HEATING-7, Multidimensional Finite-Difference Heat Conduction Analysis
International Nuclear Information System (INIS)
2000-01-01
1 - Description of program or function: HEATING 7.2i and 7.3 are the most recent developments in a series of heat-transfer codes and obsolete all previous versions distributed by RSICC as SCA-1/HEATING5 and PSR-199/HEATING 6. Note that Unix and PC versions of HEATING7 are available in the CCC-545/SCALE 4.4 package. HEATING can solve steady-state and/or transient heat conduction problems in one-, two-, or three-dimensional Cartesian, cylindrical, or spherical coordinates. A model may include multiple materials, and the thermal conductivity, density, and specific heat of each material may be both time- and temperature-dependent. The thermal conductivity may also be anisotropic. Materials may undergo change of phase. Thermal properties of materials may be input or may be extracted from a material properties library. Heat- generation rates may be dependent on time, temperature, and position, and boundary temperatures may be time- and position-dependent. The boundary conditions, which may be surface-to-environment or surface-to-surface, may be specified temperatures or any combination of prescribed heat flux, forced convection, natural convection, and radiation. The boundary condition parameters may be time- and/or temperature-dependent. General gray body radiation problems may be modeled with user-defined factors for radiant exchange. The mesh spacing may be variable along each axis. HEATING uses a run-time memory allocation scheme to avoid having to recompile to match memory requirements for each specific problem. HEATING utilizes free-form input. In June 1997 HEATING 7.3 was added to the HEATING 7.2i packages, and the Unix and PC versions of both 7.2i and 7.3 were merged into one package. HEATING 7.3 is being released as a beta-test version; therefore, it does not entirely replace HEATING 7.2i. There is no published documentation for HEATING 7.3; but a listing of input specifications, which reflects changes for 7.3, is included in the PSR-199 documentation. For 3-D
International Nuclear Information System (INIS)
Grigull, U.; Sandner, H.
1984-01-01
Included are discussions of rates of heat transfer by conduction, the effects of varying and changing properties, thermal explosions, distributed heat sources, moving heat sources, and non-steady three-dimensional conduction processes. Throughout, the importance of thinking both numerically and symbolically is stressed, as this is essential to the development of the intuitive understanding of numerical values needed for successful designing. Extensive tables of thermophysical properties, including thermal conductivity and diffusivity, are presented. Also included are exact and approximate solutions to many of the problems that arise in practical situations
Fourier analysis of conductive heat transfer for glazed roofing materials
Energy Technology Data Exchange (ETDEWEB)
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah [Faculty of Computer and Mathematical Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia); Zakaria, Nor Zaini [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia)
2014-07-10
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
DEFF Research Database (Denmark)
Rode, Carsten
1998-01-01
Analytical theory of transient heat conduction.Fourier's law. General heat conducation equation. Thermal diffusivity. Biot and Fourier numbers. Lumped analysis and time constant. Semi-infinite body: fixed surface temperature, convective heat transfer at the surface, or constant surface heat flux...
Heat conduction analysis of multi-layered FGMs considering the finite heat wave speed
International Nuclear Information System (INIS)
Rahideh, H.; Malekzadeh, P.; Golbahar Haghighi, M.R.
2012-01-01
Highlights: ► Using a layerwise-incremental differential quadrature for heat transfer of FGMs. ► Superior accuracy with fewer degrees of freedom of the method with respect to FEM. ► Considering multi-layered functionally graded materials. ► Hyperbolic heat transfer analysis of thermal system with heat generation. ► Showing the effect of heat wave speed on thermal characteristic of the system. - Abstract: In this work, the heat conduction with finite wave heat speed of multi-layered domain made of functionally graded materials (FGMs) subjected to heat generation is simulated. For this purpose, the domain is divided into a set of mathematical layers, the number of which can be equal or greater than those of the physical layers. Then, in each mathematical layer, the non-Fourier heat transfer equations are employed. Since, the governing equations have variable coefficients due to FGM properties, as an efficient and accurate method the differential quadrature method (DQM) is adopted to discretize both spatial and temporal domains in each layer. This results in superior accuracy with fewer degrees of freedom than conventional finite element method (FEM). To verify this advantages through some comparison studies, a finite element solution are also obtained. After demonstrating the convergence and accuracy of the method, the effects of heat wave speed for two different set of boundary conditions on the temperature distribution and heat flux of the domain are studied.
Analysis of temperature distribution in a heat conducting fiber with ...
African Journals Online (AJOL)
The temperature distribution in a heat conducting fiber is computed using the Galerkin Finite Element Method in the present study. The weak form of the governing differential equation is obtained and nodal temperatures for linear and quadratic interpolation functions for different mesh densities are calculated for Neumann ...
Heat Conduction Analysis Using Semi Analytical Finite Element Method
International Nuclear Information System (INIS)
Wargadipura, A. H. S.
1997-01-01
Heat conduction problems are very often found in science and engineering fields. It is of accrual importance to determine quantitative descriptions of this important physical phenomena. This paper discusses the development and application of a numerical formulation and computation that can be used to analyze heat conduction problems. The mathematical equation which governs the physical behaviour of heat conduction is in the form of second order partial differential equations. The numerical resolution used in this paper is performed using the finite element method and Fourier series, which is known as semi-analytical finite element methods. The numerical solution results in simultaneous algebraic equations which is solved using the Gauss elimination methodology. The computer implementation is carried out using FORTRAN language. In the final part of the paper, a heat conduction problem in a rectangular plate domain with isothermal boundary conditions in its edge is solved to show the application of the computer program developed and also a comparison with analytical solution is discussed to assess the accuracy of the numerical solution obtained
Multidimensional Heat Conduction
DEFF Research Database (Denmark)
Rode, Carsten
1998-01-01
Analytical theory of multidimensional heat conduction. General heat conduction equation in three dimensions. Steay state, analytical solutions. The Laplace equation. Method of separation of variables. Principle of superposition. Shape factors. Transient, multidimensional heat conduction....
Numerical Analysis of Heat Storage and Heat Conductivity in the Concrete Hollow Core Deck Element
DEFF Research Database (Denmark)
Pomianowski, Michal Zbigniew; Heiselberg, Per; Jensen, Rasmus Lund
2011-01-01
extent these simplified models estimate the heat storage potential of precast hollow-core concrete decks correctly. This study investigates various approaches on how to model the heat transfer within the air void in the deck. Furthermore, it is analysed how different heat transfer models influence...... the overall heat transfer and heat storage in the hollow-core decks. The presented results allow comparison between detailed results from 2D-COMSOL simulations and simple 1D calculations from the whole building simulation tool such as BSim program and moreover, it is possible to validate the calculation...... method in BSim for the concrete deck element with air voids. Finally, this paper presents a comparison of the calculated heat conductivity of the hollow-core concrete deck and the measured heat conductivity for the same deck by using hot box apparatus....
Analysis of transient heat conduction in a PWR fuel rod by an improved lumped parameter approach
Energy Technology Data Exchange (ETDEWEB)
Dourado, Eneida Regina G. [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil); Cotta, Renato M. [Coordenacao de Pos-Graduacao e Pesquisa de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Mecanica; Jian, Su, E-mail: eneidadourado@gmail.com, E-mail: sujian@nuclear.ufrj.br, E-mail: cotta@mecanica.ufrj.br [Coordenacao de Pos-Graduacao e Pesquisa de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear
2017-07-01
This paper aims to analyze transient heat conduction in a nuclear fuel rod by an improved lumped parameter approach. One-dimensional transient heat conduction is considered, with the circumferential symmetry assumed and the axial conduction neglected. The thermal conductivity and specific heat in the fuel pellet are considered temperature dependent, while the thermophysical properties of the cladding are considered constant. Hermite approximation for integration is used to obtain the average temperature and heat flux in the radial direction. Significant improvement over the classical lumped parameter formulation has been achieved. The proposed model can be also used in dynamic analysis of PWR and nuclear power plant simulators. (author)
Analysis of transient heat conduction in a PWR fuel rod by an improved lumped parameter approach
International Nuclear Information System (INIS)
Dourado, Eneida Regina G.; Cotta, Renato M.; Jian, Su
2017-01-01
This paper aims to analyze transient heat conduction in a nuclear fuel rod by an improved lumped parameter approach. One-dimensional transient heat conduction is considered, with the circumferential symmetry assumed and the axial conduction neglected. The thermal conductivity and specific heat in the fuel pellet are considered temperature dependent, while the thermophysical properties of the cladding are considered constant. Hermite approximation for integration is used to obtain the average temperature and heat flux in the radial direction. Significant improvement over the classical lumped parameter formulation has been achieved. The proposed model can be also used in dynamic analysis of PWR and nuclear power plant simulators. (author)
Lumped thermal capacitance analysis of transient heat conduction ...
African Journals Online (AJOL)
Lumped thermal capacitance analysis has been undertaken to investigate the transient temperature variations, associated induced thermal stress distributions, and the structural integrity of Ghana Research Reactor-1 (GHAR R-1) vessel after 15 years of operation. The beltline configuration of the cylindrical vessel of the ...
Chen, Ming-Ming; Faghri, Amir
1990-01-01
A numerical analysis is presented for the overall performance of heat pipes with single or multiple heat sources. The analysis includes the heat conduction in the wall and liquid-wick regions as well as the compressibility effect of the vapor inside the heat pipe. The two-dimensional elliptic governing equations in conjunction with the thermodynamic equilibrium relation and appropriate boundary conditions are solved numerically. The solutions are in agreement with existing experimental data for the vapor and wall temperatures at both low and high operating temperatures.
Ratto, Luca; Satta, Francesca; Tanda, Giovanni
2018-06-01
This paper presents an experimental and numerical investigation of heat transfer in the endwall region of a large scale turbine cascade. The steady-state liquid crystal technique has been used to obtain the map of the heat transfer coefficient for a constant heat flux boundary condition. In the presence of two- and three-dimensional flows with significant spatial variations of the heat transfer coefficient, tangential heat conduction could lead to error in the heat transfer coefficient determination, since local heat fluxes at the wall-to-fluid interface tend to differ from point to point and surface temperatures to be smoothed out, thus making the uniform-heat-flux boundary condition difficult to be perfectly achieved. For this reason, numerical simulations of flow and heat transfer in the cascade including the effect of tangential heat conduction inside the endwall have been performed. The major objective of numerical simulations was to investigate the influence of wall heat conduction on the convective heat transfer coefficient determined during a nominal iso-flux heat transfer experiment and to interpret possible differences between numerical and experimental heat transfer results. Results were presented and discussed in terms of local Nusselt number and a convenient wall heat flux function for two values of the Reynolds number (270,000 and 960,000).
A three-region conduction-controlled rewetting analysis by the Heat Balance Integral Method
International Nuclear Information System (INIS)
Sahu, S.K.; Das, P.K.; Bhattacharyya, S.
2009-01-01
Conduction-controlled rewetting of two-dimensional objects is analyzed by the Heat Balance Integral Method (HBIM) considering three distinct regions: a dry region ahead of wet front, the sputtering region immediately behind the wet front and a continuous film region further upstream. The HBIM yields solutions for wet front velocity, sputtering length and temperature field with respect to wet front. Employing this method, it is seen that heat transfer mechanism is dependent upon two temperature parameters. One of them characterizes the initial wall temperature while the other specifies the range of temperature for sputtering region. Additionally, the mechanism of heat transfer is found to be dependent on two Biot numbers comprising a convective heat transfer in the wet region and a boiling heat transfer in the sputtering region. The present solution exactly matches with the one-dimensional analysis of K.H. Sun, G.E. Dix, C.L. Tien [Cooling of a very hot vertical surface by falling liquid film, ASME J. Heat Transf. 96 (1974) 126-131] for low Biot numbers. Good agreement with experimental results is also observed. (authors)
A two-parameter nondiffusive heat conduction model for data analysis in pump-probe experiments
Ma, Yanbao
2014-12-01
Nondiffusive heat transfer has attracted intensive research interests in last 50 years because of its importance in fundamental physics and engineering applications. It has unique features that cannot be described by the Fourier law. However, current studies of nondiffusive heat transfer still focus on studying the effective thermal conductivity within the framework of the Fourier law due to a lack of a well-accepted replacement. Here, we show that nondiffusive heat conduction can be characterized by two inherent material properties: a diffusive thermal conductivity and a ballistic transport length. We also present a two-parameter heat conduction model and demonstrate its validity in different pump-probe experiments. This model not only offers new insights of nondiffusive heat conduction but also opens up new avenues for the studies of nondiffusive heat transfer outside the framework of the Fourier law.
Energy Technology Data Exchange (ETDEWEB)
Russell, M.B. [University of Hertfordshire, Hatfield (United Kingdom). Department of Aerospace, Automotive and Design Engineering; Probert, S.D. [Cranfield University, Bedfordshire (United Kingdom). School of Engineering
2004-12-01
The growing requirement for energy thrift and hence the increasing emphasis on 'low-purchased-energy' designs are stimulating the need for more accurate insights into the thermal behaviours of buildings and their components. This better understanding is preferably achieved, rather than by using 'closed software' or teaching the relevant mathematics outside heat-transfer lessons, but from embedding the pertinent tutoring while dealing with heat-transfer problems using an open-source code approach. Hence a finite-difference software program (FDiff3) has been composed to show the principles of numerical analysis as well as improve the undergraduates' perception of transient conduction. The pedagogic approach behind the development, its present capabilities and applications to sample test-cases are discussed. (author)
Analysis of heat conduction in a drum brake system of the wheeled armored personnel carriers
Puncioiu, A. M.; Truta, M.; Vedinas, I.; Marinescu, M.; Vinturis, V.
2015-11-01
This paper is an integrated study performed over the Braking System of the Wheeled Armored Personnel Carriers. It mainly aims to analyze the heat transfer process which is present in almost any industrial and natural process. The vehicle drum brake systems can generate extremely high temperatures under high but short duration braking loads or under relatively light but continuous braking. For the proper conduct of the special vehicles mission in rough terrain, we are talking about, on one hand, the importance of the possibility of immobilization and retaining position and, on the other hand, during the braking process, the importance movement stability and reversibility or reversibility, to an encounter with an obstacle. Heat transfer processes influence the performance of the braking system. In the braking phase, kinetic energy transforms into thermal energy resulting in intense heating and high temperature states of analyzed vehicle wheels. In the present work a finite element model for the temperature distribution in a brake drum is developed, by employing commercial finite element software, ANSYS. These structural and thermal FEA models will simulate entire braking event. The heat generated during braking causes distortion which modifies thermoelastic contact pressure distribution drum-shoe interface. In order to capture the effect of heat, a transient thermal analysis is performed in order to predict the temperature distribution transitional brake components. Drum brakes are checked both mechanical and thermal. These tests aim to establish their sustainability in terms of wear and the variation coefficient of friction between the friction surfaces with increasing temperature. Modeling using simulation programs led eventually to the establishment of actual thermal load of the mechanism of brake components. It was drawn the efficiency characteristic by plotting the coefficient of effectiveness relative to the coefficient of friction shoe-drum. Thus induced
Second law analysis of coupled conduction-radiation heat transfer with phase change
International Nuclear Information System (INIS)
Makhanlall, D.; Liu, L.H.
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 radiative heat transfer during the phase change process is calculated by post processing procedures. In this work, the radiation exergy loss in the medium and at the enclosure boundary is taken into consideration. It is found that radiation exergy loss is significant in the high-temperature phase change process. Parametric investigation is also carried out to study the effects of Stefan number, Biot number, Planck number, single scattering albedo and wall emissivity on exergy loss. The results show that the total exergy loss increases with Biot number, single scattering albedo and wall emissivity. The second law effects of the conduction-radiation coupling in the energy equation are also shown in this work. (authors)
Kot, V. A.
2017-11-01
The modern state of approximate integral methods used in applications, where the processes of heat conduction and heat and mass transfer are of first importance, is considered. Integral methods have found a wide utility in different fields of knowledge: problems of heat conduction with different heat-exchange conditions, simulation of thermal protection, Stefantype problems, microwave heating of a substance, problems on a boundary layer, simulation of a fluid flow in a channel, thermal explosion, laser and plasma treatment of materials, simulation of the formation and melting of ice, inverse heat problems, temperature and thermal definition of nanoparticles and nanoliquids, and others. Moreover, polynomial solutions are of interest because the determination of a temperature (concentration) field is an intermediate stage in the mathematical description of any other process. The following main methods were investigated on the basis of the error norms: the Tsoi and Postol’nik methods, the method of integral relations, the Gudman integral method of heat balance, the improved Volkov integral method, the matched integral method, the modified Hristov method, the Mayer integral method, the Kudinov method of additional boundary conditions, the Fedorov boundary method, the method of weighted temperature function, the integral method of boundary characteristics. It was established that the two last-mentioned methods are characterized by high convergence and frequently give solutions whose accuracy is not worse that the accuracy of numerical solutions.
Verification of combined thermal-hydraulic and heat conduction analysis code FLOWNET/TRUMP
International Nuclear Information System (INIS)
Maruyama, Soh; Fujimoto, Nozomu; Sudo, Yukio; Kiso, Yoshihiro; Murakami, Tomoyuki.
1988-09-01
This report presents the verification results of the combined thermal-hydraulic and heat conduction analysis code, FLOWNET/TRUMP which has been utilized for the core thermal hydraulic design, especially for the analysis of flow distribution among fuel block coolant channels, the determination of thermal boundary conditions for fuel block stress analysis and the estimation of fuel temperature in the case of fuel block coolant channel blockage accident in the design of the High Temperature Engineering Test Reactor(HTTR), which the Japan Atomic Energy Research Institute has been planning to construct in order to establish basic technologies for future advanced very high temperature gas-cooled reactors and to be served as an irradiation test reactor for promotion of innovative high temperature new frontier technologies. The verification of the code was done through the comparison between the analytical results and experimental results of the Helium Engineering Demonstration Loop Multi-channel Test Section(HENDEL T 1-M ) with simulated fuel rods and fuel blocks. (author)
Verification of combined thermal-hydraulic and heat conduction analysis code FLOWNET/TRUMP
Maruyama, Soh; Fujimoto, Nozomu; Kiso, Yoshihiro; Murakami, Tomoyuki; Sudo, Yukio
1988-09-01
This report presents the verification results of the combined thermal-hydraulic and heat conduction analysis code, FLOWNET/TRUMP which has been utilized for the core thermal hydraulic design, especially for the analysis of flow distribution among fuel block coolant channels, the determination of thermal boundary conditions for fuel block stress analysis and the estimation of fuel temperature in the case of fuel block coolant channel blockage accident in the design of the High Temperature Engineering Test Reactor(HTTR), which the Japan Atomic Energy Research Institute has been planning to construct in order to establish basic technologies for future advanced very high temperature gas-cooled reactors and to be served as an irradiation test reactor for promotion of innovative high temperature new frontier technologies. The verification of the code was done through the comparison between the analytical results and experimental results of the Helium Engineering Demonstration Loop Multi-channel Test Section(HENDEL T(sub 1-M)) with simulated fuel rods and fuel blocks.
An analysis of heat conduction in polar bear hairs using one-dimensional fractional model
Directory of Open Access Journals (Sweden)
Zhu Wei-Hong
2016-01-01
Full Text Available Hairs of a polar bear are of superior properties such as the excellent thermal protection. The polar bears can perennially live in an extremely cold environment and can maintain body temperature at around 37 °C. Why do polar bears can resist such cold environment? Its membrane-pore structure plays an important role. In the previous work, we established a 1-D fractional heat conduction equation to reveal the hidden mechanism for the hairs. In this paper, we further discuss solutions and parameters of the equation established and analyze heat conduction in polar bear hairs.
Efficiency analysis of straight fin with variable heat transfer coefficient and thermal conductivity
International Nuclear Information System (INIS)
Sadri, Somayyeh; Raveshi, Mohammad Reza; Amiri, Shayan
2012-01-01
In this study, one type of applicable analytical method, differential transformation method (DTM), is used to evaluate the efficiency and behavior of a straight fin with variable thermal conductivity and heat transfer coefficient. Fins are widely used to enhance heat transfer between primary surface and the environment in many industrial applications. The performance of such a surface is significantly affected by variable thermal conductivity and heat transfer coefficient, particularly for large temperature differences. General heat transfer equation related to the fin is derived and dimensionalized. The concept of differential transformation is briefly introduced, and then this method is employed to derive solutions of nonlinear equations. Results are evaluated for several cases such as: laminar film boiling or condensation, forced convection, laminar natural convection, turbulent natural convection, nucleate boiling, and radiation. The obtained results from DTM are compared with the numerical solution to verify the accuracy of the proposed method. The effects of design parameters on temperature and efficiency are evaluated by some figures. The major aim of the present study, which is exclusive for this article, is to find the effect of the modes of heat transfer on fin efficiency. It has been shown that for radiation heat transfer, thermal efficiency reaches its maximum value
An improved local radial point interpolation method for transient heat conduction analysis
Wang, Feng; Lin, Gao; Zheng, Bao-Jing; Hu, Zhi-Qiang
2013-06-01
The smoothing thin plate spline (STPS) interpolation using the penalty function method according to the optimization theory is presented to deal with transient heat conduction problems. The smooth conditions of the shape functions and derivatives can be satisfied so that the distortions hardly occur. Local weak forms are developed using the weighted residual method locally from the partial differential equations of the transient heat conduction. Here the Heaviside step function is used as the test function in each sub-domain to avoid the need for a domain integral. Essential boundary conditions can be implemented like the finite element method (FEM) as the shape functions possess the Kronecker delta property. The traditional two-point difference method is selected for the time discretization scheme. Three selected numerical examples are presented in this paper to demonstrate the availability and accuracy of the present approach comparing with the traditional thin plate spline (TPS) radial basis functions.
An improved local radial point interpolation method for transient heat conduction analysis
International Nuclear Information System (INIS)
Wang Feng; Lin Gao; Hu Zhi-Qiang; Zheng Bao-Jing
2013-01-01
The smoothing thin plate spline (STPS) interpolation using the penalty function method according to the optimization theory is presented to deal with transient heat conduction problems. The smooth conditions of the shape functions and derivatives can be satisfied so that the distortions hardly occur. Local weak forms are developed using the weighted residual method locally from the partial differential equations of the transient heat conduction. Here the Heaviside step function is used as the test function in each sub-domain to avoid the need for a domain integral. Essential boundary conditions can be implemented like the finite element method (FEM) as the shape functions possess the Kronecker delta property. The traditional two-point difference method is selected for the time discretization scheme. Three selected numerical examples are presented in this paper to demonstrate the availability and accuracy of the present approach comparing with the traditional thin plate spline (TPS) radial basis functions
Heat characteristic analysis of a conduction cooling toroidal-type SMES magnet
International Nuclear Information System (INIS)
Kim, K.M.; Kim, A.R.; Kim, J.G.; Kim, D.W.; Park, M.; Yu, I.K.; Eom, B.Y.; Sim, K.; Kim, S.H.; Shon, M.H.; Kim, H.J.; Bae, H.J.; Seong, K.C.
2010-01-01
This paper analyzed the heat characteristics of a conduction cooling toroidal-type SMES magnet. The authors designed and manufactured a conduction cooling toroidal-type SMES magnet which consists of 30 double pancake coils. One (a single pancake coil) of a double pancake coil is arranged at an angle of 6 o from each other. The shape of the toroidal-type SMES magnet was designed by a 3D CAD program. The heat invasion was investigated under no-load condition and the thermal characteristic of the toroidal-type SMES magnet was analyzed using the Finite Elements Method program. Both the analyzed and the experiment results are compared and discussed in detail.
Directory of Open Access Journals (Sweden)
Miroslav M Živković
2010-01-01
Full Text Available This paper deals with transient nonlinear heat conduction through the insulation wall of the tank for transportation of liquid aluminum. Tanks designed for this purpose must satisfy certain requirements regarding temperature of loading and unloading, during transport. Basic theoretical equations are presented, which describe the problem of heat conduction finite element (FE analysis, starting from the differential equation of energy balance, taking into account the initial and boundary conditions of the problem. General 3D problem for heat conduction is considered, from which solutions for two- and one-dimensional heat conduction can be obtained, as special cases. Forming of the finite element matrices using Galerkin method is briefly described. The procedure for solving equations of energy balance is discussed, by methods of resolving iterative processes of nonlinear transient heat conduction. Solution of this problem illustrates possibilities of PAK-T software package, such as materials properties, given as tabular data, or analytical functions. Software also offers the possibility to solve nonlinear and transient problems with incremental methods. Obtained results for different thicknesses of the tank wall insulation materials enable its comparison in regards to given conditions
Heat conduction within linear thermoelasticity
Day, William Alan
1985-01-01
J-B. J. FOURIER'S immensely influential treatise Theorie Analytique de la Chaleur [21J, and the subsequent developments and refinements of FOURIER's ideas and methods at the hands of many authors, provide a highly successful theory of heat conduction. According to that theory, the growth or decay of the temperature e in a conducting body is governed by the heat equation, that is, by the parabolic partial differential equation Such has been the influence of FOURIER'S theory, which must forever remain the classical theory in that it sets the standard against which all other theories are to be measured, that the mathematical investigation of heat conduction has come to be regarded as being almost identicalt with the study of the heat equation, and the reader will not need to be reminded that intensive analytical study has t But not entirely; witness, for example, those theories which would replace the heat equation by an equation which implies a finite speed of propagation for the temperature. The reader is refe...
ANALYSIS, OPTIMAL CONTROL, AND SIMULATION OF CONDUCTIVE-RADIATIVE HEAT TRANSFER
Directory of Open Access Journals (Sweden)
Peter Philip
2011-01-01
Full Text Available This article surveys recent results regarding the existence of weaksolutions to quasilinear partial differential equations(PDEcouplednonlocally by the integral operator of the radiosity equation, modeling conductive-radiative heat transfer. Both the stationary and the transient case are considered. For the stationary case, an optimal control problem with control constraints is presented withfirst-order necessary optimality conditions, where recent results on the solution theory of the linearized state equation allow to close a previous gap.Afinite volume scheme for the discretization of the stationary system is described and, based on this scheme, a numerical computation of the temperaturefield(solution of the state equationis shown as well as the numerical solution to a realistic control problem in the context of industrial applications in crystal growth.
Modeling and analysis of waves in a heat conducting thermo-elastic plate of elliptical shape
Directory of Open Access Journals (Sweden)
R. Selvamani
Full Text Available Wave propagation in heat conducting thermo elastic plate of elliptical cross-section is studied using the Fourier expansion collocation method based on Suhubi's generalized theory. The equations of motion based on two-dimensional theory of elasticity is applied under the plane strain assumption of generalized thermo elastic plate of elliptical cross-sections composed of homogeneous isotropic material. The frequency equations are obtained by using the boundary conditions along outer and inner surface of elliptical cross-sectional plate using Fourier expansion collocation method. The computed non-dimensional frequency, velocity and quality factor are plotted in dispersion curves for longitudinal and flexural (symmetric and antisymmetric modes of vibrations.
Sensitivity Analysis of Gap Conductance for Heat Split in an Annular Fuel Rod
International Nuclear Information System (INIS)
Chun, Kun Ho; Chun, Tae Hyun; In, Wang Kee; Song, Keun Woo
2006-01-01
To increase of the core power density in the current PWR cores, an annular fuel rod was proposed by MIT. This annular fuel rod has two coolant channels and two cladding-pellet gaps unlike the current solid fuel rod. It's important to predict the heat split reasonably because it affects coolant enthalpy rise in each channel and Departure from Nuclear Boiling Ratio (DNBR) in each channel. Conversely, coolant conditions affect fuel temperature and heat split. In particular if the heat rate leans to either inner or outer channel, it is out of a thermal equilibrium. To control a thermal imbalance, placing another gap in the pellet is introduced. The heat flow distribution between internal and external channels as well as fuel and cladding temperature profiles is calculated with and without the fuel gap between the inner and outer pellets
Heat Conduction of Air in Nano Spacing
Directory of Open Access Journals (Sweden)
Zhang Yao-Zhong
2009-01-01
Full Text Available Abstract The scale effect of heat conduction of air in nano spacing (NS is very important for nanodevices to improve their life and efficiency. By constructing a special technique, the changes of heat conduction of air were studied by means of measuring the heat conduction with heat conduction instrument in NS between the hot plate and the cooling plate. Carbon nanotubes were used to produce the nano spacing. The results show that when the spacing is small down to nanometer scale, heat conduction plays a prominent role in NS. It was found that the thickness of air is a non-linear parameter for demarcating the heat conduction of air in NS and the rate of heat conduction in unit area could be regard as a typical parameter for the heat conduction characterization at nanometer scale.
Solving hyperbolic heat conduction using electrical simulation
International Nuclear Information System (INIS)
Gheitaghy, A. M.; Talaee, M. R.
2013-01-01
In the present study, the electrical network simulation method is proposed to solve the hyperbolic and parabolic heat conduction problem considering Cattaneo-Vernoute (C.V) constitutive relation. Using this new proposed numerical model and the electrical circuit simulation program HSPICE, transient temperature and heat flux profiles at slab can be obtained easily and quickly. To verify the proposed method, the obtained numerical results for cases of one dimensional two-layer slab under periodic boundary temperature with perfect and imperfect thermal contact are compared with the published results. Comparisons show the proposed technique might be considered as a useful tool in the analysis of parabolic and hyperbolic thermal problems.
Numerical analysis of transient heat conduction in downward-facing curved sections during quenching
International Nuclear Information System (INIS)
Gao, C.; El-Genk, M.S.
1996-01-01
Pool boiling from downward-facing surfaces is of interest in many applications such as cooling of electric cables, handling of containers of hazardous liquids and external cooling of nuclear reactor vessels. Here, a two-dimensional numerical analysis was performed to determine pool boiling curves from downward-facing curved stainless-steel and copper surfaces during quenching in saturated water. To ensure stability and accuracy of the numerical solution, the alternating direction implicit (ADI) method based on finite control volume representations was employed. A time dependent boundary condition was provided by the measured temperature at nine interior locations near the boiling surface. Best results were obtained using a grid of 20x20 CVs and a non-iterative approach. Calculated temperatures near the top surface of the metal sections agreed with measured values to within 0.5 K and 2.5 K for the copper and stainless-steel sections, respectively. The running time on a Pentium 90 MHz PC for the entire boiling curve was 7% of the real transient time and 4% of that of a simplified Gaussian elimination (SGE) method for the Crank-Nicolson scheme
Pereverzev, Andrey; Sewell, Tommy
2018-03-01
Lattice heat-current time correlation functions for insulators and semiconductors obtained using molecular dynamics (MD) simulations exhibit features of both pure exponential decay and oscillatory-exponential decay. For some materials the oscillatory terms contribute significantly to the lattice heat conductivity calculated from the correlation functions. However, the origin of the oscillatory terms is not well understood, and their contribution to the heat conductivity is accounted for by fitting them to empirical functions. Here, a translationally invariant expression for the heat current in terms of creation and annihilation operators is derived. By using this full phonon-picture definition of the heat current and applying the relaxation-time approximation we explain, at least in part, the origin of the oscillatory terms in the lattice heat-current correlation function. We discuss the relationship between the crystal Hamiltonian and the magnitude of the oscillatory terms. A solvable one-dimensional model is used to illustrate the potential importance of terms that are omitted in the commonly used phonon-picture expression for the heat current. While the derivations are fully quantum mechanical, classical-limit expressions are provided that enable direct contact with classical quantities obtainable from MD.
International Nuclear Information System (INIS)
Kadri, M.
1983-01-01
The time dependent heat conduction equation in the x-y Cartesian geometry is formulated in terms of a nine-point finite difference relation using a Taylor series expansion technique. The accuracy of the nine-point formulation over the five-point formulation has been tested and evaluated for various reactor fuel-cladding plate configurations using a computer program. The results have been checked against analytical solutions for various model problems. The following cases were considered in the steady-state condition: (a) The thermal conductivity and the heat generation were uniform. (b) The thermal conductivity was constant, the heat generation variable. (c) The thermal conductivity varied linearly with the temperature, the heat generation was uniform. (d) Both thermal conductivity and heat generation vary. In case (a), approximately, for the same accuracy, 85% fewer grid points were needed for the nine-point relation which has a 14% higher convergence rate as compared to the five-point relation. In case (b), on the average, 84% fewer grid points were needed for the nine-point relation which has a 65% higher convergence rate as compared to the five-point relation. In case (c) and (d), there is significant accuracy (91% higher than the five-point relation) for the nine-point relation when a worse grid was used. The numerical solution of the nine-point formula in the time dependent case was also more accurate and converges faster than the numerical solution of the five-point formula for all comparative tests related to heat conduction problems in a nuclear fuel element
Member for conducting excess heat away from heat sources
International Nuclear Information System (INIS)
Cooke-Yarborough, E.H.
1975-01-01
Should a radioisotope-powered engine (e.g., a Stirling cycle engine for generating electricity) stop working for any reason, the radioisotope heat source will continue to generate heat. This will result in a rise in temperature which may cause overheating of and possible damage to the engine as well as to the heat source itself. The invention provides a support/location member for conducting excess heat from the heat source and which, in normal operation of the engine, will impede the conduction of heat away from the heat source and so reduce thermal losses. The member is of elongated form and comprises a stack of heat-conductive slugs disposed in a tube and in interspaced relationship along the axis of the tube. The tube supports the slugs in axial alignment. Means are provided for attaching an end one of the slugs to the heat source and means operable on overheating of said end one of the slugs are also provided whereby the slugs are able to move into heat-conducting contact with each other so as to conduct the excess heat away from said heat source. The slugs may be brazed to the tube whereby progressive overheating of the slugs along the stack results in an overheated slug being freed from attachment to the tube so as to allow the overheated slug to move along the stack and engage the next slug in line in heat-conducting contact. (U.S.)
Heat conductivity of buffer materials
International Nuclear Information System (INIS)
Boergesson, L.; Fredrikson, Anders; Johannesson, L.E.
1994-11-01
The report deals with the thermal conductivity of bentonite based buffer materials. An improved technique for measuring the thermal conductivity of buffer materials is described. Measurements of FLAC calculations applying this technique have led to a proposal of how standardized tests should be conducted and evaluated. The thermal conductivity of bentonite with different void ratio and degree of water saturation has been determined in the following different ways: * Theoretically according to three different investigations by other researchers. * Laboratory measurements with the proposed method. * Results from back-calculated field tests. Comparison and evaluation showed that these results agreed very well, when the buffer material was almost water saturated. However, the influence of the degree of saturation was not very well predicted with the theoretical methods. Furthermore, the field tests showed that the average thermal conductivity in situ of buffer material (compacted to blocks) with low degree of water saturation was lower than expected from laboratory tests. 12 refs, 29 figs, 11 tabs
Johnson, Alexander; Brace, Christopher
2015-01-01
Interventional oncology procedures such as thermal ablation are becoming widely used for many tumours in the liver, kidney and lung. Thermal ablation refers to the focal destruction of tissue by generating cytotoxic temperatures in the treatment zone. Hydrodissection - separating tissues with fluids - protects healthy tissues adjacent to the ablation treatment zone to improve procedural safety, and facilitate more aggressive power application or applicator placement. However, fluids such as normal saline and 5% dextrose in water (D5W) can migrate into the peritoneum, reducing their protective efficacy. As an alternative, a thermo-gelable poloxamer 407 (P407) solution has been recently developed to facilitate hydrodissection procedures. We hypothesise that the P407 gel material does not provide convective heat dissipation from the ablation site, and therefore may alter the heat transfer dynamics compared to liquid materials during hydrodissection-assisted thermal ablation. The purpose of this study was to investigate the heat dissipation mechanics within D5W, liquid P407 and gel P407 hydrodissection barriers. Overall it was shown that the gel P407 dissipated heat primarily through conduction, whereas the liquid P407 and D5W dissipated heat through convection. Furthermore, the rate of temperature change within the gel P407 was greater than liquid P407 and D5W. Testing to evaluate the in vivo efficacy of the fluids with different modes of heat dissipation seems warranted for further study.
Documentation of the heat conduction code TRANCO
International Nuclear Information System (INIS)
Callahan, G.D.
1975-01-01
A transient heat conduction code used for thermal, thermoelastic, thermoelastic/plastic, and thermo/viscoelastic analyses is presented. The code can solve two-dimensional X-Y and axially symmetric R-theta-z thermal problems with the following conditions: constant temperature, constant flux, convective, or adiabatic boundary conditions; time-dependent or constant internal heat generation; and anisotropic thermal conductivities
Irfan, M.; Khan, M.; Khan, W. A.
Inspired by modern deeds of nanotechnology and nanoscience and their abundant applications in the field of science and engineering, we establish a mathematical relation for unsteady 3D forced convective flow of Carreau nanofluid over a bidirectional stretched surface. Heat transfer phenomena of Carreau nanofluid is inspected through the variable thermal conductivity and heat generation/absorption impact. Furthermore, this research paper presents a more convincing approach for heat and mass transfer phenomenon of nanoliquid by utilizing new mass flux condition. Practically, zero mass flux condition is more adequate because in this approach we assume nanoparticle amends itself accordingly on the boundaries. Now the features of Buongiorno's relation for Carreau nanofluid can be applied in a more efficient way. An appropriate transformation is vacant to alter the PDEs into ODEs and then tackled numerically by employing bvp4c scheme. The numerous consequence of scheming parameters on the Carreau nanoliquid velocity components, temperature and concentration fields are portrayed graphically and deliberated in detail. The numerical outcomes for local skin friction and the wall temperature gradient for nanoliquid are intended and vacant through tables. The outcomes conveyed here manifest that impact of Brownian motion parameter Nb on the rate of heat transfer for nanoliquids becomes negligible for the recently recommended revised relation. Addationally, for authentication of the present relation, the achieved results are distinguished with earlier research works in specific cases and marvelous agreement has been noted.
International Nuclear Information System (INIS)
Chalabi, H; Lorenzini, M; Morini, G L; Saraceno, L; Boccardi, G; Celata, G P
2012-01-01
A first experimental attempt has been realized in order to measure the heat transfer between a heated platinum wire having a diameter (d) of 0.15 mm, disposed along the axis of a cylindrical shell in stainless steel having an inner diameter (D) of 100 mm, and air from atmospheric conditions down to 10 −3 mbar. Temperature differences between the wire and the external stainless steel cylindrical shell in the range of 50–125 K were imposed and the heat power transferred from the wire to the surround was measured as a function of the gas pressure. The experimental results demonstrates that for an accurate measurement of the heat conduction when the pressure goes down to 0.05 mbar is very important to be able to quantify accurately the radiative contribution which becomes predominant at low pressure. The main limitations of the test rig described in this paper have been analysed in order to highlight the modifications which can be suggested to obtain experimental results comparable with theoretical models.
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 , Proc. Natl. Acad. Sci. USA PNASA60027-842410.1073/pnas.1000488107107, 4511 (2010)], which is of high diversity but low accuracy. By decreasing the temperatures of small-degree objects, we present an improved algorithm, called biased heat conduction, which could simultaneously enhance the accuracy and diversity. Extensive experimental analyses demonstrate that the accuracy on MovieLens, Netflix, and Delicious datasets could be improved by 43.5%, 55.4% and 19.2%, respectively, compared with the standard heat conduction algorithm and also the diversity is increased or approximately unchanged. Further statistical analyses suggest that the present algorithm could simultaneously identify users' mainstream and special tastes, resulting in better performance than the standard heat conduction algorithm. This work provides a creditable way for highly efficient information filtering.
Information filtering via weighted heat conduction algorithm
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.
International Nuclear Information System (INIS)
Mahapatra, S.K.; Dandapat, B.K.; Sarkar, A.
2006-01-01
The current study addresses the mathematical modeling aspects of coupled conductive and radiative heat transfer in the presence of absorbing, emitting and isotropic scattering gray medium within two-dimensional square enclosure. A blended method where the concepts of modified differential approximation employed by combining discrete ordinate method and spherical harmonics method, has been developed for modeling the radiative transport equation. The gray participating medium is bounded by isothermal walls of two-dimensional enclosure which are considered to be opaque, diffuse and gray. The effect of various influencing parameters i.e., radiation-conduction parameter, surface emissivity, single scattering albedo and optical thickness has been illustrated. The adaptability of the present method has also been addressed
CASKETSS-HEAT: a finite difference computer program for nonlinear heat conduction problems
International Nuclear Information System (INIS)
Ikushima, Takeshi
1988-12-01
A heat conduction program CASKETSS-HEAT has been developed. CASKETSS-HEAT is a finite difference computer program used for the solution of multi-dimensional nonlinear heat conduction problems. Main features of CASKETSS-HEAT are as follows. (1) One, two and three-dimensional geometries for heat conduction calculation are available. (2) Convection and radiation heat transfer of boundry can be specified. (3) Phase change and chemical change can be treated. (4) Finned surface heat transfer can be treated easily. (5) Data memory allocation in the program is variable according to problem size. (6) The program is a compatible heat transfer analysis program to the stress analysis program SAP4 and SAP5. (7) Pre- and post-processing for input data generation and graphic representation of calculation results are available. In the paper, brief illustration of calculation method, input data and sample calculation are presented. (author)
Elementary heat transfer analysis
Whitaker, Stephen; Hartnett, James P
1976-01-01
Elementary Heat Transfer Analysis provides information pertinent to the fundamental aspects of the nature of transient heat conduction. This book presents a thorough understanding of the thermal energy equation and its application to boundary layer flows and confined and unconfined turbulent flows. Organized into nine chapters, this book begins with an overview of the use of heat transfer coefficients in formulating the flux condition at phase interface. This text then explains the specification as well as application of flux boundary conditions. Other chapters consider a derivation of the tra
Heat conduction using Green’s functions
Cole, Kevin D; Haji-Sheikh, A; Litkouhi, Bahman
2010-01-01
Introduction to Green's FunctionsHeat Flux and TemperatureDifferential Energy EquationBoundary and Initial ConditionsIntegral Energy EquationDirac Delta FunctionSteady Heat Conduction in One DimensionGF in the Infinite One-Dimensional BodyTemperature in an Infinite One-Dimensional BodyTwo Interpretations of Green's FunctionsTemperature in Semi-Infinite BodiesFlat PlatesProperties Common to Transient Green's FunctionsHeterogeneous BodiesAnisotropic BodiesTransformationsNon-Fourier Heat ConductionNumbering System in Heat ConductionGeometry and Boundary Condition Numbering SystemBoundary Condition ModifiersInitial Temperature DistributionInterface DescriptorsNumbering System for g(x, t)Examples of Numbering SystemAdvantages of Numbering SystemDerivation of the Green's Function Solution EquationDerivation of the One-Dimensional Green's Function Solution EquationGeneral Form of the Green's Function Solution EquationAlternative Green's Function Solution EquationFin Term m2TSteady Heat ConductionMoving SolidsMethods...
Ion heat conduction losses in Extrap
International Nuclear Information System (INIS)
Tennfors, E.
1989-08-01
The classical ion heat conduction losses in Extrap discharges are calculated using polynomial magnetic field profiles and compared to the power input. For polynomials matched to magnetic field profiles measured in present experiments, these losses are small. By varying the coefficients of the polynomials, a region is found, where the power input can balance the classical heat conduction losses. Each set of coefficients corresponds to values of the parameters F and Θ used in RFP physics. The region determines a region in an F-Θ diagram, including the usual RFP region but extending to higher values of Θ and βΘ
Nonstationary Heat Conduction in Atomic Systems
Singh, Amit K.
Understanding heat at the atomistic level is an interesting exercises. It is fascinating to note how the vibration of atoms result into thermodynamic concept of heat. This thesis aims to bring insights into different constitutive laws of heat conduction. We also develop a framework in which the interaction of thermostats to the system can be studied and a well known Kapitza effect can be reduced. The thesis also explores stochastic and continuum methods to model the latent heat release in the first order transition of ideal silicon surfaces into dimers. We divide the thesis into three works which are connected to each other: 1. Fourier's law leads to a diffusive model of heat transfer in which a thermal signal propagates infinitely fast and the only material parameter is the thermal conductivity. In micro- and nano-scale systems, non-Fourier effects involving coupled diffusion and wavelike propagation of heat can become important. An extension of Fourier's law to account for such effects leads to a Jeffreys-type model for heat transfer with two relaxation times. In this thesis, we first propose a new Thermal Parameter Identification (TPI) method for obtaining the Jeffreys-type thermal parameters from molecular dynamics simulations. The TPI method makes use of a nonlinear regression-based approach for obtaining the coefficients in analytical expressions for cosine and sine-weighted averages of temperature and heat flux over the length of the system. The method is applied to argon nanobeams over a range of temperature and system sizes. The results for thermal conductivity are found to be in good agreement with standard Green-Kubo and direct method calculations. The TPI method is more efficient for systems with high diffusivity and has the advantage, that unlike the direct method, it is free from the influence of thermostats. In addition, the method provides the thermal relaxation times for argon. Using the determined parameters, the Jeffreys-type model is able to
Heat Rejection from a Variable Conductance Heat Pipe Radiator Panel
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.
International Nuclear Information System (INIS)
Giles, G.E.; DeVault, R.M.; Turner, W.D.; Becker, B.R.
1976-05-01
A description is given of the development and verification of a generalized coupled conduction-convection, multichannel heat transfer computer program to analyze specific safety questions involving high temperature gas-cooled reactors (HTGR). The HEXEREI code was designed to provide steady-state and transient heat transfer analysis of the HTGR active core using a basic hexagonal mesh and multichannel coolant flow. In addition, the core auxiliary cooling systems were included in the code to provide more complete analysis of the reactor system during accidents involving reactor trip and cooling down on the auxiliary systems. Included are brief descriptions of the components of the HEXEREI code and sample HEXEREI analyses compared with analytical solutions and other heat transfer codes
Thermal conductivity and heat transfer in superlattices
Energy Technology Data Exchange (ETDEWEB)
Chen, G; Neagu, M; Borca-Tasciuc, T
1997-07-01
Understanding the thermal conductivity and heat transfer processes in superlattice structures is critical for the development of thermoelectric materials and devices based on quantum structures. This work reports progress on the modeling of thermal conductivity of superlattice structures. Results from the models established based on the Boltzmann transport equation could explain existing experimental results on the thermal conductivity of semiconductor superlattices in both in plane and cross-plane directions. These results suggest the possibility of engineering the interfaces to further reduce thermal conductivity of superlattice structures.
Analytical Evalution of Heat Transfer Conductivity with Variable Properties
DEFF Research Database (Denmark)
Rahimi, Masoume; Hosseini, Mohammad Javad; Barari, Amin
2011-01-01
The homotopy analysis method (HAM) as a new technique which is powerful and easy-to-use, is applied to solve heat transfer problems. In this paper, we use HAM for heat transfer conductivity equation with variable properties which may contain highly nonlinear terms. The obtained results are also...
Conductivity of rf-heated plasma
International Nuclear Information System (INIS)
Fisch, N.J.
1984-05-01
The electron velocity distribution of rf-heated plasma may be so far from Maxwellian that Spitzer conductivity no longer holds. A new conductivity for such plasmas is derived and the result can be put in a remarkably general form. The new expression should be of great practical value in examining schemes for current ramp-up in tokamaks by means of lower-hybrid or other waves
International Nuclear Information System (INIS)
2003-08-01
This book deals with analysis of heat transfer which includes nonlinear analysis examples, radiation heat transfer, analysis of heat transfer in ANSYS, verification of analysis result, analysis of heat transfer of transition with automatic time stepping and open control, analysis of heat transfer using arrangement of ANSYS, resistance of thermal contact, coupled field analysis such as of thermal-structural interaction, cases of coupled field analysis, and phase change.
Heat conduction in superconducting lead thallium alloys
International Nuclear Information System (INIS)
Ho, J.L.N.
1975-01-01
The heat conduction of six strong coupling superconducting Pb--Tl alloy specimens (1 to 20 percent wt Tl) was investigated with the emphasis on the effects of impurities upon the phonon thermal conductivity. All the specimens were annealed at 275 0 C for one week. Results show that the superconducting state phonon thermal conductivity of Pb--Tl is in reasonably good agreement with BRT theory. The strong coupling superconductivity of lead alloys can be handled by scaling the gap parameter using a constant factor. The results presented also show that the phonon thermal conductivity at low temperatures of well annealed lead-thallium alloys can be analyzed in terms of phonon scattering by the grain boundaries, point defects, conduction electrons, and other phonons. The phonon-dislocation scattering was found to be unimportant. The phonon relaxation rate due to point defects is in reasonably good agreement with the Klemens theory for the long range strain field scattering introduced by the thallium impurities. At low temperatures, the normal state phonon thermal conductivity showed an increase in the phonon-electron relaxation rate as the thallium concentration increases. The increase of the phonon-electron relaxation rate is attributed to the change of the Fermi surface caused by the presence of thallium impurity. The effect of the strong electron-phonon coupling character upon the phonon-electron relaxation rate has also been considered in terms of the electron-phonon enhancement factor found in the specific heat measurements
Temperature distributions of a conductively heated filament
International Nuclear Information System (INIS)
Tamura, Koji; Ohba, Hironori; Shibata, Takemasa
1999-07-01
Temperature distributions of a heated filament were measured. A W-Re(5%) filament (0.25 mm in diameter, 24.7 mm in length) was conductively heated by currents between 5A and 7A with a DC power supply, and the surface of the filament was imaged with a charge coupled device (CCD) camera through a monochromatic filter. The spectral radiation intensity at the filament center region was almost uniform. Since the temperature distribution was also uniform and the energy loss by thermal conduction was negligible, temperature in this region was determined from the energy balance between applied power and radiation loss. Temperature distribution of the filament was determined based on the Planck's law of radiation from the spectral radiation intensity ratio of the filament surface using obtained temperature as a reference. It was found that temperature distribution of a filament was easily measured by this method. (author)
Microscale Heat Conduction Models and Doppler Feedback
International Nuclear Information System (INIS)
Hawari, Ayman I.; Ougouag, Abderrafi
2015-01-01
The objective of this project is to establish an approach for providing the fundamental input that is needed to estimate the magnitude and time-dependence of the Doppler feedback mechanism in Very High Temperature reactors. This mechanism is the foremost contributor to the passive safety of gas-cooled, graphite-moderated high temperature reactors that use fuel based on Tristructural-Isotropic (TRISO) coated particles. Therefore, its correct prediction is essential to the conduct of safety analyses for these reactors. Since the effect is directly dependent on the actual temperature reached by the fuel during transients, the underlying phenomena of heat deposition, heat transfer and temperature rise must be correctly predicted. To achieve the above objective, this project will explore an approach that accounts for lattice effects as well as local temperature variations and the correct definition of temperature and related local effects.
Vernotte-Cattaneo approximation for heat conduction in fuel rod
International Nuclear Information System (INIS)
Espinosa P, G.; Espinosa M, E. G.
2009-10-01
In this paper we explore the applicability of a fuel rod mathematical model based on the Vernotte-Cattaneo transient heat conduction as constitutive law (Non-Fourier approach) for light water reactors transient analysis. In the classical theory of diffusion, the Fourier law of heat conduction is used to describe the relation between the heat conduction is used to describe the relation between the heat flux vector and the temperature gradient assuming that the heat propagation speeds are infinite. The motivation for this research was to eliminate the paradox of an infinite. The motivation for this research was to eliminate the paradox of an infinite thermal wave speed. The time-dependent heat sources were considered in the fuel rod heat transfer model. The close of the main steam isolated valves transient in a boiling water reactor was analyzed for different relaxation times. The results show that for long-times the heat fluxes on the clad surface under Vernotte-Cattaneo approach can be important, while for short-times and from the engineering point of view the changes are very small. (Author)
International Nuclear Information System (INIS)
Bergese, Paolo
2006-01-01
A microwave (MW) field can induce in a dielectric material an oscillatory polarization. By this mechanism part of the energy carried by the waves is converted into chaotic agitation, and the material heats up. MW heating is a nonequilibrium phenomenon, while conventional heating can generally be considered as quasi-static. Excess (or nonthermal) effects of MWs with respect to conventional heating lie in this difference. Macroscopically, MW heating can be described in the framework of linear nonequilibrium thermodynamics (NET). This approach indicates that in a dielectric material under MW heating the specific heat has a dynamic component linked to the variation of polarization with temperature, and that polarization and heat conduction are intertwined. In particular, linear NET provides a new phenomenological equation for heat conduction that is composed of the classic Fourier's law and an additional term due to polarization relaxation. This term quantitatively describes the excess effect of MWs on thermal conduction
Modeling of heat conduction via fractional derivatives
Fabrizio, Mauro; Giorgi, Claudio; Morro, Angelo
2017-09-01
The modeling of heat conduction is considered by letting the time derivative, in the Cattaneo-Maxwell equation, be replaced by a derivative of fractional order. The purpose of this new approach is to overcome some drawbacks of the Cattaneo-Maxwell equation, for instance possible fluctuations which violate the non-negativity of the absolute temperature. Consistency with thermodynamics is shown to hold for a suitable free energy potential, that is in fact a functional of the summed history of the heat flux, subject to a suitable restriction on the set of admissible histories. Compatibility with wave propagation at a finite speed is investigated in connection with temperature-rate waves. It follows that though, as expected, this is the case for the Cattaneo-Maxwell equation, the model involving the fractional derivative does not allow the propagation at a finite speed. Nevertheless, this new model provides a good description of wave-like profiles in thermal propagation phenomena, whereas Fourier's law does not.
Electron heat conduction and suprathermal particles
International Nuclear Information System (INIS)
Bakunin, O.G.; Krasheninnikov, S.I.
1991-01-01
As recognized at present, the applicability of Spitzer-Harm's theory on electron heat conduction along the magnetic field is limited by comparatively small values of the thermal electron mean free path ratio, λ to the characteristic length of changes in plasma parameters, L: γ=λ/L≤10 -2 . The stationary kinetic equation for the electron distribution function inhomogeneous along the x-axis f e (v,x) allows one to have solutions in the self-similar variables. The objective of a given study is to generalize the solutions for the case of arbitrary Z eff , that will allow one to compare approximate solutions to the kinetic equation with the precise ones in a wide range of parameters. (author) 8 refs., 2 figs
THERMAL CONDUCTIVITY ANALYSIS OF GASES
Clark, W.J.
1949-06-01
This patent describes apparatus for the quantitative analysis of a gaseous mixture at subatmospheric pressure by measurement of its thermal conductivity. A heated wire forms one leg of a bridge circuit, while the gas under test is passed about the wire at a constant rate. The bridge unbalance will be a measure of the change in composition of the gas, if compensation is made for the effect due to gas pressure change. The apparatus provides a voltage varying with fluctuations of pressure in series with the indicating device placed across the bridge, to counterbalance the voltage change caused by fluctuations in the pressure of the gaseous mixture.
Neoclassical electron heat conduction in tokamaks performed by the ions
International Nuclear Information System (INIS)
Ware, A.A.
1987-07-01
The increment to neoclassical ion heat conduction caused by electron collisions is shown to act like electron heat conduction since the energy is taken from and given back to the electrons at each diffusion step length. It can exceed electron neoclassical heat conduction by an order of magnitude
International Nuclear Information System (INIS)
Sarkar, J.; Bhattacharyya, Souvik
2007-01-01
In the present study, the overall conductance and the overall heat transfer area per unit capacity of refrigeration and heat pump systems have been minimized analytically considering both internal and external irreversibilities with variable temperature (finite capacity) heat reservoirs. Hot and cold side refrigerant temperatures, conductance and heat transfer area ratios have been optimized to attain this goal. The results have been verified with the more elaborate numerical optimization results obtained for ammonia based vapour compression refrigeration and heat pump systems working with variable temperature reservoirs. It is observed that the analytical results for optimum refrigerant temperatures, minimum overall conductance and heat transfer area deviate marginally from the numerically optimized results (within 1%), if one assumes a constant heat rejection temperature. The deviation of minimum overall conductance and heat transfer area is more (about 20%), if one considers both the desuperheating and condensation regions separately. However, in the absence of complex and elaborate numerical models, the simple analytical results obtained here can be used as reasonably accurate preliminary guidelines for optimization of refrigeration and heat pump systems
Effect of heat treatment temperature on binder thermal conductivities
International Nuclear Information System (INIS)
Wagner, P.
1975-12-01
The effect of heat treatment on the thermal conductivities of a pitch and a polyfurfuryl alcohol binder residue was investigated. Graphites specially prepared with these two binders were used for the experiments. Measured thermal conductivities were treated in terms of a two-component system, and the binder thermal conductivities were calculated. Both binder residues showed increased thermal conductivity with increased heat treatment temperature
Directory of Open Access Journals (Sweden)
Ghania Henini
2012-01-01
Full Text Available We present the thermal behavior of a batch reactor to jacket equipped with a monofluid heating/cooling system. Heating and cooling are provided respectively by an electrical resistance and two plate heat exchangers. The control of the temperature of the reaction is based on the supervision system. This strategy of management of the thermal devices is based on the usage of the thermal flux as manipulated variable. The modulation of the monofluid temperature by acting on the heating power or on the opening degrees of an air-to-open valve that delivers the monofluid to heat exchanger. The study shows that the application of this method for the conduct of the pilot reactor gives good results in simulation and that taking into account the dynamics of the various apparatuses greatly improves ride quality of conduct. In addition thermal control of an exothermic reaction (mononitration shows that the consideration of heat generated in the model representation improve the results by elimination any overshooting of the set-point temperature.
International Nuclear Information System (INIS)
Terres, H; Lizardi, A; Chávez, S; López, R; Vaca, M
2017-01-01
In this work, an exergy evaluation to determine the energy availability across to glass covers, place where the solar radiation enters toward a solar cooker box-type is done. Considering the heating process of water, the energy not used is quantified by means of exergy. The results allow identifying the glasses in the cover as the zone where the solar cooker could be improved. The conduction heat transfer losses for the glasses is most big than 75%. Because the values for the conduction heat losses are around 90%, which are very important, this allows to identify the cover glass as the area where improvements could be made in this type of solar cookers. (paper)
International Nuclear Information System (INIS)
Findikakis, A.
2004-01-01
The purpose of this report is to provide heat capacity values for the host and surrounding rock layers for the waste repository at Yucca Mountain. The heat capacity representations provided by this analysis are used in unsaturated zone (UZ) flow, transport, and coupled processes numerical modeling activities, and in thermal analyses as part of the design of the repository to support the license application. Among the reports that use the heat capacity values estimated in this report are the ''Multiscale Thermohydrologic Model'' report, the ''Drift Degradation Analysis'' report, the ''Ventilation Model and Analysis Report, the Igneous Intrusion Impacts on Waste Packages and Waste Forms'' report, the ''Dike/Drift Interactions report, the Drift-Scale Coupled Processes (DST and TH Seepage) Models'' report, and the ''In-Drift Natural Convection and Condensation'' report. The specific objective of this study is to determine the rock-grain and rock-mass heat capacities for the geologic stratigraphy identified in the ''Mineralogic Model (MM3.0) Report'' (BSC 2004 [DIRS 170031], Table 1-1). This report provides estimates of the heat capacity for all stratigraphic layers except the Paleozoic, for which the mineralogic abundance data required to estimate the heat capacity are not available. The temperature range of interest in this analysis is 25 C to 325 C. This interval is broken into three separate temperature sub-intervals: 25 C to 95 C, 95 C to 114 C, and 114 C to 325 C, which correspond to the preboiling, trans-boiling, and postboiling regimes. Heat capacity is defined as the amount of energy required to raise the temperature of a unit mass of material by one degree (Nimick and Connolly 1991 [DIRS 100690], p. 5). The rock-grain heat capacity is defined as the heat capacity of the rock solids (minerals), and does not include the effect of water that exists in the rock pores. By comparison, the rock-mass heat capacity considers the heat capacity of both solids and pore
Improvements in or relating to devices for conducting excess heat away from heat sources
International Nuclear Information System (INIS)
Cooke-Yarborough, E.H.
1976-01-01
Reference is made to radioisotope powered heat engines. Should such an engine stop working for any reason the radioisotope heat source will continue to generate heat, and this may cause overheating and possible damage to the engine as well as the heat source. A device is described for conducting excess heat from the heat source to a heat sink but which in normal operation of the engine will impede heat conduction and so reduce thermal losses. The device may be used to support and/or locate the heat source. Constructional and operational details are given. (U.K.)
Heat conduction errors and time lag in cryogenic thermometer installations
Warshawsky, I.
1973-01-01
Installation practices are recommended that will increase rate of heat exchange between the thermometric sensing element and the cryogenic fluid and that will reduce the rate of undesired heat transfer to higher-temperature objects. Formulas and numerical data are given that help to estimate the magnitude of heat-conduction errors and of time lag in response.
Anisotropy of heat conduction in Mo/Si multilayers
International Nuclear Information System (INIS)
Medvedev, V. V.; Yakshin, A. E.; Kruijs, R. W. E. van de; Bijkerk, F.; Yang, J.; Schmidt, A. J.; Zoethout, E.
2015-01-01
This paper reports on the studies of anisotropic heat conduction phenomena in Mo/Si multilayers with individual layer thicknesses selected to be smaller than the mean free path of heat carriers. We applied the frequency-domain thermoreflectance technique to characterize the thermal conductivity tensor. While the mechanisms of the cross-plane heat conduction were studied in detail previously, here we focus on the in-plane heat conduction. To analyze the relative contribution of electron transport to the in-plane heat conduction, we applied sheet-resistance measurements. Results of Mo/Si multilayers with variable thickness of the Mo layers indicate that the net in-plane thermal conductivity depends on the microstructure of the Mo layers
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 < 0.001) and the heat conduction depth correlation analysis (intraclass correlation coefficient: 0.93, p < 0.001) showed statistically significant high correlations between the porcine burn wound and our model. Our model showed good correlation with porcine skin burn injury and replicated its heat conduction patterns. © 2014 by the Wound Healing Society.
Nonsteady heat conduction code with radiation boundary conditions
International Nuclear Information System (INIS)
Fillo, J.A.; Benenati, R.; Powell, J.
1975-01-01
A heat-transfer model for studying the temperature build-up in graphite blankets for fusion reactors is presented. In essence, the computer code developed is for two-dimensional, nonsteady heat conduction in heterogeneous, anisotropic solids with nonuniform internal heating. Thermal radiation as well as bremsstrahlung radiation boundary conditions are included. Numerical calculations are performed for two design options by varying the wall loading, bremsstrahlung, surface layer thickness and thermal conductivity, blanket dimensions, time step and grid size. (auth)
Energy Technology Data Exchange (ETDEWEB)
Hussain, A.K.; Hussain, T.A.; Shahad, Haroun A.K. [Babylon Univ., Dept. of Mechanical Engineering, Babylon (Iraq)
2003-05-01
The problem of non-equilibrium heat conduction in a semi-infinite medium subjected to a step change in temperature is analyzed thermodynamically using the extended irreversible thermodynamic approach. The results show clearly the wave nature of the dimensionless temperature distribution, Stanton number and the dimensionless entropy change profiles. The non-equilibrium profiles approach the equilibrium profiles as the speed of wave propagation is increased. The results also show that the non-equilibrium temperature is higher than the equilibrium temperature but the difference decreases as the wave propagation speed increases. (Author)
Quantum-limited heat conduction over macroscopic distances
Partanen, Matti; Tan, Kuan Yen; Govenius, Joonas; Lake, Russell E.; Mäkelä, Miika K.; Tanttu, Tuomo; Möttönen, Mikko
2016-05-01
The emerging quantum technological apparatuses, such as the quantum computer, call for extreme performance in thermal engineering. Cold distant heat sinks are needed for the quantized electric degrees of freedom owing to the increasing packaging density and heat dissipation. Importantly, quantum mechanics sets a fundamental upper limit for the flow of information and heat, which is quantified by the quantum of thermal conductance. However, the short distance between the heat-exchanging bodies in the previous experiments hinders their applicability in quantum technology. Here, we present experimental observations of quantum-limited heat conduction over macroscopic distances extending to a metre. We achieved this improvement of four orders of magnitude in the distance by utilizing microwave photons travelling in superconducting transmission lines. Thus, it seems that quantum-limited heat conduction has no fundamental distance cutoff. This work establishes the integration of normal-metal components into the framework of circuit quantum electrodynamics, which provides a basis for the superconducting quantum computer. Especially, our results facilitate remote cooling of nanoelectronic devices using faraway in situ-tunable heat sinks. Furthermore, quantum-limited heat conduction is important in contemporary thermodynamics. Here, the long distance may lead to ultimately efficient mesoscopic heat engines with promising practical applications.
Heat pipes with variable thermal conductance property for space applications
Energy Technology Data Exchange (ETDEWEB)
Kravets, V.; Alekseik, Ye.; Alekseik, O.; Khairnasov, S. [National Technical University of Ukraine, Kyiv (Ukraine); Baturkin, V.; Ho, T. [Explorationssysteme RY-ES, Bremen (Germany); Celotti, L. [Active Space Technologies GmbH, Berlin (Germany)
2017-06-15
The activities presented in this paper demonstrate a new approach to provide passive thermal control using heat pipes, as demonstrated on the electronic unit of DLR’s MASCOT lander, which embarked on the NEA sample return mission Hayabusa 2 (JAXA). The focus is on the development and testing of heat pipes with variable thermal conductance in a predetermined temperature range. These heat pipes act as thermal switches. Unlike standard gasloaded heat pipes and thermal-diode heat pipes construction of presented heat pipes does not include any additional elements. Copper heat pipes with metal fibrous wicks were chosen as baseline design. We obtained positive results by choosing the heat carrier and structural parameters of the wick (i.e., pore diameter, porosity, and permeability). The increase in the thermal conductivity of the heat pipes from 0.04 W/K to 2.1 W/K was observed in the temperature range between −20 °C and +55 °C. Moreover, the heat pipes transferred the predetermined power of not less than 10 W within the same temperature range. The heat pipes have been in flight since December 2014, and the supporting telemetry data were obtained in September 2015. The data showed the nominal operation of the thermal control system.
Želi, Velibor; Zorica, Dušan
2018-02-01
Generalization of the heat conduction equation is obtained by considering the system of equations consisting of the energy balance equation and fractional-order constitutive heat conduction law, assumed in the form of the distributed-order Cattaneo type. The Cauchy problem for system of energy balance equation and constitutive heat conduction law is treated analytically through Fourier and Laplace integral transform methods, as well as numerically by the method of finite differences through Adams-Bashforth and Grünwald-Letnikov schemes for approximation derivatives in temporal domain and leap frog scheme for spatial derivatives. Numerical examples, showing time evolution of temperature and heat flux spatial profiles, demonstrate applicability and good agreement of both methods in cases of multi-term and power-type distributed-order heat conduction laws.
Thermodynamical Approach for The Determination of The Speed of Heat Propagation in Heat Conduction
International Nuclear Information System (INIS)
Shnaid, I.
1998-01-01
In this work, a thermodynamical approach for the determination of the speed of heat propagation in a heat conductive body is developed. It employs equations of the First and the Second Laws of thermodynamics. The present analyses show that no time delay exists between time moments of heat extraction and heat supply. Therefore, an infinite speed of heat propagation is proven. It is also predicted that there is no time lag between heat flow and temperature difference. A theoretical approach straightforwardly leading from basic equations of the First and the Second Laws of thermodynamics to a kinetic equation describing heat conduction in an isotropic continuum is also developed. It is shown that Fourier's equation is a particular case of the derived kinetic equation. Based on the kinetic equation, the governing heat conduction equation is of tile parabolic type, thus, confirming that speed of heat propagation is infinite
Heat conduction boundary layers of condensed clumps in cooling flows
International Nuclear Information System (INIS)
Boehringer, H.; Fabian, A.C.
1989-01-01
The structure of heat conduction boundary layers of gaseous condensations embedded in the hot intergalactic gas in clusters of galaxies is investigated by means of steady, one-dimensional, hydrodynamic models. It is assumed that heat conduction is effective only on scales much smaller than the total region of the cooling flow. Models are calculated for an arbitrary scaling factor, accounting for the reduction in heat conduction efficiency compared to the classical Spitzer case. The results imply a lower limit to the size spectrum of the condensations. The enhancement of cooling in the ambient medium due to heat conduction losses is calculated for a range of clump parameters. The luminosity of several observable emission lines, the extreme ultraviolet (EUV) and soft X-ray emission spectrum, and the column density of some important ions are determined for the model boundary layers and compared with observations. (author)
Fractional Heat Conduction Models and Thermal Diffusivity Determination
Directory of Open Access Journals (Sweden)
Monika Žecová
2015-01-01
Full Text Available The contribution deals with the fractional heat conduction models and their use for determining thermal diffusivity. A brief historical overview of the authors who have dealt with the heat conduction equation is described in the introduction of the paper. The one-dimensional heat conduction models with using integer- and fractional-order derivatives are listed. Analytical and numerical methods of solution of the heat conduction models with using integer- and fractional-order derivatives are described. Individual methods have been implemented in MATLAB and the examples of simulations are listed. The proposal and experimental verification of the methods for determining thermal diffusivity using half-order derivative of temperature by time are listed at the conclusion of the paper.
An appraisal of computational techniques for transient heat conduction equation
International Nuclear Information System (INIS)
Kant, T.
1983-01-01
A semi-discretization procedure in which the ''space'' dimension is discretized by the finite element method is emphasized for transient problems. This standard methodology transforms the space-time partial differential equation (PDE) system into a set of ordinary differential equations (ODE) in time. Existing methods for transient heat conduction calculations are then reviewed. Existence of two general classes of time integration schemes- implicit and explicit is noted. Numerical stability characteristics of these two methods are elucidated. Implicit methods are noted to be numerically stable, permitting large time steps, but the cost per step is high. On the otherhand, explicit schemes are noted to be inexpensive per step, but small step size is required. Low computational cost of the explicit schemes make it very attractive for nonlinear problems. However, numerical stability considerations requiring use of very small time steps come in the way of its general adoption. Effectiveness of the fourth-order Runge-Kutta-Gill explicit integrator is then numerically evaluated. Finally we discuss some very recent works on development of computational algorithms which not only achieve unconditional stability, high accuracy and convergence but involve computations on matrix equations of elements only. This development is considered to be very significant in the light of our experience gained for simple heat conduction calculations. We conclude that such algorithms have the potential for further developments leading to development of economical methods for general transient analysis of complex physical systems. (orig.)
Fractional model for heat conduction in polar bear hairs
Directory of Open Access Journals (Sweden)
Wang Qing-Li
2012-01-01
Full Text Available Time-fractional differential equations can accurately describe heat conduction in fractal media, such as wool fibers, goose down and polar bear hair. The fractional complex transform is used to convert time-fractional heat conduction equations with the modified Riemann-Liouville derivative into ordinary differential equations, and exact solutions can be easily obtained. The solution process is straightforward and concise.
Constructal entransy dissipation minimization for 'volume-point' heat conduction
International Nuclear Information System (INIS)
Chen Lingen; Wei Shuhuan; Sun Fengrui
2008-01-01
The 'volume to point' heat conduction problem, which can be described as to how to determine the optimal distribution of high conductivity material through the given volume such that the heat generated at every point is transferred most effectively to its boundary, has became the focus of attention in the current constructal theory literature. In general, the minimization of the maximum temperature difference in the volume is taken as the optimization objective. A new physical quantity, entransy, has been identified as a basis for optimizing heat transfer processes in terms of the analogy between heat and electrical conduction recently. Heat transfer analyses show that the entransy of an object describes its heat transfer ability, just as the electrical energy in a capacitor describes its charge transfer ability. Entransy dissipation occurs during heat transfer processes, as a measure of the heat transfer irreversibility with the dissipation related thermal resistance. By taking equivalent thermal resistance (it corresponds to the mean temperature difference), which reflects the average heat conduction effect and is defined based on entransy dissipation, as an optimization objective, the 'volume to point' constructal problem is re-analysed and re-optimized in this paper. The constructal shape of the control volume with the best average heat conduction effect is deduced. For the elemental area and the first order construct assembly, when the thermal current density in the high conductive link is linear with the length, the optimized shapes of assembly based on the minimization of entransy dissipation are the same as those based on minimization of the maximum temperature difference, and the mean temperature difference is 2/3 of the maximum temperature difference. For the second and higher order construct assemblies, the thermal current densities in the high conductive link are not linear with the length, and the optimized shapes of the assembly based on the
Ballistic heat conduction and mass disorder in one dimension.
Ong, Zhun-Yong; Zhang, Gang
2014-08-20
It is well-known that in the disordered harmonic chain, heat conduction is subballistic and the thermal conductivity (κ) scales asymptotically as lim(L--> ∞) κ ∝ L(0.5) where L is the chain length. However, using the nonequilibrium Green's function (NEGF) method and analytical modelling, we show that there exists a critical crossover length scale (LC) below which ballistic heat conduction (κ ∝ L) can coexist with mass disorder. This ballistic-to-subballistic heat conduction crossover is connected to the exponential attenuation of the phonon transmittance function Ξ i.e. Ξ(ω, L) = exp[-L/λ(ω)], where λ is the frequency-dependent attenuation length. The crossover length can be determined from the minimum attenuation length, which depends on the maximum transmitted frequency. We numerically determine the dependence of the transmittance on frequency and mass composition as well as derive a closed form estimate, which agrees closely with the numerical results. For the length-dependent thermal conductance, we also derive a closed form expression which agrees closely with numerical results and reproduces the ballistic to subballistic thermal conduction crossover. This allows us to characterize the crossover in terms of changes in the length, mass composition and temperature dependence, and also to determine the conditions under which heat conduction enters the ballistic regime. We describe how the mass composition can be modified to increase ballistic heat conduction.
Ballistic heat conduction and mass disorder in one dimension
International Nuclear Information System (INIS)
Ong, Zhun-Yong; Zhang, Gang
2014-01-01
It is well-known that in the disordered harmonic chain, heat conduction is subballistic and the thermal conductivity (κ) scales asymptotically as lim L→∞ κ∝L 0.5 where L is the chain length. However, using the nonequilibrium Green's function (NEGF) method and analytical modelling, we show that there exists a critical crossover length scale (L C ) below which ballistic heat conduction (κ∝L) can coexist with mass disorder. This ballistic-to-subballistic heat conduction crossover is connected to the exponential attenuation of the phonon transmittance function Ξ i.e. Ξ(ω, L) = exp[−L/λ(ω)], where λ is the frequency-dependent attenuation length. The crossover length can be determined from the minimum attenuation length, which depends on the maximum transmitted frequency. We numerically determine the dependence of the transmittance on frequency and mass composition as well as derive a closed form estimate, which agrees closely with the numerical results. For the length-dependent thermal conductance, we also derive a closed form expression which agrees closely with numerical results and reproduces the ballistic to subballistic thermal conduction crossover. This allows us to characterize the crossover in terms of changes in the length, mass composition and temperature dependence, and also to determine the conditions under which heat conduction enters the ballistic regime. We describe how the mass composition can be modified to increase ballistic heat conduction. (paper)
Optical sensor for heat conduction measurement in biological tissue
International Nuclear Information System (INIS)
Gutierrez-Arroyo, A; Sanchez-Perez, C; Aleman-Garcia, N
2013-01-01
This paper presents the design of a heat flux sensor using an optical fiber system to measure heat conduction in biological tissues. This optoelectronic device is based on the photothermal beam deflection of a laser beam travelling in an acrylic slab this deflection is measured with a fiber optic angle sensor. We measure heat conduction in biological samples with high repeatability and sensitivity enough to detect differences in tissues from three chicken organs. This technique could provide important information of vital organ function as well as the detect modifications due to degenerative diseases or physical damage caused by medications or therapies.
Mojahedi, Mahdi; Shekoohinejad, Hamidreza
2018-02-01
In this paper, temperature distribution in the continuous and pulsed end-pumped Nd:YAG rod crystal is determined using nonclassical and classical heat conduction theories. In order to find the temperature distribution in crystal, heat transfer differential equations of crystal with consideration of boundary conditions are derived based on non-Fourier's model and temperature distribution of the crystal is achieved by an analytical method. Then, by transferring non-Fourier differential equations to matrix equations, using finite element method, temperature and stress of every point of crystal are calculated in the time domain. According to the results, a comparison between classical and nonclassical theories is represented to investigate rupture power values. In continuous end pumping with equal input powers, non-Fourier theory predicts greater temperature and stress compared to Fourier theory. It also shows that with an increase in relaxation time, crystal rupture power decreases. Despite of these results, in single rectangular pulsed end-pumping condition, with an equal input power, Fourier theory indicates higher temperature and stress rather than non-Fourier theory. It is also observed that, when the relaxation time increases, maximum amounts of temperature and stress decrease.
High temperature heat capacities and electrical conductivities of boron carbides
International Nuclear Information System (INIS)
Matsui, Tsuneo; Arita, Yuri; Naito, Keiji; Imai, Hisashi
1991-01-01
The heat capacities and the electrical conductivities of B x C(x=3, 4, 5) were measured by means of direct heating pulse calorimetry in the temperature range from 300 to 1500 K. The heat capacities of B x C increased with increasing x value. This increase in the heat capacity is probably related to the change of the lattice vibration mode originated from the reduction of the stiffness of the intericosahedral chain accompanied with a change from C-B-C to C-B-B chains. A linear relationship between the logarithm of σT (σ is the electrical conductivity and T is the absolute temperature) of B x C and the reciprocal temperature was observed, indicating the presence of small polaron hopping as the predominant conduction mechanism. The electrical conductivity of B x C also increased with increasing x value (from 4 to 5) due to an increase of the polaron hopping of holes between carbon atoms at geometrically nonequivalent sites, since these nonequivalent sites of carbon atoms were considered to increase in either B 11 C icosahedra or in icosahedral chains with increasing x. The electrical conductivity of B 3 C was higher than that of B 4 C, which is probably due to the precipitation of high-conducting carbon. The thermal conductivity and the thermodynamic quantities of B 4 C were also determined precisely from the heat capacity value. (orig.)
Directory of Open Access Journals (Sweden)
S.N. Nnamchi
2010-01-01
Full Text Available Determination of the thermal conductivity and the specific heat capacity of neem seeds (Azadirachta indica A. Juss usingthe inverse method is the main subject of this work. One-dimensional formulation of heat conduction problem in a spherewas used. Finite difference method was adopted for the solution of the heat conduction problem. The thermal conductivityand the specific heat capacity were determined by least square method in conjunction with Levenberg-Marquardt algorithm.The results obtained compare favourably with those obtained experimentally. These results are useful in the analysis ofneem seeds drying and leaching processes.
Heat transfer in the thermal entrance region of a circular tube with axial heat conduction
International Nuclear Information System (INIS)
Zhang Changquan.
1985-01-01
This paper recounts the effects of axial heat conduction and convective boundary conditions on the heat transfer in the thermal entrance region of a circular tube under uniform flow, and the corresponding calculation is made. It will be profitable for the heat transfer studies on the pipe entrance region of low Prandtl number (liquid metal), or flow of low Peclet number. (author)
Irreversibility and Action of the Heat Conduction Process
Directory of Open Access Journals (Sweden)
Yu-Chao Hua
2018-03-01
Full Text Available Irreversibility (that is, the “one-sidedness” of time of a physical process can be characterized by using Lyapunov functions in the modern theory of stability. In this theoretical framework, entropy and its production rate have been generally regarded as Lyapunov functions in order to measure the irreversibility of various physical processes. In fact, the Lyapunov function is not always unique. In the represent work, a rigorous proof is given that the entransy and its dissipation rate can also serve as Lyapunov functions associated with the irreversibility of the heat conduction process without the conversion between heat and work. In addition, the variation of the entransy dissipation rate can lead to Fourier’s heat conduction law, while the entropy production rate cannot. This shows that the entransy dissipation rate, rather than the entropy production rate, is the unique action for the heat conduction process, and can be used to establish the finite element method for the approximate solution of heat conduction problems and the optimization of heat transfer processes.
International Nuclear Information System (INIS)
Kim, Yeung Chan
2016-01-01
A study on the measurement of critical heat flux using the transient inverse heat conduction method in spray cooling was performed. The inverse heat conduction method estimates the surface heat flux or temperature using a measured interior temperature history. The effects of the measuring time interval and location of temperature measurement on the measurement of critical heat flux were primarily investigated. The following results were obtained. The estimated critical heat flux decreased as the time interval of temperature measurement increased. Meanwhile, the effect of measurement location on critical heat flux was not significant. It was also found, from the experimental results, that the critical superheat increased as the measurement location of thermocouple neared the heat transfer surface.
Energy Technology Data Exchange (ETDEWEB)
Kim, Yeung Chan [Andong Nat’l Univ., Andong (Korea, Republic of)
2016-10-15
A study on the measurement of critical heat flux using the transient inverse heat conduction method in spray cooling was performed. The inverse heat conduction method estimates the surface heat flux or temperature using a measured interior temperature history. The effects of the measuring time interval and location of temperature measurement on the measurement of critical heat flux were primarily investigated. The following results were obtained. The estimated critical heat flux decreased as the time interval of temperature measurement increased. Meanwhile, the effect of measurement location on critical heat flux was not significant. It was also found, from the experimental results, that the critical superheat increased as the measurement location of thermocouple neared the heat transfer surface.
International Nuclear Information System (INIS)
Sarkar, J.; Bhattacharyya, Souvik; Ram Gopal, M.
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 sinks considering both internal and external irreversibilities. Expressions are obtained for optimum hot and cold side refrigerant temperatures, conductance and heat exchanger area ratios. The analytical results have been confirmed by those obtained from a detailed numerical simulation of actual ammonia based refrigeration and heat pump systems, and good agreement is observed. Such theoretical models can be employed as simple yet effective design guidelines for real systems as demonstrated here
Energy Technology Data Exchange (ETDEWEB)
Ranganayakulu, C. [Aeronautical Development Agency, Bangalore (India); Seetharamu, K.N. [School of Mechanical Engineering, Univ. of Southern Malaysia (KCP), Tronoh (Malaysia)
2000-05-01
An analysis of a crossflow plate-fin compact heat exchanger, accounting for the combined effect of two-dimensional longitudinal heat conduction through the exchanger wall and nonuniform inlet fluid flow distribution on both hot and cold fluid sides is carried out using a finite element method. Using the fluid flow maldistribution models, the exchanger effectiveness and its deterioration due to the combined effects of longitudinal heat conduction and flow nonuniformity are calculated for various design and operating conditions of the exchanger. It was found that the performance deteriorations are quite significant in some typical applications due to the combined effects of wall longitudinal heat conduction and inlet fluid flow nonuniformity on crossflow plate-fin heat exchanger. (orig.)
The effect of substrate conduction on boiling data on pin-fin heat sinks
International Nuclear Information System (INIS)
McNeil, D.A.; Raeisi, A.H.; Kew, P.A.; Hamed, R.S.
2015-01-01
Heat-transfer experiments for a copper heat sink containing pin-fins with a cross section of 1 mm by 1 mm and a height of 1 mm have been reported previously. The pin-fins were manufactured on a 5 mm thick, 50 mm square base plate in a square, in-line arrangement with a pitch of 2 mm. Data were produced while boiling R113 and water at atmospheric pressure. The heat sink was heated from below through a 5 mm thick aluminium wall by an electrical heating method that is normally associated with the uniform heat flux boundary condition. However, variations in the heat-transfer coefficient and the liquid subcooling interacted with the high thermal conductivity of the aluminium and copper materials to produce a near isothermal wall boundary condition. Thus, heat conduction effects had to be taken into account when determining the heat-flux distribution required in the analysis of the data. Many experiments like these have used the uniform heat-flux assumption to analyse the data. The discrepancies produced from this approach are explored. Single-phase flows across a pin-fin surface produce a reasonably uniform distribution of heat-transfer coefficient. However, the liquid temperature increases as it moves across the heat sink. This produces a non-uniform heat flux distribution at the solid–fluid interface. The uniform heat-flux assumption is shown to lead to errors of ±17% in the estimation of the heat-transfer coefficient. The original boiling flow experiments found that the water data were confined and that the majority of the R113 data were not. The confined and unconfined data are processed with the thermal conduction in the walls taken into account and by assuming a uniform heat flux at the solid–fluid interface. The uniform heat-flux distribution analysis for unconfined flows shows errors in the heat-transfer coefficient to be typically ±17%. Confined flows produce smaller errors, typically ±12%, close to the onset of nucleation. However, these damp out
Structure of fast shocks in the presence of heat conduction
International Nuclear Information System (INIS)
Tsai, C. L.; Chen, H. H.; Wu, B. H.; Lee, L. C.
2007-01-01
There are three types of magnetohydrodynamic (MHD) shocks: the fast shock, intermediate shock, and slow shock. The structure of slow shocks and intermediate shocks in the presence of heat conduction has been studied earlier [C. L. Tsai, R. H. Tsai, B. H. Wu, and L. C. Lee, Phys. Plasmas 9, 1185 (2002); C. L. Tsai, B. H. Wu, and L. C. Lee, Phys. Plasmas 12, 82501 (2005)]. Based on one-dimensional MHD numerical simulations with a heat conduction term, the evolution and structure of fast shocks are studied. The fast shock will form a foreshock in the presence of heat conduction. The foreshock is formed due to the heat flow from downstream to upstream and located in the immediate upstream of the main shock. In the steady state, the value of diffusion velocity V d in the foreshock is found to nearly equal the upstream convection velocity in the fast shock frame. It is found that the density jump across the main shock in high Mach number case can be much larger than 4 in the early simulation time. However the density jump will gradually evolve to a value smaller than 4 at steady state. By using the modified Rankine-Hugoniot relations with heat flux, the density jump across the fast shock is examined for various upstream parameters. The results show that the calculated density jump with heat flux is very close to the simulation value and the density jump can far exceed the maximum value of 4 without heat conduction. The structure of foreshock and main shock is also studied under different plasma parameters, such as the heat conductivity K 0 , the ratio of upstream plasma pressure to magnetic pressure β 1 , Alfven Mach number M A1 , and the angle θ 1 between shock normal and magnetic field. It is found that as the upstream shock parameters K 0 , β 1 , and M A1 increase or θ 1 decreases, the width of foreshock L d increases. The present results can be applied to fast shocks in the solar corona, solar wind, and magnetosphere, in which the heat conduction effects are
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.
An experiment in heat conduction using hollow cylinders
Energy Technology Data Exchange (ETDEWEB)
Ortuno, M; Marquez, A; Gallego, S; Neipp, C; Belendez, A, E-mail: a.belendez@ua.es [Departamento de Fisica, IngenierIa de Sistemas y TeorIa de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)
2011-07-15
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 analysed, and when the process reaches the steady state regime the thermal conductivity can be easily calculated. Several materials such as wood, plastic and metals are considered and the values of their thermal conductivities, obtained experimentally, are compared with those given in the reference list.
Wave propagation model of heat conduction and group speed
Zhang, Long; Zhang, Xiaomin; Peng, Song
2018-03-01
In view of the finite relaxation model of non-Fourier's law, the Cattaneo and Vernotte (CV) model and Fourier's law are presented in this work for comparing wave propagation modes. Independent variable translation is applied to solve the partial differential equation. Results show that the general form of the time spatial distribution of temperature for the three media comprises two solutions: those corresponding to the positive and negative logarithmic heating rates. The former shows that a group of heat waves whose spatial distribution follows the exponential function law propagates at a group speed; the speed of propagation is related to the logarithmic heating rate. The total speed of all the possible heat waves can be combined to form the group speed of the wave propagation. The latter indicates that the spatial distribution of temperature, which follows the exponential function law, decays with time. These features show that propagation accelerates when heated and decelerates when cooled. For the model media that follow Fourier's law and correspond to the positive heat rate of heat conduction, the propagation mode is also considered the propagation of a group of heat waves because the group speed has no upper bound. For the finite relaxation model with non-Fourier media, the interval of group speed is bounded and the maximum speed can be obtained when the logarithmic heating rate is exactly the reciprocal of relaxation time. And for the CV model with a non-Fourier medium, the interval of group speed is also bounded and the maximum value can be obtained when the logarithmic heating rate is infinite.
Finite element model for heat conduction in jointed rock masses
International Nuclear Information System (INIS)
Gartling, D.K.; Thomas, R.K.
1981-01-01
A computatonal procedure for simulating heat conduction in a fractured rock mass is proposed and illustrated in the present paper. The method makes use of a simple local model for conduction in the vicinity of a single open fracture. The distributions of fractures and fracture properties within the finite element model are based on a statistical representation of geologic field data. Fracture behavior is included in the finite element computation by locating local, discrete fractures at the element integration points
Heating and conduction in laser-produced plasmas
International Nuclear Information System (INIS)
Shay, H.D.; Zimmerman, G.B.; Nuckolls, J.H.
1974-01-01
A series of experiments conducted by G. McCall of LASL provides important clues concerning the electron distributions heated in the absorption of intense (less than or approximately equal to 10/sup lb/ W/cm 2 ) laser radiation and the thermal transport of energy. Presented here is a tentative interpretation of these experiments obtained from LASNEX calculations. (U.S.)
Non-Fourier Vernotte-Cattaneo numerical model for heat conduction in a BWR fuel rod
Energy Technology Data Exchange (ETDEWEB)
Espinosa-Martinez, E.G.; Vazquez-Rodriguez, A.; Varela-Ham, J.R.; Espinosa-Paredes, G., E-mail: gepe@xanum.uam.mx [Universidad Autonoma Metropolitana, Area de Ingenieria en Recursos Energeticos, Iztapalapa (Mexico)
2014-07-01
A fuel rod mathematical model based on transient heat conduction as constitutive Non-Fourier law for Light Water Reactors (LWRs) transient analysis is presented. The structure of the fuel pellet is affected due to high temperatures and irradiation, which eventually produce fracture or cracks. In principle the fractures are saturated of gas. Then, the Fourier law of the heat conduction is not strictly applicable to describe these phenomena, where the physical properties such as thermal conductivity, heat capacity and density correspond to a heterogeneous material due to gas, and therefore the thermal diffusion process due to molecular transport in the fuel pellet is affected. From the point of view of nuclear reactor safety analysis, the heat transfer from the fuel to the coolant is crucial and superheating of the wall can cause the cladding failure. In the classical theory of diffusion, the Fourier law of heat conduction is used to describe the relation between the heat flux vector and the temperature gradient assuming that the heat propagation speeds are infinite. The Non-Fourier approach presented in this work eliminates the assumption of an infinite thermal wave speed, therefore time-dependent heat sources were considered in the fuel rod heat transfer model. The numerical experiments in a BWR, show that the Non-Fourier approach is crucial in the pressurization transients such as turbine trip and reactor isolation. (author)
Non-Fourier Vernotte-Cattaneo numerical model for heat conduction in a BWR fuel rod
International Nuclear Information System (INIS)
Espinosa-Martinez, E.G.; Vazquez-Rodriguez, A.; Varela-Ham, J.R.; Espinosa-Paredes, G.
2014-01-01
A fuel rod mathematical model based on transient heat conduction as constitutive Non-Fourier law for Light Water Reactors (LWRs) transient analysis is presented. The structure of the fuel pellet is affected due to high temperatures and irradiation, which eventually produce fracture or cracks. In principle the fractures are saturated of gas. Then, the Fourier law of the heat conduction is not strictly applicable to describe these phenomena, where the physical properties such as thermal conductivity, heat capacity and density correspond to a heterogeneous material due to gas, and therefore the thermal diffusion process due to molecular transport in the fuel pellet is affected. From the point of view of nuclear reactor safety analysis, the heat transfer from the fuel to the coolant is crucial and superheating of the wall can cause the cladding failure. In the classical theory of diffusion, the Fourier law of heat conduction is used to describe the relation between the heat flux vector and the temperature gradient assuming that the heat propagation speeds are infinite. The Non-Fourier approach presented in this work eliminates the assumption of an infinite thermal wave speed, therefore time-dependent heat sources were considered in the fuel rod heat transfer model. The numerical experiments in a BWR, show that the Non-Fourier approach is crucial in the pressurization transients such as turbine trip and reactor isolation. (author)
Fractional single-phase-lagging heat conduction model for describing anomalous diffusion
Directory of Open Access Journals (Sweden)
T.N. Mishra
2016-03-01
Full Text Available The fractional single-phase-lagging (FSPL heat conduction model is obtained by combining scalar time fractional conservation equation to the single-phase-lagging (SPL heat conduction model. Based on the FSPL heat conduction model, anomalous diffusion within a finite thin film is investigated. The effect of different parameters on solution has been observed and studied the asymptotic behavior of the FSPL model. The analytical solution is obtained using Laplace transform method. The whole analysis is presented in dimensionless form. Numerical examples of particular interest have been studied and discussed in details.
International Nuclear Information System (INIS)
Peletier, Mark A.; Redig, Frank; Vafayi, Kiamars
2014-01-01
We consider three one-dimensional continuous-time Markov processes on a lattice, each of which models the conduction of heat: the family of Brownian Energy Processes with parameter m (BEP(m)), a Generalized Brownian Energy Process, and the Kipnis-Marchioro-Presutti (KMP) process. The hydrodynamic limit of each of these three processes is a parabolic equation, the linear heat equation in the case of the BEP(m) and the KMP, and a nonlinear heat equation for the Generalized Brownian Energy Process with parameter a (GBEP(a)). We prove the hydrodynamic limit rigorously for the BEP(m), and give a formal derivation for the GBEP(a). We then formally derive the pathwise large-deviation rate functional for the empirical measure of the three processes. These rate functionals imply gradient-flow structures for the limiting linear and nonlinear heat equations. We contrast these gradient-flow structures with those for processes describing the diffusion of mass, most importantly the class of Wasserstein gradient-flow systems. The linear and nonlinear heat-equation gradient-flow structures are each driven by entropy terms of the form −log ρ; they involve dissipation or mobility terms of order ρ 2 for the linear heat equation, and a nonlinear function of ρ for the nonlinear heat equation
One-dimensional nonlinear inverse heat conduction technique
International Nuclear Information System (INIS)
Hills, R.G.; Hensel, E.C. Jr.
1986-01-01
The one-dimensional nonlinear problem of heat conduction is considered. A noniterative space-marching finite-difference algorithm is developed to estimate the surface temperature and heat flux from temperature measurements at subsurface locations. The trade-off between resolution and variance of the estimates of the surface conditions is discussed quantitatively. The inverse algorithm is stabilized through the use of digital filters applied recursively. The effect of the filters on the resolution and variance of the surface estimates is quantified. Results are presented which indicate that the technique is capable of handling noisy measurement data
A multilevel method for conductive-radiative heat transfer
Energy Technology Data Exchange (ETDEWEB)
Banoczi, J.M.; Kelley, C.T. [North Carolina State Univ., Raleigh, NC (United States)
1996-12-31
We present a fast multilevel algorithm for the solution of a system of nonlinear integro-differential equations that model steady-state combined radiative-conductive heat transfer. The equations can be formulated as a compact fixed point problem with a fixed point map that requires both a solution of the linear transport equation and the linear heat equation for its evaluation. We use fast transport solvers developed by the second author, to construct an efficient evaluation of the fixed point map and then apply the Atkinson-Brakhage, method, with Newton-GMRES as the coarse mesh solver, to the full nonlinear system.
International Nuclear Information System (INIS)
Satoh, Isao; Kurosaki, Yasuo
1987-01-01
This paper dealt with the numerical calculations of the heat transfer of a tube partially heated on its circumference, considering two-dimensional heat conduction within the wall. The contribution of the unheated region of the tube wall to heat tranfer of the heated region was explained by the term of 'fin efficiency of psuedo-fin', it was clarified that the fin efficiency of the unheated region was little affected by the temperature difference between the inner and outer surfaces of the wall, and could be approximated by the fin efficency of a rectangular fin. Both the circumferential and radial heat conductions within the wall affected the temperature difference between the inner and outer surfaces of the heated region; however, the effect of the temperature difference on the circumferentially average Nusselt number could be obtained by using the analytical solution of radially one-dimensional heat conduction. Using these results, a diagram showing the effect of wall conduction on heat transfer, which is useful for designing the circumferentially nonuniformly heated coolant passages, was obtained. (author)
Thermal conductance of heat transfer interfaces for conductively cooled superconducting magnets
International Nuclear Information System (INIS)
Cooper, T.L.; Walters, J.D.; Fikse, T.H.
1996-01-01
Minimizing thermal resistances across interfaces is critical for efficient thermal performance of conductively cooled superconducting magnet systems. Thermal conductance measurements have been made for a flexible thermal coupling, designed to accommodate magnet-to-cryocooler and cryocooler-to-shield relative motion, and an interface incorporating Multilam designed as a sliding thermal connector for cryocoolers. Temperature changes were measured across each interface as a function of heat input. Thermal conductances have been calculated for each interface, and the impact of each interface on conductively cooled magnet systems will be discussed
Efficient formulation of the finite element method for heat conduction in solids
International Nuclear Information System (INIS)
Sandsmark, N.; Aamodt, B.; Medonos, S.
1977-01-01
The purpose of the paper is to describe efficient methods and computer programs for analysis of heat conduction problems related to design and control of components of nuclear power plants and similar structures where thermal problems are of interest. A short presentation of basic equations and the finite element formulation of three-dimensional stationary and transient heat conduction is given. The finite element types that are used are isoparametric hexahedrons with eight or twenty nodes. The use of consistent as well as diagonal capacity matrices is discussed. Reduction of the transient heat conduction problem may be accomplished by means of the 'master-slave' technique. Furthermore, the superelement technique is discussed for both stationary and transient heat conduction. For the solution of transient problems, the trapezoidal time integration scheme is used. The methods and principles outlined in the paper are materialized in a computer program, NV615, which is one of the application programs in the program system SESAM-69. A brief description is given of NV615. Furthermore, attention is given to combined heat conduction and subsequent thermal stress analysis. Data representing geometry, calculated temperature distribution etc. may be transferred automatically from the heat conduction program to stress analysis programs. As an example of practical application the temperature distribution versus time in a turbine wheel during start up is analysed. Thermal stresses are calculated at selected time instants
Heat conduction in graphene: experimental study and theoretical interpretation
International Nuclear Information System (INIS)
Ghosh, S; Nika, D L; Pokatilov, E P; Balandin, A A
2009-01-01
We review the results of our experimental investigation of heat conduction in suspended graphene and offer a theoretical interpretation of its extremely high thermal conductivity. The direct measurements of the thermal conductivity of graphene were performed using a non-contact optical technique and special calibration procedure with bulk graphite. The measured values were in the range of ∼3000-5300 W mK -1 near room temperature and depended on the lateral dimensions of graphene flakes. We explain the enhanced thermal conductivity of graphene as compared to that of bulk graphite basal planes by the two-dimensional nature of heat conduction in graphene over the whole range of phonon frequencies. Our calculations show that the intrinsic Umklapp-limited thermal conductivity of graphene grows with the increasing dimensions of graphene flakes and can exceed that of bulk graphite when the flake size is on the order of a few micrometers. The detailed theory, which includes the phonon-mode-dependent Gruneisen parameter and takes into account phonon scattering on graphene edges and point defects, gives numerical results that are in excellent agreement with the measurements for suspended graphene. Superior thermal properties of graphene are beneficial for all proposed graphene device applications.
Sobolev, S. L.
2018-02-01
Some analogies between different nonequilibrium heat conduction models, particularly random walk, the discrete variable model, and the Boltzmann transport equation with the single relaxation time approximation, have been discussed. We show that, under an assumption of a finite value of the heat carrier velocity, these models lead to the hyperbolic heat conduction equation and the modified Fourier law with relaxation term. Corresponding effective temperature and entropy have been introduced and analyzed. It has been demonstrated that the effective temperature, defined as a geometric mean of the kinetic temperatures of the heat carriers moving in opposite directions, acts as a criterion for thermalization and is a nonlinear function of the kinetic temperature and heat flux. It is shown that, under highly nonequilibrium conditions when the heat flux tends to its maximum possible value, the effective temperature, heat capacity, and local entropy go to zero even at a nonzero equilibrium temperature. This provides a possible generalization of the third law to nonequilibrium situations. Analogies and differences between the proposed effective temperature and some other definitions of a temperature in nonequilibrium state, particularly for active systems, disordered semiconductors under electric field, and adiabatic gas flow, have been shown and discussed. Illustrative examples of the behavior of the effective temperature and entropy during nonequilibrium heat conduction in a monatomic gas and a strong shockwave have been analyzed.
Heat conduction in diatomic chains with correlated disorder
Savin, Alexander V.; Zolotarevskiy, Vadim; Gendelman, Oleg V.
2017-01-01
The paper considers heat transport in diatomic one-dimensional lattices, containing equal amounts of particles with different masses. Ordering of the particles in the chain is governed by single correlation parameter - the probability for two neighboring particles to have the same mass. As this parameter grows from zero to unity, the structure of the chain varies from regular staggering chain to completely random configuration, and then - to very long clusters of particles with equal masses. Therefore, this correlation parameter allows a control of typical cluster size in the chain. In order to explore different regimes of the heat transport, two interatomic potentials are considered. The first one is an infinite potential wall, corresponding to instantaneous elastic collisions between the neighboring particles. In homogeneous chains such interaction leads to an anomalous heat transport. The other one is classical Lennard-Jones interatomic potential, which leads to a normal heat transport. The simulations demonstrate that the correlated disorder of the particle arrangement does not change the convergence properties of the heat conduction coefficient, but essentially modifies its value. For the collision potential, one observes essential growth of the coefficient for fixed chain length as the limit of large homogeneous clusters is approached. The thermal transport in these models remains superdiffusive. In the Lennard-Jones chain the effect of correlation appears to be not monotonous in the limit of low temperatures. This behavior stems from the competition between formation of long clusters mentioned above, and Anderson localization close to the staggering ordered state.
FDTD simulation of induction heating of conducting ceramic ware
Energy Technology Data Exchange (ETDEWEB)
White, M.J.; Iskander, M.F.; Bringhurst, S. [Univ. of Utah, Salt Lake City, UT (United States). Electrical Engineering Dept.
1996-12-31
Induction heating for the treatment of metals has been in commercial use since the mid 1960`s. Traditional advantages of induction heating over the convection or radiation processes include speed of heating, possible energy savings, and the ability to customize the coil design to optimize the heating process. In this paper the authors used the Finite-Difference Time-Domain (FDTD) technique to simulate and analyze the induction heating process for highly conducting ceramics. In order to analyze frequency effects, simulations were performed at 300 kHz, 2 MHz, and 25 MHz. It is found that at higher frequencies coils with a pitch of 2 in. or greater became capacitive and generate a large, axial, electric-field component. This new axial electric field, in addition to the normally encountered azimuthal field, causes an improvement in the uniformity of the power deposition in the ceramic sample. If the sample occupies a large portion of the coil, uniformity may also be improved by using a variable-pitch coil, or by extending the length of the coil a few turns beyond the length of the sample. In a production-line arrangement, where multiple samples are placed inside the coil, it is shown that maximum uniformity is achieved when the samples are placed coaxially.
Heat conduction in diatomic chains with correlated disorder
Energy Technology Data Exchange (ETDEWEB)
Savin, Alexander V., E-mail: asavin@center.chph.ras.ru [Semenov Institute of Chemical Physics, Russian Academy of Sciences, 4 Kosygin str., 119991 Moscow (Russian Federation); Zolotarevskiy, Vadim; Gendelman, Oleg V. [Faculty of Mechanical Engineering, Technion – Israel Institute of Technology, Haifa 32000 (Israel)
2017-01-23
The paper considers heat transport in diatomic one-dimensional lattices, containing equal amounts of particles with different masses. Ordering of the particles in the chain is governed by single correlation parameter – the probability for two neighboring particles to have the same mass. As this parameter grows from zero to unity, the structure of the chain varies from regular staggering chain to completely random configuration, and then – to very long clusters of particles with equal masses. Therefore, this correlation parameter allows a control of typical cluster size in the chain. In order to explore different regimes of the heat transport, two interatomic potentials are considered. The first one is an infinite potential wall, corresponding to instantaneous elastic collisions between the neighboring particles. In homogeneous chains such interaction leads to an anomalous heat transport. The other one is classical Lennard–Jones interatomic potential, which leads to a normal heat transport. The simulations demonstrate that the correlated disorder of the particle arrangement does not change the convergence properties of the heat conduction coefficient, but essentially modifies its value. For the collision potential, one observes essential growth of the coefficient for fixed chain length as the limit of large homogeneous clusters is approached. The thermal transport in these models remains superdiffusive. In the Lennard–Jones chain the effect of correlation appears to be not monotonous in the limit of low temperatures. This behavior stems from the competition between formation of long clusters mentioned above, and Anderson localization close to the staggering ordered state.
Nonlinear Thermal Instability in Compressible Viscous Flows Without Heat Conductivity
Jiang, Fei
2018-04-01
We investigate the thermal instability of a smooth equilibrium state, in which the density function satisfies Schwarzschild's (instability) condition, to a compressible heat-conducting viscous flow without heat conductivity in the presence of a uniform gravitational field in a three-dimensional bounded domain. We show that the equilibrium state is linearly unstable by a modified variational method. Then, based on the constructed linearly unstable solutions and a local well-posedness result of classical solutions to the original nonlinear problem, we further construct the initial data of linearly unstable solutions to be the one of the original nonlinear problem, and establish an appropriate energy estimate of Gronwall-type. With the help of the established energy estimate, we finally show that the equilibrium state is nonlinearly unstable in the sense of Hadamard by a careful bootstrap instability argument.
Mars Exploration Rover Heat Shield Recontact Analysis
Raiszadeh, Behzad; Desai, Prasun N.; Michelltree, Robert
2011-01-01
The twin Mars Exploration Rover missions landed successfully on Mars surface in January of 2004. Both missions used a parachute system to slow the rover s descent rate from supersonic to subsonic speeds. Shortly after parachute deployment, the heat shield, which protected the rover during the hypersonic entry phase of the mission, was jettisoned using push-off springs. Mission designers were concerned about the heat shield recontacting the lander after separation, so a separation analysis was conducted to quantify risks. This analysis was used to choose a proper heat shield ballast mass to ensure successful separation with low probability of recontact. This paper presents the details of such an analysis, its assumptions, and the results. During both landings, the radar was able to lock on to the heat shield, measuring its distance, as it descended away from the lander. This data is presented and is used to validate the heat shield separation/recontact analysis.
Colliding winds: Interaction regions with strong heat conduction
International Nuclear Information System (INIS)
Imamura, J.N.; Chevalier, R.A.
1984-01-01
The interaction of fast stellar wind with a slower wind from previous mass loss gives rise to a region of hot, shocked gas. We obtain self-similar solutions for the interaction region under the assumptions of constant mass loss rate and wind velocity for the two winds, conversion of energy in the shock region, and either isothermal electrons and adiabatic ions or isothermal electrons ad ions in the shocked region. The isothermal assumption is intended to show the effects of strog heat conduction. The solutions have no heat conduction through the shock waves and assume that the electron and ion temperatures are equilibriated in the shock waves. The one-temperature isothermal solutions have nearly constant density through the shocked region, while the two-temperature solutions are intermediate between the one-temperature adiabatic and isothermal solutions. In the two-temperature solutions, the ion temperature goes to zero at the point where the gas comoves with the shocked region and the density peaks at this point. The solution may qualitatively describe the effects of heat conduction on interaction regions in the solar wind. It will be important to determine whether the assumption of no thermal waves outside the shocked region applies to shock waves in the solar wind
Homogenization of a Conductive-Radiative Heat Transfer Problem
Directory of Open Access Journals (Sweden)
Habibi Zakaria
2012-04-01
Full Text Available This paper focuses on the contribution of the second order corrector in periodic homogenization applied to a conductive-radiative heat transfer problem. Especially, for a heat conduction problem in a periodically perforated domain with a non-local boundary condition modelling the radiative heat transfer, if this model contains an oscillating thermal source and a thermal exchange with the perforations, the second order corrector helps us to model the gradients which appear between the source area and the perforations. Ce papier est consacré à montrer l’influence du correcteur de second ordre en homogénéisation périodique. Dans l’homogénéisation d’un problème de conduction rayonnement dans un domaine périodiquement perforé par plusieurs trous, on peut voir une contribution non négligeable de ce correcteur lors de la présence d’une source thermique oscillante et d’un échange thermique dans les perforations. Ce correcteur nous permet de modéliser les gradients qui apparaissent entre la zone de la source thermique et les perforations.
Impact of the Flameholder Heat Conductivity on Combustion Instability Characteristics
Hong, Seunghyuck
2012-06-11
In this paper, we investigate the impact of heat transfer between the flame and the flame-holder on the dynamic stability characteristics in a 50-kW backward facing step combustor. We conducted tests where we use a backward step block made of two different materials: ceramic and stainless steel whose thermal conductivities are 1.06 and 12 W/m/K, respectively. A set of experiments was conducted using a propane/air mixture at Re = 6500 for the inlet temperature of 300 - 500 K at atmospheric pressure. We measure the dynamic pressure and flame chemiluminescence to examine distinct stability characteristics using each flame-holder material over a range of operating conditions. We find that for tests with a flame-holder made of ceramic, the onset of instability is significantly delayed in time and, for certain operating conditions, disappears altogether. Stated differently, for certain operating conditions, the combustor can be stabilized by reducing the thermal conductivity of the flame-holder. As the thermal conductivity of the flame-holder increases, the combustor becomes increasingly unstable over a range of operating conditions. These results imply that the dynamic stability characteristics depend strongly on the heat transfer between the flame and the combustor wall near the flame anchoring region. Copyright © 2012 by ASME.
International Nuclear Information System (INIS)
Senve, Vinay; Narasimham, G.S.V.L.
2011-01-01
Highlights: → Transport processes in isothermal hexagonal sheath with 19 heat generating rods is studied. → Correlation is given to predict the maximum temperature considering all transport processes. → Effective thermal conductivity of rod bundle can be obtained using max temperature. → Data on the critical Rayleigh numbers for p/d ratios of 1.1-2.0 is presented. → Radiative heat transfer contributes to heat dissipation of 38-65% of total heat. - Abstract: A numerical study of conjugate natural convection and surface radiation in a horizontal hexagonal sheath housing 19 solid heat generating rods with cladding and argon as the fill gas, is performed. The natural convection in the sheath is driven by the volumetric heat generation in the solid rods. The problem is solved using the FLUENT CFD code. A correlation is obtained to predict the maximum temperature in the rod bundle for different pitch-to-diameter ratios and heat generating rates. The effective thermal conductivity is related to the heat generation rate, maximum temperature and the sheath temperature. Results are presented for the dimensionless maximum temperature, Rayleigh number and the contribution of radiation with changing emissivity, total wattage and the pitch-to-diameter ratio. In the simulation of a larger system that contains a rod bundle, the effective thermal conductivity facilitates simplified modelling of the rod bundle by treating it as a solid of effective thermal conductivity. The parametric studies revealed that the contribution of radiation can be 38-65% of the total heat generation, for the parameter ranges chosen. Data for critical Rayleigh number above which natural convection comes into effect is also presented.
Sodium Variable Conductance Heat Pipe for Radioisotope Stirling Systems
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.
Baston, Daniel P.; Kueper, Bernard H.
2009-02-01
A two-dimensional semi-analytical heat transfer solution is developed and a parameter sensitivity analysis performed to determine the relative importance of rock material properties (density, thermal conductivity and heat capacity) and hydrogeological properties (hydraulic gradient, fracture aperture, fracture spacing) on the ability to heat fractured rock using thermal conductive heating (TCH). The solution is developed using a Green's function approach in which an integral equation is constructed for the temperature in the fracture. Subsurface temperature distributions are far more sensitive to hydrogeological properties than material properties. The bulk ground water influx ( q) can provide a good estimate of the extent of influx cooling when influx is low to moderate, allowing the prediction of temperatures during heating without specific knowledge of the aperture and spacing of fractures. Target temperatures may not be reached or may be significantly delayed when the groundwater influx is large.
Heat conduction in multifunctional nanotrusses studied using Boltzmann transport equation
International Nuclear Information System (INIS)
Dou, Nicholas G.; Minnich, Austin J.
2016-01-01
Materials that possess low density, low thermal conductivity, and high stiffness are desirable for engineering applications, but most materials cannot realize these properties simultaneously due to the coupling between them. Nanotrusses, which consist of hollow nanoscale beams architected into a periodic truss structure, can potentially break these couplings due to their lattice architecture and nanoscale features. In this work, we study heat conduction in the exact nanotruss geometry by solving the frequency-dependent Boltzmann transport equation using a variance-reduced Monte Carlo algorithm. We show that their thermal conductivity can be described with only two parameters, solid fraction and wall thickness. Our simulations predict that nanotrusses can realize unique combinations of mechanical and thermal properties that are challenging to achieve in typical materials
International Nuclear Information System (INIS)
Huang, C.-H.; Wu, H.-H.
2006-01-01
In the present study an inverse hyperbolic heat conduction problem is solved by the conjugate gradient method (CGM) in estimating the unknown boundary heat flux based on the boundary temperature measurements. Results obtained in this inverse problem will be justified based on the numerical experiments where three different heat flux distributions are to be determined. Results show that the inverse solutions can always be obtained with any arbitrary initial guesses of the boundary heat flux. Moreover, the drawbacks of the previous study for this similar inverse problem, such as (1) the inverse solution has phase error and (2) the inverse solution is sensitive to measurement error, can be avoided in the present algorithm. Finally, it is concluded that accurate boundary heat flux can be estimated in this study
On parameterization of heat conduction in coupled soil water and heat flow modelling
Czech Academy of Sciences Publication Activity Database
Votrubová, J.; Dohnal, M.; Vogel, T.; Tesař, Miroslav
2012-01-01
Roč. 7, č. 4 (2012), s. 125-137 ISSN 1801-5395 R&D Projects: GA ČR GA205/08/1174 Institutional research plan: CEZ:AV0Z20600510 Keywords : advective heat flux * dual-permeability model * soil heat transport * soil thermal conductivity * surface energy balance Subject RIV: DA - Hydrology ; Limnology Impact factor: 0.333, year: 2012
Effect of Cattaneo-Christov heat flux on Jeffrey fluid flow with variable thermal conductivity
Hayat, Tasawar; Javed, Mehwish; Imtiaz, Maria; Alsaedi, Ahmed
2018-03-01
This paper presents the study of Jeffrey fluid flow by a rotating disk with variable thickness. Energy equation is constructed by using Cattaneo-Christov heat flux model with variable thermal conductivity. A system of equations governing the model is obtained by applying boundary layer approximation. Resulting nonlinear partial differential system is transformed to ordinary differential system. Homotopy concept leads to the convergent solutions development. Graphical analysis for velocities and temperature is made to examine the influence of different involved parameters. Thermal relaxation time parameter signifies that temperature for Fourier's heat law is more than Cattaneo-Christov heat flux. A constitutional analysis is made for skin friction coefficient and heat transfer rate. Effects of Prandtl number on temperature distribution and heat transfer rate are scrutinized. It is observed that larger Reynolds number gives illustrious temperature distribution.
Coupled heat conduction and thermal stress formulation using explicit integration
International Nuclear Information System (INIS)
Marchertas, A.H.; Kulak, R.F.
1982-06-01
The formulation needed for the conductance of heat by means of explicit integration is presented. The implementation of these expressions into a transient structural code, which is also based on explicit temporal integration, is described. Comparisons of theoretical results with code predictions are given both for one-dimensional and two-dimensional problems. The coupled thermal and structural solution of a concrete crucible, when subjected to a sudden temperature increase, shows the history of cracking. The extent of cracking is compared with experimental data
Reactor fuel element heat conduction via numerical Laplace transform inversion
International Nuclear Information System (INIS)
Ganapol, Barry D.; Furfaro, Roberto
2001-01-01
A newly developed numerical Laplace transform inversion (NLTI) will be presented to determine the transient temperature distribution within a nuclear reactor fuel element. The NLTI considered in this presentation has evolved to its present state over the past 10 years of application. The methodology adopted is one that relies on acceleration of the convergence of an infinite series towards its limit. The inversion will be applied to the prediction of the transient temperature distribution within an MTR type nuclear fuel element through a novel formulation of the solution to the transformed heat conduction equation. (author)
Reactor fuel element heat conduction via numerical Laplace transform inversion
Energy Technology Data Exchange (ETDEWEB)
Ganapol, Barry D.; Furfaro, Roberto [University of Arizona, Tucson, AZ (United States). Dept. of Aerospace and Mechanical Engineering], e-mail: ganapol@cowboy.ame.arizona.edu
2001-07-01
A newly developed numerical Laplace transform inversion (NLTI) will be presented to determine the transient temperature distribution within a nuclear reactor fuel element. The NLTI considered in this presentation has evolved to its present state over the past 10 years of application. The methodology adopted is one that relies on acceleration of the convergence of an infinite series towards its limit. The inversion will be applied to the prediction of the transient temperature distribution within an MTR type nuclear fuel element through a novel formulation of the solution to the transformed heat conduction equation. (author)
Conductive Cotton Fabrics for Motion Sensing and Heating Applications
Directory of Open Access Journals (Sweden)
Mengyun Yang
2018-05-01
Full Text Available Conductive cotton fabric was prepared by coating single-wall carbon nanotubes (CNTs on a knitted cotton fabric surface through a “dip-and-dry” method. The combination of CNTs and cotton fabric was analyzed using scanning electron microscopy (SEM and Raman scattering spectroscopy. The CNTs coating improved the mechanical properties of the fabric and imparted conductivity to the fabric. The electromechanical performance of the CNT-cotton fabric (CCF was evaluated. Strain sensors made from the CCF exhibited a large workable strain range (0~100%, fast response and great stability. Furthermore, CCF-based strain sensors was used to monitor the real-time human motions, such as standing, walking, running, squatting and bending of finger and elbow. The CCF also exhibited strong electric heating effect. The flexible strain sensors and electric heaters made from CCF have potential applications in wearable electronic devices and cold weather conditions.
International Nuclear Information System (INIS)
Robinson, J.A.; Windebank, S.R.
1988-01-01
Condensation heat transfer coefficients have been measured in a pressurised chamber containing a mixture of saturated steam and air. They were determined as a function of the air-steam ratio in nominally stagnant conditions. The effect of pressure is assessed and preliminary measurements with a forced convective component of velocity are presented. A novel measurement technique was adopted, namely to use a vertical heat pipe whose conductance could easily be varied. It transported heat from an evaporator located inside the chamber to a condenser section outside, at which the heat flow was measured. Heat flux at the evaporator could then be determined and a condensation heat transfer coefficient derived. The range of coefficients covered was from 150 W/m 2 0 K at high air-steam ratios to 20,000 W/m 2 0 K in pure steam. Results show that increasing either total pressure or velocity enhances condensation heat transfer over the range of air/steam ratios considered. (author)
International Nuclear Information System (INIS)
Kazakov, E.K.; Chernukhina, G.M.
1974-01-01
Results of calculation of the temperature distribution in an annular fuel element at transient thermal conductivity and heat release values are given. The calculation has been carried out by the mesh technique with the third-order boundary conditions for the inner surface assumed and with heat fluxes and temperatures at the zone boundaries to be equal. Three variants of solving the problem of a stationary temperature field are considered for failed fuel elements with clad flaking or cracks. The results obtained show the nonuniformity of the fuel element temperature field to depend strongly on the perturbation parameter at transient thermal conductivity and heat release values. In case of can flaking at a short length, the core temperature rises quickly after flaking. While evaluating superheating, one should take into account the symmetry of can flaking [ru
Magnetohydrodynamic flow and heat transfer around a heated cylinder of arbitrary conductivity
Tassone, A.; Nobili, M.; Caruso, G.
2017-11-01
The interaction of the liquid metal with the plasma confinement magnetic field constitutes a challenge for the design of fusion reactor blankets, due to the arise of MHD effects: increased pressure drops, heat transfer suppression, etc. To overcome these issues, a dielectric fluid can be employed as coolant for the breeding zone. A typical configuration involves pipes transverse to the liquid metal flow direction. This numerical study is conducted to assess the influence of pipe conductivity on the MHD flow and heat transfer. The CFD code ANSYS CFX was employed for this purpose. The fluid is assumed to be bounded by rectangular walls with non-uniform thickness and subject to a skewed magnetic field with the main component aligned with the cylinder axis. The simulations were restricted to Re = (20; 40) and M = (10; 50). Three different scenarios for the obstacle were considered: perfectly insulating, finite conductivity and perfectly conducting. The electrical conductivity was found to affect the channel pressure penalty due to the obstacle insertion only for M = 10 and just for the two limiting cases. A general increment of the heat transfer with M was found due to the tendency of the magnetic field to equalize the flow rate between the sub-channels individuated by the pipe. The best results were obtained with the insulating pipe, due to the reduced electromagnetic drag. The generation of counter-rotating vortices close to the lateral duct walls was observed for M = 50 and perfectly conducting pipe as a result of the modified currents distribution.
Low-temperature specific heat and thermal conductivity of silica aerogels
DEFF Research Database (Denmark)
Sleator, T.; Bernasconi, A.; Posselt, D.
1991-01-01
Specific-heat and thermal-conductivity measurements were made on a series of base-catalyzed silica aerogels at temperatures between 0.05 and 20 K. Evidence for a crossover between regimes of characteristically different excitations was observed. The data analysis indicates a "bump" in the density...
Numerical modeling of thermal conductive heating in fractured bedrock.
Baston, Daniel P; Falta, Ronald W; Kueper, Bernard H
2010-01-01
Numerical modeling was employed to study the performance of thermal conductive heating (TCH) in fractured shale under a variety of hydrogeological conditions. Model results show that groundwater flow in fractures does not significantly affect the minimum treatment zone temperature, except near the beginning of heating or when groundwater influx is high. However, fracture and rock matrix properties can significantly influence the time necessary to remove all liquid water (i.e., reach superheated steam conditions) in the treatment area. Low matrix permeability, high matrix porosity, and wide fracture spacing can contribute to boiling point elevation in the rock matrix. Consequently, knowledge of these properties is important for the estimation of treatment times. Because of the variability in boiling point throughout a fractured rock treatment zone and the absence of a well-defined constant temperature boiling plateau in the rock matrix, it may be difficult to monitor the progress of thermal treatment using temperature measurements alone. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.
Optimization method for an evolutional type inverse heat conduction problem
International Nuclear Information System (INIS)
Deng Zuicha; Yu Jianning; Yang Liu
2008-01-01
This paper deals with the determination of a pair (q, u) in the heat conduction equation u t -u xx +q(x,t)u=0, with initial and boundary conditions u(x,0)=u 0 (x), u x vertical bar x=0 =u x vertical bar x=1 =0, from the overspecified data u(x, t) = g(x, t). By the time semi-discrete scheme, the problem is transformed into a sequence of inverse problems in which the unknown coefficients are purely space dependent. Based on the optimal control framework, the existence, uniqueness and stability of the solution (q, u) are proved. A necessary condition which is a couple system of a parabolic equation and parabolic variational inequality is deduced
Optimization method for an evolutional type inverse heat conduction problem
Deng, Zui-Cha; Yu, Jian-Ning; Yang, Liu
2008-01-01
This paper deals with the determination of a pair (q, u) in the heat conduction equation u_t-u_{xx}+q(x,t)u=0, with initial and boundary conditions u(x,0)=u_0(x),\\qquad u_x|_{x=0}=u_x|_{x=1}=0, from the overspecified data u(x, t) = g(x, t). By the time semi-discrete scheme, the problem is transformed into a sequence of inverse problems in which the unknown coefficients are purely space dependent. Based on the optimal control framework, the existence, uniqueness and stability of the solution (q, u) are proved. A necessary condition which is a couple system of a parabolic equation and parabolic variational inequality is deduced.
Polovnikov, V. Yu.
2018-05-01
This paper presents the results of numerical analysis of thermal regimes and heat losses of underground channel heating systems under flooding conditions with the use of a convective-conductive heat transfer model with the example of the configuration of the heat pipeline widely used in the Russian Federation — a nonpassage ferroconcrete channel (crawlway) and pipelines insulated with mineral wool and a protective covering layer. It has been shown that convective motion of water in the channel cavity of the heat pipeline under flooding conditions has no marked effect on the intensification of heat losses. It has been established that for the case under consideration, heat losses of the heat pipeline under flooding conditions increase from 0.75 to 52.39% due to the sharp increase in the effective thermal characteristics of the covering layer and the heat insulator caused by their moistening.
High Thermal Conductivity Polymer Composites for Low Cost Heat Exchangers
Energy Technology Data Exchange (ETDEWEB)
None
2017-08-01
This factsheet describes a project that identified and evaluated commercially available and state-of-the-art polymer-based material options for manufacturing industrial and commercial non-metallic heat exchangers. A heat exchanger concept was also developed and its performance evaluated with heat transfer modeling tools.
SOLUTION OF TRANSIENT HEAT CONDUCTION PROBLEM BY THE FINITE ELEMENT METHOD
Directory of Open Access Journals (Sweden)
Süleyman TAŞGETİREN
1995-01-01
Full Text Available Determination of temperature distribution is generally the first step in the design of machine elements subjected to ubnormal temperatures in their service life and for selection of materials. During this heat transfer analysis, the boundary and enviromental conditions must be modeled realistically and the geometry must be well represented. A variety of materials deviating from simple constant property isotropic material to composit materials having different properties according to direction of reinforcements are to be analysed. Then, the finite element method finds a large application area due to its use of same notation in heat transfer analysis and mechanical analysis of elements. In this study, the general formulation of two dimensional transient heat conduction is developed and a sample solution is given for arectangular bar subjected to convection baundary condition.
Effect of heat treatment time on microstructure and electrical conductivity in LATP glass ceramics
Energy Technology Data Exchange (ETDEWEB)
Sonigra, Dhiren, E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in; Soman, Swati, E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in; Kulkarni, Ajit R., E-mail: somans@iitb.ac.in, E-mail: ajit.kulkarni@iitb.ac.in [Dept. of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai-400076 (India)
2014-04-24
Glass-ceramic is prepared by heat treatment of melt quenched 14Li{sub 2}O−9Al{sub 2}O{sub 3}−38TiO{sub 2}−39P{sub 2}O{sub 5} glass in the vicinity of crystallization temperature. Growth of ceramic phase is controlled by tuning heat treatment time at fixed temperature. Ceramic phase was identified to be LiTi{sub 2}(PO{sub 4}){sub 3} from X Ray Diffraction analysis. Microstructural evolution of this phase with hold time was observed under high resolution Scanning Electron Microscope. DC conductivity is observed to increase by 4-5 orders of magnitude in this glass-ceramic compared to parent glass. However, formation of pores and cracks with very large heat treatment time seem to hinder further increase of conductivity.
Memory behaviors of entropy production rates in heat conduction
Li, Shu-Nan; Cao, Bing-Yang
2018-02-01
Based on the relaxation time approximation and first-order expansion, memory behaviors in heat conduction are found between the macroscopic and Boltzmann-Gibbs-Shannon (BGS) entropy production rates with exponentially decaying memory kernels. In the frameworks of classical irreversible thermodynamics (CIT) and BGS statistical mechanics, the memory dependency on the integrated history is unidirectional, while for the extended irreversible thermodynamics (EIT) and BGS entropy production rates, the memory dependences are bidirectional and coexist with the linear terms. When macroscopic and microscopic relaxation times satisfy a specific relationship, the entropic memory dependences will be eliminated. There also exist initial effects in entropic memory behaviors, which decay exponentially. The second-order term are also discussed, which can be understood as the global non-equilibrium degree. The effects of the second-order term are consisted of three parts: memory dependency, initial value and linear term. The corresponding memory kernels are still exponential and the initial effects of the global non-equilibrium degree also decay exponentially.
Modeling the overall heat conductive and convective properties of open-cell graphite foam
International Nuclear Information System (INIS)
Tee, C C; Yu, N; Li, H
2008-01-01
This work develops analytic models on the overall thermal conductivity, pressure drop and overall convective heat transfer coefficient of graphite foam. The models study the relationship between the overall heat conductive and convective properties, and foam microstructure, temperature, foam surface friction characteristics and cooling fluid properties. The predicted thermal conductivity, convective heat transfer coefficient and pressure drop agree well with experimental data
A small-plane heat source method for measuring the thermal conductivities of anisotropic materials
Cheng, Liang; Yue, Kai; Wang, Jun; Zhang, Xinxin
2017-07-01
A new small-plane heat source method was proposed in this study to simultaneously measure the in-plane and cross-plane thermal conductivities of anisotropic insulating materials. In this method the size of the heat source element is smaller than the sample size and the boundary condition is thermal insulation due to no heat flux at the edge of the sample during the experiment. A three-dimensional model in a rectangular coordinate system was established to exactly describe the heat transfer process of the measurement system. Using the Laplace transform, variable separation, and Laplace inverse transform methods, the analytical solution of the temperature rise of the sample was derived. The temperature rises calculated by the analytical solution agree well with the results of numerical calculation. The result of the sensitivity analysis shows that the sensitivity coefficients of the estimated thermal conductivities are high and uncorrelated to each other. At room temperature and in a high-temperature environment, experimental measurements of anisotropic silica aerogel were carried out using the traditional one-dimensional plane heat source method and the proposed method, respectively. The results demonstrate that the measurement method developed in this study is effective and feasible for simultaneously obtaining the in-plane and cross-plane thermal conductivities of the anisotropic materials.
International Nuclear Information System (INIS)
Rice, Jarrett A.; Pokorny, Richard; Schweiger, Michael J.; Hrma, Pavel R.
2014-01-01
The heat conductivity (λ) and the thermal diffusivity (a) of reacting glass batch, or melter feed, control the heat flux into and within the cold cap, a layer of reacting material floating on the pool of molten glass in an all-electric continuous waste glass melter. After previously estimating λ of melter feed at temperatures up to 680 deg C, we focus in this work on the λ(T) function at T > 680 deg C, at which the feed material becomes foamy. We used a customized experimental setup consisting of a large cylindrical crucible with an assembly of thermocouples, which monitored the evolution of the temperature field while the crucible with feed was heated at a constant rate from room temperature up to 1100°C. Approximating measured temperature profiles by polynomial functions, we used the heat transfer equation to estimate the λ(T) approximation function, which we subsequently optimized using the finite-volume method combined with least-squares analysis. The heat conductivity increased as the temperature increased until the feed began to expand into foam, at which point the conductivity dropped. It began to increase again as the foam turned into a bubble-free glass melt. We discuss the implications of this behavior for the mathematical modeling of the cold cap
International Nuclear Information System (INIS)
Guzman-Vargas, L; Reyes-Ramirez, I; Sanchez, N
2005-01-01
In a recent paper (Santillan et al 2001 J. Phys. D: Appl. Phys. 34 2068-72) the local stability of a Curzon-Ahlborn-Novikov (CAN) engine with equal conductances in the coupling with thermal baths was analysed. In this work, we present a local stability analysis of an endoreversible engine operating at maximum power output, for common heat transfer laws, and for different heat conductances α and β, in the isothermal couplings of the working substance with the thermal sources T 1 and T 2 (T 1 > T 2 ). We find that the relaxation times, in the cases analysed here, are a function of α, β, the heat capacity C, T 1 and T 2 . Besides, the eigendirections in a phase portrait are also functions of τ = T 1 /T 2 and the ratio β/α. From these findings, phase portraits for the trajectories after a small perturbation over the steady-state values of internal temperatures are presented, for some significant situations. Finally, we discuss the local stability and energetic properties of the endoreversible CAN heat engine
Evaluation of heat transfer in acupuncture needles: convection and conduction approaches.
Tzou, Chieh-Han John; Yang, Tzyy-Yih; Chung, Ya-Chien
2015-04-01
Originating in ancient China, acupuncture using needles has been developed for thousands of years and has received attention for its reported medical remedies, such as pain relief and chronic disease treatment. Heat transfer through the needles, which might have effects on the biomechanism of acupuncture, providing a stimulus and regulating homeostasis, has never been studied. This article analyzes the significance of heat transfer through needles via convection and conduction, approached by means of computational analysis. The needle is a cylindrical body, and an axis symmetrical steady-state heat-transfer model that viscosity and static pressure was not applied. This article evaluates heat transfer via acupuncture needles by using five metal materials: silver, copper, brass, iron, and stainless steel. A silver needle of the type extensively applied in acupuncture can dissipate more than seven times as much heat as a stainless steel needle of the same type. Heat transfer through such a needle is significant, compared to natural body-energy consumption over a range of ambient temperatures. The mechanism by which heat flows in or out of the body through the needles may be crucial in the remedial efficacy of acupuncture. Copyright © 2015. Published by Elsevier B.V.
Heat and electrical conductivity of thermotropic liquid crystals
International Nuclear Information System (INIS)
Saidov, N.S.; Majidov, H.; Saburov, B.S.; Safarov, M.M.
1989-01-01
A results of thermal conduction and electrical conduction of chemo tropic liquid crystals are brought in this article. An installation dependence formula of thermal conduction investigating things from the electrical conduction and temperatures is constructed
Heat transfer capability analysis of heat pipe for space reactor
International Nuclear Information System (INIS)
Li Huaqi; Jiang Xinbiao; Chen Lixin; Yang Ning; Hu Pan; Ma Tengyue; Zhang Liang
2015-01-01
To insure the safety of space reactor power system with no single point failures, the reactor heat pipes must work below its heat transfer limits, thus when some pipes fail, the reactor could still be adequately cooled by neighbor heat pipes. Methods to analyze the reactor heat pipe's heat transfer limits were presented, and that for the prevailing capillary limit analysis was improved. The calculation was made on the lithium heat pipe in core of heat pipes segmented thermoelectric module converter (HP-STMC) space reactor power system (SRPS), potassium heat pipe as radiator of HP-STMC SRPS, and sodium heat pipe in core of scalable AMTEC integrated reactor space power system (SAIRS). It is shown that the prevailing capillary limits of the reactor lithium heat pipe and sodium heat pipe is 25.21 kW and 14.69 kW, providing a design margin >19.4% and >23.6%, respectively. The sonic limit of the reactor radiator potassium heat pipe is 7.88 kW, providing a design margin >43.2%. As the result of calculation, it is concluded that the main heat transfer limit of HP-STMC SRPS lithium heat pipe and SARIS sodium heat pipe is prevailing capillary limit, but the sonic limit for HP-STMC SRPS radiator potassium heat pipe. (authors)
Radiation and gas conduction heat transport across a helium dewer multilayer insulation system
Energy Technology Data Exchange (ETDEWEB)
Green, M.A. [Lawrence Berkeley Lab., CA (United States)
1995-02-01
This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulated a 4K liquid helium cryostat. The method described 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.
International Nuclear Information System (INIS)
Kishimoto, Akira; Ayano, Keiko; Hayashi, Hidetaka
2011-01-01
Ionic conductivity in yttria-stabilized zirconia ceramics under millimeter-wave irradiation heating was compared with that obtained using conventional heating. The former was found to result in higher conductivity than the latter. Enhancement of the ionic conductivity and the reduction in activation energy seemed to depend on self-heating resulting from the millimeter-wave irradiation. Millimeter-wave irradiation heating restricted the degradation in conductivity accompanying over-substitution, suggesting the optimum structure that provided the maximum conductivity could be different between the two heating methods.
Totally Asymmetric Limit for Models of Heat Conduction
De Carlo, Leonardo; Gabrielli, Davide
2017-08-01
We consider one dimensional weakly asymmetric boundary driven models of heat conduction. In the cases of a constant diffusion coefficient and of a quadratic mobility we compute the quasi-potential that is a non local functional obtained by the solution of a variational problem. This is done using the dynamic variational approach of the macroscopic fluctuation theory (Bertini et al. in Rev Mod Phys 87:593, 2015). The case of a concave mobility corresponds essentially to the exclusion model that has been discussed in Bertini et al. (J Stat Mech L11001, 2010; Pure Appl Math 64(5):649-696, 2011; Commun Math Phys 289(1):311-334, 2009) and Enaud and Derrida (J Stat Phys 114:537-562, 2004). We consider here the convex case that includes for example the Kipnis-Marchioro-Presutti (KMP) model and its dual (KMPd) (Kipnis et al. in J Stat Phys 27:6574, 1982). This extends to the weakly asymmetric regime the computations in Bertini et al. (J Stat Phys 121(5/6):843-885, 2005). We consider then, both microscopically and macroscopically, the limit of large externalfields. Microscopically we discuss some possible totally asymmetric limits of the KMP model. In one case the totally asymmetric dynamics has a product invariant measure. Another possible limit dynamics has instead a non trivial invariant measure for which we give a duality representation. Macroscopically we show that the quasi-potentials of KMP and KMPd, which are non local for any value of the external field, become local in the limit. Moreover the dependence on one of the external reservoirs disappears. For models having strictly positive quadratic mobilities we obtain instead in the limit a non local functional having a structure similar to the one of the boundary driven asymmetric exclusion process.
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
Naya, Daniel E; Spangenberg, Lucía; Naya, Hugo; Bozinovic, Francisco
2013-09-22
Thermal conductance measures the ease with which heat leaves or enters an organism's body. Although the analysis of this physiological variable in relation to climatic and ecological factors can be traced to studies by Scholander and colleagues, only small advances have occurred ever since. Here, we analyse the relationship between minimal thermal conductance estimated during summer (Cmin) and several ecological, climatic and geographical factors for 127 rodent species, in order to identify the exogenous factors that have potentially affected the evolution of thermal conductance. In addition, we evaluate whether there is compensation between Cmin and basal metabolic rate (BMR)-in such a way that a scale-invariant ratio between both variables is equal to one-as could be expected from the Scholander-Irving model of heat transfer. Our major findings are (i) annual mean temperature is the best single predictor of mass-independent Cmin. (ii) After controlling for the effect of body mass, there is a strong positive correlation between log10 (Cmin) and log10 (BMR). Further, the slope of this correlation is close to one, indicating an almost perfect compensation between both physiological variables. (iii) Structural equation modelling indicated that Cmin values are adjusted to BMR values and not the other way around. Thus, our results strongly suggest that BMR and thermal conductance integrate a coordinated system for heat regulation in endothermic animals and that summer conductance values are adjusted (in an evolutionary sense) to track changes in BMRs.
Two-dimensional heat conducting simulation of plasma armatures
International Nuclear Information System (INIS)
Huerta, M.A.; Boynton, G.
1991-01-01
This paper reports on our development of a two-dimensional MHD code to simulate internal motions in a railgun plasma armature. The authors use the equations of resistive MHD, with Ohmic heating, and radiation heat transport. The authors use a Flux Corrected Transport code to advance all quantities in time. Our runs show the development of complex flows, subsequent shedding of secondary arcs, and a drop in the acceleration of the armature
Heat Conductivity Model in the Rock Masses of the Kochani Depression
International Nuclear Information System (INIS)
Karakashev, Deljo; Delipetrov, Todor
2006-01-01
The numerous regional geologic and hydrogeological explorations carried out in the Kochani depression by the end of the last century and those carried out lately indicate that the area possesses large thermal potentiality. The physical analysis presents one physical model which explain the thermal flow and heat conductivity who fluidity yielding in the rock masses of the Kochani depression. The models offer a clear picture on the geothermal energy, which becomes important for the economics in developing and developed countries. The results obtained and the calculations carried out on the heat flow in individual geothermal zones in the Kochani depression made it possible to conclude that the central zone possesses the highest heat flow. This points out to the higher heat circulation in the central part than in the periphery. Based on this it can be said that the major source and the main heat supply in the valley comes from the central part. The north-eastern part of the depression distinguished as a geothermal source is of high capacity in which large amounts of geothermal energy can be exploited. On the other hand, the south-west of the depression is the poorest with regard to thermal energy and heat flow in the rocks compared with the other two zones in the depression. (Author)
Damping by heat conduction in the Timoshenko system: Fourier and Cattaneo are the same
Said-Houari, Belkacem; Kasimov, Aslan R.
2013-01-01
We consider the Cauchy problem for the one-dimensional Timoshenko system coupled with heat conduction, wherein the latter is described by either the Cattaneo law or the Fourier law. We prove that heat dissipation alone is sufficient to stabilize
Thermal conductivity analysis and applications of nanocellulose materials
Uetani, Kojiro; Hatori, Kimihito
2017-01-01
Abstract In this review, we summarize the recent progress in thermal conductivity analysis of nanocellulose materials called cellulose nanopapers, and compare them with polymeric materials, including neat polymers, composites, and traditional paper. It is important to individually measure the in-plane and through-plane heat-conducting properties of two-dimensional planar materials, so steady-state and non-equilibrium methods, in particular the laser spot periodic heating radiation thermometry method, are reviewed. The structural dependency of cellulose nanopaper on thermal conduction is described in terms of the crystallite size effect, fibre orientation, and interfacial thermal resistance between fibres and small pores. The novel applications of cellulose as thermally conductive transparent materials and thermal-guiding materials are also discussed. PMID:29152020
Energy Technology Data Exchange (ETDEWEB)
De Beer, M., E-mail: maritz.db@gmail.com [School of Mechanical and Nuclear Engineering, North-West University, Private Bag X6001, Potchefstroom 2520 (South Africa); Du Toit, C.G., E-mail: Jat.DuToit@nwu.ac.za [School of Mechanical and Nuclear Engineering, North-West University, Private Bag X6001, Potchefstroom 2520 (South Africa); Rousseau, P.G., E-mail: pieter.rousseau@uct.ac.za [Department of Mechanical Engineering, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa)
2017-04-01
Highlights: • The radiation and conduction components of the effective thermal conductivity are separated. • Near-wall effects have a notable influence on the effective thermal conductivity. • Effective thermal conductivity is a function of the macro temperature gradient. • The effective thermal conductivity profile shows a characteristic trend. • The trend is a result of the interplay between conduction and radiation. - Abstract: The effective thermal conductivity represents the overall heat transfer characteristics of a packed bed of spheres and must be considered in the analysis and design of pebble bed gas-cooled reactors. During depressurized loss of forced cooling conditions the dominant heat transfer mechanisms for the passive removal of decay heat are radiation and conduction. Predicting the value of the effective thermal conductivity is complex since it inter alia depends on the temperature level and temperature gradient through the bed, as well as the pebble packing structure. The effect of the altered packing structure in the wall region must therefore also be considered. Being able to separate the contributions of radiation and conduction allows a better understanding of the underlying phenomena and the characteristics of the resultant effective thermal conductivity. This paper introduces a purpose-designed test facility and accompanying methodology that combines physical measurements with Computational Fluid Dynamics (CFD) simulations to separate the contributions of radiation and conduction heat transfer, including the wall effects. Preliminary results obtained with the methodology offer important insights into the trends observed in the experimental results and provide a better understanding of the interplay between the underlying heat transfer phenomena.
Variable Conductance Heat Pipe Cooling of Stirling Convertor and General Purpose Heat Source
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
Heat transfer analysis of short helical borehole heat exchangers
International Nuclear Information System (INIS)
Zarrella, Angelo; De Carli, Michele
2013-01-01
Highlights: ► Vertical ground heat exchanger with a helical shaped pipe is analyzed. ► The model considers the interaction between the ground and the environment. ► The results of the model are in good agreement with the experimental values. ► The weather conditions considerably affect the fluid heat carrier temperature. ► The pitch between the turns does not affect the behaviour of the heat exchanger. -- Abstract: In this paper a numerical model to analyze the thermal behaviour of vertical ground heat exchangers with a helical shaped pipe is presented. This type of configuration can be a suitable alternative to conventional ground heat exchangers, especially when the heating and cooling loads of the building are very low. The model describes the heat transfer problem by means of a network of interconnected thermal resistances and capacitances. Moreover, as the investigated ground heat exchanger is usually installed in shallow depth, the model takes into account the interaction between the ground and the ambient environment which affects the fluid heat carrier temperature into the heat exchanger and, as a consequence, the energy efficiency of the heat pump. After a sensitivity analysis on the mesh parameters, the presented model is compared with experimental data and the simulation results show good agreement with the measurements. Finally, analyses to investigate the influence of the weather conditions, of the axial heat transfer and of the pitch between the turns of the helical pipe for two types of ground are carried out.
Fundamental characteristics of heat conduction enhancement in oscillating viscous flow-dream pipe
International Nuclear Information System (INIS)
Katsuta, M.; Nagata, K.; Maruyama, Y.; Tsujimori, A.
1991-01-01
This paper reports that to confirm the heat conduction augmentation technique via sinusoidal oscillation experimentally and to establish a fundamental data base of this device, systematic measurements using almost identically scaled with Kurzweg's apparatus for demonstration were conducted. In this heat exchanger, the fluid occupied a capillary tube or its bundle that connected two reservoirs at different temperature; a special constructed oscillation driving unit generated a pulsed motion of working fluid. Operation took place at various tube diameters, oscillated frequency and stroke using pure water and ethanol as working liquid. As a result, a new factor so-called heat transport coefficient which indicates the heat transfer rate multiplying temperature gradient between hot and cold reservoir was introduced. This factor increased with increasing oscillated frequency and stroke, however, beyond a critical frequency, this trend disappeared. Using modified Reynolds number and stroke ratio, a new empirical formula which correlated the data regardless of the difference of working liquid was proposed. A discussion of tube bundle was also made using this correlation. Finally, an attempt was performed to correlate the data using effective thermal diffusivity predicted by simple lumped capacitance analysis and characteristic period
Development and adaptation of conduction and radiation heat-transfer computer codes for the CFTL
International Nuclear Information System (INIS)
Conklin, J.C.
1981-08-01
RODCON and HOTTEL are two computational methods used to calculate thermal and radiation heat transfer for the Core Flow Test Loop (CFTL) analysis efforts. RODCON was developed at ORNL to calculate the internal temperature distribution of the fuel rod simulator (FRS) for the CFTL. RODCON solves the time-dependent heat transfer equation in two-dimensional (R angle) cylindrical coordinates at an axial plane with user-specified radial material zones and time- and position-variant surface conditions at the FRS periphery. Symmetry of the FRS periphery boundary conditions is not necessary. The governing elliptic, partial differential heat equation is cast into a fully implicit, finite-difference form by approximating the derivatives with a forward-differencing scheme with variable mesh spacing. The heat conduction path is circumferentially complete, and the potential mathematical problem at the rod center can be effectively ignored. HOTTEL is a revision of an algorithm developed by C.B. Baxi at the General Atomic Company (GAC) to be used in calculating radiation heat transfer in a rod bundle enclosed in a hexagonal duct. HOTTEL uses geometric view factors, surface emissivities, and surface areas to calculate the gray-body or composite view factors in an enclosure having multiple reflections in a nonparticipating medium
Transient heat conduction in a pebble fuel applying fractional model
International Nuclear Information System (INIS)
Gomez A, R.; Espinosa P, G.
2009-10-01
In this paper we presents the equation of thermal diffusion of temporary-fractional order in the one-dimensional space in spherical coordinates, with the objective to analyze the heat transference between the fuel and coolant in a fuel element of a Pebble Bed Modular Reactor. The pebble fuel is the heterogeneous system made by microsphere constitutes by U O, pyrolytic carbon and silicon carbide mixed with graphite. To describe the heat transfer phenomena in the pebble fuel we applied a constitutive law fractional (Non-Fourier) in order to analyze the behaviour transient of the temperature distribution in the pebble fuel with anomalous thermal diffusion effects a numerical model is developed. (Author)
Heat conduction thru supports between 3000K and 40K
International Nuclear Information System (INIS)
Nicol, T.H.
1983-11-01
Of fundamental importance in the design of any superconducting machinery is a reasonable prediction of the heat flow between the outside world at 300 0 K and a helium volume at roughly 4 0 K. As machines grow larger and energy costs higher the accuracy with which these estimates are made becomes more critical. Unfortunately, as cryogenic vessels become more complex so does the procedure for making estimates accurately
Heat conduction in caricature models of the Lorentz gas
International Nuclear Information System (INIS)
Kramli, A.; Simanyi, N.; Szasz, D.
1987-01-01
Heat transport coefficients are calculated for various random walks with internal states (the Markov partition of the Sinai billiard connects these walks with the Lorentz gas among a periodic configuration of scatterers). Models with reflecting or absorbing barriers and also those without or with local thermal equilibrium are investigated. The method is unified and is based on the Keldysh expansion of the resolvent of a matrix polynomial
Assessment of Gap Conductance Impact on Heat Split in Dual Cooled Annular Fuel
Energy Technology Data Exchange (ETDEWEB)
Chun, Kun Ho; Chun, Tae Hyun; In, Wang Kee; Yang, Yong Sik; Song, Kun Woo
2007-07-15
As a next generation fuel for PWR, a dual cooling annular fuel is being considered promisingly due to various advantage. It is able to increase the thermal margin significantly from not only large heat transfer area but also thin fuel pellet thickness. But the thermal margin at nominal condition could be degraded at certain burnup range because of the inappropriate heat split to inner and outer flow channels. A key factor to influence the heat split is the gap conductances in inner and outer clearances, which varies in terms of thermal expansion, swelling, creep, and so on in the cladding and pellet. As results of the investigation, particularly in the case of low gap conductance when the fuel rod burnup is relatively high, there is high probability that design targets might be violated. Therefore some effort is inevitable to address the concern. But, in parallel, it is necessary to more in detail investigate whether the assumed gap conductance for this analysis and the present design targets are reasonable through further reviews.
Electrode phenomena, tensor conductivity and electrode heating in seeded argon
Energy Technology Data Exchange (ETDEWEB)
Croitoru, Z.; de Montardy, A.
1963-04-15
Contact potential drops along the electrodes often prevent measurements of ionized gas conductivity. In order to avoid such potential drops, a measurement cell using double probe technique was realized. By adding a third probe, it is also possible to measure the conductivity tensor components. Formulas commonly used are shown to be incorrect. In order to evaluate non- equilibrium conductivity, the excitation temperature of the seed is to be considered, rather than electron temperature, especially in small scale experiments, where charged particle losses by ambipolar diffusion are to be expected. (auth)
Heat conduction problem of an evaporating liquid wedge
Directory of Open Access Journals (Sweden)
Tomas Barta
2015-02-01
Full Text Available We consider the stationary heat transfer near the contact line of an evaporating liquid wedge surrounded by the atmosphere of its pure vapor. In a simplified setting, the problem reduces to the Laplace equation in a half circle, subject to a non-homogeneous and singular boundary condition. By classical tools (conformal mapping, Green's function, we reformulate the problem as an integral equation for the unknown Neumann boundary condition in the setting of appropriate fractional Sobolev and weighted space. The unique solvability is then obtained by means of the Fredholm theorem.
Numerical modeling of the conduction and radiation heating in precision glass moulding
DEFF Research Database (Denmark)
Sarhadi, Ali; Hattel, Jesper Henri; Hansen, Hans Nørgaard
2012-01-01
wafer, heating can be performed by either conduction or radiation. The numerical simulation of these two heating mechanisms in the wafer based glass moulding process is the topic of the present paper. First, the transient heating of the glass wafer is simulated by the FEM software ABAQUS. Temperature...
Jiang, Q. F.; Zhuang, M.; Zhu, Z. G.; Y Zhang, Q.; Sheng, L. H.
2017-12-01
Counter-flow plate-fin heat exchangers are commonly utilized in cryogenic applications due to their high effectiveness and compact size. For cryogenic heat exchangers in helium liquefaction/refrigeration systems, conventional design theory is no longer applicable and they are usually sensitive to longitudinal heat conduction, heat in-leak from surroundings and variable fluid properties. Governing equations based on distributed parameter method are developed to evaluate performance deterioration caused by these effects. The numerical model could also be applied in many other recuperators with different structures and, hence, available experimental data are used to validate it. For a specific case of the multi-stream heat exchanger in the EAST helium refrigerator, quantitative effects of these heat losses are further discussed, in comparison with design results obtained by the common commercial software. The numerical model could be useful to evaluate and rate the heat exchanger performance under the actual cryogenic environment.
Conducting Meta-Analysis Using SAS
Arthur, Winfried; Huffcutt, Allen I; Arthur, Winfred
2001-01-01
Conducting Meta-Analysis Using SAS reviews the meta-analysis statistical procedure and shows the reader how to conduct one using SAS. It presents and illustrates the use of the PROC MEANS procedure in SAS to perform the data computations called for by the two most commonly used meta-analytic procedures, the Hunter & Schmidt and Glassian approaches. This book serves as both an operational guide and user's manual by describing and explaining the meta-analysis procedures and then presenting the appropriate SAS program code for computing the pertinent statistics. The practical, step-by-step instru
Effect of spatial variation of thermal conductivity on non-fourier heat conduction in a finite slab
International Nuclear Information System (INIS)
Goharkhah, Mohammad; Amiri, Shahin; Shokouhmand, Hossein
2009-01-01
The non-Fourier heat conduction problem in a finite slab is studied analytically. Dependence of thermal conductivity on space has been considered. The Laplace transform method is used to remove the time-dependent terms in the governing equation and the boundary conditions. The hyperbolic heat conduction (HHC) equation has been solved by employing trial solution method and collocation optimization criterion. Results show that the space-dependent thermal conductivity strongly affects the temperature distribution. A temperature peak on the insulated wall of the slab has been observed due to linear variation of thermal conductivity. It has been shown that the magnitude of the temperature peak increases with increasing the dimensionless relaxation time. To validate the approach, the results have been compared with the analytical solution obtained for a special case which shows a good agreement
Radial heat conduction in a power reactor fuel element
International Nuclear Information System (INIS)
Ventura, M.A.
1998-01-01
Two radial conduction models, one for steady state and another for unsteady state, in a nuclear power reactor fuel element are developed. The objective is to obtain the temperatures in the fuel pellet and the cladding. The lumped-parameter hypothesis are adopted to represent the system. Both models are verified and their results are compared with similar ones. A method to calculate the conductance in the gap between the UO 2 pellet and the clad and its associated uncertainty is included in the steady state model. (author) [es
Heat transfer and thermal stress analysis in grooved tubes
Indian Academy of Sciences (India)
Heat transfer and thermal stresses, induced by temperature differencesin the internally grooved tubes of heat transfer equipment, have been analysed numerically. The analysis has been conducted for four different kinds of internally grooved tubes and three different mean inlet water velocities. Constant temperature was ...
On the Jeans Criterion of a Stratified Heat Conducting Gaseous ...
Indian Academy of Sciences (India)
sations in nebulae may be due to thermal effects. Abbassi et al. (2008) considered the possibility of the thermal conduction in the presence of toroidal magnetic field. – which had been a largely neglected ingredient before – could affect the global properties of the hot accretion flows substantially and investigated the effect of ...
Directory of Open Access Journals (Sweden)
Chen Jie-Dong
2016-01-01
Full Text Available In this paper, we investigate the local fractional Laplace equation in the steady heat-conduction problem. The solutions involving the non-differentiable graph are obtained by using the characteristic equation method (CEM via local fractional derivative. The obtained results are given to present the accuracy of the technology to solve the steady heat-conduction in fractal media.
Analysis of heat transfer in plain carbon steels
International Nuclear Information System (INIS)
Han, Heung Nam; Lee, Kyung Jong
1999-01-01
During cooling of steels, the heat transfer was controlled by radiation, convection, conduction and heat evolution from phase transformation. To analyze the heat transfer during cooling precisely, the material constants such as density, heat capacity and the heat evolved during transformation were obtained as functions of temperature and chemical composition for each phase observed in plain carbon steel using a thermodynamic analysis based on the sublattice model of Fe-C-Mn system. The results were applied to 0.049 wt% and 0.155 wt% carbon steels with an austenitic stainless steel as reference by developing a proper heat transfer governing equation. The equation was solved using the lumped system method. In addition, using a transformation dilatometer with adequate experimental conditions to clarify the individual heat transfer effect, the transformation heat evolved during cooling and the transformation behavior as well as the temperature change were observed. The predicted temperature profiles during cooling were well agreed with the measured ones
DEFF Research Database (Denmark)
Bernasconi, A.; Sleator, T.; Posselt, D.
1992-01-01
The specific heat C(p) and the thermal conductivity lambda of a series of base-catalyzed silica aerogels have been measured at temperatures between 0.05 and 20 K. The results confirm that the different length-scale regions observed in the aerogel structure are reflected in the dynamic behavior of...... SiO2 are most likely not due to fractal behavior....... the possibility of two spectral dimensions characterizing the fracton modes. Our data imply important differences between the physical mechanisms dominating the low-temperature behavior of aerogels and dense glasses, respectively. From our analysis we also conclude that the low-temperature properties of amorphous...
The isothermal conductivity improvement in zirconia-based ceramics under 24 GHz microwave heating
International Nuclear Information System (INIS)
Kishimoto, Akira; Ayano, Keiko; Teranishi, Takashi; Hayashi, Hidetaka
2014-01-01
Abstract Under 24-GHz millimetre-wave irradiation heating ionic conductivity of zirconia base ceramics was up to 20 times higher than that of a conventionally-heated sample at the same temperature of 400 °C. The degree of enhancement could be altered by changing the stabilising atom from Y to Yb. Enhancement of ionic conduction was prominent in the setup condition of larger self-heating ratio and larger MMW absorbing materials. The isothermal improvement of ionic conductivity under MMW irradiation would be ascribed to the non-thermal effect. - Highlights: • Under millimetre-wave irradiation heating ionic conductivity of zirconia ceramics was examined. • It was up to 20 times higher than that of a conventionally heating condition. • The activation process was examined in relation to the non-thermal effects. • The operation temperature could be lowered while maintaining the ionic conductivity
Kenjeres, S.
2016-09-01
In the present paper we give a concise review of some recent highlights of our research dealing with electromagnetic control of flow, mixing and heat transfer of electrically conductive or magnetized fluids. We apply a combination of state-of-art numerical (DNS and LES) and experimental (PIV and LIF) techniques to provide fundamental insights into the complex phenomena of interactions between imposed (or induced) electromagnetic fields and underlying fluid flow. Our analysis covers an extensive range of working fluids, i.e. weakly- and highly-electrically-conductive, as well as magnetized fluids. These interactions are defined through the presence of different types of body forces acting per volume of fluid. A fully closed system of governing equations containing an extended set of the Navier-Stokes and a simplified set of the Maxwell equations is presented. The four characteristic examples are selected: the electromagnetic control of self-sustained jet oscillations, the electromagnetic enhancement of heat transfer in thermal convection, the wake interactions behind magnetic obstacles and finally, the thermo-magnetic convection in differentially heated cubical enclosure. The comparative assessment between experimental and numerical results is presented. It is concluded that generally good agreement between simulations and experiments is obtained for all cases considered, proving the concept of electromagnetic modulation, which can be used in numerous technological applications.
Energy Technology Data Exchange (ETDEWEB)
Luna, N. [Direccion de Operacion Petrolera, Direccion General de Exploracion y Explotacion de Hidrocarburos, Secretaria de Energia, 03100 Mexico DF (Mexico); Mendez, F. [Facultad de Ingenieria, UNAM, 04510 Mexico DF (Mexico)
2005-07-01
The steady-state analysis of conjugated heat transfer process for the hydrodynamically developed forced convection flow on a heated flat plate embedded in a porous medium is studied. The governing equations for the fluid-saturated porous medium are solved analytically using the integral boundary layer approximation. This integral solution is coupled to the energy equation for the flat plate, where the longitudinal heat conduction effects are taken into account. The resulting equations are then reduced to an integro-differential equation which is solved by regular perturbation techniques and numerical methods. The analytical and numerical predictions for the temperature profile of the plate and appropriate local and average Nusselt numbers are plotted for finite values of the conduction parameter, {alpha}, which represents the presence of the longitudinal heat conduction effects. (authors)
Point kinetics model with one-dimensional (radial) heat conduction formalism
International Nuclear Information System (INIS)
Jain, V.K.
1989-01-01
A point-kinetics model with one-dimensional (radial) heat conduction formalism has been developed. The heat conduction formalism is based on corner-mesh finite difference method. To get average temperatures in various conducting regions, a novel weighting scheme has been devised. The heat conduction model has been incorporated in the point-kinetics code MRTF-FUEL. The point-kinetics equations are solved using the method of real integrating factors. It has been shown by analysing the simulation of hypothetical loss of regulation accident in NAPP reactor that the model is superior to the conventional one in accuracy and speed of computation. (author). 3 refs., 3 tabs
Anomalous heat conduction in a one-dimensional ideal gas.
Casati, Giulio; Prosen, Tomaz
2003-01-01
We provide firm convincing evidence that the energy transport in a one-dimensional gas of elastically colliding free particles of unequal masses is anomalous, i.e., the Fourier law does not hold. Our conclusions are confirmed by a theoretical and numerical analysis based on a Green-Kubo-type approach specialized to momentum-conserving lattices.
Heat flux estimation for neutral beam line components using inverse heat conduction procedures
International Nuclear Information System (INIS)
Bharathi, P.; Prahlad, V.; Quereshi, K.; Bansal, L.K.; Rambabu, S.; Sharma, S.K.; Parmar, S.; Patel, P.J.; Baruah, U.K.; Patel, Ravi
2015-01-01
In this work, we describe and compare the analytical IHCP methods such-as semi-infinite method, finite slab method and a numerical method called Stolz method for estimating the incident heat flux from the experimentally measured temperature data. In case of analytical methods, the finite time response of the sensor is needed to be accounted for an accurate power density estimations. The modified models corrected for the response time of the sensors are also discussed in this paper. Application of these methods using example temperature waveforms obtained on the SST1-NBI test stand is presented and discussed. For choosing the suitable method for the calorimetry on beam line components, the estimated results are also validated using the ANSYS analysis done on these beam Iine components. As a conclusion, the finite slab method corrected for the influence of the sensor response time found out to be the most suitable method for the inversion of temperature data in case of neutral beam line components
First Principles Modeling of Phonon Heat Conduction in Nanoscale Crystalline Structures
International Nuclear Information System (INIS)
Mazumder, Sandip; Li, Ju
2010-01-01
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
Entropic Constitutive Relation and Modeling for Fourier and Hyperbolic Heat Conductions
Directory of Open Access Journals (Sweden)
Shu-Nan Li
2017-12-01
Full Text Available Most existing phenomenological heat conduction models are expressed by temperature and heat flux distributions, whose definitions might be debatable in heat conductions with strong non-equilibrium. The constitutive relations of Fourier and hyperbolic heat conductions are here rewritten by the entropy and entropy flux distributions in the frameworks of classical irreversible thermodynamics (CIT and extended irreversible thermodynamics (EIT. The entropic constitutive relations are then generalized by Boltzmann–Gibbs–Shannon (BGS statistical mechanics, which can avoid the debatable definitions of thermodynamic quantities relying on local equilibrium. It shows a possibility of modeling heat conduction through entropic constitutive relations. The applicability of the generalizations by BGS statistical mechanics is also discussed based on the relaxation time approximation, and it is found that the generalizations require a sufficiently small entropy production rate.
Evaluation of thermal conductivity of heat-cured acrylic resin mixed with A1203
Directory of Open Access Journals (Sweden)
Ebadian B.
2002-08-01
Full Text Available One of the most important characteristics of denture base is thermal conductivity. This property has a major role in secretions of salivary glands and their enzymes, taste of the food and gustatory response. Polymethyl methacrylate used in prosthodontics is relatively an insulator. Different materials such as metal fillers and ceramics have been used to solve this problem. The aim of this study was the evaluation of AI2O3 effect on thermal conductivity of heat-cured acrylic resin. Acrylic resin was mixed with AI2O3 in two different weight rates (15 and 20 % of weight. So, group 1 and 2 were divided on this basis. Samples with pure acrylic resin were considered as control group. 18 cylindrical patterns were made in 9x9 mm dimensions and thermocouple wires embedded in each sample to act as conductor. The specimens were put in water with 70±1°C thermal range for 10 minutes. Then, thermal conductivity was measured. The results were analyzed with variance analysis and Dunken test. There was significant difference between thermal conductivity of all groups in all period times. It the first seconds, thermal conductivity in groups 1 and 2 were more than control group. Therefore, for developing of thermal conductivity of acrylic resin, A1203 can be used. Certainly, other characteristic of new resin should be evaluated.
Beyond the classical theory of heat conduction: a perspective view of future from entropy
Lai, Xiang; Zhu, Pingan
2016-01-01
Energy is conserved by the first law of thermodynamics; its quality degrades constantly due to entropy generation, by the second law of thermodynamics. It is thus important to examine the entropy generation regarding the way to reduce its magnitude and the limit of entropy generation as time tends to infinity regarding whether it is bounded or not. This work initiates such an analysis with one-dimensional heat conduction. The work not only offers some fundamental insights of universe and its future, but also builds up the relation between the second law of thermodynamics and mathematical inequalities via developing the latter of either new or classical nature. A concise review of entropy is also included for the interest of performing the analysis in this work and the similar analysis for other processes in the future. PMID:27843400
International Nuclear Information System (INIS)
Vilchiz, Luis Enrique; Pacheco-Vega, Arturo; Handy, Brent E.
2005-01-01
Mathematical models of a Tian-Calvet microcalorimeter were solved numerically by the finite-element method in an effort to understand the relative importance of the three basic heat transfer mechanisms operative during gas dosing experiments typically used to determine heats of adsorption on catalysts and adsorbents. The analysis pays particular attention to the quantitative release of heat through various elements of the cell and sensor cups to assess time delays and the deg.ree of thermal shunting that may result in inaccuracies in calorimetric measurements. Conductive transfer predominates in situations where there is high gas headspace pressure. The convection currents that arise when dosing with considerable gas pressure in the cell headspace region are not sufficiently strong to shunt significant amounts of sample heat away from being sensed by the surrounding thermopiles. Therefore, the heat capture fraction (heat sensed/heat produced) does not vary significantly with gas headspace pressure. During gas dosing under very low gas headspace pressure, radiation losses from the top of the sample bed may significantly affect the heat capture fraction, leading to underestimations of adsorption heats, unless the heat radiated from the top of the catalyst bed is effectively reflected back to the sample region or absorbed by an inert packing layer also in thermal contact with the thermopile wall
Case studies of heat conduction in rotary drums with L-shaped lifters via DEM
Directory of Open Access Journals (Sweden)
Qiang Xie
2018-03-01
Full Text Available Rotary drums are widely used in numerous processes in industry to handle granular materials. In present work, heat transfer processes in drums with L-shaped lifters have been investigated by coupling the discrete element method (DEM with heat transfer model. Effects of both operational and structural parameters have been analyzed. It is found that increasing rotational speed could improve heat transfer to a certain extent, however, just in relatively low speed stage. When lifter number increases, the heat transfer speed slightly decreases. An increasing lifter height could promote heat transfer first and then reduces it, but the amplitude of variation keeps small. The heat transfer rate descends with increasing lifter width. The heat transfer mechanisms have also been discussed by comparing mixing rates, total contact areas for thermal conduction, time constants (TC indicating apparent heat transfer rate and effective heat transfer coefficients(HTC. It is concluded that dynamic conduction due to particle flow is dominated in all cases. The L-shaped lifers are turned out not a good choice when heat conduction between particles is prominent.
International Nuclear Information System (INIS)
Kuroyanagi, Toshiyuki
1983-07-01
Based on an idea that surface conditions should be a reflection of interior temperature and interior heat flux variation as inverse as interior conditions has been determined completely by the surface temperature and/on surface heat flux as boundary conditions, a method is presented for determining the surface temperature and the surface heat flux of a solid when the temperature and heat flux at an interior point are a prescribed function of time. The method is developed by the integration of Duhumels' integral which has unknown temperature or unknown heat flux in its integrand. Specific forms of surface condition determination are developed for a sample inverse problem: slab. Ducussing the effect of a degree of avairable informations at an interior point due to damped system and the effect of variation of surface conditions on those formulations, it is shown that those formulations are capable of representing the unknown surface conditions except for small time interval followed by discontinuous change of surface conditions. The small un-resolved time interval is demonstrated by a numerical example. An evaluation method of heat flux at an interior point, which is requested by those formulations, is discussed. (author)
DEFF Research Database (Denmark)
Shapiro, Alexander
2004-01-01
The theory of transport properties in multicomponent gas and liquid mixtures, which was previously developed for diffusion coefficients, is extended onto thermodiffusion coefficients and heat conductivities. The derivation of the expressions for transport properties is based on the general statis...... of the heat conductivity coefficient for ideal gas. (C) 2003 Elsevier B.V. All rights reserved.......The theory of transport properties in multicomponent gas and liquid mixtures, which was previously developed for diffusion coefficients, is extended onto thermodiffusion coefficients and heat conductivities. The derivation of the expressions for transport properties is based on the general...
Effect of thermal conductivities of shape stabilized PCM on under-floor heating system
International Nuclear Information System (INIS)
Cheng, Wenlong; Xie, Biao; Zhang, Rongming; Xu, Zhiming; Xia, Yuting
2015-01-01
Highlights: • HCE-SSPCM was prepared and used in under-floor heating system. • Enhancing thermal conductivity improved the efficiency of energy and space. • Too high thermal conductivity over a range was meaningless. • The economic benefits of the phase change energy storage system were the best. - Abstract: A kind of heat conduction-enhanced shape-stabilized PCM (HCE-SSPCM) was utilized in the under-floor heating system for house heating in winter. This system charges heat by using cheap nighttime electricity and provides heating needs throughout all day. The effect of thermal conductivity of the PCM on energy savings and economic benefits of the system were theoretically and experimentally studied. HCE-SSPCM plates, made of (solid paraffin + liquid paraffin)/high density polyethylene/expanded graphite, were introduced to a test room with under-floor heating system. And the operating characteristics of the system were compared with that of the non-phase change energy storage system and the conventional air conditioning system. The results showed that enhancing the thermal conductivity of PCM in a certain range could significantly improve the energy efficiency of the heating system and reduce the thickness of thermal insulating materials. But the improving effect was not obvious when the thermal conductivity was beyond 1.0 W/m K. The phase change energy storage system had a comfortable temperature environment and the best economic benefits among the three different heating types especially when the ratio of peak-valley electric price was high. Therefore, increasing the thermal conductivity of SSPCM will be of great significance for house heating
Denys, S; Van Loey, A M; Hendrickx, M E
2000-01-01
A numerical heat transfer model for predicting product temperature profiles during high-pressure thawing processes was recently proposed by the authors. In the present work, the predictive capacity of the model was considerably improved by taking into account the pressure dependence of the latent heat of the product that was used (Tylose). The effect of pressure on the latent heat of Tylose was experimentally determined by a series of freezing experiments conducted at different pressure levels. By combining a numerical heat transfer model for freezing processes with a least sum of squares optimization procedure, the corresponding latent heat at each pressure level was estimated, and the obtained pressure relation was incorporated in the original high-pressure thawing model. Excellent agreement with the experimental temperature profiles for both high-pressure freezing and thawing was observed.
Multiregional coupled conduction--convection model for heat transfer in an HTGR core
International Nuclear Information System (INIS)
Giles, G.E. Jr.; Childs, K.W.; Sanders, J.P.
1978-01-01
HEXEREI is a three-dimensional, coupled conduction-convection heat transfer and multichannel fluid dynamic analysis computer code with both steady-state and transient capabilities. The program was developed to provide thermal-fluid dynamic analysis of a core following the general design for high-temperature gas-cooled reactors (HTGRs); its purpose was to provide licensing evaluations for the U.S. Nuclear Regulatory Commission. In order to efficiently model the HTGR core, the nodal geometry of HEXEREI was chosen as a regular hexagonal array perpendicular to the axis of and bounded by a right circular cylinder. The cylindrical nodal geometry surrounds the hexagonal center portion of the mesh; these two different types of nodal geometries must be connected by interface nodes to complete the accurate modeling of the HTGR core. HEXEREI will automatically generate a nodal geometry that will accurately model a complex assembly of hexagonal and irregular prisms. The accuracy of the model was proven by a comparison of computed values with analytical results for steady-state and transient heat transfer problems. HEXEREI incorporates convective heat transfer to the coolant in many parallel axial flow channels. Forced and natural convection (which permits different flow directions in parallel channels) is included in the heat transfer and fluid dynamic models. HEXEREI incorporates a variety of steady-state and transient solution techniques that can be matched with a particular problem to minimize the computational time. HEXEREI was compared with a code of similar capabilities that was based on a Cartesian mesh. This code modeled only one specific core design, and the mesh spacing was closer than that generated by HEXEREI. Good agreement was obtained with the detail provided by the representations
He, Lijuan; Hu, Shengbiao; Huang, Shaopeng; Yang, Wencai; Wang, Jiyang; Yuan, Yusong; Yang, Shuchun
2008-02-01
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 logs show a transient mean thermal gradient that has increased from 24.38 to 25.28 K km-1 over a period of about 1.5 years. We measured thermal conductivities and radiogenic heat productions on more than 400 core samples from CCSD MH. The measured thermal conductivities range between 1.71 and 3.60 W m-1 K-1, and the radiogenic heat productions vary from 0.01 μW m-3 to over 5.0 μW m-3, with a mean value of 1.23 ± 0.82 μW m-3 for the upper 5-km layer of the crust. The heat productions in CCSD MH appear to be more rock-type than depth-dependent and, over the depth range of CCSD MH, do not fit the popular model of heat production decreasing exponentially with increasing depth. The measured heat flow decreases with depth from ˜75 mW m-2 near the surface to ˜66 mW m-2 at a depth of 4600 m. High heat flow anomalies occur at ˜1000 and ˜2300 m, and low anomalies occur at 3300-4000 m. A preliminary two-dimensional numerical model suggests that both radiogenic heat production and thermal refraction due to structural heterogeneity are at least partially responsible for the vertical variation of heat flow in CCSD MH.
Li, Shu-Nan; Cao, Bing-Yang
2017-09-01
The second law of thermodynamics governs the direction of heat transport, which provides the foundational definition of thermodynamic Clausius entropy. The definitions of entropy are further generalized for the phenomenological heat transport models in the frameworks of classical irreversible thermodynamics and extended irreversible thermodynamics (EIT). In this work, entropic functions from mathematics are combined with phenomenological heat conduction models and connected to several information-geometrical conceptions. The long-time behaviors of these mathematical entropies exhibit a wide diversity and physical pictures in phenomenological heat conductions, including the tendency to thermal equilibrium, and exponential decay of nonequilibrium and asymptotics, which build a bridge between the macroscopic and microscopic modelings. In contrast with the EIT entropies, the mathematical entropies expressed in terms of the internal energy function can avoid singularity paired with nonpositive local absolute temperature caused by non-Fourier heat conduction models.
International Nuclear Information System (INIS)
Azimi, A.; Hannani, S.K.; Farhanieh, B.
2005-01-01
In this article, a comparison between two iterative inverse techniques to solve simultaneously two unknown functions of axisymmetric transient inverse heat conduction problems in semi complex geometries is presented. The multi-block structured grid together with blocked-interface nodes is implemented for geometric decomposition of physical domain. Numerical scheme for solution of transient heat conduction equation is the finite element method with frontal technique to solve algebraic system of discrete equations. The inverse heat conduction problem involves simultaneous unknown time varying heat generation and time-space varying boundary condition estimation. Two parameter-estimation techniques are considered, Levenberg-Marquardt scheme and conjugate gradient method with adjoint problem. Numerically computed exact and noisy data are used for the measured transient temperature data needed in the inverse solution. The results of the present study for a configuration including two joined disks with different heights are compared to those of exact heat source and temperature boundary condition, and show good agreement. (author)
Some problems in steady-state thermal conductivity with variable heat transfer rate
International Nuclear Information System (INIS)
Malov, Yu.I.; Martinson, L.K.; Pavlov, K.B.
1975-01-01
Some boundary-value problems of steady heat conductivity with an alternating heat exchange coefficient have been solved for a cylindrical region. The solutions have been performed as expansion in series with respect to eigenfunctions with the coefficients consistent with infinite systems of linear algebraic equations. A reduction method has been substantiated for those systems. The paper presents results of calculation of the temperature distribution inside the infinite cylinder with concrete tasks of heat exchange coefficient variations on the cylinder surface
International Nuclear Information System (INIS)
Son, Hyung M.; Suh, Kune Y.
2012-01-01
Highlights: ► Performed experiment for the upward SCO 2 flow surrounded by highly conducting metal. ► Selected dimensionless groups representing the property variations and buoyancy. ► Developed the heat transfer correlation for the mixed thermal boundary condition. ► Wrote a finite element heat transfer code to find the appropriate correlation. ► Coupled the 1D convection and 2D heat conduction via heat transfer coefficient. - Abstract: This paper presents heat transfer characteristics of supercritical carbon dioxide flow inside vertical circular pipe surrounded by highly conducting material, and develops an adequate tool to test the performance of available heat transfer correlations with. The possible situations are illustrated for the nuclear power plant to which the above-mentioned geometric configuration might be applicable. An experimental loop with vertical circular geometry is designed and constructed to test the upward flow in supercritical state when the axial heat transfer is enhanced by the surrounding metals, resulting in a wall boundary condition between the constant heat flux and temperature. The set of correlations and important findings are critically reviewed from extensive literature survey. Incorporating nondimensional groups resorting to past insights from the available literature, a convective heat transfer correlation is proposed. The optimization procedure is described which utilizes a random walk method along with the in-house finite element heat transfer code to determine the coefficients of the proposed heat transfer correlation. The proposed methodology can be applied to evaluation of heat transfer when the heat transfer coefficient data cannot directly be determined from the experiment.
International Nuclear Information System (INIS)
Choi, C. Y.
1997-01-01
A geometrical inverse heat conduction problem is solved for the infrared scanning cavity detection by the boundary element method using minimal energy technique. By minimizing the kinetic energy of temperature field, boundary element equations are converted to the quadratic programming problem. A hypothetical inner boundary is defined such that the actual cavity is located interior to the domain. Temperatures at hypothetical inner boundary are determined to meet the constraints of measurement error of surface temperature obtained by infrared scanning, and then boundary element analysis is performed for the position of an unknown boundary (cavity). Cavity detection algorithm is provided, and the effects of minimal energy technique on the inverse solution method are investigated by means of numerical analysis
INVESTIGATION OF HEAT CONDUCTION AND SPECIFIC ELECTRIC IMPEDANCE OF POROUS MATERIALS
Directory of Open Access Journals (Sweden)
E. S. Golubtsova
2004-01-01
Full Text Available In this article there was investigated the influence of porosity and temperature change on heat condition and electrical resistance of porous iron (PZh4M nickel and steel 14X17H2. There are received the adequate equations of regression, establishing connection between heat conduction and electrical resistance of the investigated materials with their porosity and temperature.
Directory of Open Access Journals (Sweden)
Hansol Lim
2018-03-01
Full Text Available This study aims to estimate the performance of thermoelectric module (TEM heat pump for simultaneous liquid cooling and heating and propose empirical models for predicting the heat exchange effectiveness. The experiments were conducted to investigate and collect the performance data of TEM heat pump where the working fluid was water. A total of 57 sets of experimental data were statistically analyzed to estimate the effects of each independent variable on the heat exchange effectiveness using analysis of variance (ANOVA. To develop the empirical model, the six design parameters were measured: the number of transfer units (NTU of the heat exchangers (i.e., water blocks, the inlet water temperatures and temperatures of water blocks at the cold and hot sides of the TEM. As a result, two polynomial equations predicting heat exchange effectiveness at the cold and hot sides of the TEM heat pump were derived as a function of the six selected design parameters. Also, the proposed models and theoretical model of conventional condenser and evaporator for heat exchange effectiveness were compared with the additional measurement data to validate the reliability of the proposed models. Consequently, two conclusions have been made: (1 the possibility of using the TEM heat pump for simultaneous cooling and heating was examined with the maximum temperature difference of 30 °C between cold and hot side of TEM, and (2 it is revealed that TEM heat pump has difference with the conventional evaporator and condenser from the comparison results between the proposed models and theoretical model due to the heat conduction and Joule effect in TEM.
Fully coupled heat conduction and deformation analyses of nonlinear viscoelastic composites
Khan, Kamran; Muliana, Anastasia Hanifah
2012-01-01
This study presents an integrated micromechanical model-finite element framework for analyzing coupled heat conduction and deformations of particle-reinforced composite structures. A simplified micromechanical model consisting of four sub-cells, i
CTE-Matched, Liquid-Cooled, High Thermal Conductivity Heat Sink, Phase I
National Aeronautics and Space Administration — We propose the development of a CTE-matched, liquid-cooled, high thermal conductivity heat sink for use in spacecraft thermal management applications. The material...
A heat source probe for measuring thermal conductivity in waste rock dumps
International Nuclear Information System (INIS)
Blackford, M.G.; Harries, J.R.
1985-10-01
The development and use of a heat source probe to measure the thermal conductivity of the material in a waste rock dump is described. The probe releases heat at a constant rate into the surrounding material and the resulting temperature rise is inversely related to the thermal conductivity. The probe was designed for use in holes in the dump which are lined with 50 mm i.d. polyethylene liners. The poor thermal contact between the probe and the liner and the unknown conductivity of the backfill material around the liner necessitated long heating and cooling times (>10 hours) to ensure that the thermal conductivity of the dump material was being measured. Temperature data acquired in the field were analysed by comparing them with temperatures calculated using a two-dimensional cylindrical model of the probe and surrounding material, and the heat transfer code HEATRAN
Size effects in non-linear heat conduction with flux-limited behaviors
Li, Shu-Nan; Cao, Bing-Yang
2017-11-01
Size effects are discussed for several non-linear heat conduction models with flux-limited behaviors, including the phonon hydrodynamic, Lagrange multiplier, hierarchy moment, nonlinear phonon hydrodynamic, tempered diffusion, thermon gas and generalized nonlinear models. For the phonon hydrodynamic, Lagrange multiplier and tempered diffusion models, heat flux will not exist in problems with sufficiently small scale. The existence of heat flux needs the sizes of heat conduction larger than their corresponding critical sizes, which are determined by the physical properties and boundary temperatures. The critical sizes can be regarded as the theoretical limits of the applicable ranges for these non-linear heat conduction models with flux-limited behaviors. For sufficiently small scale heat conduction, the phonon hydrodynamic and Lagrange multiplier models can also predict the theoretical possibility of violating the second law and multiplicity. Comparisons are also made between these non-Fourier models and non-linear Fourier heat conduction in the type of fast diffusion, which can also predict flux-limited behaviors.
Transient Analysis of a Magnetic Heat Pump
Schroeder, E. A.
1985-01-01
An experimental heat pump that uses a rare earth element as the refrigerant is modeled using NASTRAN. The refrigerant is a ferromagnetic metal whose temperature rises when a magnetic field is applied and falls when the magnetic field is removed. The heat pump is used as a refrigerator to remove heat from a reservoir and discharge it through a heat exchanger. In the NASTRAN model the components modeled are represented by one-dimensional ROD elements. Heat flow in the solids and fluid are analyzed. The problem is mildly nonlinear since the heat capacity of the refrigerant is temperature-dependent. One simulation run consists of a series of transient analyses, each representing one stroke of the heat pump. An auxiliary program was written that uses the results of one NASTRAN analysis to generate data for the next NASTRAN analysis.
A new approach to the theory of heat conduction with finite wave speeds
Directory of Open Access Journals (Sweden)
Vito Antonio Cimmelli
1991-05-01
Full Text Available Relations between the physical models describing the heat conduction in solids and a phenomenological model leading to quasi-linear hyperbolic equations and systems of conservation laws are presented. A new semi-empirical temperature scale is introduced in terms of which a modified Fourier law is formulated. The hyperbolicity of the heat conduction equation is discussed together with some wave propagation problems.
Radiative heat exchange of a meteor body in the approximation of radiant heat conduction
International Nuclear Information System (INIS)
Pilyugin, N.N.; Chernova, T.A.
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 exchange (which is the determining factor under these conditions) for large meteor bodies as they move with hypersonic velocities in an atmosphere. The solution of this problem enables one to find the ablation of a meteorite during its aerodynamic heating and to determine the initial conditions for the solution of problems of the breakup of large bodies and their subsequent motion and ablation. Hypersonic flow of an inviscid gas stream over an axisymmetric blunt body is analyzed with allowance for radiative transfer in a thick-thin approximation. The gas-dynamic problem of the flow of an optically thick gas over a large body is solved by the method of asymptotic joined expansions, using a hypersonic approximation and local self-similarity. An equation is obtained for the coefficient of radiant heat exchange and the peculiarities of such heat exchange for meteor bodies of large size are noted
Non-Fourier heat conduction and phase transition in laser ablation of polytetrafluoroethylene (PTFE)
Zhang, Yu; Zhang, Daixian; Wu, Jianjun; Li, Jian; He, Zhaofu
2017-11-01
The phase transition in heat conduction of polytetrafluoroethylene-like polymers was investigated and applied in many fields of science and engineering. Considering more details including internal absorption of laser radiation, reflectivity of material and non-Fourier effect etc., the combined heat conduction and phase transition in laser ablation of polytetrafluoroethylene were modeled and investigated numerically. The thermal and mechanic issues in laser ablation were illustrated and analyzed. Especially, the phenomenon of temperature discontinuity formed in the combined phase transition and non-Fourier heat conduction was discussed. Comparisons of target temperature profiles between Fourier and non-Fourier heat conduction in melting process were implemented. It was indicated that the effect of non-Fourier plays an important role in the temperature evolvement. The effect of laser fluence was proven to be significant and the thermal wave propagation was independent on the laser intensity for the non-Fourier heat conduction. Besides, the effect of absorption coefficients on temperature evolvements was studied. For different ranges of absorption coefficients, different temperature evolvements can be achieved. The above numerical simulation provided insight into physical processes of combined non-Fourier heat conduction and phase transition in laser ablation.
Convective mechanism for inhibition of heat conduction in laser produced plasmas
International Nuclear Information System (INIS)
Lee, P.H.Y.; Willi, O.; Trainor, R.J.
1984-01-01
In laser-produced plasmas, the laser energy is absorbed only below and up to the critical density. For laser fusion applications, this energy must be transported beyond the corona via electron thermal conduction towards colder, higher density regions of the target to heat up material and cause ablation, which in turn generates an inward pressure to compress the fusion fuel. If the heat conduction is inhibited, the consequences will be a weaker ablation and therefore a weaker implosion. For many years now, the inhibition of heat conduction, i.e., the reduction of heat conduction relative to classical conduction, in laser-produced plasmas at relevant irradiances has been apparent from the large body of experimental evidence. Many mechanisms, such as dc magnetic fields, ion acoustic turbulence, and Weibel instabilities, have been proposed to be the cause of inhibition of heat conduction. Even improved calculations of the classical heat flux have been carried out to solve this problem. Nevertheless, no single one of the above mentioned mechanisms can explain the large inhibition observed in the experiments
An immersed-boundary method for conjugate heat transfer analysis
Energy Technology Data Exchange (ETDEWEB)
Song, Jeong Chul; Lee, Joon Sik [Seoul National University, Seoul (Korea, Republic of); Ahn, Joon [Kookmin University, Seoul (Korea, Republic of)
2017-05-15
An immersed-boundary method is proposed for the analysis of conjugate problems of convective heat transfer in conducting solids. In- side the solid body, momentum forcing is applied to set the velocity to zero. A thermal conductivity ratio and a heat capacity ratio, between the solid body and the fluid, are introduced so that the energy equation is reduced to the heat diffusion equation. At the solid fluid interface, an effective conductivity is introduced to satisfy the heat flux continuity. The effective thermal conductivity is obtained by considering the heat balance at the interface or by using a harmonic mean formulation. The method is first validated against the analytic solution to the heat transfer problem in a fully developed laminar channel flow with conducting solid walls. Then it is applied to a laminar channel flow with a heated, block-shaped obstacle to show its validity for geometry with sharp edges. Finally the validation for a curvilinear solid body is accomplished with a laminar flow through arrayed cylinders.
Phase Image Analysis in Conduction Disturbance Patients
International Nuclear Information System (INIS)
Kwark, Byeng Su; Choi, Si Wan; Kang, Seung Sik; Park, Ki Nam; Lee, Kang Wook; Jeon, Eun Seok; Park, Chong Hun
1994-01-01
It is known that the normal His-Purkinje system provides for nearly synchronous activation of right (RV) and left (LV) ventricles. When His-Purkinje conduction is abnormal, the resulting sequence of ventricular contraction must be correspondingly abnormal. These abnormal mechanical consequences were difficult to demonstrate because of the complexity and the rapidity of its events. To determine the relationship of the phase changes and the abnormalities of ventricular conduction, we performed phase image analysis of Tc-RBC gated blood pool scintigrams in patients with intraventricular conduction disturbances (24 complete left bundle branch block (C-LBBB), 15 complete right bundle branch block (C-RBBB), 13 Wolff-Parkinson-White syndrome (WPW), 10 controls). The results were as follows; 1) The ejection fraction (EF), peak ejection rate (PER), and peak filling rate (PFR) of LV in gated blood pool scintigraphy (GBPS) were significantly lower in patients with C-LBBB than in controls (44.4 ± 13.9% vs 69.9 ± 4.2%, 2.48 ± 0.98 vs 3.51 ± 0,62, 1.76 ± 0.71 vs 3.38 ± 0.92, respectively, p<0.05). 2) In the phase angle analysis of LV, Standard deviation (SD), width of half maximum of phase angle (FWHM), and range of phase angle were significantly increased in patients with C-LBBB than in controls (20.6 + 18.1 vs S.6 + I.8, 22. 5 + 9.2 vs 16.0 + 3.9, 95.7 + 31.7 vs 51.3 + 5.4, respectively, p<0.05). 3) There was no significant difference in EF, PER, PFR between patients with the WolffParkinson-White syndrome and controls. 4) Standard deviation and range of phase angle were significantly higher in patients with WPW syndrome than in controls (10.6 + 2.6 vs 8.6 + 1.8, p<0.05, 69.8 + 11.7 vs 51.3 + 5 4, p<0.001, respectively), however, there was no difference between the two groups in full width of half maximum. 5) Phase image analysis revealed relatively uniform phase across the both ventriles in patients with normal conduction, but markedly delayed phase in the left ventricle
Phase Image Analysis in Conduction Disturbance Patients
Energy Technology Data Exchange (ETDEWEB)
Kwark, Byeng Su; Choi, Si Wan; Kang, Seung Sik; Park, Ki Nam; Lee, Kang Wook; Jeon, Eun Seok; Park, Chong Hun [Chung Nam University Hospital, Daejeon (Korea, Republic of)
1994-03-15
It is known that the normal His-Purkinje system provides for nearly synchronous activation of right (RV) and left (LV) ventricles. When His-Purkinje conduction is abnormal, the resulting sequence of ventricular contraction must be correspondingly abnormal. These abnormal mechanical consequences were difficult to demonstrate because of the complexity and the rapidity of its events. To determine the relationship of the phase changes and the abnormalities of ventricular conduction, we performed phase image analysis of Tc-RBC gated blood pool scintigrams in patients with intraventricular conduction disturbances (24 complete left bundle branch block (C-LBBB), 15 complete right bundle branch block (C-RBBB), 13 Wolff-Parkinson-White syndrome (WPW), 10 controls). The results were as follows; 1) The ejection fraction (EF), peak ejection rate (PER), and peak filling rate (PFR) of LV in gated blood pool scintigraphy (GBPS) were significantly lower in patients with C-LBBB than in controls (44.4 +- 13.9% vs 69.9 +- 4.2%, 2.48 +- 0.98 vs 3.51 +- 0,62, 1.76 +- 0.71 vs 3.38 +- 0.92, respectively, p<0.05). 2) In the phase angle analysis of LV, Standard deviation (SD), width of half maximum of phase angle (FWHM), and range of phase angle were significantly increased in patients with C-LBBB than in controls (20.6 + 18.1 vs S.6 + I.8, 22. 5 + 9.2 vs 16.0 + 3.9, 95.7 + 31.7 vs 51.3 + 5.4, respectively, p<0.05). 3) There was no significant difference in EF, PER, PFR between patients with the WolffParkinson-White syndrome and controls. 4) Standard deviation and range of phase angle were significantly higher in patients with WPW syndrome than in controls (10.6 + 2.6 vs 8.6 + 1.8, p<0.05, 69.8 + 11.7 vs 51.3 + 5 4, p<0.001, respectively), however, there was no difference between the two groups in full width of half maximum. 5) Phase image analysis revealed relatively uniform phase across the both ventriles in patients with normal conduction, but markedly delayed phase in the left ventricle
DEFF Research Database (Denmark)
Zajas, Jan Jakub; Heiselberg, Per
The LFA 447 can be successfully used for measurements of thermal diffusivity, specific heat and thermal conductivity of various samples. It is especially useful when determining the properties of materials on a very small scale. The matrix measurement mode allows for determining the local...... that the heat losses from both samples during the measurement are similar. Finally, the leveling of the samples is very important. Very small discrepancies can cause a massive error in the derivation of specific heat capacity and, as a result, thermal conductivity....
Energy Technology Data Exchange (ETDEWEB)
Thibaud-Erkey, Catherine [United Technologies reserach Center, East Hartford, CT (United States); Alahyari, Abbas [United Technologies reserach Center, East Hartford, CT (United States)
2016-12-28
Heat exchangers (HXs) are critical components in a wide range of heat transfer applications, from HVAC (Heating Ventilation and Cooling) to automobiles to manufacturing plants. They require materials capable of transferring heat at high rates while also minimizing thermal expansion over the usage temperature range. Conventionally, metals are used for applications where effective and efficient heat exchange is required, since many metals exhibit thermal conductivity over 100 W/m K. While metal HXs are constantly being improved, they still have some inherent drawbacks due to their metal construction, in particular corrosion. Polymeric material can offer solution to such durability issues and allow designs that cannot be afforded by metal construction either due to complexity or cost. A major drawback of polymeric material is their low thermal conductivity (0.1-0.5? W/mK) that would lead to large system size. Recent improvements in the area of filled polymers have highlighted the possibility to greatly improve the thermal conductivity of polymeric materials while retaining their inherent manufacturing advantage, and have been applied to heat sink applications. Therefore, the objective of this project was to develop a robust review of materials for the manufacturing of industrial and commercial non-metallic heat exchangers. This review consisted of material identification, literature evaluation, as well as empirical and model characterization, resulting in a database of relevant material properties and characteristics to provide guidance for future heat exchanger development.
Development, manufacturing and testing of a gas-loaded variable conductance methanol heat pipe
Vanbuggenum, R. I. J.; Daniels, D. H. W.
1987-02-01
The experimental technology required to measure the performance of moderate temperature heat pipes is presented. The heat pipe manufacturing process is described. The hydrodynamic characteristics of the porous structure inside the heat pipe envelope were examined using a specially developed test rig, based upon a steady-state evaporation test. A fully automated test facility was developed and validated by testing constant conductance and variable conductance heat pipes (VCHP). Theoretical performance predictions are illustrated in terms of pressure, depicted in 3D-plots, and compared with the test results of the heat pipe performance tests. The design of the VCHP was directed towards the verification of the VCHP mathematical model. The VCHP design is validated and ready for the final testing and model verification.
Directory of Open Access Journals (Sweden)
Ryoichi Chiba
2018-01-01
Full Text Available An analytical solution is derived for one-dimensional transient heat conduction in a composite slab consisting of n layers, whose heat transfer coefficient on an external boundary is an arbitrary function of time. The composite slab, which has thermal contact resistance at n-1 interfaces, as well as an arbitrary initial temperature distribution and internal heat generation, convectively exchanges heat at the external boundaries with two different time-varying surroundings. To obtain the analytical solution, the shifting function method is first used, which yields new partial differential equations under conventional types of external boundary conditions. The solution for the derived differential equations is then obtained by means of an orthogonal expansion technique. Numerical calculations are performed for two composite slabs, whose heat transfer coefficient on the heated surface is either an exponential or a trigonometric function of time. The numerical results demonstrate the effects of temporal variations in the heat transfer coefficient on the transient temperature field of composite slabs.
A multipoint flux approximation of the steady-state heat conduction equation in anisotropic media
Salama, Amgad; Sun, Shuyu; El-Amin, M. F.
2013-01-01
In this work, we introduce multipoint flux (MF) approximation method to the problem of conduction heat transfer in anisotropic media. In such media, the heat flux vector is no longer coincident with the temperature gradient vector. In this case, thermal conductivity is described as a second order tensor that usually requires, at least, six quantities to be fully defined in general three-dimensional problems. The two-point flux finite differences approximation may not handle such anisotropy and essentially more points need to be involved to describe the heat flux vector. In the framework of mixed finite element method (MFE), the MFMFE methods are locally conservative with continuous normal fluxes. We consider the lowest order Brezzi-Douglas-Marini (BDM) mixed finite element method with a special quadrature rule that allows for nodal velocity elimination resulting in a cell-centered system for the temperature. We show comparisons with some analytical solution of the problem of conduction heat transfer in anisotropic long strip. We also consider the problem of heat conduction in a bounded, rectangular domain with different anisotropy scenarios. It is noticed that the temperature field is significantly affected by such anisotropy scenarios. Also, the technique used in this work has shown that it is possible to use the finite difference settings to handle heat transfer in anisotropic media. In this case, heat flux vectors, for the case of rectangular mesh, generally require six points to be described. Copyright © 2013 by ASME.
A multipoint flux approximation of the steady-state heat conduction equation in anisotropic media
Salama, Amgad
2013-03-20
In this work, we introduce multipoint flux (MF) approximation method to the problem of conduction heat transfer in anisotropic media. In such media, the heat flux vector is no longer coincident with the temperature gradient vector. In this case, thermal conductivity is described as a second order tensor that usually requires, at least, six quantities to be fully defined in general three-dimensional problems. The two-point flux finite differences approximation may not handle such anisotropy and essentially more points need to be involved to describe the heat flux vector. In the framework of mixed finite element method (MFE), the MFMFE methods are locally conservative with continuous normal fluxes. We consider the lowest order Brezzi-Douglas-Marini (BDM) mixed finite element method with a special quadrature rule that allows for nodal velocity elimination resulting in a cell-centered system for the temperature. We show comparisons with some analytical solution of the problem of conduction heat transfer in anisotropic long strip. We also consider the problem of heat conduction in a bounded, rectangular domain with different anisotropy scenarios. It is noticed that the temperature field is significantly affected by such anisotropy scenarios. Also, the technique used in this work has shown that it is possible to use the finite difference settings to handle heat transfer in anisotropic media. In this case, heat flux vectors, for the case of rectangular mesh, generally require six points to be described. Copyright © 2013 by ASME.
International Nuclear Information System (INIS)
Assoufid, L.; Khounsary, A.M.
1996-01-01
Results of an experimental study of the contact heat conductance across a single diamond crystal interface with OFHC copper (Cu) are reported. Gallium-indium (GaIn) eutectic was used as an interstitial material. Contact conductance data are important in the design and the prediction of the performance of x-ray diamond monochromators under high-heat-load conditions. Two sets of experiments were carried out. In one, the copper surface in contact with diamond was polished and then electroless plated with 1 μm of nickel, while in the other, the copper contact surface was left as machined. Measured average interface heat conductances are 44.7 ±8 W/cm 2 -K for nonplated copper and 23.0 ±3 W/cm 2 -K for nickel-plated copper. For reference, the thermal contact conductances at a copper-copper interface (without diamond) were also measured, and the results are reported. A typical diamond monochromator, 0.2 mm thick, will absorb about 44 W under a standard undulator beam at the Advanced Photon Source. The measured conductance for nickel-plated copper suggests that the temperature drop across the interface of diamond and nickel-plated copper, with a 20 mm 2 contact area, will be about 10 degree C. Therefore temperature rises are rather modest, and the accuracy of the measured contact conductances presented here are sufficient for design purposes
International Nuclear Information System (INIS)
Futami, Hikaru; Arai, Tsunenori; Yashiro, Hideki; Nakatsuka, Seishi; Kuribayashi, Sachio; Izumi, Youtaro; Tsukada, Norimasa; Kawamura, Masafumi
2006-01-01
To develop an evaluation method for the curative field when using X-ray CT imaging during percutaneous transthoracic cryoablation for lung cancer, we constructed a finite-element heat conduction simulator to estimate temperature distribution in the lung during cryo-treatment. We calculated temperature distribution using a simple two-dimensional finite element model, although the actual temperature distribution spreads in three dimensions. Temperature time-histories were measured within 10 minutes using experimental ex vivo and in vivo lung cryoablation conditions. We adjusted specific heat and thermal conductivity in the heat conduction calculation and compared them with measured temperature time-histories ex vivo. Adjusted lung specific heat was 3.7 J/ (g·deg C) for unfrozen lung and 1.8 J/ (g·deg C) for frozen lung. Adjusted lung thermal conductivity in our finite element model fitted proportionally to the exponential function of lung density. We considered the heat input by blood flow circulation and metabolic heat when we calculated the temperature time-histories during in vivo cryoablation of the lung. We assumed that the blood flow varies in inverse proportion to the change in blood viscosity up to the maximum blood flow predicted from cardiac output. Metabolic heat was set as heat generation in the calculation. The measured temperature time-histories of in vivo cryoablation were then estimated with an accuracy of ±3 deg C when calculated based on this assumption. Therefore, we successfully constructed a two-dimensional heat conduction simulator that is capable of estimating temperature distribution in the lung at the time of first freezing during cryoablation. (author)
Directory of Open Access Journals (Sweden)
Vongsetskul Thammasit
2017-01-01
Full Text Available Graphene oxide-loaded shortening (GOS, an environmentally friendly heat transfer fluid with high thermal conductivity, was successfully prepared by mixing graphene oxide (GO with a shortening. Scanning electron microscopy revealed that GO particles, prepared by the modified Hummer’s method, dispersed well in the shortening. In addition, the latent heat of GOS decreased while their viscosity and thermal conductivity increased with increasing the amount of loaded GO. The thermal conductivity of the GOS with 4% GO was higher than that of pure shortening of ca. three times, from 0.1751 to 0.6022 W/mK, and increased with increasing temperature. The GOS started to be degraded at ca. 360°C. After being heated and cooled at 100°C for 100 cycles, its viscosity slightly decreased and no chemical degradation was observed. Therefore, the prepared GOS is potentially used as environmentally friendly heat transfer fluid at high temperature.
Cooling permafrost embankment by enhancing oriented heat conduction in asphalt pavement
International Nuclear Information System (INIS)
Yinfei, Du; Shengyue, Wang; Shuangjie, Wang; Jianbing, Chen
2016-01-01
Highlights: • Solar radiation heat was prevented from entering the embankment in summer. • The downward heat transfer efficiency in asphalt pavement and embankment reduced. • The net heat accumulation in the embankment decreased. - Abstract: In this paper, a new method was proposed to decrease the heat accumulation in permafrost embankment by controlling an oriented heat transfer in asphalt pavement. Two highly oriented heat-induced structures, named G-OHIS (only gradient thermal conductivity) and G+R-OHIS (combined gradient thermal conductivity and heat reflective layer), were designed by using two indexes of summertime daily heat absorption and annual net heat accumulation on the top of embankment. The results showed that the heat absorptions on the top of embankments of the G-OHIS and G+R-OHIS in summer decreased by 9.9% and 23.2% respectively. The annual net heat accumulation on the top of embankment decreased by 6.2% for the G-OHIS and 37.9% for the G+R-OHIS. Moreover, the summertime mean daily temperatures on the top of embankments of the G-OHIS and G+R-OHIS reduced by 0.74 °C and 1.66 °C respectively. The annual temperature difference on the top of embankment reduced by 1.07 °C for the G-OHIS and 1.96 °C for the G+R-OHIS. The effectiveness of the G-OHIS in reducing pavement temperature was validated by an indoor irradiation test. It is expected to reduce permafrost thawing and other pavement distresses caused by permafrost thawing by controlling an oriented heat transfer in asphalt pavement.
International Nuclear Information System (INIS)
Choi, C. Y.; Park, C. T.; Kim, T. H.; Han, K. N.; Choe, S. H.
1995-01-01
A geometrical inverse heat conduction problem is solved for the development of Infrared Computerized-Axial-Tomography (IR CAT) Scan by using a boundary element method in conjunction with regularization procedure. In this problem, an overspecified temperature condition by infrared scanning is provided on the surface, and is used together with other conditions to solve the position of an unknown boundary (cavity). An auxiliary problem is introduced in the solution of this problem. By defining a hypothetical inner boundary for the auxiliary problem domain, the cavity is located interior to the domain and its position is determined by solving a potential problem. Boundary element method with regularization procedure is used to solve this problem, and the effects of regularization on the inverse solution method are investigated by means of numerical analysis
International Nuclear Information System (INIS)
Soltani, Reza; Dincer, Ibrahim; Rosen, Marc A.
2015-01-01
A Rankine cycle-driven heat pump system is modeled for district heating applications with superheated steam and hot water as products. Energy and exergy analyses are performed, followed by parametric studies to determine the effects of varying operating conditions and environmental parameters on the system performance. The district heating section is observed to be the most inefficient part of system, exhibiting a relative irreversibility of almost 65%, followed by the steam evaporator and the condenser, with relative irreversibilities of about 18% and 9%, respectively. The ambient temperature is observed to have a significant influence on the overall system exergy destruction. As the ambient temperature decreases, the system exergy efficiency increases. The electricity generated can increase the system exergy efficiency at the expense of a high refrigerant mass flow rate, mainly due to the fact that the available heat source is low quality waste heat. For instance, by adding 2 MW of excess electricity on top of the targeted 6 MW of product heat, the refrigerant mass flow rate increases from 12 kg/s (only heat) to 78 kg/s (heat and electricity), while the production of 8 MW of product heat (same total output, but in form of heat) requires a refrigerant mass flow rate of only 16 kg/s. - Highlights: • A new integrated heat pump system is developed for district heating applications. • An analysis and assessment study is undertaken through exergy analysis methodology. • A comparative efficiency evaluation is performed for practical applications. • A parametric study is conducted to investigate how varying operating conditions and state properties affect energy and exergy efficiencies.
Ahmed, Muneeb; Liu, Zhengjun; Humphries, Stanley; Goldberg, S Nahum
2008-11-01
To use an established computer simulation model of radiofrequency (RF) ablation to characterize the combined effects of varying perfusion, and electrical and thermal conductivity on RF heating. Two-compartment computer simulation of RF heating using 2-D and 3-D finite element analysis (ETherm) was performed in three phases (n = 88 matrices, 144 data points each). In each phase, RF application was systematically modeled on a clinically relevant template of application parameters (i.e., varying tumor and surrounding tissue perfusion: 0-5 kg/m(3)-s) for internally cooled 3 cm single and 2.5 cm cluster electrodes for tumor diameters ranging from 2-5 cm, and RF application times (6-20 min). In the first phase, outer thermal conductivity was changed to reflect three common clinical scenarios: soft tissue, fat, and ascites (0.5, 0.23, and 0.7 W/m- degrees C, respectively). In the second phase, electrical conductivity was changed to reflect different tumor electrical conductivities (0.5 and 4.0 S/m, representing soft tissue and adjuvant saline injection, respectively) and background electrical conductivity representing soft tissue, lung, and kidney (0.5, 0.1, and 3.3 S/m, respectively). In the third phase, the best and worst combinations of electrical and thermal conductivity characteristics were modeled in combination. Tissue heating patterns and the time required to heat the entire tumor +/-a 5 mm margin to >50 degrees C were assessed. Increasing background tissue thermal conductivity increases the time required to achieve a 50 degrees C isotherm for all tumor sizes and electrode types, but enabled ablation of a given tumor size at higher tissue perfusions. An inner thermal conductivity equivalent to soft tissue (0.5 W/m- degrees C) surrounded by fat (0.23 W/m- degrees C) permitted the greatest degree of tumor heating in the shortest time, while soft tissue surrounded by ascites (0.7 W/m- degrees C) took longer to achieve the 50 degrees C isotherm, and complete ablation
Unsteady free convection MHD flow between two heated vertical parallel conducting plates
International Nuclear Information System (INIS)
Sanyal, D.C.; Adhikari, A.
2006-01-01
Unsteady free convection flow of a viscous incompressible electrically conducting fluid between two heated conducting vertical parallel plates subjected to a uniform transverse magnetic field is considered. The approximate analytical solutions for velocity, induced field and temperature distribution are obtained for small and large values of magnetic Reynolds number. The problem is also extended to thermometric case. (author)
Numerical simulation on the thermal response of heat-conducting asphalt pavements
Energy Technology Data Exchange (ETDEWEB)
Wang Hong; Wu Shaopeng; Chen Mingyu; Zhang Yuan, E-mail: wusp@whut.edu.c [Key Laboratory of Silicate Materials Science and Engineering, Ministry of Education, Wuhan University of Technology, Wuhan 430070 (China)
2010-05-01
Using asphalt pavements as a solar collector is a subject of current interest all over the world because the sun provides a cheap and abundant source of clean and renewable energy, which can be captured by black asphalt pavements. A heat-conducting device is designed to absorb energy from the sun. In order to validate what parameters are critical in the asphalt collector, a finite element model is developed to predict the thermal response of the heat-conducting device compared to the conventional asphalt mixture. Some factors that may affect the asphalt pavement collector are considered, including the coefficient of heat conductivity of the asphalt pavement, the distance between pipes with the medium, water, and the pipe's diameter. Ultimately, the finite element model can provide pavement engineers with an efficient computational tool that can be a guide to the conductive asphalt solar collector's experiment in the laboratory.
Numerical simulation on the thermal response of heat-conducting asphalt pavements
International Nuclear Information System (INIS)
Wang Hong; Wu Shaopeng; Chen Mingyu; Zhang Yuan
2010-01-01
Using asphalt pavements as a solar collector is a subject of current interest all over the world because the sun provides a cheap and abundant source of clean and renewable energy, which can be captured by black asphalt pavements. A heat-conducting device is designed to absorb energy from the sun. In order to validate what parameters are critical in the asphalt collector, a finite element model is developed to predict the thermal response of the heat-conducting device compared to the conventional asphalt mixture. Some factors that may affect the asphalt pavement collector are considered, including the coefficient of heat conductivity of the asphalt pavement, the distance between pipes with the medium, water, and the pipe's diameter. Ultimately, the finite element model can provide pavement engineers with an efficient computational tool that can be a guide to the conductive asphalt solar collector's experiment in the laboratory.
Heating of a thermally conducting stratified medium. II. A simple plane model of an atmosphre
International Nuclear Information System (INIS)
Lerche, I.; Low, B.C.
1980-01-01
Exact solutions of the following theroretical problem are present: A plane atmosphere is in hydrostatic equilibrium with a uniform gravity. The ideal gas law is assumed. Heat is generated everywhere at a rate proportional to the local density. The atmosphere is maintained in a steady state through cooling by thermal conduction and radiation. This problem is reducible to quadratures for a thermal conductivity which is an arbitrary, but prescribed, function of the temperature, and for a radiative loss which is expressible as the product of the density and an arbitrary, but prescribed, function of the pressure. The analysis is carried out for the case of power law thermal conductivity, and a radiative loss proportional to the square of the density and to the first power of the temperature. The radiative cooling function adopted here has the basic mathematical form for an optically thin medium. The solutions reproduce the macroscopic ordering of a hot ''corona'' separated from a ''photosphere'' by a layer of temperature minimum. The analytic solutions allow direct illustration of the interplay between steady energy transport and the requirements of hydorstatic equilibrium
Thermal conductivity from hierarchical heat sinks using carbon nanotubes and graphene nanosheets.
Hsieh, Chien-Te; Lee, Cheng-En; Chen, Yu-Fu; Chang, Jeng-Kuei; Teng, Hsi-sheng
2015-11-28
The in-plane (kip) and through-plane (ktp) thermal conductivities of heat sinks using carbon nanotubes (CNTs), graphene nanosheets (GNs), and CNT/GN composites are extracted from two experimental setups within the 323-373 K temperature range. Hierarchical three-dimensional CNT/GN frameworks display higher kip and ktp values, as compared to the CNT- and GN-based heat sinks. The kip and ktp values of the CNT/GN-based heat sink reach as high as 1991 and 76 W m(-1) K(-1) at 323 K, respectively. This improved thermal conductivity is attributed to the fact that the hierarchical heat sink offers a stereo thermal conductive network that combines point, line, and plane contact, leading to better heat transport. Furthermore, the compression treatment provided an efficient route to increase both kip and ktp values. This result reveals that the hierarchical carbon structures become denser, inducing more thermal conductive area and less thermal resistivity, i.e., a reduced possibility of phonon-boundary scattering. The correlation between thermal and electrical conductivity (ε) can be well described by two empirical equations: kip = 567 ln(ε) + 1120 and ktp = 20.6 ln(ε) + 36.1. The experimental results are obtained within the temperature range of 323-373 K, suitably complementing the thermal management of chips for consumer electronics.
Dry aerosol jet printing of conductive silver lines on a heated silicon substrate
Efimov, A. A.; Arsenov, P. V.; Protas, N. V.; Minkov, K. N.; Urazov, M. N.; Ivanov, V. V.
2018-02-01
A new method for dry aerosol jet printing conductive lines on a heated substrate is presented. The method is based on the use of a spark discharge generator as a source of dry nanoparticles and a heating plate for their sintering. This method allows creating conductive silver lines on a heated silicon substrate up to 300 °C without an additional sintering step. It was found that for effective sintering lines of silver nanoparticles the temperature of the heated substrate should be about more than 200-250 °C. Average thickness of the sintered silver lines was equal to ∼20 µm. Printed lines showed electrical resistivity equal to 35 μΩ·cm, which is 23 times greater than the resistivity of bulk silver.
Energy Technology Data Exchange (ETDEWEB)
Donne, M.D.; Piazza, G. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reaktortechnik; Goraieb, A.; Sordon, G.
1998-01-01
The four ITER partners propose to use binary beryllium pebble bed as neutron multiplier. Recently this solution has been adopted for the ITER blanket as well. In order to study the heat transfer in the blanket the effective thermal conductivity and the wall heat transfer coefficient of the bed have to be known. Therefore at Forschungszentrum Karlsruhe heat transfer experiments have been performed with a binary bed of beryllium pebbles and the results have been correlated expressing thermal conductivity and wall heat transfer coefficients as a function of temperature in the bed and of the difference between the thermal expansion of the bed and of that of the confinement walls. The comparison of the obtained correlations with the data available from the literature show a quite good agreement. (author)
Aguilar-Reynosa, Alejandra; Romaní, Aloia; Rodríguez-Jasso, Rosa M; Aguilar, Cristóbal N; Garrote, Gil; Ruiz, Héctor A
2017-11-01
This work describes the application of two forms of heating for autohydrolysis pretreatment on isothermal regimen: conduction-convection heating and microwave heating processing using corn stover as raw material for bioethanol production. Pretreatments were performed using different operational conditions: residence time (10-50 min) and temperature (160-200°C) for both pretreatments. Subsequently, the susceptibility of pretreated solids was studied using low enzyme loads, and high substrate loads. The highest conversion was 95.1% for microwave pretreated solids. Also solids pretreated by microwave heating processing showed better ethanol conversion in simultaneous saccharification and fermentation process (92% corresponding to 33.8g/L). Therefore, microwave heating processing is a promising technology in the pretreatment of lignocellulosic materials. Copyright © 2017 Elsevier Ltd. All rights reserved.
Wang, Xiaowei; Li, Huiping; Li, Zhichao
2018-04-01
The interfacial heat transfer coefficient (IHTC) is one of the most important thermal physical parameters which have significant effects on the calculation accuracy of physical fields in the numerical simulation. In this study, the artificial fish swarm algorithm (AFSA) was used to evaluate the IHTC between the heated sample and the quenchant in a one-dimensional heat conduction problem. AFSA is a global optimization method. In order to speed up the convergence speed, a hybrid method which is the combination of AFSA and normal distribution method (ZAFSA) was presented. The IHTC evaluated by ZAFSA were compared with those attained by AFSA and the advanced-retreat method and golden section method. The results show that the reasonable IHTC is obtained by using ZAFSA, the convergence of hybrid method is well. The algorithm based on ZAFSA can not only accelerate the convergence speed, but also reduce the numerical oscillation in the evaluation of IHTC.
Heat transfer analysis of frictional heat dissipation during articulation of femoral implants.
Davidson, J A; Gir, S; Paul, J P
1988-12-01
Previous studies have shown the tendency for frictional heating to occur during articulation of total hip systems in vitro under simulated hip loading conditions. The magnitude of this heating is sufficient to accelerate wear, creep, and oxidation degradation of the UHMWPE bearing surface. It was shown that ceramic articulating systems generate less frictional heating than polished cobalt alloy against UHMWPE. This frictional heating is expected to occur primarily for younger, heavier, and more active patients. Thus, long-term performance of the articulating hip system in these patients may not be that predicted from current, body-temperature wear, creep, and degradation studies. Although the tendency to generate frictional heat has been observed only during in vitro simulated hip loading, a heat transfer analysis of this phenomenon is presented to evaluate the ability of the hip joint to dissipate such heating in vivo. Additional experiments were performed using controlled resistance heaters inside a cobalt femoral head to verify the calculated levels of frictional heat and to assess the heat dissipation under simulated in vivo conditions. The effect of blood perfusion on the effective thermal conductivity of the joint capsule is also discussed. The present study describes and analyzes the various heat dissipation mechanisms present both in vitro and in vivo during articulation of metal and ceramic hip systems. From these tests and analyses, it is concluded that frictional heating in the reconstructed hip cannot be effectively removed, and that degredative elevated temperature processes can be expected to occur in vivo to both the UHMWPE and adjacent tissue under extended periods of excessive patient activity. This is particularly true for metal cobalt alloy femoral heads articulating on UHMWPE versus ceramic heads which generate significantly lower levels of heat.
International Nuclear Information System (INIS)
Aziz, A.; Bouaziz, M.N.
2011-01-01
Highlights: → Analytical solutions for a rectangular fin with temperature dependent heat generation and thermal conductivity. → Graphs give temperature distributions and fin efficiency. → Comparison of analytical and numerical solutions. → Method of least squares used for the analytical solutions. - Abstract: Approximate but highly accurate solutions for the temperature distribution, fin efficiency, and optimum fin parameter for a constant area longitudinal fin with temperature dependent internal heat generation and thermal conductivity are derived analytically. The method of least squares recently used by the authors is applied to treat the two nonlinearities, one associated with the temperature dependent internal heat generation and the other due to temperature dependent thermal conductivity. The solution is built from the classical solution for a fin with uniform internal heat generation and constant thermal conductivity. The results are presented graphically and compared with the direct numerical solutions. The analytical solutions retain their accuracy (within 1% of the numerical solution) even when there is a 60% increase in thermal conductivity and internal heat generation at the base temperature from their corresponding values at the sink temperature. The present solution is simple (involves hyperbolic functions only) compared with the fairly complex approximate solutions based on the homotopy perturbation method, variational iteration method, and the double series regular perturbation method and offers high accuracy. The simple analytical expressions for the temperature distribution, the fin efficiency and the optimum fin parameter are convenient for use by engineers dealing with the design and analysis of heat generating fins operating with a large temperature difference between the base and the environment.
Oriented heat release in asphalt pavement induced by high-thermal-conductivity rods
International Nuclear Information System (INIS)
Du, Yinfei; Wang, Shengyue
2015-01-01
In this paper, a new principle of using aligned high-thermal-conductivity rods to enhance the oriented heat conduction in asphalt pavement was proposed. The results showed that the designed structure absorbed more heat during the day. The heat flow in the designed structure presented a non-uniform horizontal distribution. At the depth of 4 cm, the horizontal and vertical heat fluxes through steel rods were thirteen and ten times higher than those through asphalt mixture, respectively. The maximum temperature of the designed structure reduced by 3.6 °C–6.5 °C at the depth of 4 cm. The results of indoor irradiation test showed a trend consistent with those of numerical simulation. After 500 thousand times of standard axis load were applied, the rutting depth of the designed structure reduced by 43.4%. The principle proposed is expected to be used to induce an oriented heat release accumulated in asphalt pavement and reduce pavement temperature and rutting. - Highlights: • Steel rods were inserted in the middle and bottom layers to build thermal channels. • Steel rods absorbed heat from asphalt mixture and rapidly released them to subgrade. • The heat flux through asphalt mixture decreased and pavement temperature reduced.
Studies on the under ground heating in greenhouse. Measuring of thermal conductivity of soil
Energy Technology Data Exchange (ETDEWEB)
Iwao, Toshio; Takeyama, Koichi
1987-12-21
The underground heating system is an effective method of heating a greenhouse, because the system controls directly the temperature of soil near the roots. The thermal conductivity of soil was measured by the steady-state method, and the heat transfer characteristics in soil were examined in this study. In measuring the thermal conductivity through experiments, firstly the thermal conductivity of a reference plate was measured by the steady-state method, then on the basis of the above mentioned result, the thermal conuctivity of soil was obtained by the comparative method. Toyoura standard sands with particle size of 0.21-0.25mm were used as the sample. As the experiment result, the relations between the thermal conductivity of the reference plate (glass) and temperature was made clear, furthermore through the measurements using these relations, it was clarified that the apparent thermal conductivity is influenced by soil water content. It seems that the difference between the apparent thermal conductivity and the real one is caused mainly by a migration of latent heat with a migration of steam. (10 figs, 7 refs)
Laser ablation under different electron heat conduction models in inertial confinement fusion
Li, Shuanggui; Ren, Guoli; Huo, Wen Yi
2018-06-01
In this paper, we study the influence of three different electron heat conduction models on the laser ablation of gold plane target. Different from previous studies, we concentrate on the plasma conditions, the conversion efficiency from laser into soft x rays and the scaling relation of mass ablation, which are relevant to hohlraum physics study in indirect drive inertial confinement fusion. We find that the simulated electron temperature in corona region is sensitive to the electron heat conduction models. For different electron heat conduction models, there are obvious differences in magnitude and spatial profile of electron temperature. For the flux limit model, the calculated conversion efficiency is sensitive to flux limiters. In the laser ablation of gold, most of the laser energies are converted into x rays. So the scaling relation of mass ablation rate is quite different from that of low Z materials.
Fully coupled heat conduction and deformation analyses of nonlinear viscoelastic composites
Khan, Kamran
2012-05-01
This study presents an integrated micromechanical model-finite element framework for analyzing coupled heat conduction and deformations of particle-reinforced composite structures. A simplified micromechanical model consisting of four sub-cells, i.e., one particle and three matrix sub-cells is formulated to obtain the effective thermomechanical properties and micro-macro field variables due to coupled heat conduction and nonlinear thermoviscoelastic deformation of a particulate composite that takes into account the dissipation of energy from the viscoelastic constituents. A time integration algorithm for simultaneously solving the equations that govern heat conduction and thermoviscoelastic deformations of isotropic homogeneous materials is developed. The algorithm is then integrated to the proposed micromechanical model. A significant temperature generation due to the dissipation effect in the viscoelastic matrix was observed when the composite body is subjected to cyclic mechanical loadings. Heat conduction due to the dissipation of the energy cannot be ignored in predicting the factual temperature and deformation fields within the composite structure, subjected to cyclic loading for a long period. A higher creep resistant matrix material or adding elastic particles can lower the temperature generation. Our analyses suggest that using particulate composites and functionally graded materials can reduce the heat generation due to energy dissipation. © 2012 Elsevier Ltd.
Device for measuring high temperature heat conductivity of solids and melts
International Nuclear Information System (INIS)
Magomedov, Ya.B.; Gadzhiev, G.G.
1990-01-01
A modification of a device for measuring heat conductivity by a compensation method when a thermocouple with gadolinium sulfide being used is suggested. Such a device has less error of measurement (8%), wider interval of working temperatures (300-1600K) and it permits to investigate the material in the wide range of heat conductivity values (0.5-30 W/(mxK)). The stainless steel 12Kh18N10T, lanthanum sulfide and melted quartz were used for the device calibration. The results obtained and the literature data on these materials agree well between each other
The heat current density correlation function: sum rules and thermal conductivity
International Nuclear Information System (INIS)
Singh, Shaminder; Tankeshwar, K; Pathak, K N; Ranganathan, S
2006-01-01
Expressions for the second and fourth sum rules of the heat current density correlation function have been derived in an appropriate ensemble. The thermal conductivity of Lennard-Jones fluids has been calculated using these sum rules for the heat current density correlation function and the Gaussian form of the memory function. It is found that the results obtained for the thermal conductivity are in good agreement with the molecular dynamics simulation results over a wide range of densities and temperatures. Earlier results obtained using the energy current density correlation function are also discussed
The heat current density correlation function: sum rules and thermal conductivity
Energy Technology Data Exchange (ETDEWEB)
Singh, Shaminder [Department of Physics, Panjab University, Chandigarh-160 014 (India); Tankeshwar, K [Department of Physics, Panjab University, Chandigarh-160 014 (India); Pathak, K N [Department of Physics, Panjab University, Chandigarh-160 014 (India); Ranganathan, S [Department of Physics, Royal Military College, Kingston, ON, K7K 7B4 (Canada)
2006-02-01
Expressions for the second and fourth sum rules of the heat current density correlation function have been derived in an appropriate ensemble. The thermal conductivity of Lennard-Jones fluids has been calculated using these sum rules for the heat current density correlation function and the Gaussian form of the memory function. It is found that the results obtained for the thermal conductivity are in good agreement with the molecular dynamics simulation results over a wide range of densities and temperatures. Earlier results obtained using the energy current density correlation function are also discussed.
An inspection to the hyperbolic heat conduction problem in processed meat
Directory of Open Access Journals (Sweden)
Liu Kuo-Chi
2017-01-01
Full Text Available This paper analyzes a hyperbolic heat conduction problem in processed meat with the non-homogenous initial temperature. This problem is related to an experimental study for the exploration of thermal wave behavior in biological tissue. Because the fundamental solution of the hyperbolic heat conduction model is difficult to be obtained, a modified numerical scheme is extended to solve the problem. The present results deviate from that in the literature and depict that the reliability of the experimentally measured properties presented in the literature is doubtful.
Absence of local thermal equilibrium in two models of heat conduction
Dhar, Abhishek; Dhar, Deepak
1998-01-01
A crucial assumption in the conventional description of thermal conduction is the existence of local thermal equilibrium. We test this assumption in two simple models of heat conduction. Our first model is a linear chain of planar spins with nearest neighbour couplings, and the second model is that of a Lorentz gas. We look at the steady state of the system when the two ends are connected to heat baths at temperatures T1 and T2. If T1=T2, the system reaches thermal equilibrium. If T1 is not e...
International Nuclear Information System (INIS)
Vishwakarma, J P; Nath, G
2010-01-01
A self-similar solution for the propagation of a cylindrical shock wave in a dusty gas with heat conduction and radiation heat flux, which is rotating about the axis of symmetry, is investigated. The shock is assumed to be driven out by a piston (an inner expanding surface) and the dusty gas is assumed to be a mixture of non-ideal gas and small solid particles. The density of the ambient medium is assumed to be constant. The heat conduction is expressed in terms of Fourier's law and radiation is considered to be of diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient α R are assumed to vary with temperature and density. Similarity solutions are obtained, and the effects of variation of the parameter of non-idealness of the gas in the mixture, the mass concentration of solid particles and the ratio of density of solid particles to the initial density of the gas are investigated.
Becker, K.; Von Herzen, R.; Kirklin, J.; Evans, R.; Kadko, D.; Kinoshita, M.; Matsubayashi, O.; Mills, R.; Schultz, A.; Rona, P.
We report 70 measurements of conductive heat flow at the 50-m-high, 200-m-diameter TAG active hydrothermal mound, made during submersible surveys with Alvin in 1993 and 1995 and Shinkai 6500 in 1994. The stations were all measured with 5-thermistor, 0.6- or 1-m-long Alvin heat flow probes, which are capable of determining both gradient and thermal conductivity, and were transponder-navigated to an estimated accuracy of ±5-10 m relative to the 10-m-diameter central complex of black smokers. Within 20 m of this complex, conductive heat flow values are extremely variable (0.1- > 100 W/m²), which can only be due to local spatial and possible temporal variability in the immediate vicinity of the vigorous discharge sites. A similar local variability is suggested in the “Kremlin” area of white smokers to the southeast of the black smoker complex. On the south and southeast side of the mound, there is very high heat flow (3.7- > 25 W/m²) on the sedimented terraces that slope down from the Kremlin area. Heat flow is also high (0.3-3 W/m²) in the pelagic carbonate sediments on the surrounding seafloor within a few tens of meters of the southwest, northwest, and northeast sides of the mound. On the west side of the sulfide rubble plateau that surrounds the central black smoker peak, there is a coherent belt of very low heat flow (smokers, suggestive of local, shallow recharge of bottom water. The three submersible surveys spanned nearly two years, but showed no indication of any temporal variability in conductive heat flow over this time scale, whether natural or induced by ODP drilling in 1994.
High temperature thermal conductivity measurements of UO2 by Direct Electrical Heating. Final report
International Nuclear Information System (INIS)
Bassett, B.
1980-10-01
High temperature properties of reactor type UO 2 pellets were measured using a Direct Electrical Heating (DEH) Facility. Modifications to the experimental apparatus have been made so that successful and reproducible DEH runs may be carried out while protecting the pellets from oxidation at high temperature. X-ray diffraction measurements on the UO 2 pellets have been made before and after runs to assure that sample oxidation has not occurred. A computer code has been developed that will model the experiment using equations that describe physical properties of the material. This code allows these equations to be checked by comparing the model results to collected data. The thermal conductivity equation for UO 2 proposed by Weilbacher has been used for this analysis. By adjusting the empirical parameters in Weilbacher's equation, experimental data can be matched by the code. From the several runs analyzed, the resulting thermal conductivity equation is lambda = 1/4.79 + 0.0247T/ + 1.06 x 10 -3 exp[-1.62/kT/] - 4410. exp[-3.71/kT/] where lambda is in w/cm K, k is the Boltzman constant, and T is the temperature in Kelvin
Temperature dependency of the thermal conductivity of porous heat storage media
Hailemariam, Henok; Wuttke, Frank
2018-04-01
Analyzing the variation of thermal conductivity with temperature is vital in the design and assessment of the efficiency of sensible heat storage systems. In this study, the temperature variation of the thermal conductivity of a commercial cement-based porous heat storage material named - Füllbinder L is analyzed in saturated condition in the temperature range between 20 to 70°C (water based storage) with a steady state thermal conductivity and diffusivity meter. A considerable decrease in the thermal conductivity of the saturated sensible heat storage material upon increase in temperature is obtained, resulting in a significant loss of system efficiency and slower loading/un-loading rates, which when unaccounted for can lead to the under-designing of such systems. Furthermore, a new empirical prediction model for the estimation of thermal conductivity of cement-based porous sensible heat storage materials and naturally occurring crystalline rock formations as a function of temperature is proposed. The results of the model prediction are compared with the experimental results with satisfactory results.
Estimating thermal diffusivity and specific heat from needle probe thermal conductivity data
Waite, W.F.; Gilbert, L.Y.; Winters, W.J.; Mason, D.H.
2006-01-01
Thermal diffusivity and specific heat can be estimated from thermal conductivity measurements made using a standard needle probe and a suitably high data acquisition rate. Thermal properties are calculated from the measured temperature change in a sample subjected to heating by a needle probe. Accurate thermal conductivity measurements are obtained from a linear fit to many tens or hundreds of temperature change data points. In contrast, thermal diffusivity calculations require a nonlinear fit to the measured temperature change occurring in the first few tenths of a second of the measurement, resulting in a lower accuracy than that obtained for thermal conductivity. Specific heat is calculated from the ratio of thermal conductivity to diffusivity, and thus can have an uncertainty no better than that of the diffusivity estimate. Our thermal conductivity measurements of ice Ih and of tetrahydrofuran (THF) hydrate, made using a 1.6 mm outer diameter needle probe and a data acquisition rate of 18.2 pointss, agree with published results. Our thermal diffusivity and specific heat results reproduce published results within 25% for ice Ih and 3% for THF hydrate. ?? 2006 American Institute of Physics.
International Nuclear Information System (INIS)
Choudhury, M.; Hazarika, G.C.; Sibanda, P.
2013-01-01
We investigate the effects of temperature dependent viscosity and thermal conductivity on natural convection flow of a viscous incompressible electrically conducting fluid along a vertical wavy surface. The flow is permeated by uniform transverse magnetic field. The fluid viscosity and thermal conductivity are assumed to vary as inverse linear functions of temperature. The coupled non-linear systems of partial differential equations are solved using the finite difference method. The effects of variable viscosity parameter, variable thermal conductivity parameter and magnetic parameter on the flow field and the heat transfer characteristics are discussed and shown graphically. (author)
An Experimental Study on Heat Conduction and Thermal Contact Resistance for the AlN Flake
Directory of Open Access Journals (Sweden)
Huann-Ming Chou
2013-01-01
Full Text Available The electrical technology has been a fast development over the past decades. Moreover, the tendency of microelements and dense division multiplex is significantly for the electrical industries. Therefore, the high thermal conductible and electrical insulating device will be popular and important. It is well known that AlN still maintains stablility in the high temperature. This is quite attractive for the research and development department. Moreover, the thermal conduct coefficient of AlN is several times larger than the others. Therefore, it has been thought to play an important role for the radiator of heat source in the future. Therefore, this paper is focused on the studies of heat conduction and thermal contact resistance between the AlN flake and the copper specimens. The heating temperatures and the contact pressures were selected as the experimental parameters. According to the experimental results, the materials are soft and the real contact areas between the interfaces significantly increase under higher temperatures. As a result, the thermal contact resistance significantly decreases and the heat transfer rate increases with increasing the heating temperature or the contact pressures.
Gaspard, Pierre; Gilbert, Thomas
2017-04-01
We present a systematic computation of the heat conductivity of the Markov jump process modeling the energy exchanges in an array of locally confined hard spheres at the conduction threshold. Based on a variational formula (Sasada 2016 (arXiv:1611.08866)), explicit upper bounds on the conductivity are derived, which exhibit a rapid power-law convergence towards an asymptotic value. We thereby conclude that the ratio of the heat conductivity to the energy exchange frequency deviates from its static contribution by a small negative correction, its dynamic contribution, evaluated to be -0.000 373 in dimensionless units. This prediction is corroborated by kinetic Monte Carlo simulations which were substantially improved compared to earlier results.
ICRF heating analysis on ASDEX plasmas
International Nuclear Information System (INIS)
Itoh, Sanae; Itoh, Kimitaka; Fukuyama, Atsushi; Morishita, Takayuki; Steinmetz, K.; Noterdaeme, J.-M.
1988-01-01
ICRF (ion cyclotron range of frequencies) waves heating in an ASDEX tokamak are analyzed. The excitation, propagation and absorption are studied by using a global wave code. This analysis is combined with a Fokker-Planck code. The waveform in the plasma, the loading resistance and the reactance of the antenna are calculated for both the minority ion heating and the second harmonic resonance heating. Attention is given to the change of the antenna loading associated with the L/H transition. Optimum conditions for the loading are discussed. In the minority heating case, the tail generation and thermalization are analyzed. Spatial profiles of the tail-ion temperature and the power transferred to the bulk electrons and ions are obtained. Central as well as off-central heating cases are investigated. The effect of the reactive electric field is discussed in connection with rf losses and impurity production. (author)
Evaluation of thermal conductivity of heat-cured acrylic resin mixed with A1203
Ebadian B.; Parkan MA.
2002-01-01
One of the most important characteristics of denture base is thermal conductivity. This property has a major role in secretions of salivary glands and their enzymes, taste of the food and gustatory response. Polymethyl methacrylate used in prosthodontics is relatively an insulator. Different materials such as metal fillers and ceramics have been used to solve this problem. The aim of this study was the evaluation of AI2O3 effect on thermal conductivity of heat-cured acrylic resin. Acrylic res...
Heat conduction in one-dimensional chains and nonequilibrium Lyapunov spectrum
International Nuclear Information System (INIS)
Posch, H.A.; Hoover, W.G.
1998-01-01
We define and study the heat conductivity κ and the Lyapunov spectrum for a modified 'ding-a-ling' chain undergoing steady heat flow. Free and bound particles alternate along a chain. In the present work, we use a linear gravitational potential to bind all the even-numbered particles to their lattice sites. The chain is bounded by two stochastic heat reservoirs, one hot and one cold. The Fourier conductivity of the chain decreases smoothly to a finite large-system limit. Special treatment of satellite collisions with the stochastic boundaries is required to obtain Lyapunov spectra. The summed spectra are negative, and correspond to a relatively small contraction in phase space, with the formation of a multifractal strange attractor. The largest of the Lyapunov exponents for the ding-a-ling chain appears to converge to a limiting value with increasing chain length, so that the large-system Lyapunov spectrum has a finite limit. copyright 1998 The American Physical Society
Thermal conductivity and diffusivity of biomaterials measured with self-heated thermistors
Valvano, J. W.; Cochran, J. R.; Diller, K. R.
1985-05-01
This paper presents an experimental method to measure the thermal conductivity and thermal diffusivity of biomaterials. Self-heated thermistor probes, inserted into the tissue of interest, are used to deliver heat as well as to monitor the rate of heat removal. An empirical calibration procedure allows accurate thermal-property measurements over a wide range of tissue temperatures. Operation of the instrument in three media with known thermal properties shows the uncertainty of measurements to be about 2%. The reproducibility is 0.5% for the thermal-conductivity measurements and 2% for the thermal-diffusivity measurements. Thermal properties were measured in dog, pig, rabbit, and human tissues. The tissues included kidney, spleen, liver, brain, heart, lung, pancreas, colon cancer, and breast cancer. Thermal properties were measured for 65 separate tissue samples at 3, 10, 17, 23, 30, 37, and 45°C. The results show that the temperature coefficient of biomaterials approximates that of water.
Experimental investigation of thermal conduction and related phenomena in a laser heated plasma
International Nuclear Information System (INIS)
Gray, D.R.
1979-02-01
Thermal conduction in plasmas is of major importance especially in controlled nuclear fusion studies. Direct measurements are rare. When the temperature gradient in a plasma becomes large enough classical thermal conduction (Heat flux q = -kΔT) no longer applies and it is thought that q is limited to some fraction of the free streaming limit qsub(m). The main experiment is the heating of a z-pinch plasma by a fast rising, intense carbon dioxide laser pulse. Electron temperature and density in time and space are diagnosed by ruby laser scattering. The profiles obtained were consistent with a flux limited to approximately 3% of the free streaming limit. Ion acoustic turbulence is observed along the temperature gradient. It is shown that the observed turbulence level is consistent with the heat flux limitation. At electron densities > 10 17 cm -3 backscattered light is observed from the plasma whose growth rate implies that it is Brillouin scattered. (author)
One-dimensional heat conduction equation of the polar bear hair
Directory of Open Access Journals (Sweden)
Zhu Wei-Hong
2015-01-01
Full Text Available Hairs of a polar bear (Ursus maritimus possess special membrane-pore structure. The structure enables the polar bear to survive in the harsh Arctic regions. In this paper, the membrane-pore structure be approximately considered as fractal space, 1-D heat conduction equation of the polar bear hair is established and the solution of the equation is obtained.
Kenjeres, S.
2016-01-01
In the present paper we give a concise review of some recent highlights of our research dealing with electromagnetic control of flow, mixing and heat transfer of electrically conductive or magnetized fluids. We apply a combination of state-of-art numerical (DNS and LES) and experimental (PIV and
Laminar forced convective/conductive heat transfer by finite element method
International Nuclear Information System (INIS)
Kushwaha, H.S.; Kakodkar, A.
1982-01-01
The present study is directed at developing a finite element computer program for solution of decoupled convective/conductive heat transfer problems. Penalty function formulation has been used to solve momentum equations and subsequently transient energy equation is solved using modified Crank-Nicolson method. The optimal upwinding scheme has been employed in energy equation to remove oscillations at high Peclet number. (author)
International Nuclear Information System (INIS)
Mueller, P.
1977-01-01
Equipment for the evaporation of metals and other conducting materials by electron beam heating is to be improved by surrou nding the evaporation equipment with a grid, which has a negative voltage compared to the cathode. This achieves the state where the cathode is hit and damaged less by the ions formed, so that its life period is prolonged. (UWI) [de
Transmission coefficient and heat conduction of a harmonic chain with random masses
International Nuclear Information System (INIS)
Verheggen, T.
1979-01-01
We find upper and lower bounds for the transmission coefficient of a chain of random masses. Using these bounds we show that the heat conduction in such a chain does not obey Fourier's law: For different temperatures at the ends of a chain containing N particles the energy flux falls off like Nsup(-1/2) rather than N -1 . (orig.)
COYOTE: a finite element computer program for nonlinear heat conduction problems
International Nuclear Information System (INIS)
Gartling, D.K.
1978-06-01
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
Heat conduction in a plate-type fuel element with time-dependent boundary conditions
International Nuclear Information System (INIS)
Faya, A.J.G.; Maiorino, J.R.
1981-01-01
A method for the solution of boundary-value problems with variable boundary conditions is applied to solve a heat conduction problem in a plate-type fuel element with time dependent film coefficient. The numerical results show the feasibility of the method in the solution of this class of problems. (Author) [pt
Low-temperature specific-heat and thermal-conductivity of silica aerogels
DEFF Research Database (Denmark)
Bernasconi, A.; Sleator, T.; Posselt, D.
1992-01-01
Specific heat, C(p), and thermal conductivity, lambda, have been measured on a series of base-catalyzed silica aerogels at temperatures between 0.05 and 20 K. Results for both C(p)(T) and lambda(T) confirm that the different length-scale regions observed in the aerogel structure are reflected...
Kluitenberg, G.A.; Groot, S.R. de; Mazur, P.
1953-01-01
The relativistic thermodynamics of irreversible processes is developed for an isotropic mixture in which heat conduction, diffusion, viscous flow, chemical reactions and their cross-phenomena may occur. The four-vectors, representing the relative flows of matter, are defined in such a way that, in
Directory of Open Access Journals (Sweden)
B. Stojanovic
2009-06-01
Full Text Available The paper presents experimental research of thermal conductivity coefficients of the siliceous sand bed fluidized by air and an experimental investigation of the particle size influence on the heat transfer coefficient between fluidized bed and inclined exchange surfaces. The measurements were performed for the specific fluidization velocity and sand particle diameters d p=0.3, 0.5, 0.9 mm. The industrial use of fluidized beds has been increasing rapidly in the past 20 years owing to their useful characteristics. One of the outstanding characteristics of a fluidized bed is that it tends to maintain a uniform temperature even with nonuniform heat release. On the basis of experimental research, the influence of the process's operational parameters on the obtained values of the bed's thermal conductivity has been analyzed. The results show direct dependence of thermal conductivity on the intensity of mixing, the degree of fluidization, and the size of particles. In the axial direction, the coefficients that have been treated have values a whole order higher than in the radial direction. Comparison of experimental research results with experimental results of other authors shows good agreement and the same tendency of thermal conductivity change. It is well known in the literature that the value of the heat transfer coefficient is the highest in the horizontal and the smallest in the vertical position of the heat exchange surface. Variation of heat transfer, depending on inclination angle is not examined in detail. The difference between the values of the relative heat transfer coefficient between vertical and horizontal heater position for all particle sizes reduces by approximately 15% with the increase of fluidization rate.
Fourier heat conduction as a phenomenon described within the scope of the second law
Energy Technology Data Exchange (ETDEWEB)
Jesudason, Christopher G. [Chemistry Department and Center for Theoretical and Computational Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia)
2014-12-10
The historical development of the Carnot cycle necessitated the construction of isothermal and adiabatic pathways within the cycle that were also mechanically 'reversible' which lead eventually to the Kelvin-Clausius development of the entropy function S where for any reversible closed path C, ∮{sub C} dS = 0 based on an infinite number of concatenated Carnot engines that approximated the said path and where for each engine ΔQ{sub 1}/T{sub 1}+ΔQ{sub 2}/T{sub 2} = 0 where the Q's and T's are the heat absorption increments and temperature respectively with the subscripts indicating the isothermal paths (1;2) where for the Carnot engine, the heat 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
Directory of Open Access Journals (Sweden)
Victor ANJO
2012-08-01
Full Text Available The solidification of molten metal during the casting process involves heat transfer from the molten metal to the mould, then to the atmosphere. The mechanical properties and grain size of metals are determined by the heat transfer process during solidification. The aim of this study is to numerically stimulate the steady conduction heat transfer during the solidification of aluminum in green sand mould using finite difference analysis 2D. The properties of materials used are industrial AI 50/60 AFS green sand mould, pure aluminum and MATLAB 7.0.1. for the numerical simulation. The method includes; the finite difference analysis of the heat conduction equation in steady (Laplaces and transient states and using MATLAB to numerically stimulate the thermal flow and cooling curve. The results obtained are: the steady state thermal flow in 2D and transient state cooling curve of casting. The results obtain were consider relevant in the control of the grain size and mechanical properties of the casting.
Analysis of heat transfer under high heat flux nucleate boiling conditions
Energy Technology Data Exchange (ETDEWEB)
Liu, Y.; Dinh, N. [3145 Burlington Laboratories, Raleigh, NC (United States)
2016-07-15
Analysis was performed for a heater infrared thermometric imaging temperature data obtained from high heat flux pool boiling and liquid film boiling experiments BETA. With the OpenFOAM solver, heat flux distribution towards the coolant was obtained by solving transient heat conduction of heater substrate given the heater surface temperature data as boundary condition. The so-obtained heat flux data was used to validate them against the state-of-art wall boiling model developed by D. R. Shaver (2015) with the assumption of micro-layer hydrodynamics. Good agreement was found between the model prediction and data for conditions away from the critical heat flux (CHF). However, the data indicate a different heat transfer pattern under CHF, which is not captured by the current model. Experimental data strengthen the notion of burnout caused by the irreversible hot spot due to failure of rewetting. The observation forms a basis for a detailed modeling of micro-layer hydrodynamics under high heat flux.
Analysis of heat transfer under high heat flux nucleate boiling conditions
International Nuclear Information System (INIS)
Liu, Y.; Dinh, N.
2016-01-01
Analysis was performed for a heater infrared thermometric imaging temperature data obtained from high heat flux pool boiling and liquid film boiling experiments BETA. With the OpenFOAM solver, heat flux distribution towards the coolant was obtained by solving transient heat conduction of heater substrate given the heater surface temperature data as boundary condition. The so-obtained heat flux data was used to validate them against the state-of-art wall boiling model developed by D. R. Shaver (2015) with the assumption of micro-layer hydrodynamics. Good agreement was found between the model prediction and data for conditions away from the critical heat flux (CHF). However, the data indicate a different heat transfer pattern under CHF, which is not captured by the current model. Experimental data strengthen the notion of burnout caused by the irreversible hot spot due to failure of rewetting. The observation forms a basis for a detailed modeling of micro-layer hydrodynamics under high heat flux.
National Research Council Canada - National Science Library
Bjerke, Todd
2001-01-01
The temperature increase in the main body portion of a kinetic energy penetrator flying at sea level with a speed of 1,500 m/s was calculated using an analytical conduction analysis with a convective boundary condition...
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). 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.
Heat conduction in double-walled carbon nanotubes with intertube additional carbon atoms.
Cui, Liu; Feng, Yanhui; Tan, Peng; Zhang, Xinxin
2015-07-07
Heat conduction of double-walled carbon nanotubes (DWCNTs) with intertube additional carbon atoms was investigated for the first time using a molecular dynamics method. By analyzing the phonon vibrational density of states (VDOS), we revealed that the intertube additional atoms weak the heat conduction along the tube axis. Moreover, the phonon participation ratio (PR) demonstrates that the heat transfer in DWCNTs is dominated by low frequency modes. The added atoms cause the mode weight factor (MWF) of the outer tube to decrease and that of the inner tube to increase, which implies a lower thermal conductivity. The effects of temperature, tube length, and the number and distribution of added atoms were studied. Furthermore, an orthogonal array testing strategy was designed to identify the most important structural factor. It is indicated that the tendencies of thermal conductivity of DWCNTs with added atoms change with temperature and length are similar to bare ones. In addition, thermal conductivity decreases with the increasing number of added atoms, more evidently for atom addition concentrated at some cross-sections rather than uniform addition along the tube length. Simultaneously, the number of added atoms at each cross-section has a considerably more remarkable impact, compared to the tube length and the density of chosen cross-sections to add atoms.
Convective and conduction heat transfer study on a mig-type electron gun
International Nuclear Information System (INIS)
Patire Junior, H.; Barroso, J.J.
1996-01-01
A convective and conducting heat transfer study of a magnetron injection electron gun has been made to minimize the temperature distribution in the gun elements while keeping the required operating temperature at 1000 0 C of the emitter. Appropriate materials were selected to reduce thermal losses and to improve the gun design from a constructional point of view aiming at extending the capabilities of the electron gun. A thermal probe to determine the air velocity and the convective heat transfer coefficient has been constructed to determine the external boundary condition of the ceramic shell and external flanges. A study the contact resistance for all the gun elements has been made to minimize the conduction thermal losses. A software has been used to simulate a thermal model considering the three processes of thermal transfer, namely, conduction, convection and radiation and the influence of the physical properties of the materials used. (author). 7 refs., 5 figs., 1 tab
Effect of wall conductances on hydromagnetic flow and heat transfer in a rotating channel
International Nuclear Information System (INIS)
Mazumder, B.S.
1977-01-01
Wall conductance effects on the hydromagnetic flow and heat transfer between two parallel plates in a rotating frame of reference has been studied when the liquid is permeated by a transverse magnetic field. An exact solution of the governing equation has been obtained. It is found that the velocity current density and the temperature depend only on the sum of the wall conductances phi 1 + phi 2 = phi but magnetic field depends on the individual values of phi 1 and phi 2 where phi 1 and phi 2 are respectively the wall conductance ratios of the upper and lower walls. (Auth.)
Kovtanyuk, Andrey E.; Botkin, Nikolai D.; Hoffmann, Karl-Heinz
2012-01-01
Radiative-conductive heat transfer in a medium bounded by two reflecting and radiating plane surfaces is considered. This process is described by a nonlinear system of two differential equations: an equation of the radiative heat transfer
Electrical Energy Harvesting from Cooker’s Wasted Heat with Using Conduction Cooling
Directory of Open Access Journals (Sweden)
Amouzard Mahdiraji Wincent Ghafour
2018-01-01
Full Text Available In order meet the demand of electricity in current era, the need for new sources of energy even in very minimal amount, could be done with proper research and technology advancement in order to convert as much wasted energy as possible. Collecting and analyses cooker’s wasted heat as a main wasted energy source become the main interest for this research. This application can be installed either in household usage or commercial usage. Based on majority stove in household datasheet it shown that the efficiency of the stove is approximately 50%. With half of the efficiency turn into wasted heat, this application is suitable for thermoelectric generator (TEG to harvest the heat. The objective of this research is to determine whether the thermoelectric generator (TEG would able to power the 3V LED light as a small lighting system in household. Several designs with five TEGs in series circuit are tested to the application to analyses which method generated a better result. Since this research only focus in using a conduction cooling, aluminum heat sink will be utilized either for heat absorption or heat rejection. The maximum temperature differences between hot side and cold side is 209.83 °C with average power approximately 0.1 W.
Influence of heat conducting substrates on explosive crystallization in thin layers
Schneider, Wilhelm
2017-09-01
Crystallization in a thin, initially amorphous layer is considered. The layer is in thermal contact with a substrate of very large dimensions. The energy equation of the layer contains source and sink terms. The source term is due to liberation of latent heat in the crystallization process, while the sink term is due to conduction of heat into the substrate. To determine the latter, the heat diffusion equation for the substrate is solved by applying Duhamel's integral. Thus, the energy equation of the layer becomes a heat diffusion equation with a time integral as an additional term. The latter term indicates that the heat loss due to the substrate depends on the history of the process. To complete the set of equations, the crystallization process is described by a rate equation for the degree of crystallization. The governing equations are then transformed to a moving co-ordinate system in order to analyze crystallization waves that propagate with invariant properties. Dual solutions are found by an asymptotic expansion for large activation energies of molecular diffusion. By introducing suitable variables, the results can be presented in a universal form that comprises the influence of all non-dimensional parameters that govern the process. Of particular interest for applications is the prediction of a critical heat loss parameter for the existence of crystallization waves with invariant properties.
Haddout, Y.; Essaghir, E.; Oubarra, A.; Lahjomri, J.
2018-06-01
Thermally developing laminar slip flow through a micropipe and a parallel plate microchannel, with axial heat conduction and uniform wall heat flux, is studied analytically by using a powerful method of self-adjoint formalism. This method results from a decomposition of the elliptic energy equation into a system of two first-order partial differential equations. The advantage of this method over other methods, resides in the fact that the decomposition procedure leads to a selfadjoint problem although the initial problem is apparently not a self-adjoint one. The solution is an extension of prior studies and considers a first order slip model boundary conditions at the fluid-wall interface. The analytical expressions for the developing temperature and local Nusselt number in the thermal entrance region are obtained in the general case. Therefore, the solution obtained could be extended easily to any hydrodynamically developed flow and arbitrary heat flux distribution. The analytical results obtained are compared for select simplified cases with available numerical calculations and they both agree. The results show that the heat transfer characteristics of flow in the thermal entrance region are strongly influenced by the axial heat conduction and rarefaction effects which are respectively characterized by Péclet and Knudsen numbers.
Numerical methods to solve the two-dimensional heat conduction equation
International Nuclear Information System (INIS)
Santos, R.S. dos.
1981-09-01
A class of numerical methods, called 'Hopscotch Algorithms', was used to solve the heat conduction equation in cylindrical geometry. Using a time dependent heat source, the temperature versus time behaviour of cylindric rod was analysed. Numerical simulation was used to study the stability and the convergence of each different method. Another test had the temperature specified on the outer surface as boundary condition. The various Hopscotch methods analysed exhibit differing degrees of accuracy, few of them being so accurate as the ADE method, but requiring more computational operations than the later, were observed. Finally, compared with the so called ODD-EVEN method, two other Hopscotch methods, are more time consuming. (Author) [pt
Improving the conductivity of single-walled carbon nanotubes films by heat treatment
Energy Technology Data Exchange (ETDEWEB)
Wang Jiaping [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Superfine Microstructures, 1295 Dingxi Road, Shanghai 200050 (China); Sun Jing, E-mail: jingsun@mail.sic.ac.c [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Superfine Microstructures, 1295 Dingxi Road, Shanghai 200050 (China); Gao Lian, E-mail: liangaoc@online.sh.c [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Superfine Microstructures, 1295 Dingxi Road, Shanghai 200050 (China); Liu Yangqiao; Wang Yan; Zhang Jing [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Superfine Microstructures, 1295 Dingxi Road, Shanghai 200050 (China); Kajiura, Hisashi; Li Yongming; Noda, Kazuhiro [Advanced Materials Laboratories, Sony Corporation, Atsugi Tec. No. 2, 4-16-1 Okata Atsugi, Kanagawa 243-0021 (Japan)
2009-10-19
A simple heat treatment method was applied to remove surfactants remaining in the single-walled carbon nanotubes (SWNTs) films at 300 deg. C for 5 h in air. Scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and reflected light interference microscope (RLIM) were employed to verify the elimination of surfactants. The comprehensive performance, especially the conductivity, could be improved by more than one order after heat treatment. For example, using SDBS as dispersant, the sheet resistance decreased from 782,600 OMEGA/square to 40,460 OMEGA/square with the transmittance of about 99.5% at 550 nm.
DEFF Research Database (Denmark)
Zhou, Mingdong; Alexandersen, Joe; Sigmund, Ole
2016-01-01
This paper presents an industrial application of topology optimization for combined conductive and convective heat transfer problems. The solution is based on a synergy of computer aided design and engineering software tools from Dassault Systemes. The considered physical problem of steady......-state heat transfer under convection is simulated using SIMULIA-Abaqus. A corresponding topology optimization feature is provided by SIMULIA-Tosca. By following a standard workflow of design optimization, the proposed solution is able to accommodate practical design scenarios and results in efficient...
ORINC: a one-dimensional implicit approach to the inverse heat conduction problem. [PWR
Energy Technology Data Exchange (ETDEWEB)
Ott, L.J.; Hedrick, R.A.
1977-10-18
The report develops an implicit solution technique to determine both the transient surface temperature and the transient surface heat flux of electrically heated rods given the power input and an ''indicated'' internal temperature during a simulated loss-of-coolant accident. A digital computer program ORINC (ORNL Inverse Code) is developed which solves a one-dimensional, transient, lumped parameter, implicit formulation of the conduction equation at each bundle thermocouple position in the Thermal-Hydraulic Test Facility (THTF).
International Nuclear Information System (INIS)
Blanc, Gilles
1996-01-01
This work is devoted to the solution of the inverse multidimensional heat conduction problem. The first part is the determination of a methodology for determining the minimum number of sensors and the best sensor locations. The method is applied to a 20 problem but the extension to 30 problems is quite obvious. This methodology is based on the study of the rate of representation. This new concept allows to determine the quantity and the quality of the information obtain from the various sensors. The rate of representation is a useful tool for experimental design. lt can be determined very quickly by the transposed matrix method. This approach was validated with an experimental set-up. The second part is the development of a method that uses thermal strain measurement instead of temperature measurements to estimate the unknown thermal boundary conditions. We showed that this new sensor has two advantages in comparison with the classical temperature measurements: higher frequency can be estimated and smaller number of sensors can be used for 20 problems. The main weakness is, presently, the fact that the method can only be applied to beams. The results obtained from the numerical simulations were validated by the analysis of experimental data obtained on an experimental set-up especially designed and built for this study. (author) [fr
Sub-μL measurements of the thermal conductivity and heat capacity of liquids.
López-Bueno, C; Bugallo, D; Leborán, V; Rivadulla, F
2018-03-07
We present the analysis of the thermal conductivity, κ, and heat capacity, C p , of a wide variety of liquids, covering organic molecular solvents, ionic liquids and water-polymer mixtures. These data were obtained from ≈0.6 μL samples, using an experimental development based on the 3ω method, capable of the simultaneous measurement of κ and C p . In spite of the different type and strength of interactions, expected in a priori so different systems, the ratio of κ to the sound velocity is approximately constant for all of them. This is the consequence of a similar atomic density for all these liquids, notwithstanding their different molecular structures. This was corroborated experimentally by the observation of a C p /V ≈ 1.89 × 10 6 J K -1 m -3 (≈3R/2 per atom), for all liquids studied in this work. Finally, the very small volume of the sample required in this experimental method is an important advantage for the characterization of systems like nanofluids, in which having a large amount of the dispersed phase is sometimes extremely challenging.
International Nuclear Information System (INIS)
Olson, T.S.; Hiscock, W.A.
1990-01-01
Stability and causality are studied for linear perturbations about equilibrium in Carter's ''regular'' theory of relativistic heat-conducting fluids. The ''regular'' theory, when linearized around an equilibrium state having vanishing expansion and shear, is shown to be equivalent to the inviscid limit of the linearized Israel-Stewart theory of relativistic dissipative fluids for a particular choice of the second-order coefficients β 1 and γ 2 . A set of stability conditions is determined for linear perturbations of a general inviscid Israel-Stewart fluid using a monotonically decreasing energy functional. It is shown that, as in the viscous case, stability implies that the characteristic velocities are subluminal and that perturbations obey hyperbolic equations. The converse theorem is also true. We then apply this analysis to a nonrelativistic Boltzmann gas and to a strongly degenerate free Fermi gas in the ''regular'' theory. Carter's ''regular'' theory is shown to be incapable of correctly describing the nonrelativistic Boltzmann gas and the degenerate Fermi gas (at all temperatures)
Simultaneous measurement of thermal conductivity and heat capacity by flash thermal imaging methods
Tao, N.; Li, X. L.; Sun, J. G.
2017-06-01
Thermal properties are important for material applications involved with temperature. Although many measurement methods are available, they may not be convenient to use or have not been demonstrated suitable for testing of a wide range of materials. To address this issue, we developed a new method for the nondestructive measurement of the thermal effusivity of bulk materials with uniform property. This method is based on the pulsed thermal imaging-multilayer analysis (PTI-MLA) method that has been commonly used for testing of coating materials. Because the test sample for PTI-MLA has to be in a two-layer configuration, we have found a commonly used commercial tape to construct such test samples with the tape as the first-layer material and the bulk material as the substrate. This method was evaluated for testing of six selected solid materials with a wide range of thermal properties covering most engineering materials. To determine both thermal conductivity and heat capacity, we also measured the thermal diffusivity of these six materials by the well-established flash method using the same experimental instruments with a different system setup. This paper provides a description of these methods, presents detailed experimental tests and data analyses, and discusses measurement results and their comparison with literature values.
Performance Analysis of Photovoltaic Water Heating System
Directory of Open Access Journals (Sweden)
Tomas Matuska
2017-01-01
Full Text Available Performance of solar photovoltaic water heating systems with direct coupling of PV array to DC resistive heating elements has been studied and compared with solar photothermal systems. An analysis of optimum fixed load resistance for different climate conditions has been performed for simple PV heating systems. The optimum value of the fixed load resistance depends on the climate, especially on annual solar irradiation level. Use of maximum power point tracking compared to fixed optimized load resistance increases the annual yield by 20 to 35%. While total annual efficiency of the PV water heating systems in Europe ranges from 10% for PV systems without MPP tracking up to 15% for system with advanced MPP trackers, the efficiency of solar photothermal system for identical hot water load and climate conditions is more than 3 times higher.
Statistical properties of Joule heating rate, electric field and conductances at high latitudes
Directory of Open Access Journals (Sweden)
A. T. Aikio
2009-07-01
Full Text Available 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 K_{p} dependence of parameters with high temporal and spatial resolution.
All the parameters show a clear MLT variation, which is different for low and high K_{p} 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 K_{p}≥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 (K_{p}<3 and K_{p}≥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
Statistical properties of Joule heating rate, electric field and conductances at high latitudes
Directory of Open Access Journals (Sweden)
A. T. Aikio
2009-07-01
Full Text Available 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
Heat Transfer Analysis of Localized Heat-Treatment for Grade 91 Steel
Walker, Jacob D.
Many of the projects utilizing Grade 91 steel are large in scale, therefore it is necessary to assemble on site. The assembly of the major pieces requires welding in the assembly; this drastically changes the superior mechanical properties of Grade 91 steel that it was specifically developed for. Therefore, because of the adverse effects of welding on the mechanical properties of Grade 91, it is necessary to do a localized post weld heat treatment. As with most metallic materials grade 91 steel requires a very specific heat treatment process. This process includes a specific temperature and duration at that temperature to achieve the heat treatment desired. Extensive research has been done to determine the proper temperatures and duration to provide the proper microstructure for the superior mechanical properties that are inherent to Grade 91 steel. The welded sections are typically large structures that require local heat treatments and cannot be placed in an oven. The locations of these structures vary from indoors in a controlled environment to outdoors with unpredictable environments. These environments can be controlled somewhat, however in large part the surrounding conditions are unchangeable. Therefore, there is a need to develop methods to accurately apply the surrounding conditions and geometries to a theoretical model in order to provide the proper requirements for the local heat treatment procedure. Within this requirement is the requirement to define unknowns used in the heat transfer equations so that accurate models can be produced and accurate results predicted. This study investigates experimentally and numerically the heat transfer and temperature fields of Grade 91 piping in a local heat treatment. The objective of this thesis research is to determine all of the needed heat transfer coefficients. The appropriate heat transfer coefficients are determined through the inverse heat conduction method utilizing a ceramic heat blanket. This will be done
Experimental analysis of current conduction through thermally ...
Indian Academy of Sciences (India)
Electrical properties of SiO2 grown on the Si-face of the epitaxial 4H-SiC ... Thermal oxide reliability is one of the most critical concerns in the realization of ... material for high temperature, high power, high frequency, and nonvolatile .... conduction mechanism in MOSiC system with varying oxide thicknesses has been.
Analysis of ionic conductance of carbon nanotubes
Biesheuvel, P.M.; Bazant, M.Z.
2016-01-01
We use space-charge (SC) theory (also called the capillary pore model) to describe the ionic conductance, G, of charged carbon nanotubes (CNTs). Based on the reversible adsorption of hydroxyl ions to CNT pore walls, we use a Langmuir isotherm for surface ionization and make calculations as a
Near-field radiative heat transfer under temperature gradients and conductive transfer
Energy Technology Data Exchange (ETDEWEB)
Jin, Weiliang; Rodriguez, Alejandro W. [Princeton Univ., NJ (United States). Dept. of Electrical Engineering; Messina, Riccardo [CNRS-Univ. de Montpellier (France). Lab. Charles Coulomb
2017-05-01
We describe a recently developed formulation of coupled conductive and radiative heat transfer (RHT) between objects separated by nanometric, vacuum gaps. Our results rely on analytical formulas of RHT between planar slabs (based on the scattering-matrix method) as well as a general formulation of RHT between arbitrarily shaped bodies (based on the fluctuating-volume current method), which fully captures the existence of temperature inhomogeneities. In particular, the impact of RHT on conduction, and vice versa, is obtained via self-consistent solutions of the Fourier heat equation and Maxwell's equations. We show that in materials with low thermal conductivities (e.g. zinc oxides and glasses), the interplay of conduction and RHT can strongly modify heat exchange, exemplified for instance by the presence of large temperature gradients and saturating flux rates at short (nanometric) distances. More generally, we show that the ability to tailor the temperature distribution of an object can modify the behaviour of RHT with respect to gap separations, e.g. qualitatively changing the asymptotic scaling at short separations from quadratic to linear or logarithmic. Our results could be relevant to the interpretation of both past and future experimental measurements of RHT at nanometric distances.
International Nuclear Information System (INIS)
Tayal, M.
1987-01-01
Structures often operate at elevated temperatures. Temperature calculations are needed so that the design can accommodate thermally induced stresses and material changes. A finite element computer called FEAT has been developed to calculate temperatures in solids of arbitrary shapes. FEAT solves the classical equation for steady state conduction of heat. The solution is obtained for two-dimensional (plane or axisymmetric) or for three-dimensional problems. Gap elements are use to simulate interfaces between neighbouring surfaces. The code can model: conduction; internal generation of heat; prescribed convection to a heat sink; prescribed temperatures at boundaries; prescribed heat fluxes on some surfaces; and temperature-dependence of material properties like thermal conductivity. The user has a option of specifying the detailed variation of thermal conductivity with temperature. For convenience to the nuclear fuel industry, the user can also opt for pre-coded values of thermal conductivity, which are obtained from the MATPRO data base (sponsored by the U.S. Nuclear Regulatory Commission). The finite element method makes FEAT versatile, and enables it to accurately accommodate complex geometries. The optional link to MATPRO makes it convenient for the nuclear fuel industry to use FEAT, without loss of generality. Special numerical techniques make the code inexpensive to run, for the type of material non-linearities often encounter in the analysis of nuclear fuel. The code, however, is general, and can be used for other components of the reactor, or even for non-nuclear systems. The predictions of FEAT have been compared against several analytical solutions. The agreement is usually better than 5%. Thermocouple measurements show that the FEAT predictions are consistent with measured changes in temperatures in simulated pressure tubes. FEAT was also found to predict well, the axial variations in temperatures in the end-pellets(UO 2 ) of two fuel elements irradiated
Conducting a SWOT Analysis for Program Improvement
Orr, Betsy
2013-01-01
A SWOT (strengths, weaknesses, opportunities, and threats) analysis of a teacher education program, or any program, can be the driving force for implementing change. A SWOT analysis is used to assist faculty in initiating meaningful change in a program and to use the data for program improvement. This tool is useful in any undergraduate or degree…
International Nuclear Information System (INIS)
Narayan Prabhu, K.; Ravishankar, B.N.
2003-01-01
For successful modelling of the solidification process, a reliable heat transfer boundary condition data is required. These boundary conditions are significantly influenced by the casting and mould parameters. In the present work, the effect of sodium modification melt treatment on casting/chill interfacial heat transfer during upward solidification of an Al-13% Si alloy against metallic chills is investigated using thermal analysis and inverse modelling techniques. In the presence of chills, modification melt treatment resulted in an increase in the cooling rate of the solidifying casting near the casting/chill interfacial region. The corresponding interfacial heat flux transients and electrical conductivities are also found to be higher. This is attributed to (i) improvement in the casting/chill interfacial thermal contact condition brought about by the decrease in the surface tension of the liquid metal on addition of sodium and (ii) increase in the electronic heat conduction in the initial solidified shell due to change in the morphology of silicon from a acicular type to a fine fibrous structure and increase in the ratio of the modification rating to the secondary dendrite arm spacing
Correlation Function Analysis of Fiber Networks: Implications for Thermal Conductivity
Martinez-Garcia, Jorge; Braginsky, Leonid; Shklover, Valery; Lawson, John W.
2011-01-01
The heat transport in highly porous fiber structures is investigated. The fibers are supposed to be thin, but long, so that the number of the inter-fiber connections along each fiber is large. We show that the effective conductivity of such structures can be found from the correlation length of the two-point correlation function of the local conductivities. Estimation of the parameters, determining the conductivity, from the 2D images of the structures is analyzed.
The response of a harmonically forced premixed flame stabilized on a heat-conducting bluff-body
Kedia, Kushal S.
2015-01-01
© 2014 The Combustion Institute. The objective of this work is to investigate the unsteady response of a bluff-body stabilized laminar premixed flame to harmonic inlet velocity excitation. A time series analysis was performed to analyze the physical sequence of events at a fixed longitudinal forcing frequency of 100 Hz for cases with (1) two different equivalence ratios and (2) two different thermal properties of the stabilizing bluff-body. It was observed that conjugate heat exchange between the heat conducting bluff-body and the surrounding reacting flow has a crucial impact on the dynamic response. The flame area and anchoring location, the net conjugate heat transfer and the total heat release underwent significant oscillations. The latter was mean shifted and had multiple frequencies. The burning velocity varied significantly along the flame length and the recirculation zone underwent complex changes in its shape and size during an unsteady cycle. The lower equivalence ratio case exhibited vortex shedding after an initial symmetric response with periodic flame extinction and re-ignition along its surface, unlike the higher equivalence ratio case. The metal/ceramic bluff-body showed a net heat transfer directed from/to the bluff-body, to/from the reacting flow during an unsteady cycle, resulting in a significantly different flame response for the two otherwise equivalent cases.
A new model for heat conduction of nanofluids based on fractal distributions of nanoparticles
International Nuclear Information System (INIS)
Xu Jie; Yu Boming; Zou Mingqing; Xu Peng
2006-01-01
In this paper we report a new model for predicting the thermal conductivity of nanofluids by taking into account the fractal distribution of nanoparticle sizes and heat convection between nanoparticles and liquids due to the Brownian motion of nanoparticles in fluids. The proposed model is expressed as a function of the average size of nanoparticles, fractal dimension, concentration of nanoparticles, temperature and properties of fluids. The model shows the reasonable dependences of the thermal conductivity on the temperature of nanofluids, nanoparticle size and concentration. The parameter c introduced in thermal boundary layer depends on fluids, but is independent of nanoparticles added in the fluids. The model predictions are in good agreement with the available experimental data. The model also reveals that there is a critical concentration of 12.6% of nanoparticles at which the contribution from heat convection due to the Brownian movement of nanoparticles reaches the maximum value, below which the contribution from heat convection decreases with the decrease in concentration and above which the contribution from heat convection decreases with the increase in concentration
Heat conduction in a chain of colliding particles with a stiff repulsive potential
Gendelman, Oleg V.; Savin, Alexander V.
2016-11-01
One-dimensional billiards, i.e., a chain of colliding particles with equal masses, is a well-known example of a completely integrable system. Billiards with different particle masses is generically not integrable, but it still exhibits divergence of a heat conduction coefficient (HCC) in the thermodynamic limit. Traditional billiards models imply instantaneous (zero-time) collisions between the particles. We relax this condition of instantaneous impact and consider heat transport in a chain of stiff colliding particles with the power-law potential of the nearest-neighbor interaction. The instantaneous collisions correspond to the limit of infinite power in the interaction potential; for finite powers, the interactions take nonzero time. This modification of the model leads to a profound physical consequence—the probability of multiple (in particular triple) -particle collisions becomes nonzero. Contrary to the integrable billiards of equal particles, the modified model exhibits saturation of the heat conduction coefficient for a large system size. Moreover, the identification of scattering events with triple-particle collisions leads to a simple definition of the characteristic mean free path and a kinetic description of heat transport. This approach allows us to predict both the temperature and density dependencies for the HCC limit values. The latter dependence is quite counterintuitive—the HCC is inversely proportional to the particle density in the chain. Both predictions are confirmed by direct numerical simulations.
Effects of a Heat Wave on Nocturnal Stomatal Conductance in Eucalyptus camaldulensis
Directory of Open Access Journals (Sweden)
Víctor Resco de Dios
2018-06-01
Full Text Available Nocturnal transpiration constitutes a significant yet poorly understood component of the global water cycle. Modeling nocturnal transpiration has been complicated by recent findings showing that stomata respond differently to environmental drivers over day- vs. night-time periods. Here, we propose that nocturnal stomatal conductance depends on antecedent daytime conditions. We tested this hypothesis across six genotypes of Eucalyptus camaldulensis Dehnh. growing under different CO2 concentrations (ambient vs. elevated and exposed to contrasting temperatures (ambient vs. heat wave for four days prior to the night of measurements, when all plants experienced ambient temperature conditions. We observed significant effects after the heat wave that led to 36% reductions in nocturnal stomatal conductance. The response was partly driven by changes in daytime stomatal behavior but additional factors may have come into play. We also observed significant differences in response to the heat wave across genotypes, likely driven by local adaptation to their climate of origin, but CO2 played no effect. Stomatal models may need to incorporate the role of antecedent effects to improve projections particularly after drastic changes in the environment such as heat waves.
Directory of Open Access Journals (Sweden)
I. J. Uwanta
2014-01-01
Full Text Available This study investigates the unsteady natural convection and mass transfer flow of viscous reactive, heat generating/absorbing fluid in a vertical channel formed by two infinite parallel porous plates having temperature dependent thermal conductivity. The motion of the fluid is induced due to natural convection caused by the reactive property as well as the heat generating/absorbing nature of the fluid. The solutions for unsteady state temperature, concentration, and velocity fields are obtained using semi-implicit finite difference schemes. Perturbation techniques are used to get steady state expressions of velocity, concentration, temperature, skin friction, Nusselt number, and Sherwood number. The effects of various flow parameters such as suction/injection (γ, heat source/sinks (S, Soret number (Sr, variable thermal conductivity δ, Frank-Kamenetskii parameter λ, Prandtl number (Pr, and nondimensional time t on the dynamics are analyzed. The skin friction, heat transfer coefficients, and Sherwood number are graphically presented for a range of values of the said parameters.
Zhang, Jianwen; Zhao, Xiaokui
2015-01-01
In general, the resistivity is inversely proportional to the electrical conductivity, and is usually taken to be zero when the conducting fluid is of extremely high conductivity (e.g., ideal conductors). In this paper, we first establish the global well-posedness of strong solution to an initial-boundary value problem of the one-dimensional compressible, viscous, heat-conductive, non-resistive MHD equations with general heat-conductivity coefficient and large data. Then, the non-resistive lim...
Effect of recent popularity on heat-conduction based recommendation models
Li, Wen-Jun; Dong, Qiang; Shi, Yang-Bo; Fu, Yan; He, Jia-Lin
2017-05-01
Accuracy and diversity are two important measures in evaluating the performance of recommender systems. It has been demonstrated that the recommendation model inspired by the heat conduction process has high diversity yet low accuracy. Many variants have been introduced to improve the accuracy while keeping high diversity, most of which regard the current node-degree of an item as its popularity. However in this way, a few outdated items of large degree may be recommended to an enormous number of users. In this paper, we take the recent popularity (recently increased item degrees) into account in the heat-conduction based methods, and propose accordingly the improved recommendation models. Experimental results on two benchmark data sets show that the accuracy can be largely improved while keeping the high diversity compared with the original models.
Heat conductance of sintered UO{sub 2}; Toplotna provodljivost sinterovanog UO{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Katanic-Popovic, J; Stevanovic, M [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)
1966-11-15
Phenomena influencing the heat conductance of the sintered UO{sub 2} were analyzed, first of all when used as nuclear fuel. Influence of temperature, density and porosity, additives and irradiation in the reactor are shown. Based on the available literature, the measured heat conductance values were analyzed for the sintered UO{sub 2} outside the reactor and in the reactor during irradiation. Analizirane su pojave koje uticu na toplotnu provodljivost sinterovanog UO{sub 2}, pre svega, sa aspekta njegove primene kao goriva. Izlozen je uticaj temperature, gustine i poroznosti, aditiva i ozracivanja u reaktoru. Na osnovu pregleda dostupne literature kriticki su prikazani rezultati merenja toplotne provodljivosti sinterovanog UO{sub 2} van reaktora i u reaktoru pri ozracivanju (author)
Nonlinear heat conduction equations with memory: Physical meaning and analytical results
Artale Harris, Pietro; Garra, Roberto
2017-06-01
We study nonlinear heat conduction equations with memory effects within the framework of the fractional calculus approach to the generalized Maxwell-Cattaneo law. Our main aim is to derive the governing equations of heat propagation, considering both the empirical temperature-dependence of the thermal conductivity coefficient (which introduces nonlinearity) and memory effects, according to the general theory of Gurtin and Pipkin of finite velocity thermal propagation with memory. In this framework, we consider in detail two different approaches to the generalized Maxwell-Cattaneo law, based on the application of long-tail Mittag-Leffler memory function and power law relaxation functions, leading to nonlinear time-fractional telegraph and wave-type equations. We also discuss some explicit analytical results to the model equations based on the generalized separating variable method and discuss their meaning in relation to some well-known results of the ordinary case.
Oscillatory conductive heat transfer for a fiber in an ideal gas
Kuntz, H. L.; Perreira, N. D.
1985-01-01
A description of the thermal effects created by placing a cylindrical fiber in an inviscid, ideal gas, through which an acoustic wave propagates, is presented. The fibers and the gas have finite heat capacities and thermal conductivities. Expressions for the temperature distribution in the gas and in the material are determined. The temperature distribution is caused by pressure oscillations in the gas which, in turn, are caused by the passage of an acoustic wave. The relative value of a dimensionless parameter is found to be indicative of whether the exact or approximate equations should be used in the solution. This parameter is a function of the thermal conductivities and heat capacities of the fiber and gas, the acoustic frequency, and the fiber diameter.
Heat Retreat Locations in Cities - The Survey-Based Location Analysis of Heat Relief
Neht, Alice; Maximini, Claudia; Prenger-Berninghoff, Kathrin
2017-12-01
The adaptation of cities to climate change effects is one of the major strategies in urban planning to encounter the challenges of climate change (IPCC 2014). One of the fields of climate change adaption is dealing with heat events that occur more frequently and with greater intensity. Cities in particular are vulnerable to these events due to high population and infrastructure density. Proceeding urbanization calls for the existence of sufficient heat retreat locations (HRL) to enable relief for the population from heat in summer. This is why an extensive analysis of HRL is needed. This paper aims at the development of a survey-based location analysis of heat relief by identifying user groups, locations and characteristics of HRL based on a home survey that was conducted in three German cities. Key results of the study show that the majority of the participants of the survey are users of existing HRL, are affected by heat, and perceive heat as a burden in summer. Moreover, HRL that are located in close proximity are preferred by most users while their effect depends on the regional context that has to be considered in the analysis. Hence, this research presents an approach to heat relief that underlines the importance of HRL in cities by referring to selected examples of HRL types in densely populated areas of cities. HRL should especially be established and secured in densely built-up areas of cities. According to results of the survey, most HRL are located in public spaces, and the overall accessibility of HRL turned out to be an issue.
Energy Technology Data Exchange (ETDEWEB)
Sperling, P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fletcher, L. B. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Chung, H. -K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Gamboa, E. J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lee, H. J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Omarbakiyeva, Y. [International IT Univ., Almaty (Kazakhstan); Univ. Rostock (Germany); Reinholz, H. [Univ. Rostock (Germany);
2016-03-29
We measure the highly-resolved inelastic x-ray scattering spectrum of isochorically ultrafast heated aluminum. In the x-ray forward scattering spectra the electron temperature could be measured from the down- and upshifted plasmon, where the electron density of ne = 1:8 1023 cm^{3} is known a priori. We have studied the plasmon damping by applying electron-particle collision models beyond the Born approximation determining the electrical conductivity of warm dense aluminum.
2012-06-06
...Notice is hereby given that the U.S. International Trade Commission has received a complaint entitled Certain Integrated Circuit Packages Provided With Multiple Heat-Conducting Paths and Products Containing Same, DN 2899; the Commission is soliciting comments on any public interest issues raised by the complaint or complainant's filing under section 210.8(b) of the Commission's Rules of Practice and Procedure (19 CFR 210.8(b)).
TRUMP3-JR: a finite difference computer program for nonlinear heat conduction problems
International Nuclear Information System (INIS)
Ikushima, Takeshi
1984-02-01
Computer program TRUMP3-JR is a revised version of TRUMP3 which is a finite difference computer program used for the solution of multi-dimensional nonlinear heat conduction problems. Pre- and post-processings for input data generation and graphical representations of calculation results of TRUMP3 are avaiable in TRUMP3-JR. The calculation equations, program descriptions and user's instruction are presented. A sample problem is described to demonstrate the use of the program. (author)
Energy Technology Data Exchange (ETDEWEB)
Berour, Nacer; Lacroix, David E-mail: david.lacroix@lemta.uhp-nancy.fr; Boulet, Pascal; Jeandel, Gerard
2004-06-01
This paper deals with heat transfer in nongrey media which scatter, absorb and emit radiation. Considering a two dimensional geometry, radiative and conductive phenomena through the medium have been taken into account. The radiative part of the problem was solved using the discrete ordinate method with classical S{sub n} quadratures. The absorption and scattering coefficients involved in the radiative transfer equation (RTE) were obtained from the Mie theory. Conduction inside the medium was linked to the RTE through the energy conservation. Validation of the model has been achieved with several simulation of water spray curtains used as fire protection walls.
Analytical Solutions of Ionic Diffusion and Heat Conduction in Multilayered Porous Media
Directory of Open Access Journals (Sweden)
Yu Bai
2015-01-01
Full Text Available Ionic diffusion and heat conduction in a multiple layered porous medium have many important engineering applications. One of the examples is the chloride ions from deicers penetrating into concrete structures such as bridge decks. Different overlays can be placed on top of concrete surface to slowdown the chloride penetration. In this paper, the chloride ion diffusion equations were established for concrete structures with multiple layers of protective system. By using Laplace transformation, an analytical solution was developed first for chloride concentration profiles in two-layered system and then extended to multiple layered systems with nonconstant boundary conditions, including the constant boundary and linear boundary conditions. Because ionic diffusion in saturated media and heat conduction are governed by the same form of partial differential equations with different materials parameters, the analytical solution was further extended to handle heat conduction in a multiple layered system under nonconstant boundary conditions. The numerical results were compared with available test data. The basic trends of the analytical solution and the test data agreed quite well.
Design of DC Conduction Pump for PGSFR Active Decay Heat Removal System
Energy Technology Data Exchange (ETDEWEB)
Kim, Dehee; Hong, Jonggan; Lee, Taeho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2014-05-15
A DC conduction pump has been designed for the ADHRS of PGSFR. A VBA code developed by ANL was utilized to design and optimize the pump. The pump geometry dependent parameters were optimized to minimize the total current while meeting the design requirements. A double-C type dipole was employed to produce the calculated magnetic strength. Numerical simulations for the magnetic field strength and its distribution around the dipole and for the turbulent flow under magnetic force will be carried out. A Direct Current (DC) conduction Electromagnetic Pump (EMP) has been designed for Active Decay Heat Removal System (ADHRS) of PGSFR. The PGSFR has active as well as passive systems for the DHRS. The passive DHRS (PDHRS) works by natural circulation head and the ADHRS is driven by an EMP for the DHRS sodium loop and a blower for the finned-tube sodium-to-air heat exchanger (FHX). An Annular Linear Induction Pump (ALIP) can be also considered for the ADHRS, but DC conduction pump has been chosen. Selection basis of DHRS EMP is addressed and EMP design for single ADHRS loop with 1MWt heat removal capacity is introduced.
Stress analysis of HTR-10 steam generator heat exchanging tubes
International Nuclear Information System (INIS)
Dong Jianling; Zhang Xiaohang; Yin Dejian; Fu Jiyang
2001-01-01
Steam Generator (SG) heat exchanging tubes of 10 MW High Temperature Gas Cooled Reactor (HTR-10) are protective screens between the primary loop of helium with radioactivity and the secondary loop of feeding water and steam without radioactivity. Water and steam will enter into the primary loop when rupture of the heat exchanging tubes occurs, which lead to increase of the primary loop pressure and discharge of radioactive materials. Therefore it is important to guarantee the integrity of the tubes. The tube structure is spiral tube with small bending radius, which make it impossible to test with volumetric in-service detection. For such kind of spiral tube, using LBB concept to guarantee the integrity of the tubes is an important option. The author conducts stress analysis and calculation of HTR-10 SG heat exchanging tubes using the FEM code of piping stress analysis, PIPESTRESS. The maximum stress and the dangerous positions are obtained
Using Nanoparticles for Enhance Thermal Conductivity of Latent Heat Thermal Energy Storage
Directory of Open Access Journals (Sweden)
Baydaa Jaber Nabhan
2015-06-01
Full Text Available Phase change materials (PCMs such as paraffin wax can be used to store or release large amount of energy at certain temperature at which their solid-liquid phase changes occurs. Paraffin wax that used in latent heat thermal energy storage (LHTES has low thermal conductivity. In this study, the thermal conductivity of paraffin wax has been enhanced by adding different mass concentration (1wt.%, 3wt.%, 5wt.% of (TiO2 nano-particles with about (10nm diameter. It is found that the phase change temperature varies with adding (TiO2 nanoparticles in to the paraffin wax. The thermal conductivity of the composites is found to decrease with increasing temperature. The increase in thermal conductivity has been found to increase by about (10% at nanoparticles loading (5wt.% and 15oC.
Coupling heat conduction and radiation in complex 2D and 3D geometries
International Nuclear Information System (INIS)
Peniguel, C.
1997-01-01
Thermal radiation is a very important mode of heat transfer in most real industrial systems. A numerical approach coupling radiation (restricted to non participant medium) and conduction is presented. The code (SYRTHES) is able to handle 2D and 3D problems (including cases with symmetries and periodicity). Radiation is solved by a radiosity approach, and conduction by a finite element method. Accurate and efficient algorithms based on a mixing of analytical/numerical integration, and ray tracing techniques are used to compute the view factors. Validation has been performed on numerous test cases. A conjugate residual algorithm solves the radiosity system. An explicit interactive numerical procedure is then used to couple conduction and radiation. No stability problem has been encountered so far. One specificity of SYRTHES is that conduction and radiation are solved on independent grids. This brings much flexibility and allows to keep the number of independent radiation patches at a reasonable level. Several industrial examples are given as illustration. (author)
Analysis of the heat transfer in double and triple concentric tube heat exchangers
Rădulescu, S.; Negoiţă, L. I.; Onuţu, I.
2016-08-01
The tubular heat exchangers (shell and tube heat exchangers and concentric tube heat exchangers) represent an important category of equipment in the petroleum refineries and are used for heating, pre-heating, cooling, condensation and evaporation purposes. The paper presents results of analysis of the heat transfer to cool a petroleum product in two types of concentric tube heat exchangers: double and triple concentric tube heat exchangers. The cooling agent is water. The triple concentric tube heat exchanger is a modified constructive version of double concentric tube heat exchanger by adding an intermediate tube. This intermediate tube improves the heat transfer by increasing the heat area per unit length. The analysis of the heat transfer is made using experimental data obtained during the tests in a double and triple concentric tube heat exchanger. The flow rates of fluids, inlet and outlet temperatures of water and petroleum product are used in determining the performance of both heat exchangers. Principally, for both apparatus are calculated the overall heat transfer coefficients and the heat exchange surfaces. The presented results shows that triple concentric tube heat exchangers provide better heat transfer efficiencies compared to the double concentric tube heat exchangers.
Heat Transfer Analysis in Wire Bundles for Aerospace Vehicles
Rickman, S. L.; Iamello, C. J.
2016-01-01
Design of wiring for aerospace vehicles relies on an understanding of "ampacity" which refers to the current carrying capacity of wires, either, individually or in wire bundles. Designers rely on standards to derate allowable current flow to prevent exceedance of wire temperature limits due to resistive heat dissipation within the wires or wire bundles. These standards often add considerable margin and are based on empirical data. Commercial providers are taking an aggressive approach to wire sizing which challenges the conventional wisdom of the established standards. Thermal modelling of wire bundles may offer significant mass reduction in a system if the technique can be generalized to produce reliable temperature predictions for arbitrary bundle configurations. Thermal analysis has been applied to the problem of wire bundles wherein any or all of the wires within the bundle may carry current. Wire bundles present analytical challenges because the heat transfer path from conductors internal to the bundle is tortuous, relying on internal radiation and thermal interface conductance to move the heat from within the bundle to the external jacket where it can be carried away by convective and radiative heat transfer. The problem is further complicated by the dependence of wire electrical resistivity on temperature. Reduced heat transfer out of the bundle leads to higher conductor temperatures and, hence, increased resistive heat dissipation. Development of a generalized wire bundle thermal model is presented and compared with test data. The steady state heat balance for a single wire is derived and extended to the bundle configuration. The generalized model includes the effects of temperature varying resistance, internal radiation and thermal interface conductance, external radiation and temperature varying convective relief from the free surface. The sensitivity of the response to uncertainties in key model parameters is explored using Monte Carlo analysis.
Measurement of the Thermal Conductivity of Nano-fluid for the advanced heat exchanger
International Nuclear Information System (INIS)
Yoo, Shin; Lee, Jae Young
2006-01-01
The enhancement of heat transfer has been widely investigated to provide an effective way to cool down the modern electronic devices. Among the methods, Choi discovered a large amount of increase of thermal conductivity when nano sized particles were suspended in the fluid. It was first introduced by Masuda as a potential heat transfer enhancement media and since then, many researchers have investigated the nanofluids phenomena. Many researchers reported in substantially increasing the thermal conductivity of fluids by adding small amounts of suspended metallic oxide nanoparticles of Cu, CuO, Al 2 O 3 and carbon nano-tube. Masuda reported that the use Al 2 O 3 particles of 13 nm at 4.3% volume fraction increased the thermal conductivity of water by 30%. For carbon nano-tube nanofluids shows even greater enhancement. Xie et al. measured the thermal conductivity of carbon nanotube suspended in organic liquid and water with the enhancement of 10-20%. Recent studies have shown that inserting just 1% concentration of nano-particles sometimes increases about maximum 40% of thermal conductivity. However, there is still few experiments done for TiO 2 nanoparticles. Murshed found that the enhancement of thermal conductivity shows about 30% with 15nm in diameter with maximum 5% volume fraction and about 40% enhancement is observed using 15nmD x 40nm rod-shape nanoparticles of TiO 2 . The present experimental shows that a 20% maximum of enhancement in thermal conductivity using TiO 2 of 10nm for 3% volume fraction. Theses results are compared with previous research with theoretical models. As the first step of the heat transfer of nano fluid, the theories related to the nanofluids investigations have been discussed to understand not only the mechanism of thermal conductivity measurement, but also to understand the nanofluid behavior. Colloidal stability is the key to the nanofluid considered to prevent the agglomeration. Through the results, we will discuss the importance of
Electron thermal conductivity from heat wave propagation in Wendelstein 7-AS
Energy Technology Data Exchange (ETDEWEB)
Giannone, L.; Erckmann, V; Gasparino, U; Hartfuss, H J; Kuehner, G; Maassberg, H; Stroth, U; Tutter, M [Association Euratom-Max-Planck-Institut fuer Plasmaphysik, Garching (Germany); W7-AS Team; ECRH Group IPF Stuttgart; Gyrotron Group KFK Karlsruhe
1992-11-01
Heat wave propagation experiments have been carried out on the Wendelstein 7-AS stellarator. The deposition of electron cyclotron resonance heating power is highly localized in the plasma centre, so that power modulation produces heat waves which propagate away from the deposition volume. Radiometry of the electron cyclotron emission is used to measure the generated temperature perturbation. The propagation time delay of the temperature perturbation as a function of distance to the power deposition region is used to determine the electron thermal conductivity [chi][sub e]. This value is then compared with the value determined by global power balance. In contrast to sawtooth propagation experiments in tokamaks, it is found that the value of [chi][sub e] from heat wave propagation is comparable to that calculated by power balance. In addition, inward propagating waves were produced by choosing a power deposition region away from the plasma centre. Experiments were carried out at 70 GHz in the ordinary mode and at 140 GHz in the extraordinary mode. Variations of the modulation power amplitude have demonstrated that the inferred value of [chi][sub e] is independent of the amplitude of the induced temperature perturbations. (author). 29 refs, 11 figs, 5 tabs.
Directory of Open Access Journals (Sweden)
Chia-Yu Chou
2014-09-01
Full Text Available In a previous study we provided analytical and experimental evidence that some materials are able to store entropy-flow, of which the heat-conduction behaves as standing waves in a bounded region small enough in practice. In this paper we continue to develop distributed control of heat conduction in these thermal-inductive materials. The control objective is to achieve subtle temperature distribution in space and simultaneously to suppress its transient overshoots in time. This technology concerns safe and accurate heating/cooling treatments in medical operations, polymer processing, and other prevailing modern day practices. Serving for distributed feedback, spatiotemporal H ∞ /μ control is developed by expansion of the conventional 1D-H ∞ /μ control to a 2D version. Therein 2D geometrical isomorphism is constructed with the Laplace-Galerkin transform, which extends the small-gain theorem into the mode-frequency domain, wherein 2D transfer-function controllers are synthesized with graphical methods. Finally, 2D digital-signal processing is programmed to implement 2D transfer-function controllers, possibly of spatial fraction-orders, into DSP-engine embedded microcontrollers.
Self-similar variables and the problem of nonlocal electron heat conductivity
International Nuclear Information System (INIS)
Krasheninnikov, S.I.; Bakunin, O.G.
1993-10-01
Self-similar solutions of the collisional electron kinetic equation are obtained for the plasmas with one (1D) and three (3D) dimensional plasma parameter inhomogeneities and arbitrary Z eff . For the plasma parameter profiles characterized by the ratio of the mean free path of thermal electrons with respect to electron-electron collisions, γ T , to the scale length of electron temperature variation, L, one obtains a criterion for determining the effect that tail particles with motion of the non-diffusive type have on the electron heat conductivity. For these conditions it is shown that the use of a open-quotes symmetrizedclose quotes kinetic equation for the investigation of the strong nonlocal effect of suprathermal electrons on the electron heat conductivity is only possible at sufficiently high Z eff (Z eff ≥ (L/γ T ) 1/2 ). In the case of 3D inhomogeneous plasma (spherical symmetry), the effect of the tail electrons on the heat transport is less pronounced since they are spread across the radius r
Technoeconomic analysis of a biomass based district heating system
International Nuclear Information System (INIS)
Zhang, H.; Ugursal, V.I.; Fung, A.
2005-01-01
This paper discussed a proposed biomass-based district heating system to be built for the Pictou Landing First Nation Community in Nova Scotia. The community centre consists of 6 buildings and a connecting arcade. The methodology used to size and design heating, ventilating and air conditioning (HVAC) systems, as well as biomass district energy systems (DES) were discussed. Annual energy requirements and biomass fuel consumption predictions were presented, along with cost estimates. A comparative assessment of the system with that of a conventional oil fired system was also conducted. It was suggested that the design and analysis methodology could be used for any similar application. The buildings were modelled and simulated using the Hourly Analysis Program (HAP), a detailed 2-in-1 software program which can be used both for HVAC system sizing and building energy consumption estimation. A techno-economics analysis was conducted to justify the viability of the biomass combustion system. Heating load calculations were performed assuming that the thermostat was set constantly at 22 degrees C. Community centre space heating loads due to individual envelope components for 3 different scenarios were summarized, as the design architecture for the buildings was not yet finalized. It was suggested that efforts should be made to ensure air-tightness and insulation levels of the interior arcade glass wall. A hydronic distribution system with baseboard space heating units was selected, comprising of a woodchip boiler, hot water distribution system, convective heating units and control systems. The community has its own logging operation which will provide the wood fuel required by the proposed system. An outline of the annual allowable harvest covered by the Pictou Landing Forestry Management Plan was presented, with details of proposed wood-chippers for the creation of biomass. It was concluded that the woodchip combustion system is economically preferable to the
International Nuclear Information System (INIS)
Tzanos, C.P.; Dionne, B.
2011-01-01
To support the analyses related to the conversion of the BR2 core from highly-enriched (HEU) to low-enriched (LEU) fuel, the thermal-hydraulics codes PLTEMP and RELAP-3D are used to evaluate the safety margins during steady-state operation (PLTEMP), as well as after a loss-of-flow, loss-of-pressure, or a loss of coolant event (RELAP). In the 1-D PLTEMP and RELAP simulations, conduction in the azimuthal and axial directions is not accounted. The very good thermal conductivity of the cladding and the fuel meat and significant temperature gradients in the lateral directions (axial and azimuthal directions) could lead to a heat flux distribution that is significantly different than the power distribution. To evaluate the significance of the lateral heat conduction, 3-D computational fluid dynamics (CFD) simulations, using the CFD code STAR-CD, were performed. Safety margin calculations are typically performed for a hot stripe, i.e., an azimuthal region of the fuel plates/coolant channel containing the power peak. In a RELAP model, for example, a channel between two plates could be divided into a number of RELAP channels (stripes) in the azimuthal direction. In a PLTEMP model, the effect of azimuthal power peaking could be taken into account by using engineering factors. However, if the thermal mixing in the azimuthal direction of a coolant channel is significant, a stripping approach could be overly conservative by not taking into account this mixing. STAR-CD simulations were also performed to study the thermal mixing in the coolant. Section II of this document presents the results of the analyses of the lateral heat conduction and azimuthal thermal mixing in a coolant channel. Finally, PLTEMP and RELAP simulations rely on the use of correlations to determine heat transfer coefficients. Previous analyses showed that the Dittus-Boelter correlation gives significantly more conservative (lower) predictions than the correlations of Sieder-Tate and Petukhov. STAR-CD 3-D
Features of an emergency heat-conducting path in reactors about lead-bismuth and lead heat-carriers
International Nuclear Information System (INIS)
Beznosov, A.V.; Bokova, T.A.; Molodtsov, A.A.
2006-01-01
The reactor emergency heat removal systems should transfer heat from the surface of reactor core fuel element claddings to the primary circuit followed by heat transfer to the environment. One suggests three design approaches for emergency heat removal systems in lead-bismuth and lead cooled reactor circuits that take account of the peculiar nature of their features. Application of the discussed systems for emergency heat removal improves safety of lead-bismuth and lead cooled reactor plants [ru
Numerical Analysis of Microwave Heating on Saponification Reaction
Huang, Kama; Jia, Kun
2005-01-01
Currently, microwave is widely used in chemical industry to accelerate chemical reactions. Saponification reaction has important applications in industry; some research results have shown that microwave heating can significantly accelerate the reaction [1]. But so far, no efficient method has been reported for the analysis of the heating process and design of an efficient reactor powered by microwave. In this paper, we present a method to study the microwave heating process on saponification reaction, where the reactant in a test tube is considered as a mixture of dilute solution. According to the preliminary measurement results, the effective permittivity of the mixture is approximately the permittivity of water, but the conductivity, which could change with the reaction, is derived from the reaction equation (RE). The electromagnetic field equation and reaction equation are coupled by the conductivity. Following that, the whole heating processes, which is described by Maxwell's equations, the reaction equation and heat transport equation (HTE), is analyzed by finite difference time domain (FDTD) method. The temperature rising in the test tube are measured and compared with the computational results. Good agreement can be seen between the measured and calculated results.
International Nuclear Information System (INIS)
Chaabane, Raoudha; Askri, Faouzi; Ben Nasrallah, Sassi
2011-01-01
In this paper, the lattice Boltzmann method (LBM) is applied to solve the energy equation of a transient conduction-radiation heat transfer problem in a two-dimensional cylindrical enclosure filled with an emitting, absorbing and scattering media. The control volume finite element method (CVFEM) is used to obtain the radiative information. To demonstrate the workability of the LBM in conjunction with the CVFEM to conduction-radiation problems in cylindrical media, the energy equation of the same problem is also solved using the finite difference method (FDM). The effects of different parameters, such as the grid size, the scattering albedo, the extinction coefficient and the conduction-radiation parameter on temperature distribution within the medium are studied. Results of the present work are compared with those available in the literature. LBM-CVFEM results are also compared with those given by the FDM-CVFEM. In all cases, good agreement has been obtained.
Preparation of flexible and heat-resisting conductive transparent film by the pyrosol process
International Nuclear Information System (INIS)
Usami, Hisanao; Nakasa, Akihiko; Adachi, Mami; Suzuki, Eiji; Fujimatsu, Hitoshi; Ohashi, Tatsuya; Yamada, Shigeo; Tsugita, Kouhei; Taniguchi, Yoshio
2006-01-01
A pyrosol process was successfully applied for the preparation of a flexible, conductive, and transparent inorganic film, a tin-doped indium oxide (ITO) film lined with a thin mica layer. This flexible heat-resistant ITO-mica film exhibited high conductivity and transparency, comparable to ITO deposited on glass substrate. The minimum radius of bending for the film, without any recognizable change in the conductivity and appearance, was 8 mm. The ITO deposited on mica showed a large (222) diffraction peak with a smaller (400) peak, in contrast to ITO deposited with (400) orientation on an ordinary glass substrate. Using the ITO-mica film, a prototype model of a flexible organic light emitting diode was fabricated
International Nuclear Information System (INIS)
Lajoie, D.; Raffourt, C.; Wendling, J.
2010-01-01
radiation to the external walls of the cell. The main part of the heat retrieved by the injected air is transported up to the end of the cell where it is evacuated through the global ventilation system. The other part is lost by forced convection to concrete walls that are initially colder. The heat transfer towards external walls is a long term phenomenon. Surrounding concrete walls and geological medium store heat that is progressively transferred outside by conduction. Consequently, temperature at the concrete wall of the cells progressively increases while heat losses toward surrounding geological environment decrease. But, in the mean time, the heat release from storage packages slowly decreases. As a result, temperature the cell begins to raise in the first months of storage reaches a peak value and then decreases progressively as long as the heat release decreases. It is shown that the maximum of temperature is reached after one year of full storage in the cell. Heat fluxes through the geological medium are not spatially homogeneous, due to stratification effects in the cell. This drives to thermal gradients in concrete walls and surrounding geological medium. But, magnitudes of gradients are much lower than those simulated with adiabatic hypothesis. The external environment, that is thermally very inert, acts as a regulator that smoothes vertical thermal stratifications. Such results show interactions between stratified fluid flows and heat conduction through surrounding media. (authors)
Transient heat conduction in multi-layer walls: An efficient strategy for Laplace's method
Energy Technology Data Exchange (ETDEWEB)
Maestre, Ismael R.; Cubillas, Paloma R. [Escuela Politecnica Superior de Algeciras, University of Cadiz, Algeciras (Spain); Perez-Lombard, Luis [Escuela Superior de Ingenieros, University of Seville (Spain)
2010-04-15
Enhancing load calculation tools into building simulation programs requires an in-depth revision and fine tuning of the load calculation assumptions prior to the addition of the HVAC system modelling routines. It is of special interest the analysis of transient heat conduction through multi-layer walls where, in order to improve the coupling between the passive elements of the building and the HVAC systems, an improvement of the time resolution in the calculation becomes critical. Several methods have been historically used, although recently Laplace's method has been displaced by the State Space method. This paper proposes a new strategy for fine time resolution on the calculation of the response factors through Laplace's method considering a comparison with the performance of the State Space method when used to calculate conduction transfer functions. Our analysis shows that in order to achieve similar accuracy with both approaches, the State Space method requires significant additional computational time. (author)
The role of the dynamic pressure in stationary heat conduction of a rarefied polyatomic gas
Energy Technology Data Exchange (ETDEWEB)
Arima, Takashi, E-mail: arima@kanagawa-u.ac.jp [Department of Mechanical Engineering, Faculty of Engineering, Kanagawa University, Yokohama 221-8686 (Japan); Barbera, Elvira, E-mail: ebarbera@unime.it [Department of Mathematics and Computer Science, University of Messina, V.le F. D' Alcontres 31, 98166 Messina (Italy); Brini, Francesca, E-mail: francesca.brini@unibo.it [Department of Mathematics, University of Bologna, via Saragozza 8, 40123 Bologna (Italy); Sugiyama, Masaru, E-mail: sugiyama@nitech.ac.jp [Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)
2014-07-18
The effect of the dynamic pressure (non-equilibrium pressure) on stationary heat conduction in a rarefied polyatomic gas at rest is elucidated by the theory of extended thermodynamics. It is shown that this effect is observable in a non-polytropic gas. Numerical studies are presented for a para-hydrogen gas as a typical example. - Highlights: • Heat transfer problem in polyatomic rarefied gases is studied in different domains. • Non-zero dynamic pressure is predicted in non-polytropic gases. • The effect of dynamic pressure can be observed indirectly in an experiment. • The case of para-hydrogen is analyzed as an example. • Navier–Stokes, Fourier, and Extended Thermodynamics predictions are compared.
Damping by heat conduction in the Timoshenko system: Fourier and Cattaneo are the same
Said-Houari, Belkacem
2013-08-01
We consider the Cauchy problem for the one-dimensional Timoshenko system coupled with heat conduction, wherein the latter is described by either the Cattaneo law or the Fourier law. We prove that heat dissipation alone is sufficient to stabilize the system in both cases, so that additional mechanical damping is unnecessary. However, the decay of solutions without the mechanical damping is found to be slower than that with mechanical damping. Furthermore, in contrast to earlier results of Said-Houari and Kasimov (2012) [10] and Fernández Sare and Racke (2009) [12], we find that the Timoshenko-Fourier and the Timoshenko-Cattaneo systems have the same decay rate. The rate depends on a certain number α (first identified by Santos et al., 2012 [11] in a related study in a bounded domain), which is a function of the parameters of the system. © 2013 Elsevier Inc.
Determination of external measurements in aim to solve inverse heat conduction problem in piping
International Nuclear Information System (INIS)
Blanc, G.; Raynaud, M.; Chau, T.H.
1995-01-01
The inverse heat conduction problem (IHCP) to be solved involves with the reconstruction of unknown thermal loadings applied on piping internal wall. Only external temperature measurements are available as data. Different approaches can be found in the literature for solving this ill-posed problem. The most frequently used among them is the function specification method proposed by Professor BECK. However, for multidimensional IHCP, the accuracy of the solution strongly depends on the number of sensors and their location. This work focuses on the determination of minimal number and locations of the external thermocouples to get the most complete estimation of internal heat flux in a straight pipe. It more particularly concerns the preparation of experimental validation tests which will be performed on the ESTHER mock-up of Electricite de France (EDF). (authors). 4 refs., 9 figs
Layered thermal metamaterials for the directing and harvesting of conductive heat
Directory of Open Access Journals (Sweden)
P. R. Bandaru
2015-05-01
Full Text Available 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.
Hayat, T.; Ahmad, Salman; Khan, M. Ijaz; Alsaedi, A.; Waqas, M.
2018-06-01
Here we investigated stagnation point flow of second grade fluid over a stretchable cylinder. Heat transfer is characterized by non-Fourier law of heat flux and thermal stratification. Temperature dependent thermal conductivity and activation energy are also accounted. Transformations procedure is applying to transform the governing PDE's into ODE's. Obtained system of ODE's are solved analytically by HAM. Influence of flow variables on velocity, temperature, concentration, skin friction and Sherwood number are analyzed. Obtained outcome shows that velocity enhanced through curvature parameter, viscoelastic parameter and velocities ratio variable. Temperature decays for larger Prandtl number, thermal stratification, thermal relaxation and curvature parameter. Sherwood number and concentration field show opposite behavior for higher estimation of activation energy, reaction rate, curvature parameter and Schmidt number.
Energy Technology Data Exchange (ETDEWEB)
Brear, D.J. [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center
1998-01-01
When liquid fuel makes contact with steel structure the liquid can freeze as a crust and the structure can melt at the surface. The melting and freezing processes that occur can influence the mode of fuel freezing and hence fuel relocation. Furthermore the temperature gradients established in the fuel and steel phases determine the rate at which heat is transferred from fuel to steel. In this memo the 1-D transient heat conduction equations are applied to the case of initially liquid UO{sub 2} brought into contact with solid steel using up-to-date materials properties. The solutions predict criteria for fuel crust formation and steel melting and provide a simple algorithm to determine the interface temperature when one or both of the materials is undergoing phase change. The predicted steel melting criterion is compared with available experimental results. (author)
International Nuclear Information System (INIS)
Brear, D.J.
1998-01-01
When liquid fuel makes contact with steel structure the liquid can freeze as a crust and the structure can melt at the surface. The melting and freezing processes that occur can influence the mode of fuel freezing and hence fuel relocation. Furthermore the temperature gradients established in the fuel and steel phases determine the rate at which heat is transferred from fuel to steel. In this memo the 1-D transient heat conduction equations are applied to the case of initially liquid UO 2 brought into contact with solid steel using up-to-date materials properties. The solutions predict criteria for fuel crust formation and steel melting and provide a simple algorithm to determine the interface temperature when one or both of the materials is undergoing phase change. The predicted steel melting criterion is compared with available experimental results. (author)
Fully coupled heat conduction and deformation analyses of visco-elastic solids
Khan, Kamran
2012-04-21
Visco-elastic materials are known for their capability of dissipating energy. This energy is converted into heat and thus changes the temperature of the materials. In addition to the dissipation effect, an external thermal stimulus can also alter the temperature in a viscoelastic body. The rate of stress relaxation (or the rate of creep) and the mechanical and physical properties of visco-elastic materials, such as polymers, vary with temperature. This study aims at understanding the effect of coupling between the thermal and mechanical response that is attributed to the dissipation of energy, heat conduction, and temperature-dependent material parameters on the overall response of visco-elastic solids. The non-linearly viscoelastic constitutive model proposed by Schapery (Further development of a thermodynamic constitutive theory: stress formulation, 1969,Mech. Time-Depend. Mater. 1:209-240, 1997) is used and modified to incorporate temperature- and stress-dependent material properties. This study also formulates a non-linear energy equation along with a dissipation function based on the Gibbs potential of Schapery (Mech. Time-Depend. Mater. 1:209-240, 1997). A numerical algorithm is formulated for analyzing a fully coupled thermo-visco-elastic response and implemented it in a general finite-element (FE) code. The non-linear stress- and temperature-dependent material parameters are found to have significant effects on the coupled thermo-visco-elastic response of polymers considered in this study. In order to obtain a realistic temperature field within the polymer visco-elastic bodies undergoing a non-uniform heat generation, the role of heat conduction cannot be ignored. © Springer Science+Business Media, B. V. 2012.
Directory of Open Access Journals (Sweden)
Ganeshkumar Jayabalan
2017-01-01
Full Text Available This article presents the effect of adding multi wall carbon nanotubes (MWCNT in water – ethylene glycol mixture on density and various thermophysical properties such as thermal conductivity, specific heat and viscosity. Density of nanofluids was measured using standard volumetric flask method and the data showed a good agreement with the mixing theory. The maximum thermal conductivity enhancement of 11 % was noticed for the nanofluids with 0.9 wt. %. Due to lower specific heat of the MWCNT, the specific heat of the nanofluids decreased in proportion with the MWCNT concentration. The rheological analysis showed that the transition region from shear thinning to Newtonian extended to the higher shear stress range compared to that of base fluids. Viscosity ratio of the nanofluids augmented anomalously with respect to increase in temperature and about 2.25 fold increase was observed in the temperature range of 30 – 40 ˚C. The modified model of Maron and Pierce predicted the viscosity of the nanofluids with the inclusion of effect of aspect ratio of MWCNT and nanoparticle aggregates.
Thermally conductive cementitious grouts for geothermal heat pumps. Progress report FY 1998
Energy Technology Data Exchange (ETDEWEB)
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.
Energy Technology Data Exchange (ETDEWEB)
Hassaan, M.Y., E-mail: myhassaan@yahoo.com [Al-Azhar University, Faculty of Science, Physics Department, 11884 Cairo (Egypt); Ebrahim, F.M.; Mostafa, A.G. [Al-Azhar University, Faculty of Science, Physics Department, 11884 Cairo (Egypt); El-Desoky, M.M., E-mail: mmdesoky@gmail.com [Suez Canal University, Faculty of Science, Physics Department, Suez (Egypt)
2011-09-15
Highlights: {yields} Selected glasses of V{sub 2}O{sub 5}-BaO-5Fe{sub 2}O{sub 3} system have been transformed into nanomaterials by annealing at temperature close to crystallization temperature (T{sub c}) for 1 h. {yields} Glass ceramic nanocrystals are important because of their physical properties which are not obtainable in other classes of materials. {yields} Crystal and grain sizes are the most significant structural parameters in electronic nanocrystalline glassy phases. {yields} These phases have very high electrical conductivity, hence glass-ceramic nanocrystals are expected to be used, for example, as a gas sensor. - Abstract: Six glass samples with a composition of 75V{sub 2}O{sub 5} + 10BaO + 15Fe{sub 2}O{sub 3} mol%, with 0, 10, 15, 20, and 25 wt% of sulfur were prepared by using a quenching method. The samples were measured by XRD, DSC, TEM, Moessbauer spectrometry and D.C. conductivity. The prepared samples were heat treated at temperature close to their crystallization temperatures for 1 h, and then the previous measurements were repeated. The results showed that the treatment process caused the formation of V{sub 2}O{sub 5} and FeVO{sub 4} nanocrystals with size of 17-25 nm dispersed in the glass matrix. The addition of sulfur reduced only the vanadium ions to V{sup 4+}, while it was found that iron ions were Fe{sup 3+} only. D.C. conduction enhanced due to the small polaron or electron hopping from V{sup 4+} to V{sup 5+} ions. The heat treated samples exhibit much higher conductivity and much lower activation energy than the as-prepared glasses. The heat treated samples showed decreased thermal stability with the addition of sulfur. This considerable enhancement of electrical conductivity after nanocrystallization referred to the formation of extensive and dense network of electronic conduction paths which are situated between V{sub 2}O{sub 5} nanocrystals and their surfaces.
Directory of Open Access Journals (Sweden)
Tao Min
2014-01-01
Full Text Available This paper is intended to provide a numerical algorithm involving the combined use of the Levenberg-Marquardt algorithm and the Galerkin finite element method for estimating the diffusion coefficient in an inverse heat conduction problem (IHCP. In the present study, the functional form of the diffusion coefficient is unknown a priori. The unknown diffusion coefficient is approximated by the polynomial form and the present numerical algorithm is employed to find the solution. Numerical experiments are presented to show the efficiency of the proposed method.
International Nuclear Information System (INIS)
Fink, J.K.; Chasanov, M.G.; Leibowitz, L.
Equations have been derived for the enthalpy, heat capacity, thermal conductivity, and thermal diffusivity of UO 2 . In selection of these equations, we considered the traditional criterion of lowest relative standard deviation between experimental data and the function chosen to fit these data as well as consistency between the thermophysical properties. In the latter case, we considered consistency in (1) thermodynamic relations among properties, (2) the choice of physical phenomena on which to base the theoretical formulation of the equations, and (3) the existence and temperature of phase transitions
Thermodynamic analysis of chemical heat pumps
International Nuclear Information System (INIS)
Obermeier, Jonas; Müller, Karsten; Arlt, Wolfgang
2015-01-01
Thermal energy storages and heat pump units represent an important part of high efficient renewable energy systems. By using thermally driven, reversible chemical reactions a combination of thermal energy storage and heat pump can be realized. The influences of thermophysical properties of the involved components on the efficiency of a heat pump cycle is analysed and the relevance of the thermodynamic driving force is worked out. In general, the behaviour of energetic and exergetic efficiency is contrary. In a real cycle, higher enthalpies of reaction decrease the energetic efficiency but increase the exergetic efficiency. Higher enthalpies of reaction allow for lower offsets from equilibrium state for a default thermodynamic driving force of the reaction. - Highlights: • A comprehensive efficiency analysis of gas-solid heat pumps is proposed. • Link between thermodynamic driving force and equilibrium drop is shown. • Calculation of the equilibrium drop based on thermochemical properties. • Reaction equilibria of the decomposition reaction of salt hydrates. • Contrary behavior of energetic and exergetic efficiency
Jia, Yonggao; Chen, Chao; Jia, Dan; Li, Shuxin; Ji, Shulin; Ye, Changhui
2016-04-20
The uniformity of the sheet resistance of transparent conductive films is one of the most important quality factors for touch panel applications. However, the uniformity of silver nanowire transparent conductive films is far inferior to that of indium-doped tin oxide (ITO). Herein, we report a dynamic heating method using infrared light to achieve silver nanowire transparent conductive films with high uniformity. This method can overcome the coffee ring effect during the drying process and suppress the aggregation of silver nanowires in the film. A nonuniformity factor of the sheet resistance of the as-prepared silver nanowire transparent conductive films could be as low as 6.7% at an average sheet resistance of 35 Ω/sq and a light transmittance of 95% (at 550 nm), comparable to that of high-quality ITO film in the market. In addition, a mechanical study shows that the sheet resistance of the films has little change after 5000 bending cycles, and the film could be used in touch panels for human-machine interactive input. The highly uniform and mechanically stable silver nanowire transparent conductive films meet the requirement for many significant applications and could play a key role in the display market in a near future.
Heat analysis of the magnetic limiter plate for JT-60
International Nuclear Information System (INIS)
Nakamura, Hiroo; Ninomiya, Hiromasa; Shimizu, Masatsugu; Ohta, Mitsuru
1977-03-01
Heat analysis has been made of the magnetic limiter plate for JT-60. Test materials of the magnetic limiter plate are molybdenum, graphite, pyrolytic graphite and silicon carbide. It is assumed in calculation of the heat analysis that 10MW is deposited on the 2 cm wide surface of the magnetic limiter plate in about 10 sec. The magnetic limiter plate of pyrolytic graphite is a stack of pyrolytic graphite sheets, heat input is in the deposition plane to take advantage of the large heat conductivity along this plane. Pyrolytic graphite is the best in terms of temperature rise. The temperature of molybdenum and graphite rise up to 1800 0 C and 620 0 C, respectively, in an deposition of 10 MWx10sec. Silicon carbide is not suitable for the magnetic limiter plate. Because the plasma of the JT-60 discharges every 10 min, the average heat flux decreases to 17 w/cm 2 during the each interval. When the magnetic limiter plate has the above heat inflow, a maximum of above 1000 0 C occurs at the edge far from the joint to the thick ring of the vacuum vessel. To reduce heat load of the magnetic limiter plate, an alternating current (2 -- 5Hz) is superposed on the magnetic limiter coil current. The intersection of separatrix line and magnetic limiter plate then moves cyclically more than 10 cm. Concerning temperature distribution of the multi-groove magnetic limiter plate, its dimensions are determined by the limitation in vapor pressure to prevent the impurity inflow. (auth.)
Structure of slow shocks in a magnetized plasma with heat conduction
International Nuclear Information System (INIS)
Tsai, C.L.; Tsai, R.H.; Wu, B.H.; Lee, L.C.
2002-01-01
The structure of slow shocks in the presence of a heat conduction parallel to the local magnetic field is simulated from the set of magnetohydrodynamic equations. In this study, a pair of slow shocks is formed through the evolution of a current sheet initiated by the presence of a normal magnetic field. It is found that the slow shock consists of two parts: The isothermal main shock and foreshock. Significant jumps in plasma density, velocity and magnetic field occur across the main shock, but the temperature is found to be continuous across the main shock. The foreshock is featured by a smooth temperature variation and is formed due to the heat flow from downstream to upstream region. The plasma density downstream of the main shock decreases with time, while the downstream temperature increases with time, keeping the downstream pressure constant. It is shown that the jumps in plasma density, pressure, velocity, and magnetic field across the main shock are determined by the set of modified isothermal Rankine-Hugoniot conditions. It is also found that a jump in the temperature gradient is present across the main shock in order to satisfy the energy conservation. The present results can be applied to the heating in the solar corona and solar wind
Solution of the transient Fourier heat conduction equation in r,phi geometry
International Nuclear Information System (INIS)
Kowa, E.; Ehnis, L.
1978-11-01
The two-dimensional transient Fourier heat conduction equation is solved in r,phi geometry for anisotropic materials with the computer program TERFI. The Alternating-Direction-Implicit method is used for the solution of this equation with specified start- and boundary conditions, temperature dependent material properties and space dependent heat sources. The solution area is devided in a mesh grid by the finite difference method. Slidely non-orthogonaly geometry (displacement of mesh grid) can be regarded. There were some difficulties in the treatment of the boundary conditions for the circularly-closed solution area because of the continuity of temperature and heat flux on the 0 0 /360 0 -line. This problem can be solved by an iterativ method with different starting points for the solution scheme. Emphasis was put on reaching reasonable computer time for the iteration. The computer code TERFI, programed in FORTRAN IV, is a modul of the program system RSYST. As an example the temperature distribution of a PWR fuel rod is calculated. (orig.) [de
DEFF Research Database (Denmark)
Eldrup, Morten Mostgaard; Singh, B.N.
1998-01-01
The electrical conductivity of three different types of copper alloys, viz. CuNiBe, CuCrZr and Cu-Al(2)O(3) as well as of pure copper are reported. The alloys have undergone different pre-irradiation heat treatments and have been fission-neutron irradiated up to 0.3 dpa. In some cases post......-irradiation annealing has been carried out. The results are discussed with reference to equivalent Transmission Electron Microscopy results on the microstructure of the materials. The CuNiBe has the lowest conductivity (less than or equal to 55% of that of pure Cu), and Cu-Al(2)O(3) the highest (75-90% of pure Cu). (C...
Eldrup, M.; Singh, B. N.
1998-10-01
The electrical conductivity of three different types of copper alloys, viz. CuNiBe, CuCrZr and Cu-Al 2O 3 as well as of pure copper are reported. The alloys have undergone different pre-irradiation heat treatments and have been fission-neutron irradiated up to 0.3 dpa. In some cases post-irradiation annealing has been carried out. The results are discussed with reference to equivalent Transmission Electron Microscopy results on the microstructure of the materials. The CuNiBe has the lowest conductivity (⩽55% of that of pure Cu), and Cu-Al 2O 3 the highest (75-90% of pure Cu).
Two and dimensional heat analysis inside a high pressure electrical discharge tube
International Nuclear Information System (INIS)
Aghanajafi, C.; Dehghani, A. R.; Fallah Abbasi, M.
2005-01-01
This article represents the heat transfer analysis for a horizontal high pressure mercury steam tube. To get a more realistic numerical simulation, heat radiation at different wavelength width bands, has been used besides convection and conduction heat transfer. The analysis for different gases with different pressure in two and three dimensional cases has been investigated and the results compared with empirical and semi empirical values. The effect of the environmental temperature on the arc tube temperature is also studied
Spatiotemporal and economic analysis of industrial excess heat as a resource for district heating
DEFF Research Database (Denmark)
Bühler, Fabian; Petrović, Stefan; Holm, Fridolin Müller
2018-01-01
detailed analysis of the most suitable types of industries and the costs is required, allowing a targeted exploitation of this resource. This work extends the spatial and thermodynamic analysis, to account for the temporal match between industrial excess heat and district heating demands, as well...... as the costs for implementation and operation of the systems. This allows the determination of cost-effective district heating potentials, as well as the analysis of different industries and technological requirements. The results show that the temporal mismatch between excess heat and district heating demand...... and lack of demand, reduces the theoretical substitution potential by almost 30%. If heat storages are introduced, the total potential is reduced by only 10%. A majority of the excess heat can be utilised at socio-economic heating costs lower than the average Danish district heating price and the cost...
Stability of one-step methods in transient nonlinear heat conduction
International Nuclear Information System (INIS)
Hughes, J.R.
1977-01-01
The purpose of the present work is to ascertain practical stability conditions for one-step methods commonly used in transient nonlinear heat conduction analyses. The class of problems considered is governed by a temporally continuous, spatially discrete system involving the capacity matrix C, conductivity matrix K, heat supply vector, temperature vector and time differenciation. In the linear case, in which K and C are constant, the stability behavior of one-step methods is well known. But in this paper the concepts of stability, appropriate to the nonlinear problem, are thoroughly discussed. They of course reduce to the usual stability criterion for the linear, constant coefficient case. However, for nonlinear problems there are differences and these ideas are of key importance in obtaining practical stability conditions. Of particular importance is a recent result which indicates that, in a sense, the trapezoidal and midpoint families are quivalent. Thus, stability results for one family may be translated into a result for the other. The main results obtained are summarized as follows. The stability behavior of the explicit Euler method in the nonlinear regime is analogous to that for linear problems. In particular, an a priori step size restriction may be determined for each time step. The precise time step restriction on implicit conditionally stable members of the trapezoidal and midpoint families is shown not to be determinable a priori. Of considerable practical significance, unconditionally stable members of the trapezoidal and midpoint families are identified
International Nuclear Information System (INIS)
Dauvois, Yann
2016-01-01
In the present work, the effective heat transfer properties of fibrous medium are determined by taking into account a coupling of heat conduction and radiation. A virtual, statistically homogeneous, two-phase fibrous sample has been built by stacking finite absorbing cylinders in vacuum. These cylinders are dispersed according to prescribed distribution functions defining the cylinder positions and orientations. Cylinder overlappings are allowed. Extinction, absorption and scattering are characterised by radiative statistical functions which allow the Beerian behaviour of a medium to be assessed (or not). They are accurately determined with a Monte Carlo method. Whereas the gaseous phase exhibits a Beerian behaviour, the fibre phase is strongly non Beerian. The radiative power field deposited within the fibrous material is calculated by resolving a model which couples a Generalized Radiative Transfer Equation (GRTE) and a classic Radiative Transfer Equation (RTE). The model of conduction transfer is based on a random walk method without meshing. The simulation of Brownian motion of walkers in fibres allows the energy equation to be solved. The idea of the method is to characterize the temperature in an elementary volume by the density of walkers, which roam the medium. The problem is governed by boundary conditions; A constant concentration of walkers (or a constant flux) is associated with a fixed temperature (or flux). (author) [fr
Computer aided heat transfer analysis in a laboratory scaled heat exchanger unit
International Nuclear Information System (INIS)
Gunes, M.
1998-01-01
In this study. an explanation of a laboratory scaled heat exchanger unit and a software which is developed to analyze heat transfer. especially to use it in heat transfer courses, are represented. Analyses carried out in the software through sample values measured in the heat exchanger are: (l) Determination of heat transfer rate, logarithmic mean temperature difference and overall heat transfer coefficient; (2)Determination of convection heat transfer coefficient inside and outside the tube and the effect of fluid velocity on these; (3)Investigation of the relationship between Nusselt Number. Reynolds Number and Prandtl Number by using multiple non-linear regression analysis. Results are displayed on the screen graphically
Energy Technology Data Exchange (ETDEWEB)
Kovalev, A. I.; Wainstein, D. L., E-mail: d-wainstein@sprg.ru [Surface Phenomena Researches Group, Radio Str., 23/9, Bld. 2, Off. 475, CNIICHERMET, 105005 Moscow (Russian Federation); Rashkovskiy, A. Yu. [Surface Phenomena Researches Group, Radio Str., 23/9, Bld. 2, Off. 475, CNIICHERMET, 105005 Moscow (Russian Federation); National University of Science and Technology MISiS, Leninskiy pr-t, 4, 119049 Moscow (Russian Federation); Gago, R. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, E-28049 Madrid (Spain); Soldera, F. [Department of Materials Science and Engineering, Saarland University, 66123 Saarbruecken (Germany); Endrino, J. L. [School of Aerospace, Transport and Manufacturing (SATM), Surface Engineering and Nanotechnology Institute, Cranfield University, College Road, Cranfield, MK43 0AL Bedfordshire (United Kingdom)
2016-05-30
TiAlN/Ag multilayer coatings with a different number of bilayers and thicknesses of individual layers were fabricated by DC magnetron co-sputtering. Thermal conductivity was measured in dependence of Ag layer thickness. It was found anomalous low thermal conductivity of silver comparing to TiAlN and Ag bulk standards and TiAlN/TiN multilayers. The physical nature of such thermal barrier properties of the multilayer coatings was explained on the basis of reflection electron energy loss spectroscopy. The analysis shows that nanostructuring of the coating decreases the density of states and velocity of acoustic phonons propagation. At the same time, multiphonon channels of heat propagation degenerate. These results demonstrate that metal-dielectric interfaces in TiAlN/Ag coatings are insurmountable obstacles for acoustic phonons propagation.
Energy Technology Data Exchange (ETDEWEB)
Lyczkowski, R. W. [Institute of Gas Technology, Chicago, IL (United States); Solbrig, C. W. [Commonwealth Edison Co., Chicago, IL (United States); Gidaspow, D. [Illinois Inst. of Technology, Chicago, IL (United States)
1980-01-01
A numerical solution for laminar flow heat transfer between a flowing gas and its containing rectangular duct has been obtained for many different boundary conditions. The problem has been solved for the cases of insulation on no walls, one wall, two walls, and three walls with various finite resistances on the remaining walls. Results have been obtained for several duct aspect ratios in the thermal entrance and in the fully developed regions, including the constant temperature cases. When one wall is insulated and the other three are at constant temperature, the maximum temperature occurs in the fluid rather than on the insulated wall. This maximum moves toward the insulated wall with increasing axial distance. Nusselt numbers for the same constant flux on all four walls with peripheral conduction lie in a narrow band bounded by zero and infinite peripheral conduction cases. A dimensionless wall conduction group of four can be considered infinite for the purpose of estimating fully developed Nusselt numbers to within an accuracy of 3%. A decrease in wall and bulk temperatures by finite wall conduction has been demonstrated for the case of a black body radiation boundary condition.
Coupling heat conduction and radiation in complex 2D and 3D geometries
Energy Technology Data Exchange (ETDEWEB)
Peniguel, C [Electricite de France (EDF), 78 - Chatou (France). Direction des Etudes et Recherches; Rupp, I [SIMULOG, 78 - Guyancourt (France)
1998-12-31
Thermal radiation is a very important mode of heat transfer in most real industrial systems. A numerical approach coupling radiation (restricted to non participant medium) and conduction is presented. The code (SYRTHES) is able to handle 2D and 3D problems (including cases with symmetries and periodicity). Radiation is solved by a radiosity approach, and conduction by a finite element method. Accurate and efficient algorithms based on a mixing of analytical/numerical integration, and ray tracing techniques are used to compute the view factors. Validation has been performed on numerous test cases. A conjugate residual algorithm solves the radiosity system. An explicit interactive numerical procedure is then used to couple conduction and radiation. No stability problem has been encountered so far. One specificity of SYRTHES is that conduction and radiation are solved on independent grids. This brings much flexibility and allows to keep the number of independent radiation patches at a reasonable level. Several industrial examples are given as illustration. (author) 6 refs.
International Nuclear Information System (INIS)
Kuddusi, Luetfullah; Denton, Jesse C.
2007-01-01
The constructal solution for cooling of electronics requires solution of a fundamental heat conduction problem in a composite slab composed of a heat generating slab and a thin strip of high conductivity material that is responsible for discharging the generated heat to a heat sink located at one end of the strip. The fundamental 2D heat conduction problem is solved analytically by applying an integral transform method. The analytical solution is then employed in a constructal solution, following Bejan, for cooling of electronics. The temperature and heat flux distributions of the elemental heat generating slabs are assumed to be the same as those of the analytical solution in all the elemental volumes and the high conductivity strips distributed in the different constructs. Although the analytical solution of the fundamental 2D heat conduction problem improves the accuracy of the distributions in the elemental slabs, the results following Bejan's strategy do not affirm the accuracy of Bejan's constructal solution itself as applied to this problem of cooling of electronics. Several different strategies are possible for developing a constructal solution to this problem as is indicated
Analysis of the internal heat losses in a thermoelectric generator
DEFF Research Database (Denmark)
Bjørk, Rasmus; Christensen, Dennis Valbjørn; Eriksen, Dan
2014-01-01
and radiative heat losses, including surface to surface radiation. For radiative heat losses it is shown that for the temperatures considered here, surface to ambient radiation is a good approximation of the heat loss. For conductive heat transfer the module efficiency is shown to be comparable to the case...... of radiative losses. Finally, heat losses due to internal natural convection in the module is shown to be negligible for the millimetre sized modules considered here. The combined case of radiative and conductive heat transfer resulted in the lowest efficiency. The optimized load resistance is found...... to decrease for increased heat loss. The leg dimensions are varied for all heat losses cases and it is shown that the ideal way to construct a TEG module with minimal heat losses and maximum efficiency is to either use a good insulating material between the legs or evacuate the module completely, and use...
Structure of intermediate shocks and slow shocks in a magnetized plasma with heat conduction
International Nuclear Information System (INIS)
Tsai, C.L.; Wu, B.H.; Lee, L.C.
2005-01-01
The structure of slow shocks and intermediate shocks in the presence of a heat conduction parallel to the local magnetic field is simulated from the set of magnetohydrodynamic equations. This study is an extension of an earlier work [C. L. Tsai, R. H. Tsai, B. H. Wu, and L. C. Lee, Phys. Plasmas 9, 1185 (2002)], in which the effects of heat conduction are examined for the case that the tangential magnetic fields on the two side of initial current sheet are exactly antiparallel (B y =0). For the B y =0 case, a pair of slow shocks is formed as the result of evolution of the initial current sheet, and each slow shock consists of two parts: the isothermal main shock and the foreshock. In the present paper, cases with B y ≠0 are also considered, in which the evolution process leads to the presence of an additional pair of time-dependent intermediate shocks (TDISs). Across the main shock of the slow shock, jumps in plasma density, velocity, and magnetic field are significant, but the temperature is continuous. The plasma density downstream of the main shock decreases with time, while the downstream temperature increases with time, keeping the downstream pressure constant. The foreshock is featured by a smooth temperature variation and is formed due to the heat flow from downstream to upstream region. In contrast to the earlier study, the foreshock is found to reach a steady state with a constant width in the slow shock frame. In cases with B y ≠0, the plasma density and pressure increase and the magnetic field decreases across TDIS. The TDIS initially can be embedded in the slow shock's foreshock structure, and then moves out of the foreshock region. With an increasing B y , the propagation speed of foreshock leading edge tends to decrease and the foreshock reaches its steady state at an earlier time. Both the pressure and temperature downstreams of the main shock decrease with increasing B y . The results can be applied to the shock heating in the solar corona and
International Nuclear Information System (INIS)
Lin Peiyin; Soriano, Allan N.; Leron, Rhoda B.; Li Menghui
2010-01-01
As part of our systematic study on physicochemical characterization of ionic liquids, in this work, we report new measurements of electrolytic conductivity and molar heat capacity for aqueous solutions of two 1-ethyl-3-methylimidazolium-based ionic liquids, namely: 1-ethyl-3-methylimidazolium dicyanamide and 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate, at normal atmospheric condition and for temperatures up to 353.2 K. The electrolytic conductivity and molar heat capacity were measured by a commercial conductivity meter and a differential scanning calorimeter (DSC), respectively. The estimated experimental uncertainties for the electrolytic conductivity and molar heat capacity measurements were ±1% and ±2%, respectively. The property data are reported as functions of temperature and composition. A modified empirical equation from another researcher was used to correlate the temperature and composition dependence of the our electrolytic conductivity results. An excess molar heat capacity expression derived using a Redlich-Kister type equation was used to represent the temperature and composition dependence of the measured molar heat capacity and calculated excess molar heat capacity of the solvent systems considered. The correlations applied represent the our measurements satisfactorily as shown by an acceptable overall average deviation of 6.4% and 0.1%, respectively, for electrolytic conductivity and molar heat capacity.
International Nuclear Information System (INIS)
Groshev, A.I.; Anisimov, V.V.; Kashcheev, V.M.; Khudasko, V.V.; Yur'ev, Yu.S.
1987-01-01
The effect of wall material on convective heat transfer of turbulent gas flow in an annular tube with account of longitudinal diffusion both in the wall and in the liquid is studied numerically. The conjugated problem is solved for P r =0.7 (Re=10 4 -10 6 ). Based on numerical calculations it is stated that thermal conductivity of the wall and gas essentially affects the degree of preliminary heating of liquid in the range of a non-heated section
Analysis of decay heat removal by natural convection in PFBR
International Nuclear Information System (INIS)
Kasinathan, N.; Vaidyanathan, G.; Chetal, S.C.; Bhoje, S.B.
1993-01-01
PFBR is a 500 MWe, 1200 MWt pool type LMFBR. In order to assure reliable decay heat removal, four totally independent Safety Grade Decay Heat Removal Systems (SGDHRS) which removes heat directly from the hot pool, is provided. Each of the SGDHRS comprises of a hot pool dipped decay heat exchanger (DHX), a sodium - air heat exchanger (AHX) at a suitable elevation and associated piping and circuits. This paper brings out the step by step approach that have been taken to decide on the preliminary sizing of the SGDHRS components, and static and transient analysis to assess the adequacy of the Decay Heat Removal capacity of the SGDHRS during the worst of the foreseen design basis conditions. The maximum values the important safety related temperatures viz., clad hotspot, hot pool top surface, reactor inlet, fuel subassembly outlets etc., would reach, can be obtained only through a comprehensive transient analysis. In order to get quick and reasonably meaningful results, one dimensional thermal-hydraulics models for the core, hot and cold pools, IHX, DHX, AHX and various pipings were developed and a code DHDYN formulated. With this a total power failure situation followed by initiations of DHR half an hour later was studied and the results revealed the following: (i) clad hotspot temperature in the in-vessel stored spent fuel subassemblies could be held below 800 deg. C only if primary sodium flow through these subassemblies are increased up to three times the originally allocated flow in the design, (ii) hotpool top zone temperature reaches 572 deg. C, (iii) reactor inlet temperature reaches 482 deg. C, (iv) the hot pool top zone temperature cools down to 450 deg. C in about 25 h. Thus these results satisfactorily established the adequacy of the sizing and the capability of the SGDHRS. DHDYN code is also used to study the RAMONA water experiments conducted in Germany. Initial results available has brought out the conservative nature of the DHDYN predictions as compared
Hosseini Koupaie, E; Eskicioglu, C
2015-01-01
This research provides a comprehensive comparison between microwave (MW) and conductive heating (CH) sludge pretreatments under identical heating/cooling profiles at below and above boiling point temperatures. Previous comparison studies were constrained to an uncontrolled or a single heating rate due to lack of a CH equipment simulating MW under identical thermal profiles. In this research, a novel custom-built pressure-sealed vessel which could simulate MW pretreatment under identical heating/cooling profiles was used for CH pretreatment. No statistically significant difference was proven between MW and CH pretreatments in terms of sludge solubilization, anaerobic biogas yield and organics biodegradation rate (p-value>0.05), while statistically significant effects of temperature and heating rate were observed (p-value<0.05). These results explain the contradictory results of previous studies in which only the final temperature (not heating/cooling rates) was controlled. Copyright © 2015 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Tze Siong Chew
2015-07-01
Full Text Available Nanofluid has attracted great attention due to its superior thermal properties. In this study, chemical oxidative polymerization of aniline was carried out in the presence of dodecylbenzenesulfonic acid (DBSA as a dopant. Particles of DBSA-doped polyaniline (DBSA-doped PANI with the size range of 15 to 50 nm were obtained, as indicated by transmission electron microscope (TEM. Results of ultra violet-visible (UV-Vis absorption and Fourier transform infrared (FTIR spectroscopies as well as thermogravimetric analysis showed that PANI nanoparticles were doped with DBSA molecules. The doping level found was 36.8%, as calculated from elemental analysis data. Thermal conductivity of water was enhanced by 5.4% when dispersed with 1.0 wt% of DBSA-PANI nanoparticles. Specific heat capacity of water-based nanofluids decreased with increasing amount of DBSA-PANI nanoparticles.
Schoolderman, A.J.; Suttorp, L.G.
1989-01-01
The long-time behaviour of the longitudinal and the transverse heat conductivity time correlation functions for a magnetized one-component plasma is studied by means of kinetic theory. To that end these correlation functions, which are defined as the inverse Laplace transforms of the dynamic heat
Cai, Jizhe; Naraghi, Mohammad
2016-08-01
In this work, a comprehensive multi-resolution two-dimensional (2D) resistor network model is proposed to analyze the electrical conductivity of hybrid nanomaterials made of insulating matrix with conductive particles such as CNT reinforced nanocomposites and thick film resistors. Unlike existing approaches, our model takes into account the impenetrability of the particles and their random placement within the matrix. Moreover, our model presents a detailed description of intra-particle conductivity via finite element analysis, which to the authors’ best knowledge has not been addressed before. The inter-particle conductivity is assumed to be primarily due to electron tunneling. The model is then used to predict the electrical conductivity of electrospun carbon nanofibers as a function of microstructural parameters such as turbostratic domain alignment and aspect ratio. To simulate the microstructure of single CNF, randomly positioned nucleation sites were seeded and grown as turbostratic particles with anisotropic growth rates. Particle growth was in steps and growth of each particle in each direction was stopped upon contact with other particles. The study points to the significant contribution of both intra-particle and inter-particle conductivity to the overall conductivity of hybrid composites. Influence of particle alignment and anisotropic growth rate ratio on electrical conductivity is also discussed. The results show that partial alignment in contrast to complete alignment can result in maximum electrical conductivity of whole CNF. High degrees of alignment can adversely affect conductivity by lowering the probability of the formation of a conductive path. The results demonstrate approaches to enhance electrical conductivity of hybrid materials through controlling their microstructure which is applicable not only to carbon nanofibers, but also many other types of hybrid composites such as thick film resistors.
Menezes de Oliveira, Marilia; Wen, Peng; Ahfock, Tony
2016-09-01
This paper focuses on electroconvulsive therapy (ECT) and head models to investigate temperature profiles arising when anisotropic thermal and electrical conductivities are considered in the skull layer. The aim was to numerically investigate the threshold for which this therapy operates safely to the brain, from the thermal point of view. A six-layer spherical head model consisting of scalp, fat, skull, cerebro-spinal fluid, grey matter and white matter was developed. Later on, a realistic human head model was also implemented. These models were built up using the packages from COMSOL Inc. and Simpleware Ltd. In these models, three of the most common electrode montages used in ECT were applied. Anisotropic conductivities were derived using volume constraint and included in both spherical and realistic head models. The bio-heat transferring problem governed by Laplace equation was solved numerically. The results show that both the tensor eigenvalues of electrical conductivity and the electrode montage affect the maximum temperature, but thermal anisotropy does not have a significant influence. Temperature increases occur mainly in the scalp and fat, and no harm is caused to the brain by the current applied during ECT. The work assures the thermal safety of ECT and also provides a numerical method to investigate other non-invasive therapies. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
International Nuclear Information System (INIS)
Açıkkalp, Emin
2014-01-01
Highlights: • Entransy analysis was made for irreversible heat pump. • Newton and Dulong–Petit heat transfer laws were used. • Entransy dissipations were defined and determined. • Relations between entransy and other thermodynamic parameters were determined. - Abstract: An irreversible heat pump was investigated via entransy analysis and performance criteria. In the analyses, two different convective heat transfer laws were applied to the considered system: the Newton and Dulong–Petit heat transfer laws. The irreversibilities in the system are the result of a finite heat transfer rate, a heat leak and internal irreversibilities, including friction, turbulence etc. In this study, a thermodynamic analysis was performed in detail, and the numerical solutions were used for the conducted analysis. The maximum entransy dissipation (critical points) ranges from 18436.7 kW K to 18855.3 kW K according to y for Newton’s law; however, there is no maximum point for the Dulon–Petit law. It can be concluded from this study that entransy should be used among the basic thermodynamic criteria
Kedia, Kushal S.; Ghoniem, Ahmed F.
2012-01-01
The objective of this work is to investigate the flame stabilization mechanism and the conditions leading to the blowoff of a laminar premixed flame anchored downstream of a heat-conducting perforated-plate/multi-hole burner, with overall nearly
Thermal conductivity and heat transport properties of nitrogen-doped graphene.
Goharshadi, Elaheh K; Mahdizadeh, Sayyed Jalil
2015-11-01
In the present study, the thermal conductivity (TC) and heat transport properties of nitrogen doped graphene (N-graphene) were investigated as a function of temperature (107-400K) and N-doped concentration (0.0-7.0%) using equilibrium molecular dynamics simulation based on Green-Kubo method. According to the results, a drastic decline in TC of graphene observed at very low N-doped concentration (0.5 and 1.0%). Substitution of just 1.0% of carbon atoms with nitrogens causes a 77.2, 65.4, 59.2, and 53.7% reduction in TC at 107, 200, 300, and 400K, respectively. The values of TC of N-graphene at different temperatures approach to each other as N-doped concentration increases. The results also indicate that TC of N-graphene is much less sensitive to temperature compared with pristine graphene and the sensitivity decreases as N-doped concentration increases. The phonon-phonon scattering relaxation times and the phonon mean free path of phonons were also calculated. The contribution of high frequency optical phonons for pristine graphene and N-graphene with 7.0% N-doped concentration is 0-2% and 4-8%, respectively. These findings imply that it is potentially feasible to control heat transfer on the nanoscale when designing N-graphene based thermal devices. Copyright © 2015 Elsevier Inc. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Gurevich, Yu. G.; Logvinov, G. N. [Instituto Politecnico Nacional, Mexico, D.F. (Mexico); Laricheva, N. [Datmouth College, New Hampshire (United States); Mashkevich, O. L. [Kharkov University, Kharkov (Ukraine)
2001-10-01
A nonlinear temperature dependence of the kinetic coefficients of semiconductor plasma can result in the appearance of regions of negative differential conductivity (NDC) in both the high-frequency (HF) and static current-voltage characteristics (CVC). In the present paper the formation of the static NDC under simultaneous electron gas heating by HF and static electric field is studied. As is shown below, in this case the heating electromagnetic wave has a pronounced effect on the appearance of NDC caused by the overheating mechanisms and the type of the static CVC as a whole. [Spanish] Una dependencia no lineal de la temperatura de los coeficientes cineticos del plasma del semiconductor puede llevar a la aparicion de regiones con conductividad diferencial negativa (CDN) en las caracteristicas corriente voltaje (CCV) de alta frecuencia (AF) y estatica. En este articulo se estudia la formacion de la CDN estatica bajo la accion simultanea del calentamiento del gas de electrones por AF y el campo electrico estatico. Como se muestra mas adelante, en este caso la onda electromagnetica que calienta a los electrones ejerce un fuerte efecto en la aparicion de la CDN; que se obtiene por mecanismos de sobrecalentamiento, y en el tipo de CCV estatica.
Linear perturbations of a self-similar solution of hydrodynamics with non-linear heat conduction
International Nuclear Information System (INIS)
Dubois-Boudesocque, Carine
2000-01-01
The stability of an ablative flow, where a shock wave is located upstream a thermal front, is of importance in inertial confinement fusion. The present model considers an exact self-similar solution to the hydrodynamic equations with non-linear heat conduction for a semi-infinite slab. For lack of an analytical solution, a high resolution numerical procedure is devised, which couples a finite difference method with a relaxation algorithm using a two-domain pseudo-spectral method. Stability of this solution is studied by introducing linear perturbation method within a Lagrangian-Eulerian framework. The initial and boundary value problem is solved by a splitting of the equations between a hyperbolic system and a parabolic equation. The boundary conditions of the hyperbolic system are treated, in the case of spectral methods, according to Thompson's approach. The parabolic equation is solved by an influence matrix method. These numerical procedures have been tested versus exact solutions. Considering a boundary heat flux perturbation, the space-time evolution of density, velocity and temperature are shown. (author) [fr
Energy Technology Data Exchange (ETDEWEB)
Hujova, Miroslava [Laboratory of Inorganic Materials, Joint Workplace of the University of Chemistry and Technology Prague and the Institute, Institute of Rock Structure and Mechanics of the ASCR, Prague Czech Republic; Pokorny, Richard [Laboratory of Inorganic Materials, Joint Workplace of the University of Chemistry and Technology Prague and the Institute, Institute of Rock Structure and Mechanics of the ASCR, Prague Czech Republic; Klouzek, Jaroslav [Laboratory of Inorganic Materials, Joint Workplace of the University of Chemistry and Technology Prague and the Institute, Institute of Rock Structure and Mechanics of the ASCR, Prague Czech Republic; Dixon, Derek R. [Radiological Materials & Detection Group, Pacific Northwest National Laboratory, Richland Washington; Cutforth, Derek A. [Radiological Materials & Detection Group, Pacific Northwest National Laboratory, Richland Washington; Lee, Seungmin [Radiological Materials & Detection Group, Pacific Northwest National Laboratory, Richland Washington; McCarthy, Benjamin P. [Radiological Materials & Detection Group, Pacific Northwest National Laboratory, Richland Washington; Schweiger, Michael J. [Radiological Materials & Detection Group, Pacific Northwest National Laboratory, Richland Washington; Kruger, Albert A. [U.S. Department of Energy, Office of River Protection, Richland Washington; Hrma, Pavel [Radiological Materials & Detection Group, Pacific Northwest National Laboratory, Richland Washington
2017-07-10
The heat conductivity of reacting melter feed affects the heat transfer and conversion process in the cold cap (the reacting feed floating on molten glass). To investigate it, we simulated the feed conditions and morphology in the cold-cap by preparing “fast-dried slurry blocks”, formed by rapidly evaporating water from feed slurry poured onto a 200°C surface. A heat conductivity meter was used to measure heat conductivity of samples cut from the fast-dried slurry blocks, samples of a cold cap retrieved from a laboratory-scale melter, and loose dry powder feed samples. Our study indicates that the heat conductivity of the feed in the cold cap is significantly higher than that of loose dry powder feed, resulting from the feed solidification during the water evaporation from the feed slurry. To assess the heat transfer at higher temperatures when feed turns into foam, we developed a theoretical model that predicts the foam heat conductivity based on morphology data from in-situ X-ray computed tomography. The implications for the mathematical modeling of the cold cap are discussed.
Effect of the time window on the heat-conduction information filtering model
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.
A finite volume method for cylindrical heat conduction problems based on local analytical solution
Li, Wang
2012-10-01
A new finite volume method for cylindrical heat conduction problems based on local analytical solution is proposed in this paper with detailed derivation. The calculation results of this new method are compared with the traditional second-order finite volume method. The newly proposed method is more accurate than conventional ones, even though the discretized expression of this proposed method is slightly more complex than the second-order central finite volume method, making it cost more calculation time on the same grids. Numerical result shows that the total CPU time of the new method is significantly less than conventional methods for achieving the same level of accuracy. © 2012 Elsevier Ltd. All rights reserved.
2012-07-05
...Notice is hereby given that a complaint was filed with the U.S. International Trade Commission on May 31, 2012, under section 337 of the Tariff Act of 1930, as amended, on behalf of Industrial Technology Research Institute of Taiwan and ITRI International of San Jose, California. The complaint alleges violations of section 337 based upon the importation into the United States, the sale for importation, and the sale within the United States after importation of certain integrated circuit packages provided with multiple heat-conducting paths and products containing same by reason of infringement of certain claims of U.S. Patent No. 5,710,459 (``the `459 patent''). The complaint further alleges that an industry in the United States exists as required by subsection (a)(2) of section 337. The complainants request that the Commission institute an investigation and, after the investigation, issue an exclusion order and cease and desist order.
Techniques for determining thermal conductivity and heat capacity under hydrostatic pressure
Andersson, S.; Bäckström, G.
1986-08-01
The paper describes a method for measuring the pressure dependence of the thermal conductivity and the heat capacity of hard materials and single crystals. Two parallel metal strips are evaporated onto a flat surface of the specimen, one being used as a heater, the other as a resistance thermometer. The appropriate theoretical expression for a specimen in a liquid medium is fitted to the temperature, sampled at constant time intervals. The thermophysical properties of the liquid high-pressure medium are taken from hot-wire experiments. The procedure has been thoroughly tested at atmospheric pressure using an MgO crystal and glass as specimens and liquids of different characteristics in lieu of high-pressure medium. The accuracy attainable was found to be 3% or better, the standard deviation of the measurements being about 0.3%. The potential of the system was demonstrated by measurements on single-crystal MgO under pressures up to 1 GPa.
On choosing a nonlinear initial iterate for solving the 2-D 3-T heat conduction equations
International Nuclear Information System (INIS)
An Hengbin; Mo Zeyao; Xu Xiaowen; Liu Xu
2009-01-01
The 2-D 3-T heat conduction equations can be used to approximately describe the energy broadcast in materials and the energy swapping between electron and photon or ion. To solve the equations, a fully implicit finite volume scheme is often used as the discretization method. Because the energy diffusion and swapping coefficients have a strongly nonlinear dependence on the temperature, and some physical parameters are discontinuous across the interfaces between the materials, it is a challenge to solve the discretized nonlinear algebraic equations. Particularly, as time advances, the temperature varies so greatly in the front of energy that it is difficult to choose an effective initial iterate when the nonlinear algebraic equations are solved by an iterative method. In this paper, a method of choosing a nonlinear initial iterate is proposed for iterative solving this kind of nonlinear algebraic equations. Numerical results show the proposed initial iterate can improve the computational efficiency, and also the convergence behavior of the nonlinear iteration.
A finite volume method for cylindrical heat conduction problems based on local analytical solution
Li, Wang; Yu, Bo; Wang, Xinran; Wang, Peng; Sun, Shuyu
2012-01-01
A new finite volume method for cylindrical heat conduction problems based on local analytical solution is proposed in this paper with detailed derivation. The calculation results of this new method are compared with the traditional second-order finite volume method. The newly proposed method is more accurate than conventional ones, even though the discretized expression of this proposed method is slightly more complex than the second-order central finite volume method, making it cost more calculation time on the same grids. Numerical result shows that the total CPU time of the new method is significantly less than conventional methods for achieving the same level of accuracy. © 2012 Elsevier Ltd. All rights reserved.
Thermal and structural analysis of a cryogenic conduction cooling system for a HTS NMR magnet
Energy Technology Data Exchange (ETDEWEB)
In, Se Hwan; Hong, Yong Jun; Yeom, Han Kil; Ko, Hyo Bong; Park, Seong Je [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)
2016-03-15
The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling method using cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than the cryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a 400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS double pancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks and finally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermal and structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load are considered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermal design of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermal contraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each component of the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.
The study of heat conductivity properties of GdS1.48 and DyS1.48
International Nuclear Information System (INIS)
Ahmadov, O.R.
2009-01-01
The heat conductivity properties of sulfides of gadolinium and dysprosium up to 900 K with use of the average speed of ultrasound distribution, a specific thermal capacity and Viderman-Frans law have been investigated. The value of Debay temperature, thermal extension coefficient and the temperature dependence are established. It is shown that the scattering on crystal lattice phonons plays the main role in lattice heat conductivity
Guo, Zhouchao; Lu, Tao; Liu, Bo
2017-04-01
Turbulent penetration can occur when hot and cold fluids mix in a horizontal T-junction pipe at nuclear plants. Caused by the unstable turbulent penetration, temperature fluctuations with large amplitude and high frequency can lead to time-varying wall thermal stress and even thermal fatigue on the inner wall. Numerous cases, however, exist where inner wall temperatures cannot be measured and only outer wall temperature measurements are feasible. Therefore, it is one of the popular research areas in nuclear science and engineering to estimate temperature fluctuations on the inner wall from measurements of outer wall temperatures without damaging the structure of the pipe. In this study, both the one-dimensional (1D) and the two-dimensional (2D) inverse heat conduction problem (IHCP) were solved to estimate the temperature fluctuations on the inner wall. First, numerical models of both the 1D and the 2D direct heat conduction problem (DHCP) were structured in MATLAB, based on the finite difference method with an implicit scheme. Second, both the 1D IHCP and the 2D IHCP were solved by the steepest descent method (SDM), and the DHCP results of temperatures on the outer wall were used to estimate the temperature fluctuations on the inner wall. Third, we compared the temperature fluctuations on the inner wall estimated by the 1D IHCP with those estimated by the 2D IHCP in four cases: (1) when the maximum disturbance of temperature of fluid inside the pipe was 3°C, (2) when the maximum disturbance of temperature of fluid inside the pipe was 30°C, (3) when the maximum disturbance of temperature of fluid inside the pipe was 160°C, and (4) when the fluid temperatures inside the pipe were random from 50°C to 210°C.
International Nuclear Information System (INIS)
Tang Jian; Peng Muzhang; Cao Dongxing
1989-01-01
A new numerical method-nodal green's function method is used for solving heat conduction function. A heat conduction problem in cylindrical geometry with axial conduction is solved in this paper. The Kirchhoff transformation is used to deal with the problem with temperature dependent conductivity. Therefor, the calculation for the function is simplified. On the basis of the formulas developed, the code named NGMEFC is programmed. A sample problem which has been calculated by the code COBRA-IV is chosen as checking. A good agreement between both codes is achieved. The calculation shows that the calculation efficiency of the nodel green's function method is much higher than that of finite difference method
Bajargaan, Ruchi; Patel, Arvind
2018-04-01
One-dimensional unsteady adiabatic flow behind an exponential shock wave propagating in a self-gravitating, rotating, axisymmetric dusty gas with heat conduction and radiation heat flux, which has exponentially varying azimuthal and axial fluid velocities, is investigated. The shock wave is driven out by a piston moving with time according to an exponential law. The dusty gas is taken to be a mixture of a non-ideal gas and small solid particles. The density of the ambient medium is assumed to be constant. The equilibrium flow conditions are maintained and energy is varying exponentially, which is continuously supplied by the piston. The heat conduction is expressed in the terms of Fourier's law, and the radiation is assumed of diffusion type for an optically thick grey gas model. The thermal conductivity and the absorption coefficient are assumed to vary with temperature and density according to a power law. The effects of the variation of heat transfer parameters, gravitation parameter and dusty gas parameters on the shock strength, the distance between the piston and the shock front, and on the flow variables are studied out in detail. It is interesting to note that the similarity solution exists under the constant initial angular velocity, and the shock strength is independent from the self gravitation, heat conduction and radiation heat flux.
Energy Technology Data Exchange (ETDEWEB)
Zarichnyak, Yu.P.; Lisnenko, T.A.
1977-10-01
Measurements are presented of the heat physical properties of trinary alloys in the system Ti-Zr-Hf. The possibility is shown of summarizing the results of the measurement and prediction of the heat conductivity of trinary continuous disordered solid solutions. Comparison of calculated results with experimental data shows that the method of modeling of the structure and prediction of heat conductivity suggested yields good qualitative and quantitative agreement throughout the entire range of change of concentration of the components. The maximum disagreement between calculated and experimental results is about 10%. 8 references, 2 figures, 1 table.
International Nuclear Information System (INIS)
Biage, M.
1983-04-01
A heat transfer problem in parallel plates with infinite with has been solved, with axial heat conduction in the fluid and in the wall, considering steady-state laminar flow for a Newtonian fluid and a fully developed velocity profile. The duct consists of an infinite inicial part, insulated on both plates, an intermediale part of finite length, with a prescribed heat flux in the upper plate and insulated on the botton plate, and by another infinite part also insulated on both plates. The problem has been solved by a numerical combination of the integral equation method and the variational method. Both, the performance of the numerical technique employed and results obtained are analyzed in this work. It is demostrated that the heat conduction in the wall significantly modifies the heat transfer parameters. (Author) [pt
Transient thermal performance analysis of micro heat pipes
International Nuclear Information System (INIS)
Liu, Xiangdong; Chen, Yongping
2013-01-01
A theoretical analysis of transient fluid flow and heat transfer in a triangular micro heat pipes (MHP) has been conducted to study the thermal response characteristics. By introducing the system identification theory, the quantitative evaluation of the MHP's transient thermal performance is realized. The results indicate that the evaporation and condensation processes are both extended into the adiabatic section. During the start-up process, the capillary radius along axial direction of MHP decreases drastically while the liquid velocity increases quickly at the early transient stage and an approximately linear decrease in wall temperature arises along the axial direction. The MHP behaves as a first-order LTI control system with the constant input power as the 'step input' and the evaporator wall temperature as the 'output'. Two corresponding evaluation criteria derived from the control theory, time constant and temperature constant, are able to quantitatively evaluate the thermal response speed and temperature level of MHP under start-up, which show that a larger triangular groove's hydraulic diameter within 0.18–0.42 mm is able to accelerate the start-up and decrease the start-up temperature level of MHP. Additionally, the MHP starts up fastest using the fluid of ethanol and most slowly using the working fluid of methanol, and the start-up temperature reaches maximum level for acetone and minimum level for the methanol. -- Highlights: • Transient thermal response of micro heat pipe is simulated by an improved model. • Control theory is introduced to quantify the thermal response of micro heat pipe. • Evaluation criteria are proposed to represent thermal response of micro heat pipe. • Effects of groove dimensions and working fluids on start-up of micro heat pipe are evaluated
Comparative analysis of heat transfer correlations for forced convection boiling
International Nuclear Information System (INIS)
Guglielmini, G.; Nannei, E.; Pisoni, C.
1978-01-01
A critical survey was conducted of the most relevant correlations of boiling heat transfer in forced convection flow. Most of the investigations carried out on partial nucleate boiling and fully developed nucleate boiling have led to the formulation of correlations that are not able to cover a wide range of operating conditions, due to the empirical approach of the problem. A comparative analysis is therefore required in order to delineate the relative accuracy of the proposed correlations, on the basis of the experimental data presently available. The survey performed allows the evaluation of the accuracy of the different calculating procedure; the results obtained, moreover, indicate the most reliable heat transfer correlations for the different operating conditions investigated. This survey was developed for five pressure range (up to 180bar) and for both saturation and subcooled boiling condition
Influence of heat conductivity on the performance of RTV SIR coatings with different fillers
Energy Technology Data Exchange (ETDEWEB)
Siderakis, K [High Voltage Laboratory, Department of Electrical and Computer Engineering, University of Patras, GR-26110 Patras (Greece); Agoris, D [High Voltage Laboratory, Department of Electrical and Computer Engineering, University of Patras, Greece, GR-26500, Rion, Greece (Greece); Gubanski, S [High Voltage Laboratory, Department of Electric Power Engineering, Chalmers University of Technology, S-41296, Gothenburg (Sweden)
2005-10-07
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.
Heat Transfer Analysis for a Fixed CST Column
International Nuclear Information System (INIS)
Lee, S.Y.
2004-01-01
In support of a small column ion exchange (SCIX) process for the Savannah River Site waste processing program, a transient two-dimensional heat transfer model that includes the conduction process neglecting the convection cooling mechanism inside the crystalline silicotitanate (CST) column has been constructed and heat transfer calculations made for the present design configurations. For this situation, a no process flow condition through the column was assumed as one of the reference conditions for the simulation of a loss-of-flow accident. A series of the modeling calculations has been performed using a computational heat transfer approach. Results for the baseline model indicate that transit times to reach 130 degrees Celsius maximum temperature of the CST-salt solution column are about 96 hours when the 20-in CST column with 300 Ci/liter heat generation source and 25 degrees Celsius initial column temperature is cooled by natural convection of external air as a primary heat transfer mechanism. The modeling results for the 28-in column equipped with water jacket systems on the external wall surface of the column and water coolant pipe at the center of the CST column demonstrate that the column loaded with 300 Ci/liter heat source can be maintained non-boiling indefinitely. Sensitivity calculations for several alternate column sizes, heat loads of the packed column, engineered cooling systems, and various ambient conditions at the exterior wall of the column have been performed under the reference conditions of the CST-salt solution to assess the impact of those parameters on the peak temperatures of the packed column for a given transient time. The results indicate that a water-coolant pipe at the center of the CST column filled with salt solution is the most effective one among the potential design parameters related to the thermal energy dissipation of decay heat load. It is noted that the cooling mechanism at the wall boundary of the column has significant
Parametric analysis of geothermal residential heating and cooling application
Energy Technology Data Exchange (ETDEWEB)
Sagia, Zoi N.; Stegou, Athina B.; Rakopoulos, Constantinos D. [National Technical University of Athens, School of Mechanical Engineering, Department of Thermal Engineering, Heroon Polytechniou 9, 15780, Zografou, Attiki (Greece)
2012-07-01
A study is carried out to evaluate the efficiency of a Ground Source Heat Pump (GSHP) system with vertical heat exchangers applied to a three-storey terraced building, with total heated area 271.56 m2, standing on Hellinikon, Athens. The estimation of building loads is made with TRNSYS 16.1 using climatic data calculated by Meteonorm 6.1. The GSHP system is modeled with two other packages GLD 2009 and GLHEPRO 4.0. A comparison of the mean fluid temperature (fluid temperature in the borehole calculated as the average of exiting and entering fluid temperature), computed by above software, shows how close the results are. In addition, a parametric analysis is done to examine the influence of undisturbed ground temperature, ground heat exchanger (GHE) length and borehole separation distance to system’s operational characteristics so as to cover building loads. Finally, a 2D transient simulation is performed by means of COMSOL Multiphysics 4.0a. The carrier fluid in the borehole is modeled as a solid with extremely high thermal conductivity, extracting from and injecting to the ground the hourly load profile calculated by TRNSYS. The mean fluid temperature and the borehole wall temperature are computed for an entire year and compared with the values calculated by GLD.
Fundamental principles of conducting a surgery economic analysis study.
Kotsis, Sandra V; Chung, Kevin C
2010-02-01
The use of economic evaluation in surgery is scarce. Economic evaluation is used even less so in plastic surgery, in which health-related quality of life is of particular importance. This article, part of a tutorial series on evidence-based medicine, focuses on the fundamental principles of conducting a surgery economic analysis. The authors include the essential aspects of conducting a surgical cost-utility analysis by considering perspectives, costs, outcomes, and utilities. The authors also describe and give examples of how to conduct the analyses (including calculating quality-adjusted life-years and discounting), how to interpret the results, and how to report the results. Although economic analyses are not simple to conduct, a well-conducted one provides many rewards, such as recommending the adoption of a more effective treatment. For comparing and interpreting economic analysis publications, it is important that all studies use consistent methodology and report the results in a similar manner.
Kargel, J. S.; Furfaro, R.
2013-12-01
Thermal gradients within conductive layers of icy satellite and asteroids depend partly on heat flow, which is related to the secular decay of radioactive isotopes, to heat released by chemical phase changes, by conversion of gravitational potential energy to heat during differentiation, tidal energy dissipation, and to release of heat stored from prior periods. Thermal gradients are also dependent on the thermal conductivity of materials, which in turn depends on their composition, crystallinity, porosity, crystal fabric anisotropy, and details of their mixture with other materials. Small impurities can produce lattice defects and changes in polymerization, and thereby have a huge influence on thermal conductivity, as can cage-inclusion (clathrate) compounds. Heat flow and thermal gradients can be affected by fluid phase advection of mass and heat (in oceans or sublimating upper crusts), by refraction related to heterogeneities of thermal conductivity due to lateral variations and composition or porosity. Thermal profiles depend also on the surface temperature controlled by albedo and climate, surface relief, and latitude, orbital obliquity and surface insolation, solid state greenhouses, and endogenic heating of the surface. The thermal state of icy moon interiors and thermal gradients can be limited at depth by fluid phase advection of heat (e.g., percolating meteoric methane or gas emission), by the latent heat of phase transitions (melting, solid-state transitions, and sublimation), by solid-state convective or diapiric heat transfer, and by foundering. Rapid burial of thick volatile deposits can also affect thermal gradients. For geologically inactive or simple icy objects, most of these controls on heat flow and thermal gradients are irrelevant, but for many other icy objects they can be important, in some cases causing large lateral and depth variations in thermal gradients, large variations in heat flow, and dynamically evolving thermal states. Many of
Linear stability analysis of heated parallel channels
International Nuclear Information System (INIS)
Nourbakhsh, H.P.; Isbin, H.S.
1982-01-01
An analyis is presented of thermal hydraulic stability of flow in parallel channels covering the range from inlet subcooling to exit superheat. The model is based on a one-dimensional drift velocity formulation of the two phase flow conservation equations. The system of equations is linearized by assuming small disturbances about the steady state. The dynamic response of the system to an inlet flow perturbation is derived yielding the characteristic equation which predicts the onset of instabilities. A specific application is carried out for homogeneous and regional uniformly heated systems. The particular case of equal characteristic frequencies of two-phase and single phase vapor region is studied in detail. The D-partition method and the Mikhailov stability criterion are used for determining the marginal stability boundary. Stability predictions from the present analysis are compared with the experimental data from the solar test facility. 8 references
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.
CFD analysis of heat transfer in a vertical annular gas gap
International Nuclear Information System (INIS)
Borgohain, A.; Maheshwari, N.K.; Vijayan, P.K.
2011-01-01
Heat transfer analysis in a vertical annulus is carried out by using a CFD code TRIO-U. The results are used to understand heat transfer in the vertical annulus. An experimental study is taken from literature for the CFD analysis. The geometry of the test section of the experiment is simulated in TRIO-U. The operating conditions of the experiment are simulated by imposing appropriate boundary conditions. Three modes of the heat transfer, conduction, radiation and convection in the gas gap are considered in the analysis. From the analysis it is found that TRIO-U can successfully handle all modes heat transfer. The theoretical results for heat transfer have been compared with experimental data. This paper deals with the detailed CFD modelling and analysis. (author)
Conduction block of mammalian myelinated nerve by local cooling to 15–30°C after a brief heating
Zhang, Zhaocun; Lyon, Timothy D.; Kadow, Brian T.; Shen, Bing; Wang, Jicheng; Lee, Andy; Kang, Audry; Roppolo, James R.; de Groat, William C.
2016-01-01
This study aimed at understanding thermal effects on nerve conduction and developing new methods to produce a reversible thermal block of axonal conduction in mammalian myelinated nerves. In 13 cats under α-chloralose anesthesia, conduction block of pudendal nerves (n = 20) by cooling (5–30°C) or heating (42–54°C) a small segment (9 mm) of the nerve was monitored by the urethral striated muscle contractions and increases in intraurethral pressure induced by intermittent (5 s on and 20 s off) electrical stimulation (50 Hz, 0.2 ms) of the nerve. Cold block was observed at 5–15°C while heat block occurred at 50–54°C. A complete cold block up to 10 min was fully reversible, but a complete heat block was only reversible when the heating duration was less than 1.3 ± 0.1 min. A brief (block at 50–54°C or 15 min of nonblock mild heating at 46–48°C significantly increased the cold block temperature to 15–30°C. The effect of heating on cold block fully reversed within ∼40 min. This study discovered a novel method to block mammalian myelinated nerves at 15–30°C, providing the possibility to develop an implantable device to block axonal conduction and treat many chronic disorders. The effect of heating on cold block is of considerable interest because it raises many basic scientific questions that may help reveal the mechanisms underlying cold or heat block of axonal conduction. PMID:26740534
Application of Abaqus to analysis of the temperature field in elements heated by moving heat sources
Directory of Open Access Journals (Sweden)
W. Piekarska
2010-10-01
Full Text Available Numerical analysis of thermal phenomena occurring during laser beam heating is presented in this paper. Numerical models of surface andvolumetric heat sources were presented and the influence of different laser beam heat source power distribution on temperature field wasanalyzed. Temperature field was obtained by a numerical solution the transient heat transfer equation with activity of inner heat sources using finite element method. Temperature distribution analysis in welded joint was performed in the ABAQUS/Standard solver. The DFLUXsubroutine was used for implementation of the movable welding heat source model. Temperature-depended thermophysical properties for steelwere assumed in computer simulations. Temperature distribution in laser beam surface heated and butt welded plates was numericallyestimated.
Analysis of radiative heat transfer impact in cross-flow tube and fin heat exchangers
Directory of Open Access Journals (Sweden)
Hanuszkiewicz-Drapała Małgorzata
2016-03-01
Full Text Available A cross-flow, tube and fin heat exchanger of the water – air type is the subject of the analysis. The analysis had experimental and computational form and was aimed for evaluation of radiative heat transfer impact on the heat exchanger performance. The main element of the test facility was an enlarged recurrent segment of the heat exchanger under consideration. The main results of measurements are heat transfer rates, as well as temperature distributions on the surface of the first fin obtained by using the infrared camera. The experimental results have been next compared to computational ones coming from a numerical model of the test station. The model has been elaborated using computational fluid dynamics software. The computations have been accomplished for two cases: without radiative heat transfer and taking this phenomenon into account. Evaluation of the radiative heat transfer impact in considered system has been done by comparing all the received results.
International Nuclear Information System (INIS)
Aziz, Abdul; Beers-Green, Arlen B.
2009-01-01
This paper investigates the performance and optimum design of a longitudinal rectangular fin attached to a convectively heated wall of finite thickness. The exposed surfaces of the fin lose heat to the environmental sink by simultaneous convection and radiation. The tip of the fin is assumed to lose heat by convection and radiation to the same sink. The analysis and optimization of the fin is conducted numerically using the symbolic algebra package Maple. The temperature distribution, the heat transfer rates, and the fin efficiency data is presented illustrating how the thermal performance of the fin is affected by the convection-conduction number, the radiation-conduction number, the base convection Biot number, the convection and radiation Biot numbers at the tip, and the dimensionless sink temperature. Charts are presented showing the relationship between the optimum convection-conduction number and the optimum radiation-conduction number for different values of the base convection Biot number and dimensionless sink temperature and fixed values of the convection and radiation Biot numbers at the tip. Unlike the few other papers which have applied the Adomian's decomposition and the differential quadrature element method to this problem but give illustrative results for specific fin geometry and thermal variables, the present graphical data are generally applicable and can be used by fin designers without delving into the mathematical details of the computational techniques.
Performance analysis of hybrid district heating system
DEFF Research Database (Denmark)
Mikulandric, Robert; Krajačić, Goran; Khavin, Gennadii
2013-01-01
District heating system could contribute to more efficient heat generation through cogeneration power plants or waste heat utilization facilities and to increase of renewable energy sources share in total energy consumption. In the most developed EU countries, renewable energy sources have been...... as problems related to transportation, storage and environmental impacts of biomass and waste utilisation. Implementation of heat storages in district heating systems could contribute to integration of intermittent energy sources. Hybridisation of heat production facility combines two or more different energy...... more extensively used in district heating systems either separately or as a supplement to traditional fossil fuels in order to achieve national energy policy objectives. However, they are still facing problems such as high intermittences, high energy production costs and low load factors as well...
Conducting Qualitative Data Analysis: Managing Dynamic Tensions within
Chenail, Ronald J.
2012-01-01
In the third of a series of "how-to" essays on conducting qualitative data analysis, Ron Chenail examines the dynamic tensions within the process of qualitative data analysis that qualitative researchers must manage in order to produce credible and creative results. These tensions include (a) the qualities of the data and the qualitative data…
Lead and Conduct Problems: A Meta-Analysis
Marcus, David K.; Fulton, Jessica J.; Clarke, Erin J.
2010-01-01
This meta-analysis examined the association between conduct problems and lead exposure. Nineteen studies on 8,561 children and adolescents were included. The average "r" across all 19 studies was 0.19 (p less than 0.001), which is considered a medium effect size. Studies that assessed lead exposure using hair element analysis yielded…
Stability of one-step methods in transient nonlinear heat conduction
International Nuclear Information System (INIS)
Hughes, J.R.
1977-01-01
The purpose of the present work is to ascertain practical stability conditions for one-step methods commonly used in transient nonlinear heat conduction analyses. In this paper the concepts of stability, appropriate to the nonlinear problem, are thoroughly discussed. They of course reduce to the usual stability critierion for the linear, constant coefficient case. However, for nonlinear problems there are differences and theses ideas are of key importance in obtaining practical stability conditions. Of particular importance is a recent result which indicates that, in a sense, the trapezoidal and midpoint families are equivalent. Thus, stability results for one family may be translated into a result for the other. The main results obtained are: The stability behaviour of the explicit Euler method in the nonlinear regime is analogous to that for linear problems. In particular, an a priori step size restriction may be determined for each time step. The precise time step restriction on implicit conditionally stable members of the trapezoidal and midpoint families is shown not to be determinable a priori. Of considerable practical significance, unconditionally stable members of the trapezoidal and midpoint families are identified. All notions of stability employed are motivated and defined, and their interpretations in practical computing are indicated. (Auth.)
The boundary element method for the solution of the multidimensional inverse heat conduction problem
International Nuclear Information System (INIS)
Lagier, Guy-Laurent
1999-01-01
This work focuses on the solution of the inverse heat conduction problem (IHCP), which consists in the determination of boundary conditions from a given set of internal temperature measurements. This problem is difficult to solve due to its ill-posedness and high sensitivity to measurement error. As a consequence, numerical regularization procedures are required to solve this problem. However, most of these methods depend on the dimension and the nature, stationary or transient, of the problem. Furthermore, these methods introduce parameters, called hyper-parameters, which have to be chosen optimally, but can not be determined a priori. So, a new general method is proposed for solving the IHCP. This method is based on a Boundary Element Method formulation, and the use of the Singular Values Decomposition as a regularization procedure. Thanks to this method, it's possible to identify and eliminate the directions of the solution where the measurement error plays the major role. This algorithm is first validated on two-dimensional stationary and one-dimensional transient problems. Some criteria are presented in order to choose the hyper-parameters. Then, the methodology is applied to two-dimensional and three-dimensional, theoretical or experimental, problems. The results are compared with those obtained by a standard method and show the accuracy of the method, its generality, and the validity of the proposed criteria. (author) [fr
Time-Dependent Heat Conduction Problems Solved by an Integral-Equation Approach
International Nuclear Information System (INIS)
Oberaigner, E.R.; Leindl, M.; Antretter, T.
2010-01-01
Full text: A classical task of mathematical physics is the formulation and solution of a time dependent thermoelastic problem. In this work we develop an algorithm for solving the time-dependent heat conduction equation c p ρ∂ t T-kT, ii =0 in an analytical, exact fashion for a two-component domain. By the Green's function approach the formal solution of the problem is obtained. As an intermediate result an integral-equation for the temperature history at the domain interface is formulated which can be solved analytically. This method is applied to a classical engineering problem, i.e. to a special case of a Stefan-Problem. The Green's function approach in conjunction with the integral-equation method is very useful in cases were strong discontinuities or jumps occur. The initial conditions and the system parameters of the investigated problem give rise to two jumps in the temperature field. Purely numerical solutions are obtained by using the FEM (finite element method) and the FDM (finite difference method) and compared with the analytical approach. At the domain boundary the analytical solution and the FEM-solution are in good agreement, but the FDM results show a signicant smearing effect. (author)
Advances on the time differential three-phase-lag heat conduction model and major open issues
D'Apice, Ciro; Zampoli, Vittorio
2017-07-01
The main purpose of this short contribution is to summarize the recent achievements concerning the so-called time differential three-phase-lag heat conduction model, contextually focusing attention on some of the numerous open problems associated with such an attractive theory. After having briefly recalled the origin of the model at issue, the restrictions upon the delay times and the constitutive tensors able to make it thermodynamically consistent are recalled. Under these hypotheses, the investigation of the well-posedness issue has already provided important results in terms of uniqueness and continuous dependence of the solutions (even related to the thermoelastic case), as well as in terms of existence of a domain of influence of the assigned data in connection with the thermoelastic model. Finally, some of the main problems currently object of investigation are recalled, including the very challenging issues about the different possible choices of Taylor series expansion orders for the constitutive equation, the interaction of the model with energy processes that take place on the nanoscale, with multi-porous materials and with biological systems.
GIS based analysis of future district heating potential in Denmark
DEFF Research Database (Denmark)
Nielsen, Steffen; Möller, Bernd
2013-01-01
in Denmark have been mapped in a heat atlas which includes all buildings and their heat demands. This article focuses on developing a method for assessing the costs associated with supplying these buildings with DH. The analysis is based on the existing DH areas in Denmark. By finding the heat production...
International Nuclear Information System (INIS)
Shin, Dong-Ho; Cho, Hyoung-Kyu; Tak, Nam-Il; Park, Goon-Cherl
2014-01-01
Effective thermal conductivity models which can be used to analyze the heat transfer phenomena of a prismatic fuel block were evaluated by CFD analysis. In the accident condition of VHTR when forced convection is lost, the heat flows in radial direction through the hexagonal fuel blocks that contain the large number of coolant holes and fuel compacts. Due to the complex geometry of fuel block and radiation heat transfer; the detail heat transfer computation on the fuel block needs excessive computation resources. Therefore, the detail computation isn’t appropriate for the lumped parameter code. The system code such as GAMMA+ adopts effective thermal conductivity model. Despite the complexity in heat transfer modes, the accurate analysis on the heat transfer in fuel block is necessary since it is directly relevant to the integrity of nuclear fuel embedded in fuel block. To satisfy the accurate analysis of complex heat transfer modes with limited computing sources, the credible effective thermal conductivity (ETC) models in which the effects of all of heat transfer modes are lumped is necessary. In this study, various ETC models were introduced and they are evaluated with CFD calculations. It is estimated that Maxwell-based model was the most pertinent one among the introduced ETC models. (author)
DEFF Research Database (Denmark)
Cai, Hanmin; You, Shi; Wang, Jiawei
2018-01-01
This paper provides a technical assessment of electric heat boosters (EHBs) in low-energy districts. The analysis is based on a hypothetical district with 23 terraced single-family houses supplied by both a lowtemperature district heating (LTDH) network and a low-voltage network (LVN). Two case...
International Nuclear Information System (INIS)
Park, Hansaem; Kim, Min Soo
2014-01-01
The maximum efficiency of a heat engine is able to be estimated by using a Carnot cycle. Even though, in terms of efficiency, the Carnot cycle performs the role of reference very well, its application is limited to the case of infinite heat reservoirs, which is not that realistic. Moreover, considering that one of the recent key issues is to produce maximum work from low temperature and finite heat sources, which are called renewable energy sources, more advanced theoretical cycles, which can present a new standard, and the research about them are necessary. Therefore, in this paper, a sequential Carnot cycle, where multiple Carnot cycles are connected in parallel, is studied. The cycle adopts a finite heat source, which has a certain initial temperature and heat capacity, and an infinite heat sink, which is assumed to be ambient air. Heat transfer processes in the cycle occur with the temperature difference between a heat reservoir and a cycle. In order to resolve the heat transfer rate in those processes, the product of an overall heat transfer coefficient and a heat transfer area is introduced. Using these conditions, the performance of a sequential Carnot cycle is analytically calculated. Furthermore, as the efforts for enhancing the work of the cycle, the optimization research is also conducted with numerical calculation. - Highlights: • Modified sequential Carnot cycles are proposed for evaluating low grade heat sources. • Performance of sequential Carnot cycles is calculated analytically. • Optimization study for the cycle is conducted with numerical solver. • Maximum work from a heat source under a certain condition is obtained by equations
Operation strategy analysis of a geothermal step utilization heating system
International Nuclear Information System (INIS)
Zheng, Guozhong; Li, Feng; Tian, Zhe; Zhu, Neng; Li, Qianru; Zhu, Han
2012-01-01
Geothermal energy has been successfully applied in many district heating systems. In order to promote better use of geothermal energy, it is important to analyze the operation strategy of geothermal heating system. This study proposes a comprehensive and systematic operation strategy for a geothermal step utilization heating system (GSUHS). Calculation models of radiator heating system (RHS), radiant floor heating system (RFHS), heat pump (HP), gas boiler (GB), plate heat exchanger (PHE) and pump are first established. Then the operation strategy of the GSUHS is analyzed with the aim to substantially reduce the conventional energy consumption of the whole system. Finally, the energy efficiency and geothermal tail water temperature are analyzed. With the operation strategy in this study, the geothermal energy provides the main heating amount for the system. The heating seasonal performance factor is 15.93. Compared with coal-fired heating, 75.1% of the standard coal equivalent can be saved. The results provide scientific guidance for the application of an operation strategy for a geothermal step utilization heating system. -- Highlights: ► We establish calculation models for the geothermal step utilization heating system. ► We adopt minimal conventional energy consumption to determine the operation strategy. ► The geothermal energy dominates the heating quantity of the whole system. ► The utilization efficiency of the geothermal energy is high. ► The results provide guidance to conduct operation strategy for scientific operation.
Concrete Hydration Heat Analysis for RCB Basemat Considering Solar Radiation
International Nuclear Information System (INIS)
Lee, Seong-Cheol; Son, Yong-Ki; Choi, Seong-Cheol
2015-01-01
The NPP especially puts an emphasis on concrete durability for structural integrity. It has led to higher cementitious material contents, lower water-cementitious-material ratios, and deeper cover depth over reinforcing steel. These requirements have resulted in more concrete placements that are subject to high internal temperatures. The problem with high internal temperatures is the increase in the potential for thermal cracking that can decrease concrete's long-term durability and ultimate strength. Thermal cracking negates the benefits of less permeable concrete and deeper cover by providing a direct path for corrosion-causing agents to reach the reinforcing steel. The purpose of this study is to develop how to analyze and estimate accurately concrete hydration heat of the real-scale massive concrete with wide large plane. An analysis method considering concrete placement sequence was studied and solar radiation effects on the real-scale massive concrete with wide large plane were reviewed through the analytical method. In this study, the measured temperatures at the real scale structure and the analysis results of concrete hydration heat were compared. And thermal stress analysis was conducted. Through the analysis, it was found that concrete placement duration, sequence and solar radiation effects should be considered to get the accurate concrete peak temperature, maximum temperature differences and crack index
International Nuclear Information System (INIS)
Abdel-Ghany, Ahmed M.; Kozai, Toyoki
2006-01-01
A physical model for analyzing the radiative and convective heat transfer in a fog cooled, naturally ventilated greenhouse was developed for estimating the overall heat transmission coefficient based on the conduction, convection and thermal radiation heat transfer coefficients and for predicting the soil heat flux. The contribution of the water vapor of the inside air to the emission and absorption of thermal radiation was determined. Measurements of the outside and inside greenhouse environments to be used in the analysis were conducted around solar noon (12:19-13:00) on a hot sunny day to provide the maximum solar radiation transmission into the greenhouse. The net solar radiation flux measured at the greenhouse floor showed a reasonable agreement with the predicted value. The net fluxes were estimated around noon. The average net radiation (solar and thermal) at the soil surface was 220.0 W m -2 , the average soil heat flux was 155.0 W m -2 and the average contribution of the water vapor of the inside air to the thermal radiation was 22.0 W m -2 . The average overall heat transmission coefficient was 4.0 W m -2 C -1 and was in the range between 3.0 W m -2 C -1 and 6.0 W m -2 C -1 under the different hot summer conditions between the inside and outside of the naturally ventilated, fog cooled greenhouse
Goodwin, Richard J A; Nilsson, Anna; Borg, Daniel; Langridge-Smith, Pat R R; Harrison, David J; Mackay, C Logan; Iverson, Suzanne L; Andrén, Per E
2012-08-30
Analysis of whole animal tissue sections by MALDI MS imaging (MSI) requires effective sample collection and transfer methods to allow the highest quality of in situ analysis of small or hard to dissect tissues. We report on the use of double-sided adhesive conductive carbon tape during whole adult rat tissue sectioning of carboxymethyl cellulose (CMC) embedded animals, with samples mounted onto large format conductive glass and conductive plastic MALDI targets, enabling MSI analysis to be performed on both TOF and FT-ICR MALDI mass spectrometers. We show that mounting does not unduly affect small molecule MSI detection by analyzing tiotropium abundance and distribution in rat lung tissues, with direct on-tissue quantitation achieved. Significantly, we use the adhesive tape to provide support to embedded delicate heat-stabilized tissues, enabling sectioning and mounting to be performed that maintained tissue integrity on samples that had previously been impossible to adequately prepare section for MSI analysis. The mapping of larger peptidomic molecules was not hindered by tape mounting samples and we demonstrate this by mapping the distribution of PEP-19 in both native and heat-stabilized rat brains. Furthermore, we show that without heat stabilization PEP-19 degradation fragments can detected and identified directly by MALDI MSI analysis. Copyright © 2012 Elsevier B.V. All rights reserved.
Comparative analysis of heat pump and biomass boiler for small detached house heating
Directory of Open Access Journals (Sweden)
Olkowski Tomasz
2017-01-01
Full Text Available The purpose of the work is to answer the question - which of the two selected heat sources is more economically beneficial for small detached house: heat pump or biomass boiler fuelled with wood-pellets? The comparative analysis of these sources was carried out to discuss the issue. First, cost of both, equipment and operation of selected heat systems were analysed. Additionally, CO2 emission levels associated with these heat systems were determined. The comparative analysis of the costs of both considered heat systems showed that equipment cost of heat pump system is considerably bigger than the cost of biomass boiler system. The comparison of annual operation costs showed that heat pump operation cost is slightly lower than operation cost of biomass boiler. The analysis of above results shows that lower operation cost of heat pump in comparison with biomass boiler cost lets qualify heat pump as more economically justified only after 38 years of work. For both analysed devices, CO2 emission levels were determined. The considerations take into account the fact that heat pump consumes electricity. It is mostly generated through combustion of coal in Poland. The results show that in Poland biomass boiler can be described as not only more economically justified system but also as considerably more ecological.
Comparative analysis of heat pump and biomass boiler for small detached house heating
Olkowski, Tomasz; Lipiński, Seweryn; Olędzka, Aneta
2017-10-01
The purpose of the work is to answer the question - which of the two selected heat sources is more economically beneficial for small detached house: heat pump or biomass boiler fuelled with wood-pellets? The comparative analysis of these sources was carried out to discuss the issue. First, cost of both, equipment and operation of selected heat systems were analysed. Additionally, CO2 emission levels associated with these heat systems were determined. The comparative analysis of the costs of both considered heat systems showed that equipment cost of heat pump system is considerably bigger than the cost of biomass boiler system. The comparison of annual operation costs showed that heat pump operation cost is slightly lower than operation cost of biomass boiler. The analysis of above results shows that lower operation cost of heat pump in comparison with biomass boiler cost lets qualify heat pump as more economically justified only after 38 years of work. For both analysed devices, CO2 emission levels were determined. The considerations take into account the fact that heat pump consumes electricity. It is mostly generated through combustion of coal in Poland. The results show that in Poland biomass boiler can be described as not only more economically justified system but also as considerably more ecological.
National Research Council Canada - National Science Library
Shepard, Steven M; Lhota, James R; Ahmed, Tasdiq; Kim, HeeJune; Yarlagadda, Shridhar
2004-01-01
.... Our expectation at the outset of the projects was that the combination of induction heating and thermography would outperform systems based exclusively on either electromagnetic induction or thermography...
Formalev, V. F.; Kolesnik, S. A.
2017-11-01
The authors are the first to present a closed procedure for numerical solution of inverse coefficient problems of heat conduction in anisotropic materials used as heat-shielding ones in rocket and space equipment. The reconstructed components of the thermal-conductivity tensor depend on temperature (are nonlinear). The procedure includes the formation of experimental data, the implicit gradient-descent method, the economical absolutely stable method of numerical solution of parabolic problems containing mixed derivatives, the parametric identification, construction, and numerical solution of the problem for elements of sensitivity matrices, the development of a quadratic residual functional and regularizing functionals, and also the development of algorithms and software systems. The implicit gradient-descent method permits expanding the quadratic functional in a Taylor series with retention of the linear terms for the increments of the sought functions. This substantially improves the exactness and stability of solution of the inverse problems. Software systems are developed with account taken of the errors in experimental data and disregarding them. On the basis of a priori assumptions of the qualitative behavior of the functional dependences of the components of the thermal-conductivity tensor on temperature, regularizing functionals are constructed by means of which one can reconstruct the components of the thermal-conductivity tensor with an error no higher than the error of the experimental data. Results of the numerical solution of the inverse coefficient problems on reconstruction of nonlinear components of the thermal-conductivity tensor have been obtained and are discussed.
HEAT TRANSFER ANALYSIS FOR FIXED CST AND RF COLUMNS
International Nuclear Information System (INIS)
Lee, S
2007-01-01
In support of a small column ion exchange (SCIX) process for the Savannah River Site waste processing program, transient and steady state two-dimensional heat transfer models have been constructed for columns loaded with cesium-saturated crystalline silicotitanate (CST) or spherical Resorcinol-Formaldehyde (RF) beads and 6 molar sodium tank waste supernate. Radiolytic decay of sorbed cesium results in heat generation within the columns. The models consider conductive heat transfer only with no convective cooling and no process flow within the columns (assumed column geometry: 27.375 in ID with a 6.625 in OD center-line cooling pipe). Heat transfer at the column walls was assumed to occur by natural convection cooling with 35 C air. A number of modeling calculations were performed using this computational heat transfer approach. Minimal additional calculations were also conducted to predict temperature increases expected for salt solution processed through columns of various heights at the slowest expected operational flow rate of 5 gpm. Results for the bounding model with no process flow and no active cooling indicate that the time required to reach the boiling point of ∼130 C for a CST-salt solution mixture containing 257 Ci/liter of Cs-137 heat source (maximum expected loading for SCIX applications) at 35 C initial temperature is about 6 days. Modeling results for a column actively cooled with external wall jackets and the internal coolant pipe (inlet coolant water temperature: 25 C) indicate that the CST column can be maintained non-boiling under these conditions indefinitely. The results also show that the maximum temperature of an RF-salt solution column containing 133 Ci/liter of Cs-137 (maximum expected loading) will never reach boiling under any conditions (maximum predicted temperature without cooling: 88 C). The results indicate that a 6-in cooling pipe at the center of the column provides the most effective cooling mechanism for reducing the maximum
Energy Technology Data Exchange (ETDEWEB)
Yi, Kunwoo; Cho, Hyuksu; Im, Inyoung; Kim, Eunkee [KEPCO EnC, Daejeon (Korea, Republic of)
2015-10-15
Though Material reliability programs (MRPs) have a purpose to provide the evaluation or management methodologies for the operating RVI, the similar evaluation methodologies can be applied to the APR1400 fleet in the design stage for the evaluation of neutron irradiation effects. The purposes of this study are: to predict the thermal behavior whether or not irradiated structure heat source; to evaluate effective thermal conductivity (ETC) in relation to isotropic and anisotropic conductivity of porous media for APR1400 Reactor Vessel. The CFD simulations are performed so as to evaluate thermal behavior whether or not irradiated structure heat source and effective thermal conductivity for APR1400 Reactor Vessel. In respective of using irradiated structure heat source, the maximum temperature of fluid and core shroud for isotropic ETC are 325.8 .deg. C, 341.5 .deg. C. The total amount of irradiated structure heat source is about 5.41 MWth and not effect to fluid temperature.
Energy Technology Data Exchange (ETDEWEB)
Lyczkowski, R. W.; Solbrig, C. W.; Gidaspow, D.
1980-01-01
A numerical solution for laminar flow heat transfer between a flowing gas and its containing rectangular duct has been obtained for many different boundary conditions which may arise in nuclear waste repository ventilation corridors. The problem has been solved for the cases of insulation on no walls, one wall, two walls, and three walls with various finite resistances on the remaining walls. Simplifications are made to decouple the convective heat transfer problem for the far field conduction problem, but peripheral conduction is retained. Results have been obtained for several duct aspect ratios in the thermal entrance and in the fully developed regions, including the constant temperature cases. When one wall is insulated and the other three are at constant temperature, the maximum temperature occurs in the fluid rather than on the insulated wall. This maximum moves toward the insulated wall with increasing axial distance. Nusselt numbers for the same constant flux on all four walls with peripheral conduction lie in a narrow band bounded by zero and infinite peripheral conduction cases. A dimensionless wall conduction group of four can be considered infinite for the purpose of estimating fully developed Nusselt numbers to within an accuracy of 3%. A decrease in wall and bulk temperatures by finite wall conduction has been demonstrated for the case of a black body radiation boundary condition. Nusselt numbers for the case of constant temperature on the top and bottom walls and constant heat flux on the side walls exhibited unexpected behavior.
International Nuclear Information System (INIS)
Muresan, C.
2005-01-01
numerical solution of the Radiative Transfer Equation in diffused part in the case of a mono-dimensional plane geometry. The directional discretizations of each layer are selected in such a way that the discrete directions of one of the layers correspond to those refracted of the close layer and this makes it possible to avoid the use of approximations related to non coincidence of the discrete directions of a layer with those refracted by the close layer. Directional quadratures are then established in an adaptive way in each layer and for each spectral frequency. The results obtained are validated by an approach of Monte Carlo type. The coupling of this model with a Low Reynolds number RANS model will be carried out. This will be done in order to study the convective heat transfers in natural convection for configurations of double facade integration under consideration within the framework of PRI CNRS. The comparison of this model is carried out for experimental configurations of vertical channel type uniformly heated in natural convection. The prospects for this stage are multiple and consist of analyzing the influence of the mode of flow on the thermal pulling of the hybrid components, the effects of the positioning of modules statement, the air gap between the two frontages and the boundary conditions thermal generated by the modules. Lastly, in order to supplement the energy balance of such components and more particularly that governs the thermal behavior of a photosensitive cell, the electric phenomenon of conversion is approached in adequacy with the level of modeling of the coupled thermal transfers radiation - conduction within a PV component. To carry this out, we can consider the local power of spectral radiation absorbed and converted into electric output. (author)
Implementation of an implicit method into heat conduction calculation of TRAC-PF1/MOD2 code
International Nuclear Information System (INIS)
Akimoto, Hajime; Abe, Yutaka; Ohnuki, Akira; Murao, Yoshio
1990-08-01
A two-dimensional unsteady heat conduction equation is solved in the TRAC-PF/MOD2 code to calculate temperature transients in fuel rod. A large CPU time is often required to get stable solution of temperature transients in the TRAC calculation with a small axial node size (less than 1.0 mm), because the heat conduction equation is discretized explicitly. To eliminate the restriction of the maximum time step size by the heat conduction calculation, an implicit method for solving the heat condition equation was developed and implemented into the TRAC code. Several assessment calculations were performed with the original and modified TRAC codes. It is confirmed that the implicit method is reliable and is successfully implemented into the TRAC code through comparison with theoretical solutions and assessment calculation results. It is demonstrated that the implicit method makes the heat conduction calculation practical even for the analyses of temperature transients with the axial node size less than 0.1 mm. (author)
Exergoenvironmental analysis for a geothermal district heating system: An application
International Nuclear Information System (INIS)
Keçebaş, Ali
2016-01-01
Energy sources are of great importance in relation to pollution of the world. The use of renewable energy resources and the creation of more efficient energy systems make great contributions to the prevention of greenhouse gases. Recently, many studies indicate that the energy conversion systems have many advantages in terms of technical and economic point of view. In near future, environmental impact is going to play an important role in the selection/design of such energy resources and systems. In this study, the Afyon GDHS (geothermal district heating system) having actual operating conditions is investigated at the component level in terms of environmental impact by using exergoenvironmental analysis. Moreover, the effects of ambient and wellhead temperatures on the environmental impacts of the system are discussed. The results show that a great part of total environmental impact of the system occurs from the exergy destructions of the components. Therefore, the environmental impacts can be reduced by improving their exergetic efficiencies instead of design changes of the system components. The environmental impacts of the system are reduced when the ambient temperature decreases and the wellhead temperature increases. Thus, it might not be necessary to conduct separately the exergoenvironmental analysis for different ambient temperatures. - Highlights: • Using exergoenvironmental analysis in a geothermal district heating for the first time. • Evaluating environmental impact of a geothermal district heating system. • Discussing the effects of ambient and wellhead temperatures on the environmental impact. • Total environmental impact of the system occurs from exergy destructions of components. • The exergoenvironmental analysis can be done only once for all the ambient temperatures.
NUMERICAL AND EXPERIMENTAL ANALYSIS OF UNSTEADY WORK OF U-SHAPE BOREHOLE HEAT EXCHANGER
Directory of Open Access Journals (Sweden)
S. A. Filatau
2014-01-01
Full Text Available Unsteady numerical model of borehole heat exchanger heat regime was developed. General numerical modeling results are borehole heat flux, heat carrier inlet temperature and average soil temperature distribution. Proposed model is based on solution of heat conduction equation in transient plane axially symmetric formulation with boundary conditions for borehole heat exchanger and undisturbed soil domain. Solution method is finite difference method. Numerical model is verified with comparisons numerical results and experimental data from developed laboratory installation for simulation unsteady heat regime of horizontal positioned U-shape ground heat exchanger in sand medium.Cooling of water is organized in ground exchanger in experiment. Experiment includes two steps. Thermal properties of sand is determined at the first stage. Thermal conductivity of sand is determined by stationary plate method, thermal diffusivity is determined by regular regime method using cylindrical calorimeter. Determined properties are used further in processing of experimental results at second step for analysis of transient work of ground heat exchanger. Results of four experiments are analyzed with different duration and time behavior of mass flow and heat carrier temperature. Divergences of experimental and simulated results for temperature of heat carrier changes in the range 0,5–1,8 %, for sand temperature in the range 1,0–2,3 %, for heat flux in the range 3,6–5,4 %. Experimental results can be used for validation of other simulation methods of ground heat exchangers. Presented numerical model can be used for analyzing of heat supply systems with heat pumps.
Analysis of Heat Transfer in Cooling of a Hot Plate by Planar Impingement Jet
International Nuclear Information System (INIS)
Ahn, Dae Hwan; Kim, Dong Sik
2009-01-01
Water jet impingement cooling is used to remove heat from high-temperature surfaces such as hot steel plates in the steel manufacturing process (thermo-mechanical cooling process; TMCP). In those processes, uniform cooling is the most critical factor to ensure high strength steel and good quality. In this study, experiments are performed to measure the heat transfer coefficient together with the inverse heat conduction problem (IHCP) analysis for a plate cooled by planar water jet. In the inverse heat transfer analysis, spatial and temporal variations of heat transfer coefficient, with no information regarding its functional form, are determined by employing the conjugate gradient method with an adjoint problem. To estimate the two dimensional distribution of heat transfer coefficient and heat flux for planar waterjet cooling, eight thermo-couple are installed inside the plate. The results show that heat transfer coefficient is approximately uniform in the span-wise direction in the early stage of cooling. In the later stage where the forced-convection effect is important, the heat transfer coefficient becomes larger in the edge region. The surface temperature vs. heat flux characteristics are also investigated for the entire boiling regimes. In addition, the heat transfer rate for the two different plate geometries are compared at the same Reynolds number
John F. Hunt; Hongmei Gu
2006-01-01
The anisotropy of wood complicates solution of heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models use average thermal properties across either the radial or tangential direction and do not differentiate the effects of cellular alignment, earlywood/latewood differences, or...
International Nuclear Information System (INIS)
Salem, Ahmed M.
2007-01-01
The problem of flow and heat transfer of an electrically conducting viscoelastic fluid over a continuously stretching sheet in the presence of a uniform magnetic field is analyzed for the case of power-law variation in the sheet temperature. The fluid viscosity and thermal conductivity are assumed to vary as a function of temperature. The basic equations comprising the balance laws of mass, linear momentum, and energy modified to include the electromagnetic force effect, the viscous dissipation, internal heat generation or absorption and work due to deformation are solved numerically
A coupled theory for chemically active and deformable solids with mass diffusion and heat conduction
Zhang, Xiaolong; Zhong, Zheng
2017-10-01
To analyse the frequently encountered thermo-chemo-mechanical problems in chemically active material applications, we develop a thermodynamically-consistent continuum theory of coupled deformation, mass diffusion, heat conduction and chemical reaction. Basic balance equations of force, mass and energy are presented at first, and then fully coupled constitutive laws interpreting multi-field interactions and evolving equations governing irreversible fluxes are constructed according to the energy dissipation inequality and the chemical kinetics. To consider the essential distinction between mass diffusion and chemical reactions in affecting free energy and dissipations of a highly coupled system, we regard both the concentrations of diffusive species and the extent of reaction as independent state variables. This new formulation then distinguishes between the energy contribution from the diffusive species entering the solid and that from the subsequent chemical reactions occurring among these species and the host solid, which not only interact with stresses or strains in different manners and on different time scales, but also induce different variations of solid microstructures and material properties. Taking advantage of this new description, we further establish a specialized isothermal model to predict precisely the transient chemo-mechanical response of a swelling solid with a proposed volumetric constraint that accounts for material incompressibility. Coupled kinetics is incorporated to capture the volumetric swelling of the solid caused by imbibition of external species and the simultaneous dilation arised from chemical reactions between the diffusing species and the solid. The model is then exemplified with two numerical examples of transient swelling accompanied by chemical reaction. Various ratios of characteristic times of diffusion and chemical reaction are taken into account to shed light on the dependency on kinetic time scales of evolution patterns for
International Nuclear Information System (INIS)
Hadgu, T.; Webb, S.; Itamura, M.
2004-01-01
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
Energy Technology Data Exchange (ETDEWEB)
Bassett, B
1980-10-01
High temperature properties of reactor type UO/sub 2/ pellets were measured using a Direct Electrical Heating (DEH) Facility. Modifications to the experimental apparatus have been made so that successful and reproducible DEH runs may be carried out while protecting the pellets from oxidation at high temperature. X-ray diffraction measurements on the UO/sub 2/ pellets have been made before and after runs to assure that sample oxidation has not occurred. A computer code has been developed that will model the experiment using equations that describe physical properties of the material. This code allows these equations to be checked by comparing the model results to collected data. The thermal conductivity equation for UO/sub 2/ proposed by Weilbacher has been used for this analysis. By adjusting the empirical parameters in Weilbacher's equation, experimental data can be matched by the code. From the several runs analyzed, the resulting thermal conductivity equation is lambda = 1/4.79 + 0.0247T/ + 1.06 x 10/sup -3/ exp(-1.62/kT/) - 4410. exp(-3.71/kT/) where lambda is in w/cm K, k is the Boltzman constant, and T is the temperature in Kelvin.
Heat transfer and thermal stress analysis in fluid-structure coupled field
International Nuclear Information System (INIS)
Li, Ming-Jian; Pan, Jun-Hua; Ni, Ming-Jiu; Zhang, Nian-Mei
2015-01-01
In this work, three-dimensional simulation on conjugate heat transfer in a fluid-structure coupled field was carried out. The structure considered is from the dual-coolant lithium-lead (DCLL) blanket, which is the key technology of International Thermo-nuclear Experimental Reactor (ITER). The model was developed based on finite element-finite volume method and was employed to investigate mechanical behaviours of Flow Channel Insert (FCI) and heat transfer in the blanket under nuclear reaction. Temperature distribution, thermal deformation and thermal stresses were calculated in this work, and the effects of thermal conductivity, convection heat transfer coefficient and flow velocity were analyzed. Results show that temperature gradients and thermal stresses of FCI decrease when FCI has better heat conductivity. Higher convection heat transfer coefficient will result in lower temperature, thermal deformations and stresses in FCI. Analysis in this work could be a theoretical basis of blanket optimization. - Highlights: • We use FVM and FEM to investigate FCI structural safety considering heat transfer and FSI effects. • Higher convective heat transfer coefficient is beneficial for the FCI structural safety without much affect to bulk flow temperature. • Smaller FCI thermal conductivity can better prevent heat leakage into helium, yet will increase FCI temperature gradient and thermal stress. • Three-dimensional simulation on conjugate heat transfer in a fluid-structure coupled field was carried out
Heat demand mapping and district heating grid expansion analysis: Case study of Velika Gorica
Directory of Open Access Journals (Sweden)
Dorotić Hrvoje
2017-01-01
Full Text Available Highly efficient cogeneration and district heating systems have a significant potential for primary energy savings and the reduction of greenhouse gas emissions through the utilization of a waste heat and renewable energy sources. These potentials are still highly underutilized in most European countries. They also play a key role in the planning of future energy systems due to their positive impact on the increase of integration of intermittent renewable energy sources, for example wind and solar in a combination with power to heat technologies. In order to ensure optimal levels of district heating penetration into an energy system, a comprehensive analysis is necessary to determine the actual demands and the potential energy supply. Economical analysis of the grid expansion by using the GIS based mapping methods hasn’t been demonstrated so far. This paper presents a heat demand mapping methodology and the use of its output for the district heating network expansion analysis. The result are showing that more than 59% of the heat demand could be covered by the district heating in the city of Velika Gorica, which is two times more than the present share. The most important reason of the district heating's unfulfilled potential is already existing natural gas infrastructure.
Heat demand mapping and district heating grid expansion analysis: Case study of Velika Gorica
Dorotić, Hrvoje; Novosel, Tomislav; Duić, Neven; Pukšec, Tomislav
2017-10-01
Highly efficient cogeneration and district heating systems have a significant potential for primary energy savings and the reduction of greenhouse gas emissions through the utilization of a waste heat and renewable energy sources. These potentials are still highly underutilized in most European countries. They also play a key role in the planning of future energy systems due to their positive impact on the increase of integration of intermittent renewable energy sources, for example wind and solar in a combination with power to heat technologies. In order to ensure optimal levels of district heating penetration into an energy system, a comprehensive analysis is necessary to determine the actual demands and the potential energy supply. Economical analysis of the grid expansion by using the GIS based mapping methods hasn't been demonstrated so far. This paper presents a heat demand mapping methodology and the use of its output for the district heating network expansion analysis. The result are showing that more than 59% of the heat demand could be covered by the district heating in the city of Velika Gorica, which is two times more than the present share. The most important reason of the district heating's unfulfilled potential is already existing natural gas infrastructure.
Fractal analysis for heat extraction in geothermal system
Directory of Open Access Journals (Sweden)
Shang Xiaoji
2017-01-01
Full Text Available Heat conduction and convection play a key role in geothermal development. These two processes are coupled and influenced by fluid seepage in hot porous rock. A number of integer dimension thermal fluid models have been proposed to describe this coupling mechanism. However, fluid flow, heat conduction and convection in porous rock are usually non-linear, tortuous and fractal, thus the integer dimension thermal fluid flow models can not well describe these phenomena. In this study, a fractal thermal fluid coupling model is proposed to describe the heat conduction and flow behaviors in fractal hot porous rock in terms of local fractional time and space derivatives. This coupling equation is analytically solved through the fractal travelling wave transformation method. Analytical solutions of Darcy’s velocity, fluid temperature with fractal time and space are obtained. The solutions show that the introduction of fractional parameters is essential to describe the mechanism of heat conduction and convection.
Energy and exergy analysis of low temperature district heating network
International Nuclear Information System (INIS)
Li, Hongwei; Svendsen, Svend
2012-01-01
Low temperature district heating with reduced network supply and return temperature provides better match of the low quality building heating demand and the low quality heating supply from waste heat or renewable energy. In this paper, a hypothetical low temperature district heating network is designed to supply heating for 30 low energy detached residential houses. The network operational supply/return temperature is set as 55 °C/25 °C, which is in line with a pilot project carried out in Denmark. Two types of in-house substations are analyzed to supply the consumer domestic hot water demand. The space heating demand is supplied through floor heating in the bathroom and low temperature radiators in the rest of rooms. The network thermal and hydraulic conditions are simulated under steady state. A district heating network design and simulation code is developed to incorporate the network optimization procedure and the network simultaneous factor. Through the simulation, the overall system energy and exergy efficiencies are calculated and the exergy losses for the major district heating system components are identified. Based on the results, suggestions are given to further reduce the system energy/exergy losses and increase the quality match between the consumer heating demand and the district heating supply. -- Highlights: ► Exergy and energy analysis for low and medium temperature district heating systems. ► Different district heating network dimensioning methods are analyzed. ► Major exergy losses are identified in the district heating network and the in-house substations. ► Advantages to apply low temperature district heating are highlighted through exergy analysis. ► The influence of thermal by-pass on system exergy/energy performance is analyzed.
Volume conduction effects on wavelet cross-bicoherence analysis
International Nuclear Information System (INIS)
Memon, I.A.; Channa, C.
2013-01-01
Cross-bicoherence analysis is one of the important nonlinear signal processing tools which is used to measure quadratic phase coupling between frequencies of two different time series. It is frequently used in the diagnosis of various cognitive and neurological disorders in EEG (Electroencephalography) analysis. Volume conduction effects of various uncorrelated sources present in the brain can produce biased estimates into the estimated values of cross-bicoherence function. Previous studies have discussed volume conduction effects on coherence function which is used to measure linear relationship between EEG signals in terms of their phase and amplitude. However, volume conduction effect on cross-bicoherence analysis which is quite a different technique has not been investigated up to now to the best of our knowledge. This study is divided into two major parts, the first part deals with the investigation of VCUS (Volume Conduction effects due to Uncorrelated Sources) characteristics on EEG-cross-bicoherence analysis. The simulated EEG data due to uncorrelated sources present in the brain was used in this part of study. The next part of study is based upon investigating the effects of VCUS on the statistical analysis of results of EEG-based cross-bicoherence analysis. The study provides an important clinical application because most of studies based on EEG cross-bicoherence analysis have avoided the issue of VCUS. The cross-bicoherence analysis was performed by detecting the change in MSCB (Magnitude Square Cross-Bicoherence Function) between EEG activities of change detection and no-change detection trials. The real EEG signals were used. (author)
Energy Technology Data Exchange (ETDEWEB)
Yoo, Jae Hwan; Yoon, Jun Kyu [Gachon Univ., Seongnam (Korea, Republic of)
2013-04-15
In this study, the characteristics of the heat transfer coefficient and pressure drop were numerically analyzed according to the axis ratio (A R), pitch, location of vortex generator, and bump phase of the tube surface about an elliptical fin-tube heat exchanger. The boundary condition for CAD analysis was decided as a tube surface temperature of 348 K and inlet air velocity of 1.5 m/s. RCM 7th turbulent model was chosen as the numerical analysis for the sensitivity level. The analysis results indicated that the A R and transverse pitch decreased whereas the heat transfer coefficient increased. On the other hand, there was little difference in the longitudinal pitch. Furthermore, the heat transfer rate was more favorable when the vortex generator was located in front of the tube. Also, the bump phase of the tube surface indicated that the pressure drop and heat transfer were more favorable with the circle type than with the serrated type.
Three-Dimensional Heat Transfer Analysis of Metal Fasteners in Roofing Assemblies
Directory of Open Access Journals (Sweden)
Manan Singh
2016-11-01
Full Text Available Heat transfer analysis was performed on typical roofing assemblies using HEAT3, a three-dimensional heat transfer analysis software. The difference in heat transferred through the roofing assemblies considered is compared between two cases—without any steel fasteners and with steel fasteners. In the latter case, the metal roofing fasteners were arranged as per Factor Mutual Global (FMG approvals, in the field, perimeter, and corner zones of the roof. The temperature conditions used for the analysis represented summer and winter conditions for three separate Climate Zones (CZ namely Climate Zone 2 or CZ2 represented by Orlando, FL; CZ3 represented by Atlanta, GA; and CZ6 zone represented by St. Paul, MN. In all the climatic conditions, higher energy transfer was observed with increase in the number of metal fasteners attributed to high thermal conductivity of metals as compared to the insulation and other materials used in the roofing assembly. This difference in heat loss was also quantified in the form of percentage change in the overall or effective insulation of the roofing assembly for better understanding of the practical aspects. Besides, a comparison of 2D heat transfer analysis (using THERM software and 3D analysis using HEAT3 is also discussed proving the relevance of 3D over 2D heat transfer analysis.
Statistical analysis of thermal conductivity of nanofluid containing ...
Indian Academy of Sciences (India)
Thermal conductivity measurements of nanofluids were analysed via two-factor completely randomized design and comparison of data means is carried out with Duncan's multiple-range test. Statistical analysis of experimental data show that temperature and weight fraction have a reasonable impact on the thermal ...
International Nuclear Information System (INIS)
Snider, D.M.
1981-02-01
INVERT 1.0 is a digital computer program written in FORTRAN IV which calculates the surface heat flux of a one-dimensional solid using an interior-measured temperature and a physical description of the solid. By using two interior-measured temperatures, INVERT 1.0 can provide a solution for the heat flux at two surfaces, the heat flux at a boundary and the time dependent power, or the heat flux at a boundary and the time varying thermal conductivity of a material composing the solid. The analytical solution to inversion problem is described for the one-dimensional cylinder, sphere, or rectangular slab. The program structure, input instructions, and sample problems demonstrating the accuracy of the solution technique are included
Thin film heat flux sensors for accurate transient and unidirectional heat transfer analysis
International Nuclear Information System (INIS)
Azerou, B; Garnier, B; Lahmar, J
2012-01-01
Heat flux measurement is needed in many heat transfer studies. For the best unbiased heat flux sensors (HFS), the heat flux is obtained using temperature measurements at different locations and also an inverse heat conduction method (function specification...) in order to calculate the heat flux. Systematic errors can come from the uncertainty in the wire thermocouples locations and from errors in the knowledge of distances between two consecutive wire thermocouples. The main idea in this work is to use thin film thermoresistances deposited on a flexible thin polymer substrate instead of wire thermocouples welded on metallic sample. The interest of using thin film thermoresistances instead of wire thermocouples is a lower disturbance due to the smaller thickness of the thin film sensors (typically less than 1μm) and a much better knowledge of the distances between the different thin film thermoresistances which are precisely defined in the mask used for the metallic thin film pattern fabrication. In this paper, we present the fabrication of the new heat flux sensor with thin film thermoresistances, the study of the effect of the self heating (due to Joule effect in thermoresistances) and the performances of this new HFS with the comparison with classical HFS using wire thermocouples. For this study, a symmetric experimental setup is used with metallic samples equipped with an etched foil heater and both classical and new HFS. For several heating conditions, it appears that a better accuracy is always obtained with the new HFS using thin film thermoresistances.
Shokati, Naser; Mohammadkhani, Farzad; Farrokhi, Navid; Ranjbar, Faramarz
2014-12-01
During manufacture of engines, evaluation of engine performance is essential. This is accomplished in test cells. During the test, a significant portion of heat energy released by the fuel is wasted. In this study, in order to recover these heat losses, Organic Rankine Cycle (ORC) is recommended. The study has been conducted assuming the diesel oil to be composed of a single hydrocarbon such as C12H26. The composition of exhaust gases (products of combustion) have been computed (and not determined experimentally) from the stoichiometric equation representing the combustion reaction. The test cell heat losses are recovered in three separate heat exchangers (preheater, evaporator and superheater). These heat exchangers are separately designed, and the whole system is analyzed from energy and exergy viewpoints. Finally, a parametric study is performed to investigate the effect of different variables on the system performance characteristics such as the ORC net power, heat exchangers effectiveness, the first law efficiency, exergy destruction and heat transfer surfaces. The results of the study show that by utilizing ORC, heat recovery equivalent to 8.85 % of the engine power is possible. The evaporator has the highest exergy destruction rate, while the pump has the lowest among the system components. Heat transfer surfaces are calculated to be 173.6, 58.7, and 11.87 m2 for the preheater, evaporator and superheater, respectively.
Karlsen, Jonas; Bruus, Henrik
2015-11-01
We present a theoretical analysis (arxiv.org/abs/1507.01043) of the acoustic radiation force on a single small particle, either a thermoviscous fluid droplet or a thermoelastic solid particle, suspended in a viscous and heat-conducting fluid. Our analysis places no restrictions on the viscous and thermal boundary layer thicknesses relative to the particle radius, but it assumes the particle to be small in comparison to the acoustic wavelength. This is the limit relevant to scattering of ultrasound waves from sub-micrometer particles. For particle sizes smaller than the boundary layer widths, our theory leads to profound consequences for the acoustic radiation force. For example, for liquid droplets and solid particles suspended in gasses we predict forces orders of magnitude larger than expected from ideal-fluid theory. Moreover, for certain relevant choices of materials, we find a sign change in the acoustic radiation force on different-sized but otherwise identical particles. These findings lead to the concept of a particle-size-dependent acoustophoretic contrast factor, highly relevant to applications in acoustic levitation or separation of micro-particles in gases, as well as to handling of μm- and nm-sized particles such as bacteria and vira in lab-on-a-chip systems.
APOLLO 15 HEAT FLOW THERMAL CONDUCTIVITY RDR SUBSAMPLED V1.0
National Aeronautics and Space Administration — This data set comprises a reduced, subsampled set of the data returned from the Apollo 15 Heat Flow Experiment from 31 July 1971 through 31 December 1974. The...
APOLLO 17 HEAT FLOW THERMAL CONDUCTIVITY RDR SUBSAMPLED V1.0
National Aeronautics and Space Administration — This data set comprises a reduced, subsampled set of the data returned from the Apollo 17 Heat Flow Experiment from 12 December 1972 through 31 December 1974. The...
Low Cost Variable Conductance Heat Pipe for Balloon Payload, Phase I
National Aeronautics and Space Administration — While continuously increasing in complexity, the payloads of terrestrial high altitude balloons need a thermal management system to reject their waste heat and to...
The Green–Kubo formula for heat conduction in open systems
International Nuclear Information System (INIS)
Kundu, Anupam; Dhar, Abhishek; Narayan, Onuttom
2009-01-01
We obtain an exact Green–Kubo type linear response result for the heat current in an open system. The result is derived for classical Hamiltonian systems coupled to heat baths. Both lattice models and fluid systems are studied and several commonly used implementations of heat baths, stochastic as well as deterministic, are considered. The results are valid in arbitrary dimensions and for any system sizes. Our results are useful for obtaining the linear response transport properties of mesoscopic systems. Also we point out that for systems with anomalous heat transport, as is the case in low-dimensional systems, the use of the standard Green–Kubo formula is problematic and the open system formula should be used. (letter)
Kovtanyuk, Andrey E.
2012-01-01
Radiative-conductive heat transfer in a medium bounded by two reflecting and radiating plane surfaces is considered. This process is described by a nonlinear system of two differential equations: an equation of the radiative heat transfer and an equation of the conductive heat exchange. The problem is characterized by anisotropic scattering of the medium and by specularly and diffusely reflecting boundaries. For the computation of solutions of this problem, two approaches based on iterative techniques are considered. First, a recursive algorithm based on some modification of the Monte Carlo method is proposed. Second, the diffusion approximation of the radiative transfer equation is utilized. Numerical comparisons of the approaches proposed are given in the case of isotropic scattering. © 2011 Elsevier Ltd. All rights reserved.
DEFF Research Database (Denmark)
Ganio, Matthew S; Overgaard, Morten; Seifert, Thomas
2012-01-01
During moderate actual or simulated hemorrhage, as cardiac output decreases, reductions in systemic vascular conductance (SVC) maintain mean arterial pressure (MAP). Heat stress, however, compromises the control of MAP during simulated hemorrhage, and it remains unknown whether this response is due...... to a persistently high SVC and/or a low cardiac output. This study tested the hypothesis that an inadequate decrease in SVC is the primary contributing mechanism by which heat stress compromises blood pressure control during simulated hemorrhage. Simulated hemorrhage was imposed via lower body negative pressure...... normothermic is no longer adequate during a heat-stressed-simulated hemorrhage. The absence of a decrease in SVC at a time of profound reductions in MAP suggests that inadequate control of vascular conductance is a primary mechanism compromising blood pressure control during these conditions....
Heat transfer analysis of underground U-type heat exchanger of ground source heat pump system.
Pei, Guihong; Zhang, Liyin
2016-01-01
Ground source heat pumps is a building energy conservation technique. The underground buried pipe heat exchanging system of a ground source heat pump (GSHP) is the basis for the normal operation of an entire heat pump system. Computational-fluid-dynamics (CFD) numerical simulation software, ANSYS-FLUENT17.0 have been performed the calculations under the working conditions of a continuous and intermittent operation over 7 days on a GSHP with a single-well, single-U and double-U heat exchanger and the impact of single-U and double-U buried heat pipes on the surrounding rock-soil temperature field and the impact of intermittent operation and continuous operation on the outlet water temperature. The influence on the rock-soil temperature is approximately 13 % higher for the double-U heat exchanger than that of the single-U heat exchanger. The extracted energy of the intermittent operation is 36.44 kw·h higher than that of the continuous mode, although the running time is lower than that of continuous mode, over the course of 7 days. The thermal interference loss and quantity of heat exchanged for unit well depths at steady-state condition of 2.5 De, 3 De, 4 De, 4.5 De, 5 De, 5.5 De and 6 De of sidetube spacing are detailed in this work. The simulation results of seven working conditions are compared. It is recommended that the side-tube spacing of double-U underground pipes shall be greater than or equal to five times of outer diameter (borehole diameter: 180 mm).
International Nuclear Information System (INIS)
Vakulenko, M.O.
1992-01-01
Within the general renormalized statistical approach, the low-frequency short-wave stationary spectra of potential and magnetic perturbations in a finite-pressure plasma, are obtained. Anomalous heat conductivity considerably enhances due to non-linear interaction between magnetic excitations. 11 refs. (author)
Remarks on the global existence in the dynamics of a viscous, heat-conducting, one-dimensional gas
International Nuclear Information System (INIS)
Song Jiang
1994-01-01
We consider initial boundary value problems for the equations of the motion of a viscous, heat-conducting, one-dimensional gas which is confined to a fixed tube with impermeable ends and whose viscosity varies with density, and prove the global existence of smooth (large) solutions. (author). 17 refs
Design and analysis of heat recovery system in bioprocess plant
International Nuclear Information System (INIS)
Anastasovski, Aleksandar; Rašković, Predrag; Guzović, Zvonimir
2015-01-01
Highlights: • Heat integration of a bioprocess plant is studied. • Bioprocess plant produces yeast and ethyl-alcohol. • The design of a heat recovery system is performed by batch pinch analysis. • Direct and indirect heat integration approaches are used in process design. • The heat recovery system without a heat storage opportunity is more profitable. - Abstract: The paper deals with the heat integration of a bioprocess plant which produces yeast and ethyl-alcohol. The referent plant is considered to be a multiproduct batch plant which operates in a semi-continuous mode. The design of a heat recovery system is performed by batch pinch analysis and by the use of the Time slice model. The results obtained by direct and indirect heat integration approaches are presented in the form of cost-optimal heat exchanger networks and evaluated by different thermodynamic and economic indicators. They signify that the heat recovery system without a heat storage opportunity can be considered to be a more profitable solution for the energy efficiency increase in a plant
Power generation using sugar cane bagasse: A heat recovery analysis
Seguro, Jean Vittorio
The sugar industry is facing the need to improve its performance by increasing efficiency and developing profitable by-products. An important possibility is the production of electrical power for sale. Co-generation has been practiced in the sugar industry for a long time in a very inefficient way with the main purpose of getting rid of the bagasse. The goal of this research was to develop a software tool that could be used to improve the way that bagasse is used to generate power. Special focus was given to the heat recovery components of the co-generation plant (economizer, air pre-heater and bagasse dryer) to determine if one, or a combination, of them led to a more efficient co-generation cycle. An extensive review of the state of the art of power generation in the sugar industry was conducted and is summarized in this dissertation. Based on this models were developed. After testing the models and comparing the results with the data collected from the literature, a software application that integrated all these models was developed to simulate the complete co-generation plant. Seven different cycles, three different pressures, and sixty-eight distributions of the flue gas through the heat recovery components can be simulated. The software includes an economic analysis tool that can help the designer determine the economic feasibility of different options. Results from running the simulation are presented that demonstrate its effectiveness in evaluating and comparing the different heat recovery components and power generation cycles. These results indicate that the economizer is the most beneficial option for heat recovery and that the use of waste heat in a bagasse dryer is the least desirable option. Quantitative comparisons of several possible cycle options with the widely-used traditional back-pressure turbine cycle are given. These indicate that a double extraction condensing cycle is best for co-generation purposes. Power generation gains between 40 and
Electromagnetic heating processes: analysis and simulations
Calay, Rajnish Kaur
1994-01-01
Electromagnetic heating (EMH) processes are being increasingly used in the industrial and domestic sectors, yet they receive relatively little attention in the thermal engineering domain. Time-temperature characteristics in EMH are qualitatively different from those in conventional heating techniques due to the additional parameters (viz dielectric properties of the material, size and shape of the product and process frequency). From a unified theory perspective, a multi-...
Stability analysis for downflow in heated channels
International Nuclear Information System (INIS)
Sampaio, P.A.B. de.
1985-01-01
Stability and flow distribution are analysed for downflow in heated channels. It is shown that at low flow rates instabilities associated with the buoyancy forces may appear. A computer code in FORTRAN language to determine downflow distribution among n heated channels is presented. The model used to calculate downflow distribution and the onset of instability is compared with experiments performed in a test section with two parallel channels. (Author) [pt
International Nuclear Information System (INIS)
Zinkle, S.J.; Eatherly, W.S.
1997-01-01
The unirradiated tensile properties of CuCrZr produced by two different vendors have been measured following different heat treatments. Room temperature electrical resistivity measurements were also performed in order to estimate the thermal conductivity of these specimens. The thermomechanical conditions studied included solution quenched, solution quenched and aged (ITER reference heat treatment), simulated slow HIP thermal cycle (∼1 degrees C/min cooling from solutionizing temperature) and simulated fast HIP thermal cycle (∼100 degrees C/min cooling from solutionizing temperature). Specimens from the last two heat treatments were tested in both the solution-cooled condition and after subsequent precipitate aging at 475 degrees C for 2 h. Both of the simulated HIP thermal cycles caused a pronounced decreases in the strength and electrical conductivity of CuCrZr. The tensile and electrical properties were unchanged by subsequent aging in the slow HIP thermal cycles caused a pronounced decrease in the strength and electrical conductivity of CuCrZr. The tensile and electrical properties were unchanged by subsequent aging in the slow HIP thermal cycle specimens, whereas the strength and conductivity following aging in the fast HIP thermal cycle improved to ∼65% of the solution quenched and aged CuCrZr values. Limited tensile and electrical resistivity measurements were also made on two new heats of Hycon 3HP CuNiBe. High strength but poor uniform and total elongations were observed at 500 degrees C on one of these new heats of CuNiBe, similar to that observed in other heats
EXACT SOLUTION OF HEAT CONDUCTION IN A TWO-DOMAIN COMPOSITE CYLINDER WITH AN ORTHOTROPIC OUTER LAYER
International Nuclear Information System (INIS)
AVILES-RAMOS, C.; RUDY, C.
2000-01-01
The transient exact solution of heat conduction in a two-domain composite cylinder is developed using the separation of variables technique. The inner cylinder is isotropic and the outer cylindrical layer is orthotropic. Temperature solutions are obtained for boundary conditions of the first and second kinds at the outer surface of the orthotropic layer. These solutions are applied to heat flow calorimeters modeling assuming that there is heat generation due to nuclear reactions in the inner cylinder. Heat flow calorimeter simulations are carried out assuming that the inner cylinder is filled with plutonium oxide powder. The first objective in these simulations is to predict the onset of thermal equilibrium of the calorimeter with its environment. Two types of boundary conditions at the outer surface of the orthotropic layer are used to predict thermal equilibrium. The procedure developed to carry out these simulations can be used as a guideline for the design of calorimeters. Another important application of these solutions is on the estimation of thermophysical properties of orthotropic cylinders. The thermal conductivities in the vertical, radial and circumferential directions of the orthotropic outer layer can be estimated using this exact solution and experimental data. Simultaneous estimation of the volumetric heat capacity and thermal conductivities is also possible. Furthermore, this solution has potential applications to the solution of the inverse heat conduction problem in this cylindrical geometry. An interesting feature of the construction of this solution is that two different sets of eigenfunctions need to be considered in the eigenfunction expansion. These eigenfunctions sets depend on the relative values of the thermal diffusivity of the inner cylinder and the thermal diffusivity in the vertical direction of the outer cylindrical layer
Energy Technology Data Exchange (ETDEWEB)
Zinkle, S.J.; Eatherly, W.S. [Oak Ridge National Lab., TN (United States)
1997-08-01
The unirradiated tensile properties of CuCrZr produced by two different vendors have been measured following different heat treatments. Room temperature electrical resistivity measurements were also performed in order to estimate the thermal conductivity of these specimens. The thermomechanical conditions studied included solution quenched, solution quenched and aged (ITER reference heat treatment), simulated slow HIP thermal cycle ({approximately}1{degrees}C/min cooling from solutionizing temperature) and simulated fast HIP thermal cycle ({approximately}100{degrees}C/min cooling from solutionizing temperature). Specimens from the last two heat treatments were tested in both the solution-cooled condition and after subsequent precipitate aging at 475{degrees}C for 2 h. Both of the simulated HIP thermal cycles caused a pronounced decreases in the strength and electrical conductivity of CuCrZr. The tensile and electrical properties were unchanged by subsequent aging in the slow HIP thermal cycles caused a pronounced decrease in the strength and electrical conductivity of CuCrZr. The tensile and electrical properties were unchanged by subsequent aging in the slow HIP thermal cycle specimens, whereas the strength and conductivity following aging in the fast HIP thermal cycle improved to {approximately}65% of the solution quenched and aged CuCrZr values. Limited tensile and electrical resistivity measurements were also made on two new heats of Hycon 3HP CuNiBe. High strength but poor uniform and total elongations were observed at 500{degrees}C on one of these new heats of CuNiBe, similar to that observed in other heats.
Heat pump used in milk pasteurization: an energy analysis
Energy Technology Data Exchange (ETDEWEB)
Ozyurt, O.; Comakli, O.; Yilmaz, M. [Ataturk Univ., Erzurum (Turkey). Dept. of Mechanical Engineering; Karsli, S. [Ataturk Univ., Erzurum (Turkey). Vocational School of Higher Education
2004-07-01
This study investigates the applicability of heat pumps to milk pasteurization for cheese production and to compare the results with classical pasteurization systems. The experiments are conducted in a liquid-to-liquid vapour compression heat pump system and a milk-to-milk plate heat exchanger is used as an economizer. The experiments are also conducted in a double jacket boiler system and a plate pasteurization system, which are classical milk pasteurization systems. The results for the three systems are compared and the advantages/disadvantages of using heat pump for milk pasteurization instead of classical systems are determined. It is found that the heat pump consumes less energy than the other two classical systems. (Author)
The heat transfer analysis of the first stage blade
International Nuclear Information System (INIS)
Hong, Yong Ju; Choi, Bum Seog; Park, Byung Gyu; Yoon, Eui Soo
2001-01-01
To get higher efficiency of gas turbine, the designer should have more higher Turbine Inlet Temperature(TIT). Today, modern gas turbine having sophisticated cooling scheme has TIT above 1,700 .deg. C. In the Korea, many gas turbine having TIT above 1,300 .deg. C was imported and being operated, but the gas with high TIT above 1,300 .deg. C in the turbine will give damage to liner of combustor, and blade of turbine and etc. So frequently maintenance for parts enduring high temperature was performed. In this study, the heat transfer analysis of cooling air in the internal cooling channel (network analysis) and temperature analysis of the blade (Finite Element Analysis) in the first stage rotor was conducted for development of the optimal cooling passage design procedure. The results of network analysis and FEM analysis of blade show that the high temperature spot are occurred at the leading edge, trailing edge near tip, and platform. So to get more reliable performance of gas turbine, the more efficient cooling method should be applied at the leading edge and tip section and the thermal barrier coating on the blade surface has important role in cooling blade
Performance Analysis of a Hybrid District Heating System
DEFF Research Database (Denmark)
Mikulandric, Robert; Krajačić, Goran; Duic, Neven
2015-01-01
Hybridisation of district heating systems can contribute to more efficient heat generation through cogeneration power plants or through the share increase of renewable energy sources in total energy consumption while reducing negative aspects of particular energy source utilisation. In this work......, the performance of a hybrid district energy system for a small town in Croatia has been analysed. Mathematical model for process analysis and optimisation algorithm for optimal system configuration has been developed and described. The main goal of the system optimisation is to reduce heat production costs....... Several energy sources for heat production have been considered in 8 different simulation cases. Simulation results show that the heat production costs could be reduced with introduction of different energy systems into an existing district heating system. Renewable energy based district heating systems...
Teachers’ Attitudes towards Conducting Interlanguage Analysis to Prepare Better Instructions
Directory of Open Access Journals (Sweden)
Ruly Morganna
2017-10-01
Full Text Available This study focused on investigating attitudes had by English teachers in Indonesia towards preparing more qualified English instructions for further teaching processes through doing interlanguage analysis on the basis of students’ current competence of using English. The term competence in this study referred to students’ communicative competence. This study was conducted qualitatively to probe into the participants’ attitudes on doing interlanguage analysis, in that they were ten English teachers having been teaching English in Indonesian schools with varied experiences. They were selected purposively under considerations that they were experienced and taking graduate program, so that they were sufficiently familiar with this study issues, and it could be guaranteed that they managed to furnish the clarity of this study data. The data of this study were obtained through disseminating semi-structured questionnaire to the participants, and then pursuing the data was also undertaken to reach the clarity. The results indicated that despite some particular and situational constraints, all participants shared their positive attitude towards conducting interlanguage analysis on students’ English competence from the viewpoints of affection, behavior, and cognition. This study was essential since it could contribute on being one of references for English teachers to improve the quality of further instructions. This study was only delimited on the area of attitude. More researches were also expected to be conducted especially on the area of interlanguage analysis application to reveal more valuable and contributive knowledge in this issue.
Solving the inverse heat conduction problem using NVLink capable Power architecture
Directory of Open Access Journals (Sweden)
Sándor Szénási
2017-11-01
Full Text Available The accurate knowledge of Heat Transfer Coefficients is essential for the design of precise heat transfer operations. The determination of these values requires Inverse Heat Transfer Calculations, which are usually based on heuristic optimisation techniques, like Genetic Algorithms or Particle Swarm Optimisation. The main bottleneck of these heuristics is the high computational demand of the cost function calculation, which is usually based on heat transfer simulations producing the thermal history of the workpiece at given locations. This Direct Heat Transfer Calculation is a well parallelisable process, making it feasible to implement an efficient GPU kernel for this purpose. This paper presents a novel step forward: based on the special requirements of the heuristics solving the inverse problem (executing hundreds of simulations in a parallel fashion at the end of each iteration, it is possible to gain a higher level of parallelism using multiple graphics accelerators. The results show that this implementation (running on 4 GPUs is about 120 times faster than a traditional CPU implementation using 20 cores. The latest developments of the GPU-based High Power Computations area were also analysed, like the new NVLink connection between the host and the devices, which tries to solve the long time existing data transfer handicap of GPU programming.
Energy Technology Data Exchange (ETDEWEB)
Akcay, Cihan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Haut, Terry Scot [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Carlson, Neil N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-05-21
The EM module of the Truchas code currently lacks the capability to model the Joule (Ohmic) heating of highly conducting materials that are inserted into induction furnaces from time to time to change the heating profile. This effect is difficult to simulate directly because of the requirement to resolve the extremely thin skin depth of good conductors, which is computationally costly. For example, copper has a skin depth, δ ~ 1 mm, for an oscillation frequency of tens of kHz. The industry is interested in determining what fraction of the heating power is lost to the Joule heating of these good conductors inserted inside the furnaces. The approach presented in this document is one of asymptotics where the leading order (unperturbed) solution is taken as that which emerges from solving the EM problem for a perfectly conducting insert. The conductor is treated as a boundary of the domain. The perturbative correction enters as a series expansion in terms of the dimensionless skin depth δ/L, where L is the characteristic size of the EM system. The correction at each order depends on the previous. This means that the leading order correction only depends on the unperturbed solution, in other words, it does not require Truchas to perform an additional EM field solve. Thus, the Joule heating can be captured by a clever leveraging of the existing tools in Truchas with only slight modifications.
Nagihara, S.; Zacny, K.; Hedlund, M.; Taylor, P. T.
2012-01-01
Geothermal heat flow is obtained as a product of the geothermal gradient and the thermal conductivity of the vertical soil/rock/regolith interval penetrated by the instrument. Heat flow measurements are a high priority for the geophysical network missions to the Moon recommended by the latest Decadal Survey and previously the International Lunar Network. One of the difficulties associated with lunar heat flow measurement on a robotic mission is that it requires excavation of a relatively deep (approx 3 m) hole in order to avoid the long-term temporal changes in lunar surface thermal environment affecting the subsurface temperature measurements. Such changes may be due to the 18.6-year-cylcle lunar precession, or may be initiated by presence of the lander itself. Therefore, a key science requirement for heat flow instruments for future lunar missions is to penetrate 3 m into the regolith and to measure both thermal gradient and thermal conductivity. Engineering requirements are that the instrument itself has minimal impact on the subsurface thermal regime and that it must be a low-mass and low-power system like any other science instrumentation on planetary landers. It would be very difficult to meet the engineering requirements, if the instrument utilizes a long (> 3 m) probe driven into the ground by a rotary or percussive drill. Here we report progress in our efforts to develop a new, compact lunar heat flow instrumentation that meets all of these science and engineering requirements.
International Nuclear Information System (INIS)
Ezzat, M.A.; El-Bary, A.A.
2016-01-01
In this study, the constitutive relation for the heat flux vector is derived to be the Fourier's law of heat conduction with a variable thermal conductivity and time-fractional order. The Stokes' flow of unsteady incompressible thermoelectric fluid due to a moving plate in the presence of a transverse magnetic field is molded. Stokes' first problem is solved by applying Laplace transform with respect to time variable and evaluating the inverse transform integrals by using a numerical approach. Numerical results for the temperature and the velocity distributions are given and illustrated graphically for given problem. The results indicate that the thermal conductivity and time-fractional order play a major role in the temperature and velocity distributions. (authors)
International Nuclear Information System (INIS)
Pompe, G.; Gaafar, M.; Buettner, P.; Francke, T.
1983-01-01
The thermal conductivity of amorphous metallic alloys (Fe, Ni, Co)/sub 1-x/ (B, P, Si)/sub x/ is measured in the temperature range 2 to 100 K in the as-produced and heat-treated states. By taking into account the results of Matey and Anderson the influence of the nature of the metalloid and the number of metallic components can be discussed. The change of the thermal conductivity due to a structural relaxation caused by a heat treatment is very different. In the whole range of temperature a rise of the phonon thermal conductivity of the Fe-Co-B alloy is obtained, whereas no change is observed for the Fe-B alloy. At low temperature ( 80 B 20 is investigated. (author)
Analysis of slug tests in formations of high hydraulic conductivity.
Butler, James J; Garnett, Elizabeth J; Healey, John M
2003-01-01
A new procedure is presented for the analysis of slug tests performed in partially penetrating wells in formations of high hydraulic conductivity. This approach is a simple, spreadsheet-based implementation of existing models that can be used for analysis of tests from confined or unconfined aquifers. Field examples of tests exhibiting oscillatory and nonoscillatory behavior are used to illustrate the procedure and to compare results with estimates obtained using alternative approaches. The procedure is considerably simpler than recently proposed methods for this hydrogeologic setting. Although the simplifications required by the approach can introduce error into hydraulic-conductivity estimates, this additional error becomes negligible when appropriate measures are taken in the field. These measures are summarized in a set of practical field guidelines for slug tests in highly permeable aquifers.
Nath, G.; Vishwakarma, J. P.
2016-11-01
Similarity solutions are obtained for the flow behind a spherical shock wave in a non-ideal gas under gravitational field with conductive and radiative heat fluxes, in the presence of a spatially decreasing azimuthal magnetic field. The shock wave is driven by a piston moving with time according to power law. The radiation is considered to be of the diffusion type for an optically thick grey gas model and the heat conduction is expressed in terms of Fourier's law for heat conduction. Similarity solutions exist only when the surrounding medium is of constant density. The gas is assumed to have infinite electrical conductivity and to obey a simplified van der Waals equation of state. It is shown that an increase of the gravitational parameter or the Alfven-Mach number or the parameter of the non-idealness of the gas decreases the compressibility of the gas in the flow-field behind the shock, and hence there is a decrease in the shock strength. The pressure and density vanish at the inner surface (piston) and hence a vacuum is formed at the center of symmetry. The shock waves in conducting non-ideal gas under gravitational field with conductive and radiative heat fluxes can be important for description of shocks in supernova explosions, in the study of a flare produced shock in the solar wind, central part of star burst galaxies, nuclear explosion etc. The solutions obtained can be used to interpret measurements carried out by space craft in the solar wind and in neighborhood of the Earth's magnetosphere.
Conjugate heat transfer analysis for in-vessel retention with external reactor vessel cooling
International Nuclear Information System (INIS)
Park, Jong-Woon; Bae, Jae-ho; Song, Hyuk-Jin
2016-01-01
Highlights: • A conjugate heat transfer analysis method is applied for in-vessel corium retention. • 3D heat diffusion has a formidable effect in alleviating focusing heat load from metallic layer. • The focusing heat load is decreased by about 2.5 times on the external surface. - Abstract: A conjugate heat transfer analysis method for the thermal integrity of a reactor vessel under external reactor vessel cooling conditions is developed to resolve light metal layer focusing effect issue for in-vessel retention. The method calculates steady-state three-dimensional temperature distribution of a reactor vessel using coupled conjugate heat transfer between in-vessel three-layered stratified corium (metallic pool, oxide pool and heavy metal and polar-angle dependent boiling heat transfer at the outer surface of a reactor vessel). The three-layer corium heat transfer model is utilizing lumped-parameter thermal-resistance circuit method. For the ex-vessel boiling boundary conditions, nucleate, transition and film boiling are considered. The thermal integrity of a reactor vessel is addressed in terms of heat flux at the outer-most nodes of the vessel and remaining thickness profile. The vessel three-dimensional heat conduction is validated against a commercial code. It is found that even though the internal heat flux from the metal layer goes far beyond critical heat flux (CHF) the heat flux from the outermost nodes of the vessel may be maintained below CHF due to massive vessel heat diffusion. The heat diffusion throughout the vessel is more pronounced for relatively low heat generation rate in an oxide pool. Parametric calculations are performed considering thermal conditions such as peak heat flux from a light metal layer, heat generation in an oxide pool and external boiling conditions. The major finding is that the most crucial factor for success of in-vessel retention is not the mass of the molten light metal above the oxide pool but the heat generation rate
Anomalous heat transfer modes of nanofluids: a review based on statistical analysis
2011-01-01
This paper contains the results of a concise statistical review analysis of a large amount of publications regarding the anomalous heat transfer modes of nanofluids. The application of nanofluids as coolants is a novel practise with no established physical foundations explaining the observed anomalous heat transfer. As a consequence, traditional methods of performing a literature review may not be adequate in presenting objectively the results representing the bulk of the available literature. The current literature review analysis aims to resolve the problems faced by researchers in the past by employing an unbiased statistical analysis to present and reveal the current trends and general belief of the scientific community regarding the anomalous heat transfer modes of nanofluids. The thermal performance analysis indicated that statistically there exists a variable enhancement for conduction, convection/mixed heat transfer, pool boiling heat transfer and critical heat flux modes. The most popular proposed mechanisms in the literature to explain heat transfer in nanofluids are revealed, as well as possible trends between nanofluid properties and thermal performance. The review also suggests future experimentation to provide more conclusive answers to the control mechanisms and influential parameters of heat transfer in nanofluids. PMID:21711932
Anomalous heat transfer modes of nanofluids: a review based on statistical analysis
Sergis, Antonis; Hardalupas, Yannis
2011-05-01
This paper contains the results of a concise statistical review analysis of a large amount of publications regarding the anomalous heat transfer modes of nanofluids. The application of nanofluids as coolants is a novel practise with no established physical foundations explaining the observed anomalous heat transfer. As a consequence, traditional methods of performing a literature review may not be adequate in presenting objectively the results representing the bulk of the available literature. The current literature review analysis aims to resolve the problems faced by researchers in the past by employing an unbiased statistical analysis to present and reveal the current trends and general belief of the scientific community regarding the anomalous heat transfer modes of nanofluids. The thermal performance analysis indicated that statistically there exists a variable enhancement for conduction, convection/mixed heat transfer, pool boiling heat transfer and critical heat flux modes. The most popular proposed mechanisms in the literature to explain heat transfer in nanofluids are revealed, as well as possible trends between nanofluid properties and thermal performance. The review also suggests future experimentation to provide more conclusive answers to the control mechanisms and influential parameters of heat transfer in nanofluids.
Anomalous heat transfer modes of nanofluids: a review based on statistical analysis
Directory of Open Access Journals (Sweden)
Sergis Antonis
2011-01-01
Full Text Available Abstract This paper contains the results of a concise statistical review analysis of a large amount of publications regarding the anomalous heat transfer modes of nanofluids. The application of nanofluids as coolants is a novel practise with no established physical foundations explaining the observed anomalous heat transfer. As a consequence, traditional methods of performing a literature review may not be adequate in presenting objectively the results representing the bulk of the available literature. The current literature review analysis aims to resolve the problems faced by researchers in the past by employing an unbiased statistical analysis to present and reveal the current trends and general belief of the scientific community regarding the anomalous heat transfer modes of nanofluids. The thermal performance analysis indicated that statistically there exists a variable enhancement for conduction, convection/mixed heat transfer, pool boiling heat transfer and critical heat flux modes. The most popular proposed mechanisms in the literature to explain heat transfer in nanofluids are revealed, as well as possible trends between nanofluid properties and thermal performance. The review also suggests future experimentation to provide more conclusive answers to the control mechanisms and influential parameters of heat transfer in nanofluids.
Heat transfer analysis of parabolic trough solar receiver
International Nuclear Information System (INIS)
Padilla, Ricardo Vasquez; Demirkaya, Gokmen; Goswami, D. Yogi; Stefanakos, Elias; Rahman, Muhammad M.
2011-01-01
Highlights: → In this paper a detailed one dimensional numerical heat transfer analysis of a PTC is performed. → The receiver and envelope were divided into several segments and mass and energy balance were applied in each segment. → Improvements either in the heat transfer correlations or radiative heat transfer analysis are presented. → The proposed heat transfer model was validated with experimental data obtained from Sandia National Laboratory. → Our results showed a better agreement with experimental data compared to other models. -- Abstract: Solar Parabolic Trough Collectors (PTCs) are currently used for the production of electricity and applications with relatively higher temperatures. A heat transfer fluid circulates through a metal tube (receiver) with an external selective surface that absorbs solar radiation reflected from the mirror surfaces of the PTC. In order to reduce the heat losses, the receiver is covered by an envelope and the enclosure is usually kept under vacuum pressure. The heat transfer and optical analysis of the PTC is essential to optimize and understand its performance under different operating conditions. In this paper a detailed one dimensional numerical heat transfer analysis of a PTC is performed. The receiver and envelope were divided into several segments and mass and energy balance were applied in each segment. Improvements either in the heat transfer correlations or radiative heat transfer analysis are presented as well. The partial differential equations were discretized and the nonlinear algebraic equations were solved simultaneously. Finally, to validate the numerical results, the model was compared with experimental data obtained from Sandia National Laboratory (SNL) and other one dimensional heat transfer models. Our results showed a better agreement with experimental data compared to other models.
Meso-scale modelling of the heat conductivity effect on the shock response of a porous material
Resnyansky, A. D.
2017-06-01
Understanding of deformation mechanisms of porous materials under shock compression is important for tailoring material properties at the shock manufacturing of advanced materials from substrate powders and for studying the response of porous materials under shock loading. Numerical set-up of the present work considers a set of solid particles separated by air representing a volume of porous material. Condensed material in the meso-scale set-up is simulated with a viscoelastic rate sensitive material model with heat conduction formulated from the principles of irreversible thermodynamics. The model is implemented in the CTH shock physics code. The meso-scale CTH simulation of the shock loading of the representative volume reveals the mechanism of pore collapse and shows in detail the transition from a high porosity case typical for abnormal Hugoniot response to a moderate porosity case typical for conventional Hugoniot response. Results of the analysis agree with previous analytical considerations and support hypotheses used in the two-phase approach.
THERMALLY CONDUCTIVE CEMENTITIOUS GROUTS FOR GEOTHERMAL HEAT PUMPS. PROGRESS REPORT BY 1998
Energy Technology Data Exchange (ETDEWEB)
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.
Directory of Open Access Journals (Sweden)
Marcelo Ribeiro dos Santos
2014-01-01
Full Text Available During machining energy is transformed into heat due to plastic deformation of the workpiece surface and friction between tool and workpiece. High temperatures are generated in the region of the cutting edge, which have a very important influence on wear rate of the cutting tool and on tool life. This work proposes the estimation of heat flux at the chip-tool interface using inverse techniques. Factors which influence the temperature distribution at the AISI M32C high speed steel tool rake face during machining of a ABNT 12L14 steel workpiece were also investigated. The temperature distribution was predicted using finite volume elements. A transient 3D numerical code using irregular and nonstaggered mesh was developed to solve the nonlinear heat diffusion equation. To validate the software, experimental tests were made. The inverse problem was solved using the function specification method. Heat fluxes at the tool-workpiece interface were estimated using inverse problems techniques and experimental temperatures. Tests were performed to study the effect of cutting parameters on cutting edge temperature. The results were compared with those of the tool-work thermocouple technique and a fair agreement was obtained.
International Nuclear Information System (INIS)
Hossain, Md. Anwar; Rees, D.A.S.
2002-05-01
The effect of surface tension on unsteady laminar natural convection flow of a viscous incompressible fluid in a rectangle enclosure with internal heat generation and in presence of a uniform transverse magnetic field acting in the direction normal to the gravity has been investigated. The top horizontal surface of the rectangular cavity is assumed to be free and the bottom ones insulated; whereas the left vertical wall is cold and the right one is uniformly hot. The equations are non-dimensionalized and solved numerically by an upwind finite difference method together with a successive over-relaxation (SOR) technique. The effects of heat generation together with the combined effects of the magnetic field and the surface tension are presented graphically in terms of isotherms, streamlines and velocity vector plots. The effects of varying the physical parameters on the rate of heat transfer from the heated surface of the enclosure are also depicted. The fluid here has Prandtl number Pr=0.054 while the value of the Grashof number is 2x10 4 . (author)
Exergy Analysis of a Ground-Coupled Heat Pump Heating System with Different Terminals
Directory of Open Access Journals (Sweden)
Xiao Chen
2015-04-01
Full Text Available In order to evaluate and improve the performance of a ground-coupled heat pump (GCHP heating system with radiant floors as terminals, an exergy analysis based on test results is performed in this study. The system is divided into four subsystems, and the exergy loss and exergy efficiency of each subsystem are calculated using the expressions derived based on exergy balance equations. The average values of the measured parameters are used for the exergy analysis. The analysis results show that the two largest exergy losses occur in the heat pump and terminals, with losses of 55.3% and 22.06%, respectively, and the lowest exergy efficiency occurs in the ground heat exchange system. Therefore, GCHP system designers should pay close attention to the selection of heat pumps and terminals, especially in the design of ground heat exchange systems. Compared with the scenario system in which fan coil units (FCUs are substituted for the radiant floors, the adoption of radiant floors can result in a decrease of 12% in heating load, an increase of 3.24% in exergy efficiency of terminals and an increase of 1.18% in total exergy efficiency of the system. The results may point out the direction and ways of optimizing GCHP systems.
A new analytical model for conduction heating during the SAGD circulation phase
Energy Technology Data Exchange (ETDEWEB)
Duong, A.N. [Society of Petroleum Engineers, Canadian Section, Calgary, AB (Canada)]|[ConocoPhillips Canada Resources Corp., Calgary, AB (Canada); Tomberlin, T.A. [ConocoPhillips Canada Resources Corp., Calgary, AB (Canada); Cyrot, M. [Total E and P Canada Ltd., Calgary, AB (Canada)
2008-10-15
The steam assisted gravity drainage (SAGD) process has become the common procedure to recover bitumen from Alberta's oilsands. Inter-well communication must be initiated during the start-up phase of a SAGD process. The shape of an initial steam chamber that develops during the circulation phase influences the efficiency of bitumen recovery. As such, the heating conformance distributed along the horizontal wellbores must be well understood. The duration of the start-up phase varies with the characteristics of the oilsand formation and the distance between the wellbores, but it is typically a month to several months. This paper presented a newly developed analytical model that predicts the initial steam chamber. The model improves bitumen recovery efficiency by predicting the mid-point temperature front and heating efficiency of a wellpair during the SAGD circulation phase. The Excel-based model uses the exponential integral solution for radial heating in a long cylinder and superposition in space for multi-heating sources. It can predict the temperature profile if the steam temperatures or pressures are known during the circulation period. Wellbore modeling that includes any variation in distances between the wellbores is critical to both circulation time and heating conformance. This model has an advantage over numerical simulation in terms of reducing computational time and accurately modelling any variation in distance between wellbores. The results can be optimized under various operational conditions, wellbore profiles, tubing sizes and convection flow effects. This easy to use model is currently being used by ConocoPhillips Canada to optimize, predict and guide oilsands projects during the start-up phase of a SAGD process. 5 refs., 13 figs.
GIS Based Analysis of future district heating potential in Denmark
DEFF Research Database (Denmark)
Nielsen, Steffen; Möller, Bernd
2012-01-01
and their heat demand has in recent years been assessed in a heat atlas including all buildings in Denmark. The focus in this article is to further develop a method for assessing the costs associated with supplying these buildings with DH. The analysis takes departure in the existing DH areas in Denmark...
Model-based analysis and simulation of regenerative heat wheel
DEFF Research Database (Denmark)
Wu, Zhuang; Melnik, Roderick V. N.; Borup, F.
2006-01-01
The rotary regenerator (also called the heat wheel) is an important component of energy intensive sectors, which is used in many heat recovery systems. In this paper, a model-based analysis of a rotary regenerator is carried out with a major emphasis given to the development and implementation of...