 to the -10th for the solar corona) increases the spatial-derivative order of the compressible temperature-perturbation equation, and thereby eliminates the singularities which appear when perpendicular conductivity = 0. The resulting growth rate is less than 1.5 times the controlling constant-density radiation rate, and has a clear maximum at a cross-field length of order 100 times and a width of about 0.1 the magnetic shear scale for solar conditions. The profiles of the observable temperature and density perturbations are independent of the thermal conductivity, and thus agree with those found previously. An analytic solution to the short-wavelength incompressible case is also given.
Zianni, Xanthippi; Jean, Valentin; Termentzidis, Konstantinos; Lacroix, David
2014-11-21
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. PMID:25360881
HIGH CONDUCTIVITY FINS FOR GAS COOLED LIQUID-METAL HEAT EXCHANGERS
W. F. Brown; R. W. Fisher; H. M. Black
1963-01-01
Nickel-plated Cu fina are brazed to the Inconel tubes of an air-cooled ; liquid Na heat exchanger for use to 600 deg C. Methods of plating annular fins ; for tubes are discussed and test results are presented. Brazing techniques for ; fin-to-tube joints are explored, and a resistance brazing process is developed. ; From the results of tests, it
Manufacturing technique of Nb 3Al super-conductive sheet by electrically heated powder rolling
NASA Astrophysics Data System (ADS)
Mochizuki, C.; Mikami, M.
The conventional manufacturing processes of superconductive wires or sheets are complex. Nb 3Al is a well-known superconductive material. Nb 3Al could be produced from powder directly by an advanced powder rolling technique. The experimental apparatus is composed of a powder rolling mill within a vacuum chamber and a direct current power supply unit. Powder is supplied into the roll gap and heated by applying electricity during rolling. The method is called `electrically heated powder rolling'. Nb-25.4Al (mol%) powder of which particle size was under 0.15 mm was prepared by plasma melt gas atomizing (PMGA) technique. The powder consists of super-saturated solid solution of Nb and Al. But after electrically heated powder rolling, the existence of Nb 3Al (A15) phase was confirmed by X-ray diffraction. The sheet was porous and the thickness was about 0.7 mm. The sheet was re-rolled to the thickness of about 0.5 mm, then pore of the sheet was eliminated. The resistivity of the re-rolled sheet was measured at lower temperature than RT and Tc (0) of 15 K was confirmed. It is believed that electrically heated powder rolling is effective manufacturing technique for superconductive sheet such as intermetallic compounds.
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.
Conductive electron heat flow along an inhomogeneous magnetic field E. D. Helda)
Held, Eric
is derived and examined. Free-streaming and collisional effects are present in the drift kinetic equation particle trapping significantly slows electron heat transport in galaxy cluster cooling flows.2 In kinetic moment. In strongly inhomogeneous fields, the mirror force traps a substantial fraction of particles
Sufen Li; Yan Shang
2010-01-01
The three-dimension coupled thermal conduction and groundwater advection unsteady state heat transfer model in this paper is developed according to the heat-transfer process between the vertical U tube underground and its ambient soil. The feasibility of this model is verified by intermittent experiment of ground source heat pump in winter. In the model, boundary layer is replaced by velocity equation
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 ...
Thermal conductivity of pulse-heated liquid metals at melting and in the liquid phase
G. Pottlacher
1999-01-01
Thermal conductivities as a function of temperature of the elements W, Re, Ta, Mo, Nb, Fe, Co, Ni, Au and Cu are here reported for the first time in a temperature range, covering the melting point and the liquid state.
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.
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.
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. PMID:23556838
A. Manglik; D. V. Ramana; A. O. Gliko; R. N. Singh
1992-01-01
An algorithm for the solution of a nonlinear problem of phase boundary movement and evolution of temperature distribution\\u000a due to the perturbation in the basal heat flux has been discussed. The reduction of the problem to a system of nonlinear ordinary\\u000a differential equations with the help of a Fourier series method leads to a stiff system. This stiffness is taken
Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties
B. J. Hansen; M. J. White; A. Klebaner
2011-01-01
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
A. M. Runov; D. Reiter; S. V. Kasilov; M. F. Heyn; W. Kernbichler
2001-01-01
The heat balance equation is derived and solved for fusion edge plasma conditions with (partially developed) ergodic magnetic-field structures. For this purpose, a three-dimensional (3D) Monte Carlo code, ``E3D,'' based upon the ``multiple local magnetic coordinate system approach'' has been developed. Parameters typical for the Dynamic Ergodic Divertor (DED) of TEXTOR-94 (Torus Experiment for the Technology Oriented Research) [K. H.
Solutions of the heat conduction equation in multilayers for photothermal deflection experiments
NASA Technical Reports Server (NTRS)
Mcgahan, William A.; Cole, K. D.
1992-01-01
Analytical expressions for temperature and laser beam deflection in multilayer medium is derived using Green function techniques. The approach is based on calculation of the normal component of heat fluxes across the boundaries, from which either the beam deflections or the temperature anywhere in space can be found. A general expression for the measured signals for the case of four-quadrant detection is also presented and compared with previous calculations of detector response for finite probe beams.
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.
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.
Thermal energy conduction in a honey bee comb due to cell-heating bees
J. A. C. Humphreya; E. S. Dykes
2008-01-01
Theoretical analysis and numerical calculations are performed to characterize the unsteady two-dimensional conduction of thermal energy in an idealized honey bee comb. The situation explored corresponds to a comb containing a number of brood cells occupied by pupae. These cells are surrounded by other cells containing pollen which, in turn, are surrounded (above) by cells containing honey and (below) by
Innovations for reducing conduction heat losses from salt-gradient solar ponds
Lowrey
1985-01-01
A recent publication suggested using a storage zone (SZ) full of opaque water instead of a conventional lower convecting zone. This opaque SZ would be warmer on its top than bottom, and therefore thermally stratified and nonconvecting. Since the conductivity of water is less than that of many types of ground, this opaque zone would act like an added layer
Intriguing Heat Conduction of a Chain with Transverse Motions Jian-Sheng Wang
Li, Baowen
conductivity in a many-body 1D chain with momen- tum conservation. To this end, we consider a chain of N point are connected by two-dimensional harmonic springs together with bending angle interactions. Using equilibrium group analysis for a 1D hydrodynamic fluid model, it is argued that in a generic momentum conserv- ing
NASA Astrophysics Data System (ADS)
Petrov, Yu. V.; Inogamov, N. A.; Migdal, K. P.
2013-03-01
The two-temperature ( T e > T i ) thermal conductivity coefficient ?2 T and electron-ion heat transfer coefficient ?, which are necessary for the quantitative description of the processes initiated by ultrashort laser pulse, have been calculated using a kinetic equation, the matrix element for the scattering probability, and a screened Coulomb potential describing the interaction between charged particles. Quantitative information has been obtained for coefficients ?2 T and ? values for noble and transition metals, where the d-band electrons play a significant role.
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
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.
Improving the conductivity of hole injection layer by heating PEDOT:PSS
Kao-Hua Tsai; Shu-Chia Shiu; Ching-Fuh Lin
2008-01-01
Poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonic acid) (PEDOT:PSS) is a common material of hole injection layer used in polymer light emitting diodes (PLEDs) and organic solar cells. It can improve the efficiency of the charge collection at the anode. It has been reported that adding glycerol to PEDOT:PSS could increase the conductivity and improve the efficiency of PLEDs and organic solar cells. However, it
E. Krumov; V. Mankov; N. Starbov
2005-01-01
Original experimental method for evaluation of thermal diffusivity coefficient of vacuum deposited thin films with low thermal conductivity is presented. For this purpose three- layered samples are vacuum deposited onto precleaned glass substrate. Thin film of TeO2 or NaCl respectively is sandwiched between array of connected in series thin film thermocouples at the bottom and metal layer at the top.
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
Molecular Dynamics Simulation of Heat Conduction of a Carbon Nanotube Shigeo MARUYAMA1
Maruyama, Shigeo
](4) phantom Langevin phantom D 2500K Verlet 0.5 fs (5,5) acc = 1.4595Å, (10,10) acc =1 1/T (8,8) 62.9 nm (8,8) 12.4 nm Fig. 3 Temperature dependence of thermal conductivity. 1000 0 1000 al., Phys. Rev. B, 57, (1998), 4145. Energy/c(cm-1) Wave vector k (1/Å) 0 0.5 1 0 500 1000 1500 0 0
Faulkner, S H; Hupperets, M; Hodder, S G; Havenith, G
2015-06-01
Self-paced endurance performance is compromised by moderate-to-high ambient temperatures that are evident in many competitive settings. It has become common place to implement precooling prior to competition in an attempt to alleviate perceived thermal load and performance decline. The present study aimed to investigate precooling incorporating different cooling avenues via either evaporative cooling alone or in combination with conductive cooling on cycling time trial performance. Ten trained male cyclists completed a time trial on three occasions in hot (35?°C) ambient conditions with the cooling garment prepared by (a) immersion in water (COOL, evaporative); (b) immersion in water and frozen (COLD, evaporative and conductive); or (c) no precooling (CONT). COLD improved time trial performance by 5.8% and 2.6% vs CONT and COOL, respectively (both P?conductive cooling (COLD) had the greatest benefit to performance, which is suggested to be driven by reduced skin temperature following cooling. PMID:25943669
NASA Astrophysics Data System (ADS)
Ahn, J.-W.; Gan, K. F.; Scotti, F.; Lore, J. D.; Maingi, R.; Canik, J. M.; Gray, T. K.; McLean, A. G.; Roquemore, A. L.; Soukhanovskii, V. A.
2013-07-01
Toroidally non-axisymmetric divertor profiles during the 3-D field application and for ELMs are studied with simultaneous observation by a new wide angle visible camera and a high speed IR camera. A newly implemented 3-D heat conduction code, TACO, is used to obtain divertor heat flux. The wide angle camera data confirmed the previously reported result on the validity of vacuum field line tracing on the prediction of split strike point pattern by 3-D fields as well as the phase locking of ELM heat flux to the 3-D fields. TACO calculates the 2-D heat flux distribution allowing assessment of toroidal asymmetry of peak heat flux and heat flux width. The degree of asymmetry (?DA) is defined to quantify the asymmetric heat deposition on the divertor surface and is found to have a strong positive dependence on peak heat flux.
Conductively coupled multi-cell TFE with electric heating pretest ability
NASA Astrophysics Data System (ADS)
Nikolaev, Yuri V.; Kucherov, Rafail Ya.; Eryomin, Stanislav A.; Izhvanov, Oleg L.; Korolev, Vladimir U.; Lapochkin, Nikolai V.; Tsetshladze, David L.; Lechtenberg, Thomas A.; Begg, Lester L.
1998-01-01
Problems associated with the development of a multi-cell thermionic fuel element (TFE) with ability of electric heating test are discussed. A conceptual design of such TFE with trilayer emitter stack is proposed. Trilayer emitter stack consists of a strong emitter fuel clad coated with a high temperature oxide ceramic. Emitter tungsten coatings applied to a ceramic and they separated one after another by insulated gaps. Modern materials that should be base to build this trilayer emitter are presented. Results of calculational investigations of TFE output parameters are included. Results of the preliminary test of TFE and it's components are presented. It is shown that proposed TFE conceptual design from one side allows to provide high output parameters inherent to multi-cell design, and from other side to gain advantages of single cell TFE, such as TFE and reactor nuclear safety, reliability, work cost savings.
Effect of wall conduction on heat transfer for turbulent flow in a circular tube
Lin, Yie-Kuang
1980-01-01
) then ~ y+) 1+ g-7 x? ~? CmR. ~&r I'g g x I, & " pig. p()c)} f so as tm Lr=b rnn ? y Z. C R?(v)e~P( ? P X ) ~ M o (14) 2 where P =1, b. = (i+1) w. m m, ' i i+1 + + F (x )= (1 ? exp(-P x ) }/P 0 Ill Itl + . +i + F, (x )= (x -iF, (x )}/P... for the solid + + Using the dimensionless variables x , r and e=t/t H s s fe 8 = (t -t )/(t -t ) ? ? ? T s s w fe w (17) the heat equation becomes ~a'8 g ~ate) +(~)' a 8s g V" V dV' ?aX" the boundary conditions are x+ =0 : 3 8 /3x+=0 S x = 2/Gz : 3 Q...
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)
Mikhailov, A. V.; Lagun, I. M.; Polyakov, E. P.
2013-01-01
Transient heat-conduction processes occurring in the period of thermal decomposition and gasification of a crystalline oxidant — ammonium perchlorate — have been investigated and analyzed on the basis of the developed mathematical model.
Xiangdi Huang; Jing Li
2012-10-22
This paper establishes a blowup criterion for the three-dimensional viscous, compressible, and heat conducting magnetohydrodynamic (MHD) flows. It is essentially shown that for the Cauchy problem and the initial-boundary-value one of the three-dimensional compressible MHD flows with initial density allowed to vanish, the strong or smooth solution exists globally if the density is bounded from above and the velocity satisfies the Serrin's condition. Therefore, if the Serrin norm of the velocity remains bounded, it is not possible for other kinds of singularities (such as vacuum states vanish or vacuum appears in the non-vacuum region or even milder singularities) to form before the density becomes unbounded. This criterion is analogous to the well-known Serrin's blowup criterion for the three-dimensional incompressible Navier-Stokes equations, in particular, it is independent of the temperature and magnetic field and is just the same as that of the barotropic compressible Navier-Stokes equations. As a direct application, it is shown that the same result also holds for the strong or smooth solutions to the three-dimensional full compressible Navier-Stokes system describing the motion of a viscous, compressible, and heat conducting fluid.
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.
Transport of MA electron currents in ultra-fast heated conducting solids
NASA Astrophysics Data System (ADS)
Sentoku, Yasuhiko; Fuchs, Julien; D'Humieres, Emmanuel
2009-11-01
Transport of MA currents in conducting high Z solids is crucial for number of applications, e.g. the generation of efficient and fast secondary sources (ions, X-rays, g-rays, etc) or cone-guiding fast ignition of inertial fusion. We have simulated the ultra-intense ultra-short laser - solid target interaction with a particle-in-cell code, PICLS, which features the relativistic Coulomb collisions, dynamics ionization in gas and solid target, and have studied the MA current transport by irradiating an ultra-intense laser pulse (5x10^19W/cm^2, 300fs) in different conducting metal target, such as aluminum, copper, and gold. We found that the strong resistive magnetic fields are excited inside solid, and the fields become stronger in higher Z target because of ?Z induced by dynamics ionization. The transport of hot electron currents are affected by these magnetic fields, ˜10 MG in a Al target, and > 50MG in Cu or Au targets. The sheath field at target rear is also modulated because of the transport pattern. Simulations results are consistent with MeV proton beam images observed in experiments.
NASA Astrophysics Data System (ADS)
Hofmeister, A.; Dong, J.; Branlund, J. M.
2012-12-01
Comparing measurements with existing models show that phonon scattering incompletely describes lattice thermal conductivity of mantle minerals. Thermal diffusivity (D) measured as a function of temperature (T) using laser flash analysis for hundreds of geologically relevant samples (diverse minerals, isostructural analogues, silicate glasses, melts, and rocks) are fit by D = a + b/T + cT, except for material undergoing phase transitions or dehydration. Accurate high temperature data constrain the linear term. We further observe that D inversely depends on the number of infrared modes, but not on the number of total optic modes. These observations are consistent with (1) the term b/T arising from phonon-phonon scattering, which is the main heat transfer mechanism at temperatures below 1000 K. (2) The term cT requires a second heat transfer mechanism involving absorption and re-emission of IR photons. Linear dependence on T is derived from phenomenological models of radiative transfer that are limited to the IR region and occur at slow speeds of acoustic phonons. Slow speeds are mandated by this mechanism's presence in conduction experiments and by well-known coupling of IR with acoustic modes. The IR mechanism governs T>1000 K and differs from radiative transfer at high frequency by depending neither on grain size nor iron content; nor is the IR mechanism limited to transient phenomena. Our proposed model differs from existing models, which generally agree with older, contact measurements of D values below 1000 K, including those of MgO. At higher temperatures, calculations, including derivations using molecular dynamics, diverge from our most recent measurements of D for MgO (using laser-flash analysis of single crystals to avoid problems with contacts, grain boundaries and radiative transfer). The model discrepancy is consistent with our proposed mechanism. Our data indicate that D is high in the lower mantle due to both compression of the unit cell and to the Planck curve being strongly absorbed at IR frequencies (attenuations near 1 micron). Available models have underestimated values of thermal diffusivity at temperatures of the Earth. Although there may be other explanations than our proposed mechanism of IR absorption-emission, the experimentally-determined increase of D with T is universal. This behavior has implications for the deep earth. The positive increase of D with T stabilizes the lower mantle against convection. Because convection stirs heat producing elements into depths, this process enhances internal temperature. Thus, conductive gradients can provide colder temperatures . High thermal diffusivity enhances conduction across boundary layers and limitis radioactivity at depth: both aspects inhibit lower-mantle plume formation.
Nacer Berour; David Lacroix; Gérard Jeandel
2006-01-01
This article is devoted to heat transfer involving radiation and conduction. Considering a nongray, purely absorbing medium, the radiative heat transfer equation (RTE) and the energy balance equation are both solved with the finite-volume method (FVM). The energy equation is coupled to the RTE through the radiative source term. Several differencing scheme efficiencies are discussed for the case of strong
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
P. V. Korolev; A. P. Kryukov
2001-01-01
An unsteady-state flow of a liquid of high thermal conductivity (liquid metal) in a vapor-filled capillary is analyzed for the case where a heat flux of constant density is delivered to one of the interfaces. The velocity of liquid motion as a function of time is obtained. The accompanying heat and mass transfer processes are investigated. The effects associated with
Wilkenhoener, R.; Buchkremer, H.P.; Stoever, D.; Stolten, D.; Koch, A.
2000-07-01
Ceramic parts made of doped lanthanum chromite are used as interconnects and end plates in stacks for several solid oxide fuel cell (SOFC) designs. Metallic conductors have to be attached to enable a low-resistance connection between individual stacks in each SOFC unit and to permit power to be drawn from the SOFC. The resistances of the metal-ceramic bond and the metallic conductors have to be stable under operating conditions, i.e., 1,000 C in air. Consequently, heat-resistant materials have to be used. A two-step process has been developed to connect commercially available, Ni- or Fe-based metallic conductors to ceramic SOFC end plates by vacuum furnace brazing. In the first step, a metallic sheet, which acts as the current collector, is brazed onto the ceramic end plate. Thereby, the much lower electrical conductivity of the ceramic part is compensated by that of the metal. The chromium alloy CrFe5Y{sub 2}O{sub 3}1 is suitable because it is heat-resistant, and its thermal expansion coefficient is close to that of lanthanum chromite. In the second step, metallic wires or strips are brazed on the current collector. Since this joint area is significantly smaller than that of the first joint, materials with a different thermal expansion coefficient can be used, such as conventional heat-resistant nickel alloys (Inconel 617) and ferritic stainless steels (FeCrAl 25 5). Filler alloys for both brazing steps with matching melting points have been found. Hence, both brazing steps can be performed cost-effectively in one heating step. Suitable parameters for vacuum furnace brazing of both joints are presented, and the composition of the filler alloys is given. Data concerning the long-term behavior of the joint resistances in air at 1,000 C are discussed.
NASA Astrophysics Data System (ADS)
Matsumoto, Mitsuhiro
This review covers several problems in thermal engineering which require consideration in nano-scale or at molecular level. One example in nanofluidics is “nano bubbles” molecular simulation reveals that surface tension and vapor pressure of a spherical bubble hardly depend on its size and that the classical Young-Laplace equation is applicable even to a bubble as small as several nano meters. Combined with CFD schemes, molecular simulation can also treat oscillating dynamics of nanobubbles. Another example comes from solid-state physics, i.e., thermophysical properties of nano-scale elements. As the thickness of solid thin film decreases to “phonon mean free path”, the apparent thermal conductivity becomes smaller, the mechanism of which molecular simulation can explain.
NASA Astrophysics Data System (ADS)
Abyzov, Andrey M.; Shakhov, Fedor M.
2014-12-01
To measure the thermal conductivity of particle beds, a specially designed cuvette is inserted into the chamber of an ITP-MG4 device fitted with a vertical heat flux sensor. The cuvette with a transparent wall makes it possible to reduce the amount of test material to 25?cm3, to monitor visually the uniformity of a charge, to determine the bulk density of the particle bed (and to increase it if necessary using vibrocompaction) and to apply external pressure to the bed from 2.5 to 30?kPa. Using various continuous-solid and particulate materials as references, a calibration equation is obtained for thermal conductivity in the range of 0.03–1.1?W?(m K)?1. To eliminate thermal contact resistance when measuring references, the end faces of glass specimens with a departure from flatness of up to 50??m are wetted with water. To model the calibration, a calculation is carried out by the electrical circuit analogy. The calculated curve is close to the experimental points if a value for the contact thermal resistances r# = 2? × ?10?3 m2 K?W?1 is taken. Values of r# calculated by the Yovanovich model, based on the known roughnesses of the contact surfaces of the cuvette and the solid specimens, are an order of magnitude lower due to the decisive influence of nonflatness and not surface roughness at the low pressures used. The conditions under which our measurements were made are compared with the instructions of Russian, American and international standards for the measurement of thermal conductivity by the steady-state heat flow method (specimen size, flatness of working surfaces, etc). The sources of measurement inaccuracy and ways to improve the technique are examined.
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 Technical Reports Server (NTRS)
Farassat, F.; Baty, R. S.
2000-01-01
The study of the shock structure in a viscous heat conducting fluid is an old problem. We study this problem from a novel mathematical point of view. A new class of generalized functions is defined where multiplication of any two functions is allowed with the usual properties. A Heaviside function in this class has the unit jump at occurring on an infinitesimal interval of the nonstandard analysis (NSA) in the halo of . This jump has a smooth microstructure over the infinitesimal interval . From this point of view, we have a new class of Heaviside functions, and their derivatives the Dirac delta functions, which are equivalent when viewed as continuous linear functionals over the test function space of Schwartz. However, they differ in their microstructures which in applications are determined from physics of the problem as shown in our presentation.
NASA Technical Reports Server (NTRS)
Lerche, I.; Low, B. C.
1980-01-01
Exact analytic solutions are presented for equilibrium states of a self-gravitating one-dimensional cloud of gas, embedded in an external gravitational field due to a plane of 'stars' being heated at a rate proportional to the local gas density, and cooling by thermal conduction. It is found that the general topology of the solutions is such that the gas density has a minimum on the plane of 'stars', rising to an infinite but integrable peak away from the plane so that the total mass of gas in the cloud is finite. The results may be of interest in investigations of interstellar molecular clouds and of filamentary structures in supernova remnants as well as in the modeling of gas distributions around 'cocoon' protostars.
Universal Heat Conduction in the Iron Arsenide Superconductor KFe2As2: Evidence of a d-Wave State
Reid, J.-Ph.; Tanatar, Makariy A.; Juneau-Fecteau, A.; Gordon, R.T.; Rene de Cotret, S.; Doiron-Leyraud, N.; Saito, T.; Fukazawa, H.; Kohori, Y.; Kihou, K.; Lee, C.H.; Iyo, A.; Eisaki, H.; Prozorov, Ruslan; Taillefer, Louis
2012-08-21
The thermal conductivity ? of the iron arsenide superconductor KFe2As2 was measured down to 50 mK for a heat current parallel and perpendicular to the tetragonal c axis. A residual linear term at T?0, ?0/T is observed for both current directions, confirming the presence of nodes in the superconducting gap. Our value of ?0/T in the plane is equal to that reported by Dong et al. [ Phys. Rev. Lett. 104 087005 (2010)] for a sample whose residual resistivity ?0 was 10 times larger. This independence of ?0/T on impurity scattering is the signature of universal heat transport, a property of superconducting states with symmetry-imposed line nodes. This argues against an s-wave state with accidental nodes. It favors instead a d-wave state, an assignment consistent with five additional properties: the magnitude of the critical scattering rate ?c for suppressing Tc to zero; the magnitude of ?0/T, and its dependence on current direction and on magnetic field; the temperature dependence of ?(T).
A. P. van den Berg; D. A. Yuen; J. R. Allwardt
2002-01-01
The temperature-dependence of the phonon portion of the thermal conductivity \\/k(T,P) devised by Hofmeister [Science 283 1699-1706] decreases with temperature, the same as in the dependence of mantle viscosity. Such a functional relationship of \\/?k\\/?T0. Thus, there can be a tradeoff between the phonon and photon contributions in the conductivity in the presence of internal heating. We have conducted two-dimensional
Boiling Radial Flow in Fractures of Varying
Stanford University
apply only to a finite radius around the point of injection, higher values of heat flux and a boilingSGP-TR-166 Boiling Radial Flow in Fractures of Varying Wall Porosity Robb Allan Barnitt June 2000 and boiling convective heat transfer, with boiling flow in a rock fracture. A series of experiments observed
NASA Astrophysics Data System (ADS)
Rader, D. J.; Gallis, M. A.; Torczynski, J. R.; Wagner, W.
2006-07-01
The convergence behavior of the direct simulation Monte Carlo (DSMC) method is systematically investigated for near-continuum, one-dimensional Fourier flow. An argon-like, hard-sphere gas is confined between two parallel, fully accommodating, motionless walls of unequal temperature. The simulations are performed using four variations based on Bird's DSMC algorithm that differ in the ordering of the move, collide, and sample operations. The primary convergence metric studied is the ratio of the DSMC-calculated bulk thermal conductivity to the infinite-approximation Chapman-Enskog (CE) theoretical value, although temperature and heat flux are also considered. Ensemble, temporal, and spatial averaging are used to reduce statistical errors to levels that are small compared to the discretization errors from the time step (?t), the cell size (?x), and the number of computational particles per cell (Nc). The errors from these three parameters are determined using over 700 individual cases selected from the ranges 0.05conductivity ratio is found to be second-order in both time step and cell size, in good agreement with previous theoretical predictions based on Green-Kubo theory. For vanishing time step and cell size, the finite-particle-number convergence behavior is found to be O (1/Nc) if ˜30 or more particles per cell are used. The observed convergence behavior is found to be more complicated when all three discretization parameters are finite. As discretization errors are systematically reduced, the DSMC-calculated conductivity is shown to approach the infinite-approximation CE theoretical value to within 1 part in 104.
Novel radial AMTEC cell design
Mital, R.; Rasmussen, J.R.; Huang, C.; Hundal, R.; Hendricks, T.J.; Sievers, R.K.
1998-07-01
Current Series II AMTEC cells (PX-style) are small cylinders with 5--7 BASE tubes per cell, producing 6--7 W{sub e} each. These cells are about 14--18% efficient (electric power out/heat input) and have power densities in the range of 40 W/kg. This paper describes the design and development of a novel radial cell which is capable of higher efficiency (20--30%) and higher power density (125 W/kg). This cell has 96 BASE tubes and is expected to produce about 150 W. The concept was proposed last year when it was observed that the present cylindrical cells, though performing as expected, did not allow a high BASE tube packing density. When the cylindrical cells are arrayed around a heat source, there is a substantial area around the system periphery that does not have power producing BASE tubes and this increases system heat losses. The radial cell design allows a significantly higher BASE tube packing density around the heat source, thereby increasing cell power and minimizing heat loss. This paper describes the structural design, the thermal performance and the manufacturing issues for this novel cell configuration.
NASA Astrophysics Data System (ADS)
Abd-Alla, A. M.; Abo-Dahab, S. M.; El-Shahrany, H. D.
2014-08-01
In this paper, the effects of both initial stress, radially varying and gravity field on the peristaltic flow of an incompressible MHD Newtonian fluid in a vertical annulus have been studied under the assumption of long wavelength and low-Reynolds number. The analytical solution has been derived for the temperature, concentration and velocity. The results for velocity, concentration and temperature obtained in the analytical form have been evaluated numerically and discussed briefly. The effect of the non-dimensional wave amplitude, the coefficient of viscosity, Sort number, Schmidt number, initial stress, gravitational field and the dimensionless time-mean flow in the wave frame are analyzed theoretically and computed numerically. The expressions for pressure rise, temperature, concentration field, velocity and pressure gradient are sketched for various embedded parameters and interpreted. Numerical results are given and illustrated graphically in each case considered. Comparison was made with the results obtained in the presence and absence of initial stress and gravitational field.
Development of a thermal and structural analysis procedure for cooled radial turbines
NASA Technical Reports Server (NTRS)
Kumar, Ganesh N.; Deanna, Russell G.
1988-01-01
A procedure for computing the rotor temperature and stress distributions in a cooled radial turbine is considered. Existing codes for modeling the external mainstream flow and the internal cooling flow are used to compute boundary conditions for the heat transfer and stress analyses. An inviscid, quasi three-dimensional code computes the external free stream velocity. The external velocity is then used in a boundary layer analysis to compute the external heat transfer coefficients. Coolant temperatures are computed by a viscous one-dimensional internal flow code for the momentum and energy equation. These boundary conditions are input to a three-dimensional heat conduction code for calculation of rotor temperatures. The rotor stress distribution may be determined for the given thermal, pressure and centrifugal loading. The procedure is applied to a cooled radial turbine which will be tested at the NASA Lewis Research Center. Representative results from this case are included.
... Name Password Sign In Cardiology Patient Page Radial Artery Catheterization Nicholas R. Balaji , MD ; Pinak B. Shah , ... procedures. Previous Section Next Section Advantages of Radial Artery Catheterization Any catheter placement into a blood vessel ...
NASA Astrophysics Data System (ADS)
Li, Ning; Abe, Yoshio; Kawamura, Midori; Sasaki, Katsutaka; Itoh, Hidenobu; Suzuki, Tsutomu
2011-04-01
Hydrated ZrO2 thin films were prepared by reactive sputtering using H2O gas, and these films were heat treated in air at temperatures from 100 to 350 °C. Absorbance peaks due to hydrogen-bonded OH groups for these samples were observed by Fourier transform infrared spectroscopy. The peak intensities were nearly the same before and after heat treatment below 200 °C, but began to decrease at 250 °C, and the absorption peak disappeared at 350 °C. Ion conductivity of the films was evaluated by AC impedance measurements and was found to be about 3 ×10-6 S/m before and after heat treatment at 200 °C it also decreased after heat treatment above 250 °C. From these results, we considered that protons of OH and/or H2O in the films are the dominant ionic species that contribute to the ion conductivity of the films.
M. Z. I. Khan; K. C. A. Alam; B. B. Saha; Y. Hamamoto; A. Akisawa; T. Kashiwagi
2006-01-01
In the present paper, an analytic investigation of a two-stage adsorption refrigeration chiller using re-heat is performed to determine the influence of the overall thermal conductance of sorption elements and evaporator as well as the adsorbent mass on the chiller performance. The innovative chiller is driven by waste heat temperatures between 50 and 70?°C with a cooling source at 30?°C
NASA Astrophysics Data System (ADS)
Bakirova, M. I.; Dorodnitsyn, V. A.; Kurdiumov, S. P.; Samarskii, A. A.; Dimova, S. N.
The directed propagation of heat and combustion in an anisotropic medium is analyzed numerically. It is shown that at the asymptotic stage this process is described by an invariant (self-similar) solution obtained by Dorodnitsyn et al. (1983). In the isotropic case, an invariant solution is indicated which can describe circular and spiral combustion waves. The invariant solutions are obtained on the basis of the group properties of the heat-conduction equation.
McLellan, Tom M; Selkirk, Glen A
2006-07-01
This report provides a summary of research conducted through a grant provided by the Workplace Safety Insurance Board of Ontario. The research was divided into two phases; first, to define safe work limits for firefighters wearing their protective clothing and working in warm environments; and, the second, to examine strategies to reduce the thermal burden and extend the operational effectiveness of the firefighter. For the first phase, subjects wore their protective ensemble and carried their self-contained breathing apparatus (SCBA) and performed very light, light, moderate or heavy work at 25 degrees C, 30 degrees C or 35 degrees C. Thermal and evaporative resistance coefficients were obtained from thermal manikin testing that allowed the human physiological responses to be compared with modeled data. Predicted continuous work times were then generated using a heat strain model that established limits for increases in body temperature to 38.0 degrees C, 38.5 degrees C and 39.0 degrees C. Three experiments were conducted for the second phase of the project. The first study revealed that replacing the duty uniform pants that are worn under the bunker pants with shorts reduced the thermal strain for activities that lasted longer than 60 min. The second study examined the importance of fluid replacement. The data revealed that fluid replacement equivalent to at least 65% of the sweat lost increased exposure time by 15% compared with no fluid replacement. The last experiment compared active and passive cooling. Both the use of a mister or forearm and hand submersion in cool water significantly increased exposure time compared with passive cooling that involved only removing most of the protective clothing. Forearm and hand submersion proved to be most effective and produced dramatic increases in exposure time that approximated 65% compared with the passive cooling procedure. When the condition of no fluid replacement and passive cooling was compared with fluid replacement and forearm and hand submersion, exposure times were effectively doubled with the latter condition. The heat stress wheel that was generated can be used by Commanders to determine safe work limits for their firefighters during activities that involve wearing their protective clothing and carrying their SCBA. PMID:16922185
L. I. Tuchinskii; E. M. Veksler
1992-01-01
In the preceding article [1], an analytical relationship making it possible to determine the effective transverse thermal conductivity X.y of polycapillary composite materials was obtained. This relationship establishes the relationship between Xy, the volumetric concentration and thermal conductivity of the components of a polycapillary composite material, and the geometric parameters of the structure of the material. In deriving the equation,
Radial transport with perturbed magnetic field
NASA Astrophysics Data System (ADS)
Hazeltine, R. D.
2015-05-01
It is pointed out that the viscosity coefficient describing radial transport of toroidal angular momentum is proportional to the second power of the gyro-radius—like the corresponding coefficients for particle and heat transport—regardless of any geometrical symmetry. The observation is widely appreciated, but worth emphasizing because some literature gives the misleading impression that asymmetry can allow radial moment transport in first-order.
NASA Astrophysics Data System (ADS)
McDonald, James G.; Groth, Clinton P. T.
2013-09-01
The ability to predict continuum and transition-regime flows by hyperbolic moment methods offers the promise of several advantages over traditional techniques. These methods offer an extended range of physical validity as compared with the Navier-Stokes equations and can be used for the prediction of many non-equilibrium flows with a lower expense than particle-based methods. Also, the hyperbolic first-order nature of the resulting partial differential equations leads to mathematical and numerical advantages. Moment equations generated through an entropy-maximization principle are particularly attractive due to their apparent robustness; however, their application to practical situations involving viscous, heat-conducting gases has been hampered by several issues. Firstly, the lack of closed-form expressions for closing fluxes leads to numerical expense as many integrals of distribution functions must be computed numerically during the course of a flow computation. Secondly, it has been shown that there exist physically realizable moment states for which the entropy-maximizing problem on which the method is based cannot be solved. Following a review of the theory surrounding maximum-entropy moment closures, this paper shows that both of these problems can be addressed in practice, at least for a simplified one-dimensional gas, and that the resulting flow predictions can be surprisingly good. The numerical results described provide significant motivations for the extension of these ideas to the fully three-dimensional case.
Bernard Ducomet; Alexander Zlotnik
2002-06-05
We consider the Navier-Stokes system describing motions of viscous compressible heat-conducting and "self-gravitating" media. We use the state function of the form $p(\\eta,\\theta)=p_0(\\eta)+p_1(\\eta)\\theta$ linear with respect to the temperature $\\theta$, but we admit rather general nonmonotone functions $p_0$ and $p_1$ of $\\eta$, which allows us to treat various physical models of nuclear fluids (for which $p$ and $\\eta$ are the pressure and specific volume) or thermoviscoelastic solids. For an associated initial-boundary value problem with "fixed-free" boundary conditions and possibly large data, we prove a collection of estimates independent of time interval for solutions, including two-sided bounds for $\\eta$, together with its asymptotic behaviour as $t\\to \\infty$. Namely, we establish the stabilization pointwise and in $L^q$ for $\\eta$, in $L^2$ for $\\theta$, and in $L^q$ for $v$ (the velocity), for any $q\\in[2,\\infty)$.
A. P. van den Berg; D. A. Yuen; J. R. Allwardt
2002-01-01
The temperature-dependence of the phonon portion of the thermal conductivity k(T,P) devised by Hofmeister [Science 283 1699-1706] decreases with temperature, the same as in the dependence of mantle viscosity. Such a functional relationship of ?k\\/?T<0, when coupled with internal heating would present a situation very conducive for positive feedback action. On the other hand, the photon dependence of the conductivity
NASA Astrophysics Data System (ADS)
van den Berg, A. P.; Yuen, D. A.; Allwardt, J. R.
2002-02-01
The temperature-dependence of the phonon portion of the thermal conductivity k( T, P) devised by Hofmeister [Science 283 1699-1706] decreases with temperature, the same as in the dependence of mantle viscosity. Such a functional relationship of ?k/ ?T<0, when coupled with internal heating would present a situation very conducive for positive feedback action. On the other hand, the photon dependence of the conductivity has a functional relationship of ?k/ ?T>0. Thus, there can be a tradeoff between the phonon and photon contributions in the conductivity in the presence of internal heating. We have conducted two-dimensional calculations of mantle convection up to a surface Rayleigh number of around five million and an internal heating of chondritic abundance, with the extended-Boussinesq approximation in which the dissipation number has been set to 0.47 and depth-dependent thermal expansivity, decreasing by a factor of 5 across the mantle. The value of the constant mantle viscosity and the amount of internal heating are varied. For an enhanced radiative contribution [J. Geophys. Res. 84 (B4) 1603-1610] the radiative component of the thermal conductivity can exceed the phonon contribution in the upper mantle. Our results show that in all cases with basal heating the average mantle temperature of the variable conductivity models are higher than those of the corresponding constant conductivity models. But the interior thermal difference between the two conductivity models decreases (1) with greater vigor of convection, (2) an increase of internal heating and (3) an increase in the radiative contribution to the conductivity. The interior mantle temperature is significantly hotter, more than 500 °C, than the constant conductivity model, for the k( T, P) model with the less enhanced radiative component [Science 283 1699-1706]. These results would suggest that some sort of massive melting in the young earth might have occurred with k( T, P) and that there should not be so much radioactivity in the lower mantle today without incurring the wrath of some melting. We have also studied the effects of k( T, P) on slowing down the mantle secular cooling process by monitoring the gradual decrease in mantle temperature following an imposition of an adiabatic boundary condition at the core-mantle boundary. A decay time of 3.6 Gy has been taken for the mantle radioactivity and we have varied the initial amount of radioactive heating from chondritic value to four times the chondritic value. A significant delay in the cooling process of at least 1-2 Gy is found for a surface Rayleigh number of between 5×10 6 to 5×10 7. The mantle temperature can be heated up by 300-400 °C for initial radiogenic heating value characteristic of the Archean. We find the strongest deviations from the constant conductivity case for a silicate model by Hofmeister [Science 283 1699-1706] and intermediate values for an enhanced radiative conductivity model comparable to the model of Shankland et al. [J. Geophys. Res. 84 (B4) 1603-1610]. Such high mantle temperatures maintained for a long time by variable thermal conductivity would have important consequences on the thermal and petrological evolution of the mantle.
NASA Astrophysics Data System (ADS)
Suga, Eriko; Kaneko, Kenji; Futami, Hikaru; Yamashita, Erika; Arai, Tsunenori
2005-04-01
We have been proposed novel short-term (<10s) heating balloon using the combination of light-heat conversion mechanism and heated contrast medium irrigation in the balloon to improve dilatation characteristics of balloon angioplasty. Our new balloon angioplasty had suppressed intimal hyperplasia in rabbit model. We designed following experiments to understand the mechanism of suppression of intimal hyperplasia in our new thermal balloon angioplasty. We also aimed to obtain the suitable heating condition in our angioplasty to suppress intimal hyperplasia. We studied influence of the short-term heating on smooth muscle cells (SMCs) lethality in vitro. We investigated number of SMCs reduction in media in order to prevent intimal hyperplasia. We applied to our heating balloon dilatation to chronic rabbit model using normal iliac artery to study relation between heating condition and hyperplasia suppression. We estimated temperature history of the rabbit vascular wall by thermal conduction calculation. We related the estimated temperature history to the hyperplasia suppression effect in the chronic rabbit model. Finally, we obtained the relation between number of SMCs decreases and intimal hyperplasia suppression. We obtained that the short-term heating with 10s laser irradiation corresponding to estimated temperature of 50°C in the media and prevented intimal hyperplasia in the rabbit chronic model. In this case, we estimated about 30 percents of SMCs cellular lethality in media.
NSDL National Science Digital Library
This page presents activities related to Conduction from the Science & Engineering in the Lives of Students project. Activities include Chemical Reactions in Construction, Everyday Heat Transfer, Heat Resistant Glass, Hot Cup, Speed Melting, and Wall R Value. Each activity includes a detailed description, list of the materials needed, science concepts covered, and reflection questions.
NASA Technical Reports Server (NTRS)
Faghri, Amir; Chen, Ming-Ming
1989-01-01
The effects of conjugate heat transfer, vapor compressibility, and viscous dissipation in heat pipes are discussed. The accuracy of the partially parabolic versus the elliptic presentation of the governing equations is also examined. The results show that the axial wall conduction has a tendency to make the temperature distribution more uniform for heat pipes with large ratios of pipe wall to effective liquid-wick thermal conductivity. The compressible and incompressible models show very close agreement for the total pressure drop, while the local pressure variations along the heat pipe are quite different for these two models when the radial Reynolds number at the interface is high.
Whitacre, G.R.; Grinberg, I.M.
1980-01-01
CONBEC is a computer programmed model which determines the steady-state heat flow through multicomponent refractory-lined gasifier vessel walls. The model accounts for the effects of lining thickness, porosity, gaps, cracks, refractory composition, physical form, anchor spacing and configuration, gas pressure and composition, and other parameters on heat flow. CONBEC is based on a combination of the CONnected Block and Effective Conductivity techniques. The refractory wall is described as a series of blocks, each with its own effective thermal conductivity. The connected blocks are used to handle nonlinear temperature effects, material difference, and location effects. Parallel heat flow paths through the wall are used to provide for distinct material changes, gaps, conductivity changes, and hot-spot determination. The typical configuration has two parallel heat flow paths. Anchors can be treated as a separate heat flow path or can be left out. The blocks are cross-linked to account for lateral heat flow between the parallel paths. The model is extremely simple to use yet it provides considerable information regarding the importance of material, design, and operational parameters on heat flow in refractory vessel walls and on hot spots. It was developed to be used in the design of material systems for coal gasification vessels and has broad applicability to other refractory linings for furnaces or process vessels.The output results of CONBEC are in good agreement with experimental data obtained for several refractory material systems over a range of wall temperatures, gas compositions, wall thicknesses, crack and gap characteristics, and gas pressures.
B. Köstner; P. Biron; R. Siegwolf; A. Granier
1996-01-01
During the Hartheim Experiment (HartX) 1992 conducted in the upper Rhine Valley, Germany, three different methods were used to measure sap flow in Scots pine trees via heating of water transported in the xylem: (1) constant heating applied radially in the sapwood (“Granier-system”-G), (2) constant heating of a stem segment (“Cermák-system”-C), and (3) regulated variable heating of a stem segment
McKeown, Mark H. (Golden, CO); Beason, Steven C. (Lakewood, CO)
1991-01-01
The radial arm strike rail assembly is a system for measurement of bearings, directions, and stereophotography for geologic mapping, particularly where magnetic compasses are not appropriate. The radial arm, pivoting around a shaft axis, provides a reference direction determination for geologic mapping and bearing or direction determination. The centerable and levelable pedestal provide a base for the radial arm strike rail and the telescoping camera pedestal. The telescoping feature of the radial arm strike rail allows positioning the end of the rail for strike direction or bearing measurement with a goniometer.
Extended foil capacitor with radially spoked electrodes
Foster, James C. (Indian Shores, FL)
1990-01-01
An extended foil capacitor has a conductive disk electrically connected in oncrushing contact to the extended foil. A conductive paste is placed through spaces between radial spokes on the disk to electrically and mechanically connect the extended foil to the disk.
Design of a Polymer-Based Radial Thermoelectric Generator
NASA Astrophysics Data System (ADS)
Menon, Akanksha; Yee, Shannon
2014-03-01
Polymers possess desirable properties such as low thermal conductivity, low cost, and scalable processability as compared to inorganic materials. These characteristics make polymers attractive for thermoelectric (TE) applications. Current examples of polymer thin-film TE devices are limited to traditional rectangular/parallel plate geometries. The focus of this work is to investigate the effect of radial device geometry on TE performance. Each TE module consists of many divided discs of p- and n-type polymers on a thermally insulating circular substrate. In the center of the disc a channel of warm fluid flows as the source of heat, which creates a radial temperature gradient across the TE. Many discs can be stacked and connected electrically in series, thus generating an appreciable output voltage. In this work, analytic thermal and electrical models are developed to present an optimized device geometry for maximum power, maximum efficiency, and low /W scenarios. While the efficiency equation is identical to that for a rectangular geometry, the non-linear resistance of the radial device offers a higher power density and greater thermal insulation than traditional rectangular TEs. Graduate student at Georgia Tech
1D-to-3D transition of phonon heat conduction in polyethylene using molecular dynamics simulations
Henry, Asegun
The thermal conductivity of nanostructures generally decreases with decreasing size because of classical size effects. The axial thermal conductivity of polymer chain lattices, however, can exhibit the opposite trend, ...
Boiling radial flow in fractures of varying wall porosity
Barnitt, Robb Allan
2000-06-01
The focus of this report is the coupling of conductive heat transfer and boiling convective heat transfer, with boiling flow in a rock fracture. A series of experiments observed differences in boiling regimes and behavior, and attempted to quantify a boiling convection coefficient. The experimental study involved boiling radial flow in a simulated fracture, bounded by a variety of materials. Nonporous and impermeable aluminum, highly porous and permeable Berea sandstone, and minimally porous and permeable graywacke from The Geysers geothermal field. On nonporous surfaces, the heat flux was not strongly coupled to injection rate into the fracture. However, for porous surfaces, heat flux, and associated values of excess temperature and a boiling convection coefficient exhibited variation with injection rate. Nucleation was shown to occur not upon the visible surface of porous materials, but a distance below the surface, within the matrix. The depth of boiling was a function of injection rate, thermal power supplied to the fracture, and the porosity and permeability of the rock. Although matrix boiling beyond fracture wall may apply only to a finite radius around the point of injection, higher values of heat flux and a boiling convection coefficient may be realized with boiling in a porous, rather than nonporous surface bounded fracture.
NASA Astrophysics Data System (ADS)
Yang, Fan; Dames, Chris
2015-04-01
The heating-frequency dependence of the apparent thermal conductivity in a semi-infinite body with periodic planar surface heating is explained by an analytical solution to the Boltzmann transport equation. This solution is obtained using a two-flux model and gray mean free time approximation and verified numerically with a lattice Boltzmann method and numerical results from the literature. Extending the gray solution to the nongray regime leads to an integral transform and accumulation-function representation of the phonon scattering spectrum, where the natural variable is mean free time rather than mean free path, as often used in previous work. The derivation leads to an approximate cutoff conduction similar in spirit to that of Koh and Cahill [Phys. Rev. B 76, 075207 (2007), 10.1103/PhysRevB.76.075207] except that the most appropriate criterion involves the heater frequency rather than thermal diffusion length. The nongray calculations are consistent with Koh and Cahill's experimental observation that the apparent thermal conductivity shows a stronger heater-frequency dependence in a SiGe alloy than in natural Si. Finally these results are demonstrated using a virtual experiment, which fits the phase lag between surface temperature and heat flux to obtain the apparent thermal conductivity and accumulation function.
Ebert, Todd A (West Palm Beach, FL); Carella, John A (Jupiter, FL)
2012-03-13
A triple acting radial seal used as an interstage seal assembly in a gas turbine engine, where the seal assembly includes an interstage seal support extending from a stationary inner shroud of a vane ring, the interstage seal support includes a larger annular radial inward facing groove in which an outer annular floating seal assembly is secured for radial displacement, and the outer annular floating seal assembly includes a smaller annular radial inward facing groove in which an inner annular floating seal assembly is secured also for radial displacement. A compliant seal is secured to the inner annular floating seal assembly. The outer annular floating seal assembly encapsulates the inner annular floating seal assembly which is made from a very low alpha material in order to reduce thermal stress.
NASA Astrophysics Data System (ADS)
Tsuchiya, N.; Asanuma, H.; Sakaguchi, K.; Okamoto, A.; Hirano, N.; Watanabe, N.; Kizaki, A.
2013-12-01
EGS has been highlightened as a most promising method of geothermal development recently because of applicability to sites which have been considered to be unsuitable for geothermal development. Meanwhile, some critical problems have been experimentally identified, such as low recovery of injected water, difficulties to establish universal design/development methodology, and occurrence of large induced seismicity. Future geothermal target is supercritical and superheated geothermal fluids in and around ductile rock bodies under high temperatures. Ductile regime which is estimated beyond brittle zone is target region for future geothermal development due to high enthalpy fluids and relatively weak water-rock interaction. It is very difficult to determine exact depth of Brittle-Ductile boundary due to strong dependence of temperature (geotherm) and strain rate, however, ductile zone is considered to be developed above 400C and below 3 km in geothermal fields in Tohoku District. Hydrothermal experiments associated with additional advanced technology will be conducting to understand ';Beyond brittle World' and to develop deeper and hotter geothermal reservoir. We propose a new concept of the engineered geothermal development where reservoirs are created in ductile basement, expecting the following advantages: (a)simpler design and control the reservoir, (b)nearly full recovery of injected water, (c)sustainable production, (d)cost reduction by development of relatively shallower ductile zone in compression tectonic zones, (e)large quantity of energy extraction from widely distributed ductile zones, (f)establishment of universal and conceptual design/development methodology, and (g) suppression of felt earthquakes from/around the reservoirs. In ductile regime, Mesh-like fracture cloud has great potential for heat extraction between injection and production wells in spite of single and simple mega-fracture. Based on field observation and high performance hydrothermal experiments, our research goals are 1)Analysis and understanding of geothermal structure and geofluids in ductile condition of the Japanese Island arc, 2)Fundamental technologies of drilling under ductile region for geothermal reservoir, 3) Development of geothermal reservoir simulator of two phase and multiphase flow including supercritical state through rock fracture, 4) Lab scale support for ICDP-JBBP, 5) Application of new EGS technologies to conventional geothermal fields as recovery from the 2011 Great East Japan Earthquake and energy crisis in Japan. [Publications Relevant to the Research] Tsuchiya, N. and Hirano, N. (2007), ISLAND ARC, 16, 6-15. Okamoto, A., Saishu, H., Hirano, N. & Tsuchiya, N. (2010) Geochimica et Cosmochimica Acta, 74, 3692-3706. Majer, E.L., Baria, R., Stark, M., Oates, S., Bonner, J. Smith, B. & Asanuma H., (2007) Geothermics, 36, 185-222. Watanabe, N., Hirano, N. Tsuchiya, N. (2009) Journal of Geophysical Research B: Solid Earth, 114(4), B04208.
Thermal conductivity measurement of individual Bi2Se3 nano-ribbon by self-heating three-? method
NASA Astrophysics Data System (ADS)
Li, Guodong; Liang, Dong; Qiu, Richard L. J.; Gao, Xuan P. A.
2013-01-01
We report thermal conductivity measurements of individual single crystalline Bi2Se3 nano-ribbon (NR) synthesized via the gold nanoparticle catalyzed vapor-liquid-solid mechanism. By using the four-probe third harmonic method, thermal conductivity of Bi2Se3 NRs was obtained in the temperature range of 10 K to 300 K. It is found that the measured thermal conductivities are nearly two orders of magnitude smaller than the bulk value and have a maximum thermal conductivity at temperature (around 200 K) greater than the bulk. The significant reduced thermal conductivity of NRs is attributed to enhanced phonon boundary scattering in nanostructured material.
ARIES-CS Radial Builds and Compositions
everywhere (no shield-only zones). · 1% nuclear heating in LT shield and/or VV. · Shield, VV, and magnet Configuration R = 8.25 m a = 1.85 m #12;08/30/2004 10 Internal VV #12;08/30/2004 11 Flibe/FS Radial Build (Water
The interaction between two radial jets
Gruber, Thomas Clifton
1993-01-01
Arrays of impinging jets are used in industry for heat and mass transfer processes. A new type of jet was recently developed which could be utilized in such arrays. This jet is the radial jet and it offers the advantages of variable net force...
NASA Astrophysics Data System (ADS)
Hamza, V. M.; Cardoso, R. R.; Ponte Neto, C. F.
2008-04-01
Pollack and Chapman, hereafter referred to as P&C, argue that: (1) errors arising from lack of quality control in the IHFC database are not important and not properly documented, (2) resolution of spatial patterns in global heat flux distribution should not be represented by spherical harmonics and (3) heat flow in young oceanic crust and global heat loss are better represented by a contested 1-D cooling model than by the data. We disagree and provide additional information that may help clear up such misunderstandings. We also mention briefly the results of a new improved thermal model of the lithosphere that satisfactorily reproduces the main features identified in observational data sets of heat flow and ocean floor bathymetry. Thus, there is no reason to invoke the ad hoc hypothesis of large-scale hydrothermal circulation in the ocean crust.
Sharma, Dew Kumari; Andersen, Sven Bode; Ottosen, Carl-Otto; Rosenqvist, Eva
2015-02-01
The chlorophyll fluorescence parameter Fv /Fm reflects the maximum quantum efficiency of photosystem II (PSII) photochemistry and has been widely used for early stress detection in plants. Previously, we have used a three-tiered approach of phenotyping by Fv /Fm to identify naturally existing genetic variation for tolerance to severe heat stress (3 days at 40°C in controlled conditions) in wheat (Triticum aestivum L.). Here we investigated the performance of the previously selected cultivars (high and low group based on Fv /Fm value) in terms of growth and photosynthetic traits under moderate heat stress (1 week at 36/30°C day/night temperature in greenhouse) closer to natural heat waves in North-Western Europe. Dry matter accumulation after 7 days of heat stress was positively correlated to Fv /Fm . The high Fv /Fm group maintained significantly higher total chlorophyll and net photosynthetic rate (PN ) than the low group, accompanied by higher stomatal conductance (gs ), transpiration rate (E) and evaporative cooling of the leaf (?T). The difference in PN between the groups was not caused by differences in PSII capacity or gs as the variation in Fv /Fm and intracellular CO2 (Ci ) was non-significant under the given heat stress. This study validated that our three-tiered approach of phenotyping by Fv /Fm performed under increasing severity of heat was successful in identifying wheat cultivars differing in photosynthesis under moderate and agronomically more relevant heat stress. The identified cultivars may serve as a valuable resource for further studies to understand the physiological mechanisms underlying the genetic variability in heat sensitivity of photosynthesis. PMID:24962705
Changsheng Dou; Fei Jiang; Song Jiang; Yong-Fu Yang
2014-08-07
We prove that there exists a strong solution to the Dirichlet boundary value problem for the steady Navier-Stokes equations of a compressible heat-conductive fluid with large external forces in a bounded domain $R^d (d = 2, 3)$, provided that the Mach number is appropriately small. At the same time, the low Mach number limit is rigorously verified. The basic idea in the proof is to split the equations into two parts, one of which is similar to the steady incompressible Navier-Stokes equations with large forces, while another part corresponds to the steady compressible heat-conductive Navier-Stokes equations with small forces. The existence is then established by dealing with these two parts separately, establishing uniform in the Mach number a priori estimates and exploiting the known results on the steady incompressible Navier-Stokes equations.
NASA Technical Reports Server (NTRS)
Cleveland, Paul E.; Buchko, Matthew T.; Stavely, Richard A.
2003-01-01
The Variable Conductance Heat Pipe (VCHP) Assembly of the HST Wide Field Camera 3 was subjected to thermal vacuum (TN) environmental testing. The test program included both maximum and minimum environments as well as simulated on-orbit cycling. Elements of the VCHP assembly included a VCHP, an optical bench cold plate with an imbedded constant conductance heat pipe, and a VCHP reservoir radiator with a proportionally controlled heater. The purpose of the test was to characterize and demonstrate the assembly s ability to control the temperature of the cold plate, which provides a stable thermal environment for the instrument s optical bench. This paper discusses the VCHP Assembly control performance and control authority during the dynamic hot and cold 90-minute orbit cycling test phases.
Bach, Aaron J. E.; Stewart, Ian B.; Disher, Alice E.; Costello, Joseph T.
2015-01-01
Purpose Skin temperature assessment has historically been undertaken with conductive devices affixed to the skin. With the development of technology, infrared devices are increasingly utilised in the measurement of skin temperature. Therefore, our purpose was to evaluate the agreement between four skin temperature devices at rest, during exercise in the heat, and recovery. Methods Mean skin temperature (T-sk) was assessed in thirty healthy males during 30 min rest (24.0 ± 1.2°C, 56 ± 8%), 30 min cycle in the heat (38.0 ± 0.5°C, 41 ± 2%), and 45 min recovery (24.0 ± 1.3°C, 56 ± 9%). T-sk was assessed at four sites using two conductive devices (thermistors, iButtons) and two infrared devices (infrared thermometer, infrared camera). Results Bland–Altman plots demonstrated mean bias ± limits of agreement between the thermistors and iButtons as follows (rest, exercise, recovery): -0.01 ± 0.04, 0.26 ± 0.85, -0.37 ± 0.98°C; thermistors and infrared thermometer: 0.34 ± 0.44, -0.44 ± 1.23, -1.04 ± 1.75°C; thermistors and infrared camera (rest, recovery): 0.83 ± 0.77, 1.88 ± 1.87°C. Pairwise comparisons of T-sk found significant differences (p < 0.05) between thermistors and both infrared devices during resting conditions, and significant differences between the thermistors and all other devices tested during exercise in the heat and recovery. Conclusions These results indicate poor agreement between conductive and infrared devices at rest, during exercise in the heat, and subsequent recovery. Infrared devices may not be suitable for monitoring T-sk in the presence of, or following, metabolic and environmental induced heat stress. PMID:25659140
NASA Astrophysics Data System (ADS)
Abo-Eldahab, Emad M.; El Gendy, Mahmoud S.
The problem of free convection heat transfer characteristics in an electrically conducting fluid is investigated near an isothermal sheet. This has been done under the combined effect of buoyancy and radiation in the presence of uniform transverse magnetic field. The sheet is linearly stretched in the presence of a uniform free stream of constant velocity and temperature. The fluid viscosity is assumed to vary as an inverse linear function of temperature. The effects of free convection and internal heat generation or absorption are also considered. Fundamental equations are derived on the assumption of small magnetic Reynolds number. The resulting coupled nonlinear differential equations are solved numerically and the velocity and temperature profiles as well as the local Nusselt number and skin-friction coefficient are computed for various values of magnetic field, radiation, heat source and variable viscosity.
L. Benzerga; C. Lhiaubet; R. M. Meyer
1985-01-01
We present an improved version of a heat-conduction model which leads to better-computed values of the anodic voltage drops for electric discharges in a liquid dielectric, with a short interelectrode gap (about 50 ?m) and short duration (10–1000 ?s). The results obtained show monotonic variations according to the duration of the discharge and peak current, and correspond to the measured
NASA Astrophysics Data System (ADS)
Ordonez-Miranda, J.; Zambrano-Arjona, Miguel A.; Alvarado-Gil, J. J.
2010-02-01
Dual-phase lagging model is one of the most promising approaches to generalize the Fourier heat conduction equation, and it can be reduced in the appropriate limits to the hyperbolic Cattaneo-Vernotte and to the parabolic equations. In this paper it is shown that the Hamilton-Jacobi and quantum theory formulations that have been developed to study the thermal-wave propagation in the Fourier framework can be extended to include the more general approach based on dual-phase lagging. It is shown that the problem of solving the heat conduction equation can be treated as a thermal harmonic oscillator. In the classical approach a formulation in canonical variables is presented. This formalism is used to introduce a quantum mechanical approach from which the expectation values of observables such as the temperature and heat flux are obtained. These formalisms permit to use a methodology that could provide a deeper insight into the phenomena of heat transport at different time scales in media with inhomogeneous thermophysical properties.
HEat Decay Data Repository Footprint for Thermal-Hydrologic and Conduction-Only Models for TSPA-SR
N.D. Francis
2000-04-24
The repository heat decay data contained within this calculation is specified for both mountain-scale and drift-scale thermal-hydrologic (TH), thermal-hydrologic-mechanical (THM), and thermal-hydrologic-chemical (THC) simulations used in total systems performance assessments (TSPA). Repository thermal output data, and how it decays in time, is required by the models that compute changes to the geologic system as a result of a heat addition. The mountain-scale problem requires a repository-wide waste stream including the total heat output of each fuel type to be emplaced in the repository. These models apply a smeared heat source over a predefined repository footprint area specified in the model. The drift-scale problem requires the heat output of a number of representative (specific) waste package types. These models apply specific waste package heat outputs resolved at the scale of the waste package itself. The results of this calculation will supply details of the repository heat load for each model type. It also provides a schematic of the repository footprint outlines for the License Application Design Selection (LADS), the total repository footprint for TSPA site recommendation (SR) including the contingency area, and the actual loaded repository footprint. This calculation is performed under procedure AP-3.12Q, Rev. 0/ICN 0, Calculations. It is directed by the development plan TDP-MGR-HS-000001 (CRWMS M&O 1999f) which was developed under procedure AP-2.13Q, Rev. 0/ICN 1, Technical Product Development Plans for use in Performance Assessment activities.
RAVE The RAdial Velocity Experiment
Steinmetz, M
2002-01-01
RAVE (RAdial Velocity Experiment) is an ambitious program to conduct an all-sky survey (complete to V = 16) to measure the radial velocities, metallicities and abundance ratios of 50 million stars using the 1.2-m UK Schmidt Telescope of the Anglo-Australian Observatory (AAO), together with a northern counterpart, over the period 2006 - 2010. The survey will represent a giant leap forward in our understanding of our own Milky Way galaxy, providing a vast stellar kinematic database three orders of magnitude larger than any other survey proposed for this coming decade. RAVE will offer the first truly representative inventory of stellar radial velocities for all major components of the Galaxy. The survey is made possible by recent technical innovations in multi-fiber spectroscopy; specifically the development of the 'Echidna' concept at the AAO for positioning fibers using piezo-electric ball/spines. A 1m-class Schmidt telescope equipped with an Echidna fiber-optic positioner and suitable spectrograph would be ab...
RAVE: The RAdial Velocity Experiment
Matthias Steinmetz; for the RAVE science working group
2002-11-19
RAVE (RAdial Velocity Experiment) is an ambitious program to conduct an all-sky survey (complete to V = 16) to measure the radial velocities, metallicities and abundance ratios of 50 million stars using the 1.2-m UK Schmidt Telescope of the Anglo-Australian Observatory (AAO), together with a northern counterpart, over the period 2006 - 2010. The survey will represent a giant leap forward in our understanding of our own Milky Way galaxy, providing a vast stellar kinematic database three orders of magnitude larger than any other survey proposed for this coming decade. RAVE will offer the first truly representative inventory of stellar radial velocities for all major components of the Galaxy. The survey is made possible by recent technical innovations in multi-fiber spectroscopy; specifically the development of the 'Echidna' concept at the AAO for positioning fibers using piezo-electric ball/spines. A 1m-class Schmidt telescope equipped with an Echidna fiber-optic positioner and suitable spectrograph would be able to obtain spectra for over 20 000 stars per clear night. Although the main survey cannot begin until 2006, a key component of the RAVE survey is a pilot program of 100 000 stars which may be carried out using the existing 6dF facility in unscheduled bright time over the period 2003--2005.
C.-H. An
1984-01-01
The role of photospheric line-tying, i.e., solar coronal loop structures, was investigated in terms of the effect on radiative modes and the influence that different radial pressure profiles exert on the effects of line-tying on radiative MHD stability. Energy is assumed dissipated by heat conduction and radiation and zero- and first-order solutions are obtained for the radiative time scales. Line-tying
Conduct a state-of-the-art survey of existing knowledge for the design of ground-source heat pumps
NASA Astrophysics Data System (ADS)
Ball, D. A.
1982-03-01
Horizontal serpentine coils have been and are at present the most common coil configuration. Best design data exist for horizontal coils in heating only applications with moist soil. Applications in dry soil or where significant summer cooling is required are not as well understood at this time. A seasonal performance factor of about 3.0 can be expected for a properly designed and installed residential ground-coupled heat-pump system. Long-term durability of buried steel and cooper tubing has been demonstrated. Life expectancy of thin-walled polyethylene tubing in the heating-only application is expected to be equally as good: however, present experience is limited to less than five years. In the cooling application with heat-rejection temperatures exceeding 100 F, some cracking has been experienced upon subsequent cool-down for heating operation due to localized stresses induced by conformity of the tubing to bedding material (stones) when hot. Receding of the soil from the pipe after a period of several years was experienced in the late 1940's. An understanding of this phenomenon may be crucial to the long-term operating success of these systems.
NASA Astrophysics Data System (ADS)
Zink, Barry
2003-03-01
Understanding the thermal behavior of mesoscopic systems and thin films is a critical issue of both fundamental and technological solid state science. Despite the wealth of knowledge in principle available from accurate measurement of specific heat and thermal conductivity of thin films, there are relatively few results of this type, due to the difficulty of isolating the small heat capacities and thermal conductivities from the typically large background contribution of conventional apparatus. Our group at UC San Diego uses amorphous Si-N membranes to thermally isolate small samples from their environment and allow accurate thermal measurements. Recent work adds the ability to measure thermal conductivity of films as thin as 150 Angstrom over a broad temperature range [1] to our well-established techniques for measuring Cp of small samples.[2] Our microcalorimeter is also particularly well-suited for measurements of both Cp and k in high magnetic fields [3]. The micromachining techniques used to fabricate the calorimeter allow production of significant numbers of calorimeters with well-controlled dimensions and highly reproducible properties which facilitates studies of the thermal properties of thin film and tiny crystals. In this talk I will briefly review the fabrication of our microcalorimeter and the techniques for measuring Cp and k. I will present example data and results of numerical heat flow simulations used to further our understanding of heat flow in the microcalorimeter [1] B. L. Zink, B. Revaz, J. J. Cherry and F. Hellman, Submitted to RSI, Sept. 2002 [2] D. W. Denlinger et al., Rev. Sci. Inst 65, 946-59 (1994) [3] B. L. Zink, B. Revaz, R. Sappey and F. Hellman, Rev. Sci. Instrum. 73, 1841 (2002)
Magdy B. Eteiba; Mohamed Mamdouh Abdel Aziz; Jehan Hassan Shazly
2008-01-01
In this paper, the finite-element method is used to perform heat transfer analysis to obtain the steady state and the transient temperature distribution of gas cooled-insulated power transformers. All significant parameters that influence transformer operation have been included. Also, the analysis results, which are obtained from the thermal analysis, could be reviewed at any specified location within the transformer as
A. A. Jalalzadeh-Azar; W. G. Steele; G. A. Adebiyi
1996-01-01
A model is developed and experimentally verified to study the heat transfer in a high-temperature packed bed thermal energy storage system utilizing zirconium oxide pellets. The packed bed receives flue gas at elevated temperatures varying with time during the storage process and utilizes air for the recovery process. Both convection and radiation are included in the model of the total
Gary F. Forjan
2009-01-01
Explaining the nature of the million degree solar corona is a question that has been challenging astrophysicists for over 60 years. While many theories have been proposed to explain the nature of the heating mechanism, there is as yet no single answer to this question. An important step toward finding a solution would be to first determine where in the
Measurement of Apparent Thermal Conductivity of JSC-1A Under Ambient Pressure
NASA Technical Reports Server (NTRS)
Yuan, Zeng-Guang; Kleinhenz, Julie E.
2011-01-01
The apparent thermal conductivity of JSC-1A lunar regolith simulant was measured experimentally using a cylindrical apparatus. Eleven thermocouples were embedded in the simulant bed to obtain the steady state temperature distribution at various radial, axial, and azimuthal locations. The high aspect ratio of a cylindrical geometry was proven to provide a one-dimensional, axisymmetric temperature field. A test series was performed at atmospheric pressure with varying heat fluxes. The radial temperature distribution in each test fit a logarithmic function, indicating a constant thermal conductivity throughout the soil bed. However, thermal conductivity was not constant between tests at different heat fluxes. This variation is attributed to stresses created by thermal expansion of the simulant particles against the rigid chamber wall. Under stress-free conditions (20 deg C), the data suggest a temperature independent apparent conductivity of 0.1961 +/- 0.0070 W/m/ deg C
Turbulent resistive heating of solar coronal arches
NASA Technical Reports Server (NTRS)
Benford, G.
1983-01-01
The possibility that coronal heating occurs by means of anomalous Joule heating by electrostatic ion cyclotron waves is examined, with consideration given to currents running from foot of a loop to the other. It is assumed that self-fields generated by the currents are absent and currents follow the direction of the magnetic field, allowing the plasma cylinder to expand radially. Ion and electron heating rates are defined within the cylinder, together with longitudinal conduction and convection, radiation and cross-field transport, all in terms of Coulomb and turbulent effects. The dominant force is identified as electrostatic ion cyclotron instability, while ion acoustic modes remain stable. Rapid heating from an initial temperature of 10 eV to 100-1000 eV levels is calculated, with plasma reaching and maintaining a temperature in the 100 eV range. Strong heating is also possible according to the turbulent Ohm's law and by resistive heating.
Ernst Rohner; Ladislaus Rybach; Ulrich Schärli
2005-01-01
A small, light, wireless borehole probe has been developed and built which consists of pressure and temperature sensors and a mini-datalogger\\/programmed microprocessor in a closed metal tube, water-tight up to 100 bar. The probe (235mm long, 23mm dia, 99.8 g) sinks in completed but not yet working borehole heat exchangers (BHEs) through its own weight to the bottom of the
Conduct a state-of-the-art survey of existing knowledge for the design of ground-source heat pumps
NASA Astrophysics Data System (ADS)
Ball, D.
Historic and current methods for designing ground-coil heat pumps with emphasis on European and North American experiences are discussed. Approximately 27 individual design and performance evaluation method were studied with most of them employing computer techniques. Modeling categories include steady-state analytical and transient analytical lumped parameter finite difference and finite element in one, two, and three dimensions. A discussion of each is presented.
Varutt Kittichungchit; Takeshi Shibata; Hideki Noda; Hiroshi Tanaka; Akihiko Fujii; Noriaki Oyabu; Masayuki Abe; Seizo Morita; Masanori Ozaki
2008-01-01
The effect of heat treatment during evaporation of C60 on the characteristics of a photovoltaic cell with a structure of indium-tin-oxide (ITO)\\/C60\\/poly(3-hexylthiophene) (PAT6)\\/Au was studied. The C60 films were fabricated on the substrates at different temperatures and the C60\\/PAT6 heterojunction of this photovoltaic cell was fabricated by spin-coating the solution of PAT6 onto the C60 thin film formed on ITO.
The Ignitor Radial Press System
NASA Astrophysics Data System (ADS)
Capriccioli, A.; Celentano, G.; Cucchiaro, A.; Gasparotto, M.; Rita, C.; Roccella, M.; Bianchi, A.
1999-11-01
A radial press system is employed to resist the high electromagnetic forces in the Ignitor machine. A permanent pre-load of about 190 MN is applied by retaining rings, while an active press modulates the axial pressure on the Toroidal Field Coils inner legs during the pulse current flat-top. Spurious effects at the time of the plasma formation are avoided. An optimal configuration has been deviced, leading to a series of important improvements. Using a radial rather than an axial press facilitates construction, installation, and removal of the central solenoids and central post. Furthermore, the central post can now take up the repulsive forces between the coils, allowing a greater freedom in programming the currents, and hence controlling the plasma shape. A better match can be obtained between the plasma boundary and the first wall, thus reducing the danger of localized heat loads, and the possibility of creating an X-point configuration is introduced. The improved mechanical flexibility of the machine has been achieved because of the reduced loads necessary on the passive bracing rings, while maintaining the wedging of the TF inner legs for both cold and warm machine, and during the pulse.