Heat transfer and thermodynamic performance of convective–radiative cooling double layer walls with temperature-dependent thermal conductivity and internal heat generation

International Nuclear Information System (INIS)

Torabi, Mohsen; Zhang, Kaili

2015-01-01

Highlights: • First and second laws of thermodynamics have been investigated in a composite wall. • Convective–radiative heat transfer is assumed on both surfaces. • Optimum interface location is calculated to minimize the total entropy generation rate. • Thermal conductivities ratio has great effects on the temperature and entropy generation. - Abstract: Composite geometries have numerous applications in industry and scientific researches. This work investigates the temperature distribution, and local and total entropy generation rates within two-layer composite walls using conjugate convection and radiation boundary conditions. Thermal conductivities of the materials of walls are assumed temperature-dependent. Temperature-dependent internal heat generations are also incorporated into the modeling. The differential transformation method (DTM) is used as an analytical technique to tackle the highly nonlinear system of ordinary differential equations. Thereafter, the local and total entropy generation rates are calculated using the DTM formulated temperature distribution. An exact analytical solution, for the temperature-independent model without radiation effect, is also derived. The correctness and accuracy of the DTM solution are checked against the exact solution. After verification, effects of thermophysical parameters such as location of the interface, convection–conduction parameters, radiation–conduction parameters, and internal heat generations, on the temperature distribution, and both local and total entropy generation rates are examined. To deliver the minimum total entropy generation rate, optimum values for some parameters are also found. Since composite walls are widely used in many fields, the abovementioned investigation is a beneficial tool for many engineering industries and scientific fields to minimize the entropy generation, which is the exergy destruction, of the system

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

Science.gov (United States)

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.

Modeling of the coupled radiative and conductive heat transfer within fibrous media at high temperature

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

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

Application of the lattice Boltzmann method to transient conduction and radiation heat transfer in cylindrical media

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.

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

Science.gov (United States)

Nath, Gorakh

2016-07-01

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

Heat-flow patterns in Tian-Calvet microcalorimeters: Conductive, convective, and radiative transport in gas dosing experiments

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

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.

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)

An Iterative Method for Solving of Coupled Equations for Conductive-Radiative Heat Transfer in Dielectric Layers

Directory of Open Access Journals (Sweden)

Vasyl Chekurin

2017-01-01

Full Text Available The mathematical model for describing combined conductive-radiative heat transfer in a dielectric layer, which emits, absorbs, and scatters IR radiation both in its volume and on the boundary, has been considered. A nonlinear stationary boundary-value problem for coupled heat and radiation transfer equations for the layer, which exchanges by energy with external medium by convection and radiation, has been formulated. In the case of optically thick layer, when its thickness is much more of photon-free path, the problem becomes a singularly perturbed one. In the inverse case of optically thin layer, the problem is regularly perturbed, and it becomes a regular (unperturbed one, when the layer’s thickness is of order of several photon-free paths. An iterative method for solving of the unperturbed problem has been developed and its convergence has been tested numerically. With the use of the method, the temperature field and radiation fluxes have been studied. The model and method can be used for development of noncontact methods for temperature testing in dielectrics and for nondestructive determination of its radiation properties on the base of the data obtained by remote measuring of IR radiation emitted by the layer.

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)

COXPRO-II: a computer program for calculating radiation and conduction heat transfer in irradiated fuel assemblies

International Nuclear Information System (INIS)

Rhodes, C.A.

1984-12-01

This report describes the computer program COXPRO-II, which was written for performing thermal analyses of irradiated fuel assemblies in a gaseous environment with no forced cooling. The heat transfer modes within the fuel pin bundle are radiation exchange among fuel pin surfaces and conduction by the stagnant gas. The array of parallel cylindrical fuel pins may be enclosed by a metal wrapper or shroud. Heat is dissipated from the outer surface of the fuel pin assembly by radiation and convection. Both equilateral triangle and square fuel pin arrays can be analyzed. Steady-state and unsteady-state conditions are included. Temperatures predicted by the COXPRO-II code have been validated by comparing them with experimental measurements. Temperature predictions compare favorably to temperature measurements in pressurized water reactor (PWR) and liquid-metal fast breeder reactor (LMFBR) simulated, electrically heated fuel assemblies. Also, temperature comparisons are made on an actual irradiated Fast-Flux Test Facility (FFTF) LMFBR fuel assembly

Combined natural convection and surface radiation in the annular region between a volumetrically heated inner tube and a finite conducting outer tube

International Nuclear Information System (INIS)

Gianoulakis, S.; Klein, D.E.

1993-01-01

Buoyancy-driven natural-convection heat transfer in enclosures has been the subject of considerable research with applications to electronic packaging, solar collectors, and shipping containers for spent nuclear fuel. A numerical study has been carried out to predict combined natural-convection and radiation heat transfer in the annular region between concentric tubes. The inner tube was volumetrically heated. Both tubes were of finite conductance. The surfaces of the annular region were diffuse and gray. The gas in the annulus was assumed to be nonparticipating. A newly developed hybrid finite element finite difference method was used for the study. This method combines finite element discretization of geometries with finite difference discretized solution procedures for the governing differential equations. This study examined the effects of surface radiative properties and material conductivities on the temperature and velocity fields and on local heat transfer rates. Fluid Raleigh numbers ranging from 10 3 to 10 7 , ratios of solid to fluid region thermal conductivities ranging from 10 to 10 4 , and surface total hemispherical emissivities ranging from 0.0 to 1.0 were examined in this study. It was found that the heat transfer across the annulus was dominated by conduction and radiation for the lower Raleigh number flows. As the fluid Raleigh number increased, convection became a primary mode of heat transfer. As the surface emissivity was increased in the annulus, the average Nusselt number on the inner tube surface decreased

Near-field radiative heat transfer in mesoporous alumina

International Nuclear Information System (INIS)

Li Jing; Feng Yan-Hui; Zhang Xin-Xin; Huang Cong-Liang; Wang Ge

2015-01-01

The thermal conductivity of mesoporous material has aroused the great interest of scholars due to its wide applications such as insulation, catalyst, etc. Mesoporous alumina substrate consists of uniformly distributed, unconnected cylindrical pores. Near-field radiative heat transfer cannot be ignored, when the diameters of the pores are less than the characteristic wavelength of thermal radiation. In this paper, near-field radiation across a cylindrical pore is simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material are further analyzed. The research results show that the radiative heat transfer on a mesoscale is 2∼4 orders higher than on a macroscale. The heat flux and equivalent thermal conductivity of radiation across a cylindrical pore decrease exponentially with pore diameter increasing, while increase with temperature increasing. The calculated equivalent thermal conductivity of radiation is further developed to modify the thermal conductivity of the mesoporous alumina. The combined thermal conductivity of the mesoporous alumina is obtained by using porosity weighted dilute medium and compared with the measurement. The combined thermal conductivity of mesoporous silica decreases gradually with pore diameter increasing, while increases smoothly with temperature increasing, which is in good agreement with the experimental data. The larger the porosity, the more significant the near-field effect is, which cannot be ignored. (paper)

Performance and optimum design of convective-radiative rectangular fin with convective base heating, wall conduction resistance, and contact resistance between the wall and the fin base

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.

Near-field radiative heat transfer between clusters of dielectric nanoparticles

International Nuclear Information System (INIS)

Dong, J.; Zhao, J.M.; Liu, L.H.

2017-01-01

In this work, we explore the near-field radiative heat transfer between two clusters of silicon carbide (SiC) nanoparticles using the many-body radiative heat transfer theory. The effects of fractal dimension of clusters, many-body interaction between nanoparticles and relative orientation of clusters on the thermal conductance are studied. Meanwhile, the applicability of the equivalent volume spheres (EVS) approximation for near-field radiative heat transfer between clusters is examined. It is observed that the thermal conductance is larger for clusters with larger fractal dimension, which is more significant in the near-field. The thermal conductance of EVS resembles that of the clusters, but EVS overestimates the conductance of clusters, especially in the near-field. Compared to the case of two nanoparticles, the conductance of nanoparticle clusters decays much slower with increasing distance in the near-field, but shares similar dependence on the distance in the far-field. The thermal conductance of SiC nanoparticle clusters is inhibited by the many-body interaction when surface phonon polariton is supported but enhanced at frequencies close to the resonance frequency. The total thermal conductance is decreased due to many-body interaction among particles in the cluster. The relative orientation between the clusters is also an important factor in the near-field, especially for clusters with lower fractal dimension. - Highlights: • Near-field radiative heat transfer between clusters of nanoparticles is studied. • The many-body radiative heat transfer theory is applied for rigorous analysis. • The accuracy of equivalent volume spheres approximation is examined. • Clusters with larger fractal dimension have larger radiative thermal conductance. • Many-body interaction inhibits the total radiative thermal conductance.

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

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....

Analysis of combined conduction and radiation heat transfer in presence of participating medium by the development of hybrid method

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

Heat conduction

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

Heat transfer in Rockwool modelling and method of measurement. Modelling radiative heat transfer in fibrous materials

Energy Technology Data Exchange (ETDEWEB)

Dyrboel, Susanne

1998-05-01

Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For lager thickness dimensions the resulting heat transfer through the

Combined natural convection and radiation in a volumetrically heated fluid layer

International Nuclear Information System (INIS)

Chawla, T.C.; Chan, S.H.; Cheung, F.B.; Cho, D.H.

1980-01-01

The effect of radiation in combination with turbulent natural convection on the rates of heat transfer in volumetrically heated fluid layers characterized by high temperatures has been considered in this study. It is demonstrated that even at high Rayleigh numbers the radiation mode is as effective as the turbulent natural convection mode in removing the heat from the upper surface of the molten pools with adiabatic lower boundary. As a result of this improved heat transfer, it is shown that considerably thicker molten pools with internal heat generation can be supported without boiling inception. The total Nusselt number at a moderate but fixed value of conduction-radiation parameter, can be represented as a function of Rayleigh number in a simple power-law form. As a consequence of this relationship it is shown that maximum nonboiling pool thicknesses vary approximately inversely as the 0.9% power of internal heat generation rate. A comparison between exact analysis using the integral formulation of radiation flux and Rosseland approximation shows that the latter approximation bears out very adequately for optically thick pools with conduction-radiation parameters greater than or equal to 0.4 inspite of the fact that individual components of Nusselt number due to radiation and convection, respectively, are grossly in error. These errors in component heat fluxes are compensating due to the total heat balance constraint. However, the comparison between Rosseland approximation and exact formulation gets poorer as the value of conduction-radiation parameters decreases. This increase in error is principally incurred due to the error in estimating wall temperature differences

Combined natural convection and radiation in a volumetrically heated fluid layer

International Nuclear Information System (INIS)

Chawla, T.C.; Chan, S.H.; Cheung, F.B.; Cho, D.H.

1980-01-01

The effect of radiation in combining with turbulent natural convection on the rates of heat transfer in volumetrically heated fluid layers characterized by high temperatures has been considered in this study. It is demonstrated that even at high Rayleigh numbers the radiation mode is as effective as the turbulent natural convection mode in removing the heat from the upper surface of molten pools with adiabatic lower boundary. As a result of this improved heat transfer, it is shown that considerably thicker molten pools with internal heat generation can be supported without boiling inception. The total Nusselt number at a moderate but fixed value of conduction-radiation parameter, can be represented as a function of Rayleigh number in a simple power-law form. As a consequence of this relationship it is shown that maximum nonboiling pool thicknesses vary approximately inversely as the 0.9 power of internal heat generation rate. A comparison between exact analysis using the integral formulation of radiation flux and Rosseland approximateion shows that the latter approximation bears out very adequately for optically thick pools with conduction-radiation parameter > or approx. =0.4 inspite of the fact that individual components of Nusselt number due to radiation and convection, respectively, are grossly in error. These errors in component heat fluxes are compensating due to the total heat balance constraint. However, the comparison between Rosseland approximation and exact formulation gets poorer as the value of conduction-radiation parameter decreases. This increase in error is principally incurred due to the error in estimating wall temperature differences

Controlling thermal chaos in the mantle by positive feedback from radiative thermal conductivity

Directory of Open Access Journals (Sweden)

F. Dubuffet

2002-01-01

Full Text Available The thermal conductivity of mantle materials has two components, the lattice component klat from phonons and the radiative component krad due to photons. These two contributions of variable thermal conductivity have a nonlinear dependence in the temperature, thus endowing the temperature equation in mantle convection with a strongly nonlinear character. The temperature derivatives of these two mechanisms have different signs, with ∂klat /∂T negative and dkrad /dT positive. This offers the possibility for the radiative conductivity to control the chaotic boundary layer instabilities developed in the deep mantle. We have parameterized the weight factor between krad and klat with a dimensionless parameter f , where f = 1 corresponds to the reference conductivity model. We have carried out two-dimensional, time-dependent calculations for variable thermal conductivity but constant viscosity in an aspect-ratio 6 box for surface Rayleigh numbers between 106 and 5 × 106. The averaged Péclet numbers of these flows lie between 200 and 2000. Along the boundary in f separating the chaotic and steady-state solutions, the number decreases and the Nusselt number increases with internal heating, illustrating the feedback between internal heating and radiative thermal conductivity. For purely basal heating situation, the time-dependent chaotic flows become stabilized for values of f of between 1.5 and 2. The bottom thermal boundary layer thickens and the surface heat flow increases with larger amounts of radiative conductivity. For magnitudes of internal heating characteristic of a chondritic mantle, much larger values of f , exceeding 10, are required to quench the bottom boundary layer instabilities. By isolating the individual conductive mechanisms, we have ascertained that the lattice conductivity is partly responsible for inducing boundary layer instabilities, while the radiative conductivity and purely depth-dependent conductivity exert a stabilizing

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.)

Transient Heat Conduction

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...

The effect of radiation induced electrical conductivity (RIC) on the thermal conductivity

International Nuclear Information System (INIS)

White, D.P.

1993-01-01

Microwave heating of plasmas in fusion reactors requires the development of microwave windows through which the microwaves can pass without great losses. The degradation of the thermal conductivity of alumina in a radiation environment is an important consideration in reliability studies of these microwave windows. Several recent papers have addressed this question at higher temperatures and at low temperatures. The current paper extends the low temperature calculations to determine the effect of phonon-electron scattering on the thermal conductivity at 77 K due to RIC. These low temperature calculations are of interest because the successful application of high power (>1 MW) windows for electron cyclotron heating systems in fusion reactors will most likely require cryogenic cooling to take advantage of the low loss tangent and higher thermal conductivity of candidate window materials at these temperatures

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

Combined conduction and radiation in a two-layer planar medium with flux boundary condition

International Nuclear Information System (INIS)

Ho, C.H.; Ozisik, M.N.

1987-01-01

The interaction of conduction and radiation is investigated under both transient and steady-state conditions for an absorbing, emitting, and isotropically scattering two-layer slab having opaque coverings at both boundaries. The slab is subjected to an externally applied constant heat flux at one boundary surface and dissipates heat by radiation into external ambients from both boundary surfaces. An analytic approach is applied to solve the radiation part of the problem, and a finite-difference scheme is used to solve the conduction part. The effects of the conduction-to-radiation parameter, the single scattering albedo, the optical thickness, and the surface emissivity on the temperature distribution are examined

Development of a contact heat exchanger for a constructable radiator system

Science.gov (United States)

Howell, H. R.

1983-01-01

A development program for a contact heat exchanger to be used to transfer heat from a spacecraft coolant loop to a heat pipe radiator is described. The contact heat exchanger provides for a connectable/disconnectable joint which allows for on-orbit assembly of the radiator system and replacement or exchange of radiator panels for repair and maintenance. The contact heat exchanger does not require the transfer of fluid across the joint; the spacecraft coolant loop remains contained in an all welded system with no static or dynamic fluid seals. The contact interface is also "dry' with no conductive grease or interstitial material required.

Radiative heat transfer

CERN Document Server

Modest, Michael F

2013-01-01

The third edition of Radiative Heat Transfer describes the basic physics of radiation heat transfer. The book provides models, methodologies, and calculations essential in solving research problems in a variety of industries, including solar and nuclear energy, nanotechnology, biomedical, and environmental. Every chapter of Radiative Heat Transfer offers uncluttered nomenclature, numerous worked examples, and a large number of problems-many based on real world situations-making it ideal for classroom use as well as for self-study. The book's 24 chapters cover the four major areas in the field: surface properties; surface transport; properties of participating media; and transfer through participating media. Within each chapter, all analytical methods are developed in substantial detail, and a number of examples show how the developed relations may be applied to practical problems. It is an extensive solution manual for adopting instructors. Features: most complete text in the field of radiative heat transfer;...

Highly heat removing radiation shielding material

International Nuclear Information System (INIS)

Asano, Norio; Hozumi, Masahiro.

1990-01-01

Organic materials, inorganic materials or metals having excellent radiation shielding performance are impregnated into expanded metal materials, such as Al, Cu or Mg, having high heat conductivity. Further, the porosity of the expanded metals and combination of the expanded metals and the materials to be impregnated are changed depending on the purpose. Further, a plurality of shielding materials are impregnated into the expanded metal of the same kind, to constitute shielding materials. In such shielding materials, impregnated materials provide shielding performance against radiation rays such as neutrons and gamma rays, the expanded metals provide heat removing performance respectively and they act as shielding materials having heat removing performance as a whole. Accordingly, problems of non-informity and discontinuity in the prior art can be dissolved be provide materials having flexibility in view of fabrication work. (T.M.)

Thermal computations for electronics conductive, radiative, and convective air cooling

CERN Document Server

Ellison, Gordon

2010-01-01

IntroductionPrimary mechanisms of heat flowConductionApplication example: Silicon chip resistance calculationConvectionApplication example: Chassis panel cooled by natural convectionRadiationApplication example: Chassis panel cooled only by radiation 7Illustrative example: Simple thermal network model for a heat sinked power transistorIllustrative example: Thermal network circuit for a printed circuit boardCompact component modelsIllustrative example: Pressure and thermal circuits for a forced air cooled enclosureIllustrative example: A single chip package on a printed circuit board-the proble

Radiation Heat Transfer Effect on Thermal Sizing of Air-Cooling Heat Exchanger of Emergency Cooldown Tank

Energy Technology Data Exchange (ETDEWEB)

Moon, Joo Hyung; Kim, Young In; Kim, Keung Koo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Myoung Jun; Lee, Hee Joon [School of Mechanical Eng., Kookmin University, Seoul (Korea, Republic of)

2014-10-15

An attempt has begun to extend the life time of emergency cooldown tank (ECT) by Korea Atomic Energy Research Institute (KAERI) researchers. Moon et al. recently reported a basic concept upon how to keep the ECT in operation beyond 72 hours after an accident occurs without any active corrective actions for the postulated design basis accidents. When the SMART (System-integrated Modular Advanced Reac-Tor) received its Standard Design Approval (SDA) for the first time in the world, hybrid safety systems are applied. However, the passive safety systems of SMART are being enforced in response to the public concern for much safer reactors since the Fukushima accident occurred. The ECT is a major component of a passive residual heat removal system (PRHRS), which is one of the most important systems to enhance the safety of SMART. It is being developed in a SMART safety enhancement project to contain enough cooling water to remove a sensible heat and a decay heat from reactor core for 72 hours since an accident occurs. Moon et al. offered to install another heat exchanger above the ECT and to recirculate an evaporated steam into water, which enables the ECT to be in operation, theoretically, indefinitely. An investigation was made to determine how long and how many tubes were required to meet the purpose of the study. In their calculation, however, a radiation heat transfer effect was neglected. The present study is to consider the radiation heat transfer for the design of air-cooling heat exchanger. Radiation heat transfer is normally ignored in many situations, but this is not the case for the present study. Kim et al. conducted thermal sizing of scaled-down ECT heat exchanger, which will be used to validate experimentally the basic concept of the present study. Their calculation is also examined to see if a radiation heat transfer effect was taken into consideration. The thermal sizing of an air-cooling heat exchanger was conducted including radiation heat transfer

Annular convective-radiative fins with a step change in thickness, and temperature-dependent thermal conductivity and heat transfer coefficient

Science.gov (United States)

Barforoush, M. S. M.; Saedodin, S.

2018-01-01

This article investigates the thermal performance of convective-radiative annular fins with a step reduction in local cross section (SRC). The thermal conductivity of the fin's material is assumed to be a linear function of temperature, and heat transfer coefficient is assumed to be a power-law function of surface temperature. Moreover, nonzero convection and radiation sink temperatures are included in the mathematical model of the energy equation. The well-known differential transformation method (DTM) is used to derive the analytical solution. An exact analytical solution for a special case is derived to prove the validity of the obtained results from the DTM. The model provided here is a more realistic representation of SRC annular fins in actual engineering practices. Effects of many parameters such as conduction-convection parameters, conduction-radiation parameter and sink temperature, and also some parameters which deal with step fins such as thickness parameter and dimensionless parameter describing the position of junction in the fin on the temperature distribution of both thin and thick sections of the fin are investigated. It is believed that the obtained results will facilitate the design and performance evaluation of SRC annular fins.

Thermal radiators with embedded pulsating heat pipes: Infra-red thermography and simulations

International Nuclear Information System (INIS)

Hemadri, Vadiraj A.; Gupta, Ashish; Khandekar, Sameer

2011-01-01

With the aim of exploring potential applications of Pulsating Heat Pipes (PHP), for space/terrestrial sectors, experimental study of embedded PHP thermal radiators, having two different effective Biot numbers respectively, and subjected to conjugate heat transfer conditions on their surface, i.e., natural convection and radiation, has been carried out under different thermo-mechanical boundary conditions. High resolution infrared camera is used to obtain spatial temperature profiles of the radiators. To complement the experimental study, detailed 3D computational heat transfer simulation has also been undertaken. By embedding PHP structures, it was possible to make the net thermal resistance of the mild steel radiator plate equivalent to the aluminum radiator plate, in spite of the large difference in their respective thermal conductivities (k Al ∼ 4k MS ). The study reveals that embedded PHP structures can be beneficial only under certain boundary conditions. The degree of isothermalization achieved in these structures strongly depends on its effective Biot number. The relative advantage of embedded PHP is appreciably higher if the thermal conductivity of the radiator plate material itself is low. The study indicates that the effective thermal conductivity of embedded PHP structure is of the order of 400 W/mK to 2300 W/mK, depending on the operating conditions. - Research highlights: → Study of radiator plates with embedded Pulsating Heat Pipe by infrared thermography. → Radiator is subjected to natural convection and radiation boundary conditions. → Experimental study is supported by 3D simulation. → Effective thermal conductivity of PHPs of the order of 2000 W/mK is obtained. → Efficacy of embedded PHPs depends on the effective Biot number of the system.

Free convection effects and radiative heat transfer in MHD Stokes ...

Indian Academy of Sciences (India)

The present note deals with the effects of radiative heat transfer and free convection in MHD for a flow of an electrically conducting, incompressible, dusty viscous fluid past an impulsively started vertical non-conducting plate, under the influence of transversely applied magnetic field. The heat due to viscous dissipation and ...

Detection of radiation from a heated and modulated equatorial electrojet current system

International Nuclear Information System (INIS)

Lunnen, R.J.; Lee, H.S.; Ferraro, A.J.; Collins, T.W.

1984-01-01

In May 1983, ionospheric heating experiments were conducted using the very high frequency radar facility at Lima, Peru. Experiments involving high frequency heating of the ionosphere were successfully conducted during 1982 at Islote, Puerto Rico. These local experiments had characterized the signal radiated from a heated and modulated ionospheric current system near the mid-latitudes. A long-path signal had also been received in September 1982 at Salinas, Puerto Rico from a mid-day equatorial electrojet, heated and modulated by the Jicamarca facility. The authors have investigated the characteristics of the local signal that would be radiated from a strong equatorial electrojet when heated and modulated, and report here that at the geomagnetic equator they were similar to, but less intense than, those observed at Arecibo, Puerto Rico due to parameter differences. This radiation is believed to be the first detected from a heated and modulated equatorial electrojet current system in the Western Hemisphere. (author)

Parallel-plate submicron gap formed by micromachined low-density pillars for near-field radiative heat transfer

International Nuclear Information System (INIS)

Ito, Kota; Miura, Atsushi; Iizuka, Hideo; Toshiyoshi, Hiroshi

2015-01-01

Near-field radiative heat transfer has been a subject of great interest due to the applicability to thermal management and energy conversion. In this letter, a submicron gap between a pair of diced fused quartz substrates is formed by using micromachined low-density pillars to obtain both the parallelism and small parasitic heat conduction. The gap uniformity is validated by the optical interferometry at four corners of the substrates. The heat flux across the gap is measured in a steady-state and is no greater than twice of theoretically predicted radiative heat flux, which indicates that the parasitic heat conduction is suppressed to the level of the radiative heat transfer or less. The heat conduction through the pillars is modeled, and it is found to be limited by the thermal contact resistance between the pillar top and the opposing substrate surface. The methodology to form and evaluate the gap promotes the near-field radiative heat transfer to various applications such as thermal rectification, thermal modulation, and thermophotovoltaics

Parallel-plate submicron gap formed by micromachined low-density pillars for near-field radiative heat transfer

Energy Technology Data Exchange (ETDEWEB)

Ito, Kota, E-mail: kotaito@mosk.tytlabs.co.jp [Toyota Central Research and Development Laboratories, Nagakute, Aichi 480-1192 (Japan); Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Miura, Atsushi; Iizuka, Hideo [Toyota Central Research and Development Laboratories, Nagakute, Aichi 480-1192 (Japan); Toshiyoshi, Hiroshi [Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904 (Japan)

2015-02-23

Near-field radiative heat transfer has been a subject of great interest due to the applicability to thermal management and energy conversion. In this letter, a submicron gap between a pair of diced fused quartz substrates is formed by using micromachined low-density pillars to obtain both the parallelism and small parasitic heat conduction. The gap uniformity is validated by the optical interferometry at four corners of the substrates. The heat flux across the gap is measured in a steady-state and is no greater than twice of theoretically predicted radiative heat flux, which indicates that the parasitic heat conduction is suppressed to the level of the radiative heat transfer or less. The heat conduction through the pillars is modeled, and it is found to be limited by the thermal contact resistance between the pillar top and the opposing substrate surface. The methodology to form and evaluate the gap promotes the near-field radiative heat transfer to various applications such as thermal rectification, thermal modulation, and thermophotovoltaics.

Homogenization of some radiative heat transfer models: application to gas-cooled reactor cores

International Nuclear Information System (INIS)

El Ganaoui, K.

2006-09-01

In the context of homogenization theory we treat some heat transfer problems involving unusual (according to the homogenization) boundary conditions. These problems are defined in a solid periodic perforated domain where two scales (macroscopic and microscopic) are to be taken into account and describe heat transfer by conduction in the solid and by radiation on the wall of each hole. Two kinds of radiation are considered: radiation in an infinite medium (non-linear problem) and radiation in cavity with grey-diffuse walls (non-linear and non-local problem). The derived homogenized models are conduction problems with an effective conductivity which depend on the considered radiation. Thus we introduce a framework (homogenization and validation) based on mathematical justification using the two-scale convergence method and numerical validation by simulations using the computer code CAST3M. This study, performed for gas cooled reactors cores, can be extended to other perforated domains involving the considered heat transfer phenomena. (author)

Analysis of a radiative heat exchanger for systems for thermal control of space vehicles

International Nuclear Information System (INIS)

Vasil'ev, L.L.; Kanonchik, L.E.; Babenko, V.A.

1995-01-01

Starting from the solution of a two-dimensional heat conduction problem, a mathematical model of a heat pipe-based radiative heat exchanger is developed. Good agreement between the predicted and experimental results is obtained. The effect of operational and structural parameters on the characteristics of the radiative heat exchanger is analyzed

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.

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.)

On the determination of the overall heat transmission coefficient and soil heat flux for a fog cooled, naturally ventilated greenhouse: Analysis of radiation and convection heat transfer

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

Discrete ordinates solution of coupled conductive radiative heat transfer in a two-layer slab with Fresnel interfaces subject to diffuse and obliquely collimated irradiation

International Nuclear Information System (INIS)

Muresan, Cristian; Vaillon, Rodolphe; Menezo, Christophe; Morlot, Rodolphe

2004-01-01

The coupled conductive radiative heat transfer in a two-layer slab with Fresnel interfaces subject to diffuse and obliquely collimated irradiation is solved. The collimated and diffuse components problems are treated separately. The solution for diffuse radiation is obtained by using a composite discrete ordinates method and includes the development of adaptive directional quadratures to overcome the difficulties usually encountered at the interfaces. The complete radiation numerical model is validated against the predictions obtained by using the Monte Carlo method

Radiation effects on heat transfer in heat exchangers, (2)

International Nuclear Information System (INIS)

Mori, Yasuo; Watanabe, Kenji; Taira, Tatsuji.

1980-01-01

In a high temperature gas-cooled reactor system, in which the working fluid exchanges heat at high temperature near 1000 deg C, the heat transfer acceleration by positively utilizing the radiation heat transfer between solid surfaces should be considered. This paper reports on the results of experiment and analysis for the effects of radiant heat on the heat transfer performance at elevated temperature by applying the heat transfer-accelerating method using radiators to the heat exchanger with tube bundle composed of two channels of heating and heated sides. As the test heat exchangers, a parallel counter flow exchanger and the cross flow exchanger simulating helical tubes were employed, and the results studied on the characteristics of each heat exchanger are described. The plates placed in parallel to flow in every space of the tube bundle arranged in a matrix were used as the heat transfer accelerator. The effects of acceleration with the plates were the increase of heat transmission from 12 to 24% and 12 to 38% in the parallel flow and cross flow heat exchangers, respectively. Also, it was clarified that the theoretical analysis, in which it was assumed that the region within pitch S and two radiator plates, with a heat-transferring tube placed at the center, is the minimum domain for calculation, and that the heat exchange by radiation occurs only between the domain and the adjacent domains, can estimate the heat transfer-accelerating effect and the temperature distribution in a heat exchanger with sufficient accuracy. (Wakatsuki, Y.)

Influence of Variable Fluid Properties and Radiative Heat loss on ...

African Journals Online (AJOL)

Consequently, comparative analysis is also performed on the wall shear stress and local heat transfer of the present study with the available results.The results show that the inclusion variable viscosity and thermal conductivity, and radiative heat loss mechanism cause significant effects on the fluid flow velocity, temperature ...

Non-Fourier heat conduction and phase transition in laser ablation of polytetrafluoroethylene (PTFE)

Science.gov (United States)

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.

Engineering calculations in radiative heat transfer

CERN Document Server

Gray, W A; Hopkins, D W

1974-01-01

Engineering Calculations in Radiative Heat Transfer is a six-chapter book that first explains the basic principles of thermal radiation and direct radiative transfer. Total exchange of radiation within an enclosure containing an absorbing or non-absorbing medium is then described. Subsequent chapters detail the radiative heat transfer applications and measurement of radiation and temperature.

Models of thermal transfer by radiation and by conduction, in any geometry, in multiphase multicomponent medium

International Nuclear Information System (INIS)

Jeanne, T.

1990-03-01

A conduction model and a radiation model are proposed for the calculation of heat transfer. A multiphase multicomponent medium is considered. The conduction model allows the calculation of heat exchanges between two configurations. The heat flow from each component can be obtained. This model is well adapted to the calculation of thermal shocks in an ensemble of materials. The radiation model shows how the radiative transfers can be calculated in a cylinder composed of two opaque surfaces, with the same axis of rotation, and separated by a transparent medium. The form factors are obtained from Herman and Nusselt methods. The parts of the face-to-face surfaces which are seen and not seen are evaluated [fr

Radiation and combined heat transfer in channels

International Nuclear Information System (INIS)

Tamonis, M.

1986-01-01

This book presents numerical methods of calculation of radiative and combined heat transfer in channel flows of radiating as well as nonradiating media. Results obtained in calculations for flow conditions of combustion products from organic fuel products are given and methods used in determining the spectral optical properties of molecular gases are analyzed. The book presents applications of heat transfer in solving problems. Topic covered are as follows: optical properties of molecular gases; transfer equations for combined heat transfer; experimental technique; convective heat transfer in heated gas flows; radiative heat transfer in gaseous media; combined heat transfer; and radiative and combined heat transfer in applied problems

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.

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

Radiative heat transfer in a heat generating and turbulently convecting fluid layer

International Nuclear Information System (INIS)

Cheung, F.B.; Chan, S.H.; Chawla, T.C.; Cho, D.H.

1980-01-01

The coupled problem of radiative transport and turbulent natural convection in a volumetrically heated, horizontal gray fluid medium, bounded from above by a rigid, isothermal wall and below by a rigid, adiabatic wall, is investigated analytically. An approximate method based upon the boundary layer approach is employed to obtain the dependence of heat transfer at the upper wall on the principal parameters of the problem, which, for moderate Prandtl number, are the Rayleigh number, Ra, the optical thickness, KL, and the conduction-radiation coupling parameter, N. Also obtained in this study is the behaviour of the thermal boundary layer at the upper wall. At large kL, the contribution of thermal radiation to heat transfer in the layer is found to be negligible for N > 10, moderate for N approximately 1, and overwhelming for N < 0.1. However, at small kL, thermal radiation is found to be important only for N < 0.01. While a higher level of turbulence results in a thinner boundary layer, a larger effect of radiation is found to result in a thicker one. Thus, in the presence of strong thermal radiation, a much larger value of Ra is required for the boundary layer approach to remain valid. Under severe radiation conditions, no boundary layer flow regime is found to exist even at very high Rayleigh numbers. Accordingly, the ranges of applicability of the present results are determined and the approximate method justified. In particular, the validity of the present analysis is tested in three limiting cases, ie those of kL → infinity, N → infinity, and Ra → infinity, and is further confirmed by comparison with the numerical solution (author)

Some factors affecting radiative heat transport in PWR cores

International Nuclear Information System (INIS)

Hall, A.N.

1989-04-01

This report discusses radiative heat transport in Pressurized Water Reactor cores, using simple models to illustrate basic features of the transport process. Heat transport by conduction and convection is ignored in order to focus attention on the restrictions on radiative heat transport imposed by the geometry of the heat emitting and absorbing structures. The importance of the spacing of the emitting and absorbing structures is emphasised. Steady state temperature distributions are found for models of cores which are uniformly heated by fission product decay. In all of the models, a steady state temperature distribution can only be obtained if the central core temperature is in excess of the melting point of UO 2 . It has recently been reported that the MIMAS computer code, which takes into account radiative heat transport, has been used to model the heat-up of the Three Mile Island-2 reactor core, and the computations indicate that the core could not have reached the melting point of UO 2 at any time or any place. We discuss this result in the light of the calculations presented in this paper. It appears that the predicted stabilisation of the core temperatures at ∼ 2200 0 C may be a consequence of the artificially large spacing between the radial rings employed in the MIMAS code, rather than a result of physical significance. (author)

The log mean heat transfer rate method of heat exchanger considering the influence of heat radiation

International Nuclear Information System (INIS)

Wong, K.-L.; Ke, M.-T.; Ku, S.-S.

2009-01-01

The log mean temperature difference (LMTD) method is conventionally used to calculate the total heat transfer rate of heat exchangers. Because the heat radiation equation contains the 4th order exponential of temperature which is very complicate in calculations, thus LMTD method neglects the influence of heat radiation. From the recent investigation of a circular duct in some practical situations, it is found that even in the situation of the temperature difference between outer duct surface and surrounding is low to 1 deg. C, the heat radiation effect can not be ignored in the situations of lower ambient convective heat coefficient and greater surface emissivities. In this investigation, the log mean heat transfer rate (LMHTR) method which considering the influence of heat radiation, is developed to calculate the total heat transfer rate of heat exchangers.

CFD analysis of heat transfer performance of graphene based hybrid nanofluid in radiators

Science.gov (United States)

Bharadwaj, Bharath R.; Sanketh Mogeraya, K.; Manjunath, D. M.; Rao Ponangi, Babu; Rajendra Prasad, K. S.; Krishna, V.

2018-04-01

For Improved performance of an automobile engine, Cooling systems are one of the critical systems that need attention. With increased capacity to carry away large amounts of wasted heat, performance of an engine is increased. Current research on Nano-fluids suggests that they offer higher heat transfer rate compared to that of conventional coolants. Hence this project seeks to investigate the use of hybrid-nanofluids in radiators so as to increase its heat transfer performance. Carboxyl Graphene and Graphene Oxide based nanoparticles were selected due to the very high thermal conductivity of Graphene. System Analysis of the radiator was performed by considering a small part of the whole automobile radiator modelled using SEIMENS NX. CFD analysis was conducted using ANSYS FLUENT® for the nanofluid defined and the increase in effectiveness was compared to that of conventional coolants. Usage of such nanofluids for a fixed cooling requirement in the future can lead to significant downsizing of the radiator.

Natural element method for radiative heat transfer in a semitransparent medium with irregular geometries

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yong [School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001 (China); Yi, Hong-Liang, E-mail: yihongliang@hit.edu.cn [School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001 (China); Tan, He-Ping, E-mail: tanheping@hit.edu.cn [School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001 (China)

2013-05-15

This paper develops a numerical solution to the radiative heat transfer problem coupled with conduction in an absorbing, emitting and isotropically scattering medium with the irregular geometries using the natural element method (NEM). The walls of the enclosures, having temperature and mixed boundary conditions, are considered to be opaque, diffuse as well as gray. The NEM as a meshless method is a new numerical scheme in the field of computational mechanics. Different from most of other meshless methods such as element-free Galerkin method or those based on radial basis functions, the shape functions used in NEM are constructed by the natural neighbor interpolations, which are strictly interpolant and the essential boundary conditions can be imposed directly. The natural element solutions in dealing with the coupled heat transfer problem for the mixed boundary conditions have been validated by comparison with those from Monte Carlo method (MCM) generated by the authors. For the validation of the NEM solution to radiative heat transfer in the semicircular medium with an inner circle, the results by NEM have been compared with those reported in the literatures. For pure radiative transfer, the upwind scheme is employed to overcome the oscillatory behavior of the solutions in some conditions. The steady state and transient heat transfer problem combined with radiation and conduction in the semicircular enclosure with an inner circle are studied. Effects of various parameters such as the extinction coefficient, the scattering albedo, the conduction–radiation parameter and the boundary emissivity are analyzed on the radiative and conductive heat fluxes and transient temperature distributions.

The Lattice and Thermal Radiation Conductivity of Thermal Barrier Coatings: Models and Experiments

Science.gov (United States)

Zhu, Dongming; Spuckler, Charles M.

2010-01-01

The lattice and radiation conductivity of ZrO2-Y2O3 thermal barrier coatings was evaluated using a laser heat flux approach. A diffusion model has been established to correlate the coating apparent thermal conductivity to the lattice and radiation conductivity. The radiation conductivity component can be expressed as a function of temperature, coating material scattering, and absorption properties. High temperature scattering and absorption of the coating systems can be also derived based on the testing results using the modeling approach. A comparison has been made for the gray and nongray coating models in the plasma-sprayed thermal barrier coatings. The model prediction is found to have a good agreement with experimental observations.

Radiation detector system having heat pipe based cooling

Science.gov (United States)

Iwanczyk, Jan S.; Saveliev, Valeri D.; Barkan, Shaul

2006-10-31

A radiation detector system having a heat pipe based cooling. The radiation detector system includes a radiation detector thermally coupled to a thermo electric cooler (TEC). The TEC cools down the radiation detector, whereby heat is generated by the TEC. A heat removal device dissipates the heat generated by the TEC to surrounding environment. A heat pipe has a first end thermally coupled to the TEC to receive the heat generated by the TEC, and a second end thermally coupled to the heat removal device. The heat pipe transfers the heat generated by the TEC from the first end to the second end to be removed by the heat removal device.

Essentials of radiation heat transfer

CERN Document Server

Balaji

2014-01-01

Essentials of Radiation Heat Transfer is a textbook presenting the essential, fundamental information required to gain an understanding of radiation heat transfer and equips the reader with enough knowledge to be able to tackle more challenging problems. All concepts are reinforced by carefully chosen and fully worked examples, and exercise problems are provided at the end of every chapter. In a significant departure from other books on this subject, this book completely dispenses with the network method to solve problems of radiation heat transfer in surfaces. It instead presents the powerful radiosity-irradiation method and shows how this technique can be used to solve problems of radiation in enclosures made of one to any number of surfaces. The network method is not easily scalable. Secondly, the book introduces atmospheric radiation, which is now being considered as a potentially important area, in which engineers can contribute to the technology of remote sensing and atmospheric sciences in general, b...

Heat conduction using Green’s functions

CERN Document Server

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...

Heat conduction within linear thermoelasticity

CERN Document Server

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...

Combined conduction and radiation with phase change in teflon slabs

International Nuclear Information System (INIS)

Shih, T.M.; Hsu, I.C.; Cunnington, G.R. Jr.

1986-01-01

A new approach to investigate, numerically, an one-dimensional Stefan problem with combined radiation and conduction has been developed. This numerical scheme is a modified version of the heat flux method and the scheme tracks the moving phase changing interface by coordinate transformation. The physical problem involves the radiative heating on one side of a Teflon slab; causing the material to melt and sublime as the melt-solid interface recedes. The other side of the Teflon slab is insulated. The results of this numerical scheme has been compared with results reported in the literature; before attempting to use this scheme to predict the experimental data. Satisfactory agreement between numerical results and the results in the literature as well as the experimental data has been obtained in both comparisons

A Variationally Formulated Problem of the Stationary Heat Conduction in a Plate with Radiation Reduction Factor Increased under Temperature

Directory of Open Access Journals (Sweden)

V. S. Zarubin

2016-01-01

dependence of the absorption factor on the local intensity of this radiation. Furthermore, it can be a significant dependence of this factor on the local value of the material temperature, reflecting the above-mentioned relationship between the absorption of electromagnetic wave energy and the excitation of material microparticles. This process can be described by Boltzmann distribution function that comprises the energy to activate microparticles and the local value of temperature.This paper presents a variational formulation of the nonlinear problem of stationary heat conduction in a plate for the case when the radiation reduction factor in relation to the Bouguer law depends on the local temperature. This formulation includes a functional that can have several fixed points corresponding to different steady states of the plate temperature. Analysis of the properties of this functional enabled us to identify the stationary points, which correspond to the realized temperature distribution in the plate.

Analytical and numerical treatment of the heat conduction equation obtained via time-fractional distributed-order heat conduction law

Science.gov (United States)

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.

Study of the heat transfers spectral radiation - conduction - natural convection in hybrid photovoltaic systems for buildings

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)

A modeling approach for heat conduction and radiation diffusion in plasma-photon mixture in temperature nonequilibrium

Energy Technology Data Exchange (ETDEWEB)

Chang, Chong [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-08-09

We present a simple approach for determining ion, electron, and radiation temperatures of heterogeneous plasma-photon mixtures, in which temperatures depend on both material type and morphology of the mixture. The solution technique is composed of solving ion, electron, and radiation energy equations for both mixed and pure phases of each material in zones containing random mixture and solving pure material energy equations in subdivided zones using interface reconstruction. Application of interface reconstruction is determined by the material configuration in the surrounding zones. In subdivided zones, subzonal inter-material energy exchanges are calculated by heat fluxes across the material interfaces. Inter-material energy exchange in zones with random mixtures is modeled using the length scale and contact surface area models. In those zones, inter-zonal heat flux in each material is determined using the volume fractions.

A modeling approach for heat conduction and radiation diffusion in plasma-photon mixture in temperature nonequilibrium

International Nuclear Information System (INIS)

Chang, Chong

2016-01-01

We present a simple approach for determining ion, electron, and radiation temperatures of heterogeneous plasma-photon mixtures, in which temperatures depend on both material type and morphology of the mixture. The solution technique is composed of solving ion, electron, and radiation energy equations for both mixed and pure phases of each material in zones containing random mixture and solving pure material energy equations in subdivided zones using interface reconstruction. Application of interface reconstruction is determined by the material configuration in the surrounding zones. In subdivided zones, subzonal inter-material energy exchanges are calculated by heat fluxes across the material interfaces. Inter-material energy exchange in zones with random mixtures is modeled using the length scale and contact surface area models. In those zones, inter-zonal heat flux in each material is determined using the volume fractions.

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.

Information filtering via biased heat conduction

Science.gov (United States)

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.

The theory of heat radiation

CERN Document Server

Planck, Max

2003-01-01

Nobel laureate's classic exposition of the theory of radiant heat in terms of quantum action. Kirchoff's law, black radiation, Maxwell's radiation pressure, entropy, other topics. 1914 edition. Bibliography.

Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble's dynamics

International Nuclear Information System (INIS)

Mahdi, M.; Ebrahimi, R.; Shams, M.

2011-01-01

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack. -- Highlights: → Heat transfer and ionization energy losses were analyzed in the cavitation bubble. → Radiation of hydrodynamic bubble was approximately equal to the black body. → Radiation heat transfer did not affect the bubble dynamic. → Conduction decreased the bubble pressure and increased the bubble temperature. → Ionization decreased the temperature and increased the pressure in the bubble.

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

Method for calculating internal radiation and ventilation with the ADINAT heat-flow code

International Nuclear Information System (INIS)

Butkovich, T.R.; Montan, D.N.

1980-01-01

One objective of the spent fuel test in Climax Stock granite (SFTC) is to correctly model the thermal transport, and the changes in the stress field and accompanying displacements from the application of the thermal loads. We have chosen the ADINA and ADINAT finite element codes to do these calculations. ADINAT is a heat transfer code compatible to the ADINA displacement and stress analysis code. The heat flow problem encountered at SFTC requires a code with conduction, radiation, and ventilation capabilities, which the present version of ADINAT does not have. We have devised a method for calculating internal radiation and ventilation with the ADINAT code. This method effectively reproduces the results from the TRUMP multi-dimensional finite difference code, which correctly models radiative heat transport between drift surfaces, conductive and convective thermal transport to and through air in the drifts, and mass flow of air in the drifts. The temperature histories for each node in the finite element mesh calculated with ADINAT using this method can be used directly in the ADINA thermal-mechanical calculation

Effect of Cattaneo-Christov heat flux on buoyancy MHD nanofluid flow and heat transfer over a stretching sheet in the presence of Joule heating and thermal radiation impacts

Science.gov (United States)

Dogonchi, A. S.; Ganji, D. D.

2018-06-01

In this study, buoyancy MHD nanofluid flow and heat transfer over a stretching sheet in the presence of Joule heating and thermal radiation impacts, are studied. Cattaneo-Christov heat flux model instead of conventional Fourier's law of heat conduction is applied to investigate the heat transfer characteristics. A similarity transformation is used to transmute the governing momentum and energy equations into non-linear ordinary differential equations with the appropriate boundary conditions. The obtained non-linear ordinary differential equations are solved numerically. The impacts of diverse active parameters such as the magnetic parameter, the radiation parameter, the buoyancy parameter, the heat source parameter, the volume fraction of nanofluid and the thermal relaxation parameter are examined on the velocity and temperature profiles. In addition, the value of the Nusselt number is calculated and presented through figures. The results demonstrate that the temperature profile is lower in the case of Cattaneo-Christov heat flux model as compared to Fourier's law. Moreover, the Nusselt number raises with the raising volume fraction of nanofluid and it abates with the ascending the radiation parameter.

Quantum-limited heat conduction over macroscopic distances

Science.gov (United States)

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.

Radiative heat transfer in the extreme near field.

Science.gov (United States)

Kim, Kyeongtae; Song, Bai; Fernández-Hurtado, Víctor; Lee, Woochul; Jeong, Wonho; Cui, Longji; Thompson, Dakotah; Feist, Johannes; Reid, M T Homer; García-Vidal, Francisco J; Cuevas, Juan Carlos; Meyhofer, Edgar; Reddy, Pramod

2015-12-17

Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres (refs 4-6), quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer.

The acoustic radiation force on a small thermoviscous or thermoelastic particle suspended in a viscous and heat-conducting fluid

Science.gov (United States)

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.

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.

Super-Planckian far-field radiative heat transfer

Science.gov (United States)

Fernández-Hurtado, V.; Fernández-Domínguez, A. I.; Feist, J.; García-Vidal, F. J.; Cuevas, J. C.

2018-01-01

We present here a theoretical analysis that demonstrates that the far-field radiative heat transfer between objects with dimensions smaller than the thermal wavelength can overcome the Planckian limit by orders of magnitude. To guide the search for super-Planckian far-field radiative heat transfer, we make use of the theory of fluctuational electrodynamics and derive a relation between the far-field radiative heat transfer and the directional absorption efficiency of the objects involved. Guided by this relation, and making use of state-of-the-art numerical simulations, we show that the far-field radiative heat transfer between highly anisotropic objects can largely overcome the black-body limit when some of their dimensions are smaller than the thermal wavelength. In particular, we illustrate this phenomenon in the case of suspended pads made of polar dielectrics like SiN or SiO2. These structures are widely used to measure the thermal transport through nanowires and low-dimensional systems and can be employed to test our predictions. Our work illustrates the dramatic failure of the classical theory to predict the far-field radiative heat transfer between micro- and nanodevices.

Modeling of quench front progression and heat transfer by radiation during reflooding of a tubular test section

International Nuclear Information System (INIS)

Clement, P.; Deruaz, R.

1976-01-01

Heat transfer modeling is presented in the scope of emergency core cooling. The rewetting of a hot dry wall during reflooding is a conduction-controlled phenomenon described by a model of heat-transfer coefficient. Upstream of the quench front, a two-dimensional approach involving both axial and transverse (or radial) heat conduction is discussed in view of thick walls, high quench front velocities and nucleate boiling. Downstream of the quench-front, high wall temperatures are reached so that a thermal radiation model is required to separate the different mechanisms of heat transfer. An attempt is made to consider radiation between walls, water droplets and vapor, with scattering emission and absorption of the two phases

Application of advanced model of radiative heat transfer in a rod geometry to QUENCH and PARAMETER tests

International Nuclear Information System (INIS)

Vasiliev, A.D.; Kobelev, G.V.; Astafieva, V.O.

2007-01-01

Radiative heat transfer is very important in different fields of mechanical engineering and related technologies including nuclear reactors, heat transfer in furnaces, aerospace, different high-temperature assemblies. In particular, in the course of a hypothetical severe accident at PWR-type nuclear reactor the temperatures inside the reactor vessel reach high values at which taking into account of radiative heat exchange between the structures of reactor (including core and other reactor vessel elements) gets important. Radiative heat transfer dominates the late phase of severe accident because radiative heat fluxes (proportional to T4, where T is the temperature) are generally considerably higher than convective and conductive heat fluxes in a system. In particular, heat transfer due to radiation determines the heating and degradation of the core and surrounding steel in-vessel structures and finally influences the composition, temperature and mass of materials pouring out of the reactor vessel after its loss of integrity. Existing models of radiative heat exchange use many limitations and approximations: approximate estimation of view factors and beam lengths; the geometry change in the course of the accident is neglected; the database for emissivities of materials is not complete; absorption/emission by steam-noncondensable medium is taken into account approximately. The module MRAD was developed in this paper to model the radiative heat exchange in rod-like geometry typical of PWR-type reactor. Radiative heat exchange is computed using dividing on zones (zonal method) as in existing radiation models implemented to severe accident numerical codes such as ICARE, SCDAP/RELAP, MELCOR but improved in following aspects: new approach to evaluation of view factors and mean beam length; detailed evaluation of gas absorptivity and emissivity; account of effective radiative thermal conductivity for the large core; account of geometry modification in the course of severe

The radiative heating response to climate change

Science.gov (United States)

Maycock, Amanda

2016-04-01

The structure and magnitude of radiative heating rates in the atmosphere can change markedly in response to climate forcings; diagnosing the causes of these changes can aid in understanding parts of the large-scale circulation response to climate change. This study separates the relative drivers of projected changes in longwave and shortwave radiative heating rates over the 21st century into contributions from radiatively active gases, such as carbon dioxide, ozone and water vapour, and from changes in atmospheric and surface temperatures. Results are shown using novel radiative diagnostics applied to timeslice experiments from the UM-UKCA chemistry-climate model; these online estimates are compared to offline radiative transfer calculations. Line-by-line calculations showing spectrally-resolved changes in heating rates due to different gases will also be presented.

Influence of radiation heat transfer during a severe accident

Energy Technology Data Exchange (ETDEWEB)

Cazares R, R. I.; Epinosa P, G.; Varela H, J. R.; Vazquez R, A. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco No. 186, Col. Vicentina, 09340 Ciudad de Mexico (Mexico); Polo L, M. A., E-mail: ricardo-cazares@hotmail.com [Comision Nacional de Seguridad Nuclear y Salvaguardias, Dr. Barragan No. 779, Col. Narvarte, 03020 Ciudad de Mexico (Mexico)

2016-09-15

The aim of this work is to determine the influence of the radiation heat transfer on an average fuel channel during a severe accident of a BWR nuclear power plant. The analysis considers the radiation heat transfer in a participating medium, where the gases inside the system participate in the radiation heat transfer. We consider the steam-water mixture as an isothermal gray gas, and the boundaries of the system as a gray diffuse isothermal surface for the clad and refractory surfaces for the rest, and consider the average fuel channel as an enclosure system. During a severe accident, generation and diffusion of hydrogen begin at high temperature range (1,273 to 2,100 K), and the fuel rod cladding oxidation, but the hydrogen generated do not participate in the radiation heat transfer because it does not have any radiation properties. The heat transfer process in the fuel assembly is considered with a reduced order model, and from this, the convection and the radiation heat transfer is introduced in the system. In this paper, a system with and without the radiation heat transfer term was calculated and analyzed in order to obtain the influence of the radiation heat transfer on the average fuel channel. We show the behavior of radiation heat transfer effects on the temporal evolution of the hydrogen concentration and temperature profiles in a fuel assembly, where a stream of steam is flowing. Finally, this study is a practical complement for more accurate modeling of a severe accident analysis. (Author)

Influence of radiation heat transfer during a severe accident

International Nuclear Information System (INIS)

Cazares R, R. I.; Epinosa P, G.; Varela H, J. R.; Vazquez R, A.; Polo L, M. A.

2016-09-01

The aim of this work is to determine the influence of the radiation heat transfer on an average fuel channel during a severe accident of a BWR nuclear power plant. The analysis considers the radiation heat transfer in a participating medium, where the gases inside the system participate in the radiation heat transfer. We consider the steam-water mixture as an isothermal gray gas, and the boundaries of the system as a gray diffuse isothermal surface for the clad and refractory surfaces for the rest, and consider the average fuel channel as an enclosure system. During a severe accident, generation and diffusion of hydrogen begin at high temperature range (1,273 to 2,100 K), and the fuel rod cladding oxidation, but the hydrogen generated do not participate in the radiation heat transfer because it does not have any radiation properties. The heat transfer process in the fuel assembly is considered with a reduced order model, and from this, the convection and the radiation heat transfer is introduced in the system. In this paper, a system with and without the radiation heat transfer term was calculated and analyzed in order to obtain the influence of the radiation heat transfer on the average fuel channel. We show the behavior of radiation heat transfer effects on the temporal evolution of the hydrogen concentration and temperature profiles in a fuel assembly, where a stream of steam is flowing. Finally, this study is a practical complement for more accurate modeling of a severe accident analysis. (Author)

Control of food-borne molds by combination of heat and radiation

International Nuclear Information System (INIS)

Padwal-Desai, S.R.; Bongirwar, D.R.

1979-01-01

After enumerating the fungi responsible for food spoilage, work done on the factors influencing growth of fungi in stored foods is reviewed and the methods using heat, radiation or chemicals for control of food-borne molds are briefly surveyed. Work on combination process employing heat treatment and radiation treatment is reviewed in detail. The review covers the following aspects: (1) theory and engineering aspects of combination process of heat and radiation including modes of heat transfer, radiation physics, radiation sources, heat radiation effect and calculation of energy balance of the process, (2) biological effects of heat, radiation and heat-radiation combination treatments on mold growth with special reference to DNA and (3) application of the process for mold control in cereal products, nuts and raisins and fruits. Heat treatment and radiation treatment have been found to complement each other and when given in proper sequence show synergism. Design requirements of radiation sources and heat transfer equipment are also surveyed. (M.G.B.)

Importance of thermal radiation from heat sink in cooling of three phase PWM inverter kept inside an evacuated chamber

Directory of Open Access Journals (Sweden)

Anjan Sarkar

2017-04-01

Full Text Available The paper describes a thermal analysis of a three-phase inverter operated under a Sinusoidal Pulse Width Modulation (SPWM technique which used three sine waves displaced in 120° phase difference as reference signals. The IGBT unit is assumed to be placed with a heat sink inside an evacuated chamber and the entire heat has to be transferred by conduction and radiation. The main heat sources present here are the set of IGBTs and diodes which generates heat on a pulse basing on their switching frequencies. Melcosim (a well-known tool developed by Mitsubishi Electric Corporation has been used to generate the power pulse from one set of IGBT and diode connected to a phase. A Scilab code is written to study the conduction and thermal radiation of heat sink and their combined effect on transient growth of the junction temperature of IGBT unit against complex switching pulses. The results mainly show that how thermal radiation from heat sink plays a crucial role in maintaining the junction temperature of IGBT within a threshold limit by adjusting various heat sink parameters. As the IGBT heat generation rate becomes higher, radiative heat transfer of the heat sink increases sharply which enhances overall cooling performance of the system.

Overall conductance and heat transfer area minimization of refrigerators and heat pumps with finite heat reservoirs

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

Measurements of Bremsstrahlung radiation and X-ray heat load to cryostat on SECRAL

International Nuclear Information System (INIS)

Zhao, H.Y.; Cao, Y.; Lu, W.; Zhang, W.H.; Zhao, H.W.; Zhang, X.Z.; Zhu, Y.H.; Li, X.X.; Xie, D.Z.

2012-01-01

The measurement of Bremsstrahlung radiation from ECR (Electron Cyclotron Resonance) plasma can yield certain information about the ECR heating process and the plasma confinement, and more important it can give a plausible estimate of the X-ray heat load to the cryostat of a superconducting ECR source. To better understand the additional heat load to the cryostat due to Bremsstrahlung radiation, the axial Bremsstrahlung measurements have been conducted on SECRAL (Superconducting Electron Cyclotron Resonance ion source with Advanced design in Lanzhou) with different source parameters. In addition, the heat load induced by intense X-ray or even γ-ray was estimated in terms of liquid helium consumption. The relationship between these two parameters is presented here. Thick-target Bremsstrahlung, induced by the collision of hot electrons with the wall or the source electrode, is much more intensive compared with the radiation produced in the plasma and, consequently, much more difficult to shield off. In this paper the presence of the thick-target Bremsstrahlung is correlated with the magnetic confinement configuration, specifically, the ratio of B(last) to B(ext). And possible solutions to reduce the X-ray heat load induced by Bremsstrahlung radiation are proposed and discussed. It appears that by choosing an appropriate ratio of B(last) to B(ext) the thick-target Bremsstrahlung radiation can be avoided effectively. The paper is followed by the associated poster

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

Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble's dynamics

Energy Technology Data Exchange (ETDEWEB)

Mahdi, M. [Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of); Ebrahimi, R. [Faculty of Aerospace Engineering, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of); Shams, M., E-mail: shams@kntu.ac.ir [Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Pardis St., Molla-Sadra Ave, Vanak. Sq., P.O. Box: 19395-1999, Tehran (Iran, Islamic Republic of)

2011-06-13

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack. -- Highlights: → Heat transfer and ionization energy losses were analyzed in the cavitation bubble. → Radiation of hydrodynamic bubble was approximately equal to the black body. → Radiation heat transfer did not affect the bubble dynamic. → Conduction decreased the bubble pressure and increased the bubble temperature. → Ionization decreased the temperature and increased the pressure in the bubble.

Specific heat, polarization and heat conduction in microwave heating systems: A nonequilibrium thermodynamic point of view

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

Spacecraft Radiator Freeze Protection Using a Regenerative Heat Exchanger

Science.gov (United States)

Ungar, Eugene K.; Schunk, Richard G.

2011-01-01

An active thermal control system architecture has been modified to include a regenerative heat exchanger (regenerator) inboard of the radiator. Rather than using a radiator bypass valve a regenerative heat exchanger is placed inboard of the radiators. A regenerator cold side bypass valve is used to set the return temperature. During operation, the regenerator bypass flow is varied, mixing cold radiator return fluid and warm regenerator outlet fluid to maintain the system setpoint. At the lowest heat load for stable operation, the bypass flow is closed off, sending all of the flow through the regenerator. This lowers the radiator inlet temperature well below the system set-point while maintaining full flow through the radiators. By using a regenerator bypass flow control to maintain system setpoint, the required minimum heat load to avoid radiator freezing can be reduced by more than half compared to a radiator bypass system.

Radiation heat transfer in a pressurized water reactor lower head filled with molten corium

International Nuclear Information System (INIS)

Šadek, Siniša; Grgić, Davor; Debrecin, Nenad

2013-01-01

Highlights: ► We develop radiation heat exchange model for a reactor pressure vessel lower head. ► Model is used during a late in-vessel phase of severe accidents. ► View factors are calculated automatically for a time-dependent enclosure. ► Model is included in the RELAP5/SCDAPSIM computer code. ► Inclusion of heat radiation causes faster heat-up rate of RPV lower head structures. - Abstract: Following a core melt, molten material may slump to the lower head of a reactor pressure vessel (RPV). In that case, some structures like lower parts of fuel elements and a core support plate would remain intact. Since the melt is at high temperature and there are no obstacles between the melt and the supporting plate, the plate is exposed to an intense radiation heating. The radiation heat exchange model of the lower head was developed and applied to a finite element code COUPLE which is a part of the detailed mechanistic code RELAP5/SCDAPSIM. The radiation enclosure consisted of three surfaces: the upper surface of the relocated material, the inner surface of the RPV wall above the relocated material and the lower surface of the core support plate. View factors were calculated for the enclosure geometry that is changing in time because of intermittent accumulation of molten material. The enclosure surfaces were covered by mesh of polygonal areas and view factors were calculated, for each pair of the element areas, by solving the definite integrals using the algorithms for adaptive integrations by means of Gaussian quadrature. Algebraic equations for radiosity and irradiation vectors were solved by LU decomposition and the radiation model was explicitly coupled with the heat conduction model. The results show that there is a possibility of the core support plate failure after being heated up due to radiation heat exchange with the melt.

Effect of radiation heat transfer on the performance of high temperature heat exchanger, (2)

International Nuclear Information System (INIS)

Yamada, Yukio; Mori, Yasuo; Hijikata, Kunio.

1977-01-01

In high temperature helium gas-cooled reactors, the nuclear energy can be utilized effectively, and the safety is excellent as compared with conventional reactors. They are advantageous also in view of environmental problems. In this report, the high temperature heat exchanger used for heating steam with the helium from a high temperature gas reactor is modeled, and the case that radiating gas flow between parallel plates is considered. Analysis was made on the case of one channel and constant heat flux and on the model for a counter-flow type heat exchanger with two channels, and the effect of radiation on the heat transfer in laminar flow and turbulent flow regions was clarified theoretically. The basic equations, the method of approximate solution and the results of calculation are explained. When one dimensional radiation was considered, the representative temperature Tr regarding fluid radiation was introduced, and its relation to mean mixing temperature Tm was determined. It was clarified that the large error in the result did not arise even if Tr was taken equally to Tm, especially in case of turbulent flow. The error was practically negligible when the rate of forced convection heat transfer in case of radiating medium flow was taken same as that in the case without radiation. (Kako, I.)

Evaluation of the Anisotropic Radiative Conductivity of a Low-Density Carbon Fiber Material from Realistic Microscale Imaging

Science.gov (United States)

Nouri, Nima; Panerai, Francesco; Tagavi, Kaveh A.; Mansour, Nagi N.; Martin, Alexandre

2015-01-01

The radiative heat transfer inside a low-density carbon fiber insulator is analyzed using a three-dimensional direct simulation model. A robust procedure is presented for the numerical calculation of the geometric configuration factor to compute the radiative energy exchange processes among the small discretized surface areas of the fibrous material. The methodology is applied to a polygonal mesh of a fibrous insulator obtained from three-dimensional microscale imaging of the real material. The anisotropic values of the radiative conductivity are calculated for that geometry. The results yield both directional and thermal dependence of the radiative conductivity.

Analytical solution to convection-radiation of a continuously moving fin with temperature-dependent thermal conductivity

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Moradi Amir

2013-01-01

Full Text Available In this article, the simultaneous convection-radiation heat transfer of a moving fin of variable thermal conductivity is studied. The differential transformation method (DTM is applied for an analytic solution for heat transfer in fin with two different profiles. Fin profiles are rectangular and exponential. The accuracy of analytic solution is validated by comparing it with the numerical solution that is obtained by fourth-order Runge-Kutta method. The analytical and numerical results are shown for different values of the embedding parameters. DTM results show that series converge rapidly with high accuracy. The results indicate that the fin tip temperature increases when ambient temperature increases. Conversely, the fin tip temperature decreases with an increase in the Peclet number, convection-conduction and radiation-conduction parameters. It is shown that the fin tip temperature of the exponential profile is higher than the rectangular one. The results indicate that the numerical data and analytical method are in a good agreement with each other.

International symposium on radiative heat transfer: Book of abstracts

International Nuclear Information System (INIS)

1995-01-01

The international symposium on radiative heat transfer was held on 14-18 August 1995 Turkey. The specialists discussed radiation transfer in materials processing and manufacturing, solution of radiative heat transfer equation, transient radiation problem and radiation-turbulence interactions, raditive properties of gases, atmospheric and stellar radiative transfer , radiative transfer and its applications, optical and radiative properties of soot particles, inverse radiation problems, partticles, fibres,thermophoresis and waves and modelling of comprehensive systems at the meeting. Almost 79 papers were presented in the meeting

An Experimental Study on Heat Conduction and Thermal Contact Resistance for the AlN Flake

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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.

Fractional Heat Conduction Models and Thermal Diffusivity Determination

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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.

Improvement of boiling heat transfer by radiation induced boiling enhancement

International Nuclear Information System (INIS)

Imai, Yasuyuki; Okamoto, Koji; Madarame, Haruki; Takamasa, Tomoji

2003-01-01

For nuclear reactor systems, the critical heat flux (CHF) data is very important because it limits reactor efficiency. Improvement of CHF requires that the cooling liquid can contact the heating surface, or a high-wettability, highly hydrophilic heating surface, even if a vapor bubble layer is generated on the surface. In our previous study, we confirmed that the surface wettability changed significantly or that highly hydrophilic conditions were achieved, after irradiation of 60 Co gamma ray, by the Radiation Induced Surface Activation (RISA) phenomenon. To delineate the effect of RISA on boiling phenomena, surface wettability in a high-temperature environment and critical heat flux (CHF) of metal oxides irradiated by gamma rays were investigated. A CHF experiment in the pool boiling condition was carried out under atmospheric pressure. The heating test section made of titanium was 0.2 mm in thickness, 3 mm in height, and 60 mm in length. Oxidation of the surface was carried out by plasma jetting for 40 seconds. The test section was irradiated by 60 Co gamma ray with predetermined radiation intensity and period. The CHF of oxidized titanium was improved up to 100 percent after 800 kGy 60 Co gamma ray irradiation. We call this effect Radiation Induced Boiling Enhancement (RIBE). Before we conducted the CHF experiment, contact angles of the test pieces were measured to show the relationship between wettability and CHF. The CHF in the present experiment increases will surface wettability in the same manner as shown by Liaw and Dhir's results. (author)

Improvement of boiling heat transfer by radiation induced boiling enhancement

International Nuclear Information System (INIS)

Imai, Y.; Okamoto, K.; Madarame, H.; Takamasa, T.

2003-01-01

For nuclear reactor systems, the Critical Heat Flux (CHF) data is very important because it limits reactor efficiency. Improvement of CHF requires that the cooling liquid can contact the heating surface, or a high-wettability, highly hydrophilic heating surface, even if a vapor bubble layer is generated on the surface. In our previous study, we confirmed that the surface wettability changed significantly or that highly hydrophilic conditions were achieved, after irradiation of 60Co gamma ray, by the Radiation Induced Surface Activation (RISA) phenomenon. To delineate the effect of RISA on boiling phenomena, surface wettability in a high-temperature environment and Critical Heat Flux (CHF) of metal oxides irradiated by gamma rays were investigated. A CHF experiment in the pool boiling condition was carried out under atmospheric pressure. The heating test section made of titanium was 0.2mm in thickness, 3mm in height, and 60mm in length. Oxidation of the surfaces was carried out by plasma jetting for 40 seconds. The test section was irradiated by 60Co gamma ray with predetermined radiation intensity and period. The CHF of oxidized titanium was improved up to 100 percent after 800kGy 60Co gamma ray irradiation. We call this effect Radiation Induced Boiling Enhancement (RIBE). Before we conducted the CHF experiment, contact angles of the test pieces were measured to show the relationship between wettability and CHF. The CHF in the present experiment increases with surface wettability in the same manner as shown by Liaw and Dhir's results

Nonstationary Heat Conduction in Atomic Systems

Science.gov (United States)

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

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

Nonlinear vs. bolometric radiation response and phonon thermal conductance in graphene-superconductor junctions

International Nuclear Information System (INIS)

Vora, Heli; Nielsen, Bent; Du, Xu

2014-01-01

Graphene is a promising candidate for building fast and ultra-sensitive bolometric detectors due to its weak electron-phonon coupling and low heat capacity. In order to realize a practical graphene-based bolometer, several important issues, including the nature of radiation response, coupling efficiency to the radiation and the thermal conductance need to be carefully studied. Addressing these issues, we present graphene-superconductor junctions as a viable option to achieve efficient and sensitive bolometers, with the superconductor contacts serving as hot electron barriers. For a graphene-superconductor device with highly transparent interfaces, the resistance readout in the presence of radio frequency radiation is dominated by non-linear response. On the other hand, a graphene-superconductor tunnel device shows dominantly bolometric response to radiation. For graphene devices fabricated on SiO 2 substrates, we confirm recent theoretical predictions of T 2 temperature dependence of phonon thermal conductance in the presence of disorder in the graphene channel at low temperatures

Irreversibility and Action of the Heat Conduction Process

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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.

Analysis of radiative heat transfer impact in cross-flow tube and fin heat exchangers

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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.

Heat enhances radiation inhibition of wound healing

International Nuclear Information System (INIS)

Twomey, P.; Hill, S.; Joiner, M.; Hobson, B.; Denekamp, J.

1987-01-01

To study the effect of hyperthermia on the inhibition of healing by radiation, the authors used 2 models of wound tensile strength in mice. In one, tensile strength of 1 cm strips of wounded skin was measured. In the other, strength was measured on 2 by 1 by .3 cm surgical prosthetic sponges of polyvinyl alcohol which has been cut, resutured, and implanted subcutaneously. Granulation tissue grows into the pores of the sponges which gradually fill with collagen. Tensile strength in both models was measured on day 14 using a constant strain extensiometer. The wounds were given graduated doses of ortho-voltage radiation with or without hyperthermia. Maximum radiation sensitivity occurred during the period of rapid neovascularization in the first 5 days after wounding, when a loss of 80% in wound strength occurred with doses less than 20 gray. For single radiation doses given 48 hours after wounding, the authors found a steep dose-response curve with half maximum reduction in strength occurring in both models at approximately 10 gray. Hyperthermia was produced in two ways. Skin wounds were heated in a circulating water bath. In the sponge model, more uniform heating occurs with an RF generator scaled to the mouse. At a dose of 43 C for 30 minutes, no inhibition of healing by heat alone was found. However the combination of heat and radiation produced definite enhancement of radiation damage, with thermal enhancement ratios of up to 1.9 being observed

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

Solar radiative heating of fiber-optic cables used to monitor temperatures in water

Science.gov (United States)

Neilson, Bethany T.; Hatch, Christine E.; Ban, Heng; Tyler, Scott W.

2010-08-01

In recent years, applications of distributed temperature sensing (DTS) have increased in number and diversity. Because fiber-optic cables used for DTS are typically sheathed in dark UV-resistant materials, the question arises as to how shortwave solar radiation penetrating a water column influences the accuracy of absolute DTS-derived temperatures in aquatic applications. To quantify these effects, we completed a modeling effort that accounts for the effects of radiation and convection on a submersed cable to predict when solar heating may be important. Results indicate that for cables installed at shallow depths in clear, low-velocity water bodies, measurable heating of the cable is likely during peak solar radiation. However, at higher velocities, increased turbidity and/or greater depths, the effects of solar heating are immeasurable. A field study illustrated the effects of solar radiation by installing two types of fiber-optic cable at multiple water depths (from 0.05 to 0.8 m) in the center and along the sidewall of a trapezoidal canal. Thermistors were installed at similar depths and shielded from solar radiation to record absolute water temperatures. During peak radiation, thermistor data showed small temperature differences (˜0.003°C-0.04°C) between depths suggesting minor thermal stratification in the canal center. DTS data from cables at these same depths show differences of 0.01°C-0.17°C. The DTS differences cannot be explained by stratification alone and are likely evidence of additional heating from solar radiation. Sidewall thermistor strings also recorded stratification. However, corresponding DTS data suggested that bed conduction overwhelmed the effects of solar radiation.

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.)

Assessment of Haar Wavelet-Quasilinearization Technique in Heat Convection-Radiation Equations

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Umer Saeed

2014-01-01

Full Text Available We showed that solutions by the Haar wavelet-quasilinearization technique for the two problems, namely, (i temperature distribution equation in lumped system of combined convection-radiation in a slab made of materials with variable thermal conductivity and (ii cooling of a lumped system by combined convection and radiation are strongly reliable and also more accurate than the other numerical methods and are in good agreement with exact solution. According to the Haar wavelet-quasilinearization technique, we convert the nonlinear heat transfer equation to linear discretized equation with the help of quasilinearization technique and apply the Haar wavelet method at each iteration of quasilinearization technique to get the solution. The main aim of present work is to show the reliability of the Haar wavelet-quasilinearization technique for heat transfer equations.

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

Canine tumor and normal tissue response to heat and radiation

International Nuclear Information System (INIS)

Gillette, E.L.; McChesney, S.L.

1985-01-01

Oral squamous cell carcinomas of dogs were treated with either irradiation alone or combined with hyperthermia. Tumor control was assessed as no evidence of disease one year following treatment. Dogs were randomized to variable radiation doses which were given in ten fractions three times a week for three weeks. Heat was given three hours after the first and third radiation dose each week for seven treatments. The attempt was made to achieve a minimum tumor temperature of 42 0 C for thirty minutes with a maximum normal tissue temperature of 40 0 C. It was usually possible to selectively heat tumors. The TCD 50 for irradiation alone was about 400 rads greater than for heat plus irradiation. The dose response curve for heat plus radiation was much steeper than for radiation alone indicating less heterogeneity of tumor response. That also implies a much greater effectiveness of radiation combined with heat at higher tumor control probabilities. Early necrosis caused by heating healed with conservative management. No increase in late radiation necrosis was observed

Heat and nuclear radiation as risk factors for male infertility: results of a French case-control study

International Nuclear Information System (INIS)

Thonneau, P.F.; Rachou, E.; Ducot, B.; Multigner, L.; Velez de la Calle, J.P.; Le Martelot, M.T.

1998-01-01

Very few studies have investigated the possible effects of environmental radiation and heat exposure on male reproductive function. We conducted a case control study to evaluate the various infertility risk factors in the military population of the french town of Brest to investigate an apparently high incidence of infertility in couples in which the man may have been exposed to occupational nuclear radiation. These findings suggest that in addition to well known medical factors, 'potential' exposure to heat or nuclear radiation could also be risk factors for infertility. (N.C.)

Experimental and theoretical analysis on the effect of inclination on metal powder sintered heat pipe radiator with natural convection cooling

Science.gov (United States)

Cong, Li; Qifei, Jian; Wu, Shifeng

2017-02-01

An experimental study and theoretical analysis of heat transfer performance of a sintered heat pipe radiator that implemented in a 50 L domestic semiconductor refrigerator have been conducted to examine the effect of inclination angle, combined with a minimum entropy generation analysis. The experiment results suggest that inclination angle has influences on both the evaporator and condenser section, and the performance of the heat pipe radiator is more sensitive to the inclination change in negative inclined than in positive inclined position. When the heat pipe radiator is in negative inclination angle position, large amplitude of variation on the thermal resistance of this heat pipe radiator is observed. As the thermal load is below 58.89 W, the influence of inclination angle on the overall thermal resistance is not that apparent as compared to the other three thermal loads. Thermal resistance of heat pipe radiator decreases by 82.86 % in inclination of 60° at the set of 138.46 W, compared to horizontal position. Based on the analysis results in this paper, in order to achieve a better heat transfer performance of the heat pipe radiator, it is recommended that the heat pipe radiator be mounted in positive inclination angle positions (30°-90°), where the condenser is above the evaporator.

Evaluation method for radiative heat transfer in polydisperse water droplets

International Nuclear Information System (INIS)

Maruyama, Shigenao; Nakai, Hirotaka; Sakurai, Atsushi; Komiya, Atsuki

2008-01-01

Simplifications of the model for nongray radiative heat transfer analysis in participating media comprised of polydisperse water droplets are presented. Databases of the radiative properties for a water droplet over a wide range of wavelengths and diameters are constructed using rigorous Mie theory. The accuracy of the radiative properties obtained from the database interpolation is validated by comparing them with those obtained from the Mie calculations. The radiative properties of polydisperse water droplets are compared with those of monodisperse water droplets with equivalent mean diameters. Nongray radiative heat transfer in the anisotropic scattering fog layer, including direct and diffuse solar irradiations and infrared sky flux, is analyzed using REM 2 . The radiative heat fluxes within the fog layer containing polydisperse water droplets are compared with those in the layer containing monodisperse water droplets. Through numerical simulation of the radiative heat transfer, polydisperse water droplets can be approximated by using the Sauter diameter, a technique that can be useful in several research fields, such as engineering and atmospheric science. Although this approximation is valid in the case of pure radiative transfer problems, the Sauter diameter is reconfirmed to be the appropriate diameter for approximating problems in radiative heat transfer, although volume-length mean diameter shows better accordance in some cases. The CPU time for nongray radiative heat transfer analysis with a fog model is evaluated. It is proved that the CPU time is decreased by using the databases and the approximation method for polydisperse particulate media

Heat- and radiation-resistant scintillator for electron microscopes

International Nuclear Information System (INIS)

Kosov, A.V.; Petrov, S.A.; Puzyr', A.P.; Chetvergov, N.A.

1987-01-01

The use of a scintillator consisting of a single crystal of bismuth orthogermanate, which has high heat and radiation resistance, in REM-100, REM-200, and REM-100U electron microscopes is described. A study of the heat and radiation stabilities of single crystals of bismuth orthogermanate (Bi 4 Ge 3 O 12 ) has shown that they withstood multiple electron-beam heating redness (T ∼ 800 0 C) without changes in their properties

Radiative heat transfer in honeycomb structures-New simple analytical and numerical approaches

International Nuclear Information System (INIS)

Baillis, D; Coquard, R; Randrianalisoa, J

2012-01-01

Porous Honeycomb Structures present the interest of combining, at the same time, high thermal insulating properties, low density and sufficient mechanical resistance. However, their thermal properties remain relatively unexplored. The aim of this study is the modelling of the combined heat transfer and especially radiative heat transfer through this type of anisotropic porous material. The equivalent radiative properties of the material are determined using ray-tracing procedures inside the honeycomb porous structure. From computational ray-tracing results, simple new analytical relations have been deduced. These useful analytical relations permit to determine radiative properties such as extinction, absorption and scattering coefficients and phase function functions of cell dimensions and optical properties of cell walls. The radiative properties of honeycomb material strongly depend on the direction of propagation. From the radiative properties computed, we have estimated the radiative heat flux passing through slabs of honeycomb core materials submitted to a 1-D temperature difference between a hot and a cold plate. We have compared numerical results obtained from Discrete Ordinate Method with analytical results obtained from Rosseland-Deissler approximation. This approximation is usually used in the case of isotropic materials. We have extended it to anisotropic honeycomb materials. Indeed a mean over incident directions of Rosseland extinction coefficient is proposed. Results tend to show that Rosseland-Deissler extended approximation can be used as a first approximation. Deviation on radiative conductivity obtained from Rosseland-Deissler approximation and from the Discrete Ordinated Method are lower than 6.7% for all the cases studied.

Heat rejection efficiency research of new energy automobile radiators

Science.gov (United States)

Ma, W. S.; Shen, W. X.; Zhang, L. W.

2018-03-01

The driving system of new energy vehicle has larger heat load than conventional engine. How to ensure the heat dissipation performance of the cooling system is the focus of the design of new energy vehicle thermal management system. In this paper, the heat dissipation efficiency of the radiator of the hybrid electric vehicle is taken as the research object, the heat dissipation efficiency of the radiator of the new energy vehicle is studied through the multi-working-condition enthalpy difference test. In this paper, the test method in the current standard QC/T 468-2010 “automobile radiator” is taken, but not limited to the test conditions specified in the standard, 5 types of automobile radiator are chosen, each of them is tested 20 times in simulated condition of different wind speed and engine inlet temperature. Finally, regression analysis is carried out for the test results, and regression equation describing the relationship of radiator heat dissipation heat dissipation efficiency air side flow rate cooling medium velocity and inlet air temperature is obtained, and the influence rule is systematically discussed.

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

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

Near-drift thermal analysis including combined modes of conduction, convection, and radiation

International Nuclear Information System (INIS)

Ho, C.K.; Francis, N.D.

1995-01-01

The performance of waste packages containing high-level nuclear wastes at underground repositories such as the potential repository at Yucca Mountain, Nevada, depends, in part, on the thermodynamic environment immediately surrounding the buried waste packages. For example, degradation of the waste packages can be caused by corrosive and microbial processes, which are influenced by both the relative humidity and temperature within the emplacement drifts. In this paper, the effects of conduction, convection, and radiation are investigated for a heat-generating waste package in an empty-drift. Simulations explicitly modeling radiation from the waste package to the drift wall are compared simulations using only conduction. Temperatures, relative humidities, and vapor mass fractions are compared at various locations within the drift. In addition, the effects of convection on relative humidity and moisture distribution within the drift are presented

Sodium Variable Conductance Heat Pipe for Radioisotope Stirling Systems

Science.gov (United States)

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.

User's Manual: Routines for Radiative Heat Transfer and Thermometry

Science.gov (United States)

Risch, Timothy K.

2016-01-01

Determining the intensity and spectral distribution of radiation emanating from a heated surface has applications in many areas of science and engineering. Areas of research in which the quantification of spectral radiation is used routinely include thermal radiation heat transfer, infrared signature analysis, and radiation thermometry. In the analysis of radiation, it is helpful to be able to predict the radiative intensity and the spectral distribution of the emitted energy. Presented in this report is a set of routines written in Microsoft Visual Basic for Applications (VBA) (Microsoft Corporation, Redmond, Washington) and incorporating functions specific to Microsoft Excel (Microsoft Corporation, Redmond, Washington) that are useful for predicting the radiative behavior of heated surfaces. These routines include functions for calculating quantities of primary importance to engineers and scientists. In addition, the routines also provide the capability to use such information to determine surface temperatures from spectral intensities and for calculating the sensitivity of the surface temperature measurements to unknowns in the input parameters.

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

Science.gov (United States)

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.

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

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

Large deviations in stochastic heat-conduction processes provide a gradient-flow structure for heat conduction

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

Generating a heated fluid using an electromagnetic radiation-absorbing complex

Science.gov (United States)

Halas, Nancy J.; Nordlander, Peter; Neumann, Oara

2018-01-09

A vessel including a concentrator configured to concentrate electromagnetic (EM) radiation received from an EM radiation source and a complex configured to absorb EM radiation to generate heat. The vessel is configured to receive a cool fluid from the cool fluid source, concentrate the EM radiation using the concentrator, apply the EM radiation to the complex, and transform, using the heat generated by the complex, the cool fluid to the heated fluid. The complex is at least one of consisting of copper nanoparticles, copper oxide nanoparticles, nanoshells, nanorods, carbon moieties, encapsulated nanoshells, encapsulated nanoparticles, and branched nanostructures. Further, the EM radiation is at least one of EM radiation in an ultraviolet region of an electromagnetic spectrum, in a visible region of the electromagnetic spectrum, and in an infrared region of the electromagnetic spectrum.

Fluctuations of radiative heat exchange between two bodies

Science.gov (United States)

Biehs, S.-A.; Ben-Abdallah, P.

2018-05-01

We present a theory to describe the fluctuations of nonequilibrium radiative heat transfer between two bodies both in the far- and near-field regimes. As predicted by the blackbody theory, in the far field, we show that the variance of radiative heat flux is of the same order of magnitude as its mean value. However, in the near-field regime, we demonstrate that the presence of surface polaritons makes this variance more than one order of magnitude larger than the mean flux. We further show that the correlation time of heat flux in this regime is comparable to the relaxation time of heat carriers in each medium. This theory could open the way to an experimental investigation of heat exchanges far from the thermal equilibrium condition.

Radiative heat transfer in low-dimensional systems -- microscopic mode

Science.gov (United States)

Woods, Lilia; Phan, Anh; Drosdoff, David

2013-03-01

Radiative heat transfer between objects can increase dramatically at sub-wavelength scales. Exploring ways to modulate such transport between nano-systems is a key issue from fundamental and applied points of view. We advance the theoretical understanding of radiative heat transfer between nano-objects by introducing a microscopic model, which takes into account the individual atoms and their atomic polarizabilities. This approach is especially useful to investigate nano-objects with various geometries and give a detailed description of the heat transfer distribution. We employ this model to study the heat exchange in graphene nanoribbon/substrate systems. Our results for the distance separations, substrates, and presence of extended or localized defects enable making predictions for tailoring the radiative heat transfer at the nanoscale. Financial support from the Department of Energy under Contract No. DE-FG02-06ER46297 is acknowledged.

Influences of deforestation on radiation and heat balances in tropical peat swamp forest in Thailand

International Nuclear Information System (INIS)

Suzuki, S.; Ishida, T.; Nagano, T.; Matsukawa, S.

1997-01-01

The difference of radiation and heat balances between a natural peat swamp forest and a deforested secondary forest has been investigated in Narathiwat Province, Thailand. Micrometeorological measurements were conducted continuously on observation towers 38 m and 4 m in heights in the primary forest and the secondary forest respectively. Results show that the deforestation of peat swamp forest leads to an increase in the sensible heat flux in the secondary forest. The yearly average ratio of the sensible heat flux to the net radiation was 20.9% in the peat swamp forest, and 33.2% in the secondary forest from Aug. 1995 to Jul. 1996. A ratio more than 40% was observed only in the dry season in the secondary forest. The change in sensible heat flux seemed to be influenced by the change in ground water levels. (author)

Analysis of directional radiative behavior and heating efficiency for a gas-fired radiant burner

International Nuclear Information System (INIS)

Li, B.X.; Lu, Y.P.; Liu, L.H.; Kudo, K.; Tan, H.P.

2005-01-01

For the purpose of energy conservation and uniform heating of object surface, a gas-fired porous radiant burner with a bundle of reflecting tubes is developed. A physical model is developed to simulate the directional radiative behavior of this heating device, in which the Monte Carlo method based on the concept of radiation distribution factor is used to compute the directional radiative behavior. The effects of relating parameters on the directional behavior of radiative heating and the heating efficiency are analyzed. With the increase of the length-to-radius ratio of tube, the radiation heating efficiency decreases, but the radiation energy incident on the object surface is more collimated. The radiation heating efficiency increases with the specular reflectivity. With the increase in length of tube segment with specular reflective surface, the radiation heating efficiency increases, but the extent of concentration and collimation of radiative energy decreases. For real design of the heating device, some trade-offs are needed to balance the radiation heating efficiency and the uniformity of radiative heating of object surface

Effect of two dimensional heat conduction within the wall on heat transfer of a tube partially heated on its circumference

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)

Polymeric hollow fiber heat exchanger as an automotive radiator

International Nuclear Information System (INIS)

Krásný, Ivo; Astrouski, Ilya; Raudenský, Miroslav

2016-01-01

Highlights: • Polymeric hollow fiber heat exchanger as an automotive radiator is proposed. • The mechanism of heat transfer (HT) relies on diameter of polymeric hollow fiber. • Grimson equation is sufficient for approximate prediction of the heat transfers. - Abstract: Nowadays, different automotive parts (tubing, covers, manifolds, etc.) are made of plastics because of their superior characteristics, low weight, chemical resistance, reasonable price and several other aspects. Manufacturing technologies are already well-established and the application of plastics is proven. Following this trend, the production of compact and light all-plastic radiators seems reasonable. Two plastic heat exchangers were manufactured based on polypropylene tubes of diameter 0.6 and 0.8 mm (so-called fibers) and tested. The heat transfer performance and pressure drops were studied with hot (60 °C) ethyleneglycol-water brine flowing inside the fibers and air (20 °C) outside because these conditions are conventional for car radiator operation. It was observed that heat transfer rates (up to 10.2 kW), overall heat transfer coefficients (up to 335 W/m"2 K), and pressure drops are competitive to conventional aluminium finned-tube radiators. Moreover, influence of fiber diameter was studied. It was observed that air-side convective coefficients rise with a decrease of fiber diameter. Air-side pressure drops of plastic prototypes were slightly higher than of aluminium radiator but it is expected that additional optimization will eliminate this drawback. Experimentally obtained air-side heat transfer coefficients were compared with the theoretical prediction using the Grimson equation and the Churchill and Bernstein approach. It was found that the Grimson equation is sufficient for approximate prediction of the outer HTCs and can be used for engineering calculations. Further work will concentrate on optimizing and developing a polymeric hollow fiber heat exchanger with reduced size

Design and Modeling of a Variable Heat Rejection Radiator

Science.gov (United States)

Miller, Jennifer R.; Birur, Gajanana C.; Ganapathi, Gani B.; Sunada, Eric T.; Berisford, Daniel F.; Stephan, Ryan

2011-01-01

Variable Heat Rejection Radiator technology needed for future NASA human rated & robotic missions Primary objective is to enable a single loop architecture for human-rated missions (1) Radiators are typically sized for maximum heat load in the warmest continuous environment resulting in a large panel area (2) Large radiator area results in fluid being susceptible to freezing at low load in cold environment and typically results in a two-loop system (3) Dual loop architecture is approximately 18% heavier than single loop architecture (based on Orion thermal control system mass) (4) Single loop architecture requires adaptability to varying environments and heat loads

Thermal conductivity of multi-walled carbon nanotube sheets: radiation losses and quenching of phonon modes

Energy Technology Data Exchange (ETDEWEB)

Aliev, Ali E; Lima, Marcio H; Baughman, Ray H [Alan G MacDiarmid NanoTech Institute, University of Texas at Dallas, Richardson, TX 75083 (United States); Silverman, Edward M, E-mail: Ali.Aliev@utdallas.edu [Northrop Grumman Space Technology, Redondo Beach, CA 90278 (United States)

2010-01-22

The extremely high thermal conductivity of individual carbon nanotubes, predicted theoretically and observed experimentally, has not yet been achieved for large nanotube assemblies. Resistances at tube-tube interconnections and tube-electrode interfaces have been considered the main obstacles for effective electronic and heat transport. Here we show that, even for infinitely long and perfect nanotubes with well-designed tube-electrode interfaces, excessive radial heat radiation from nanotube surfaces and quenching of phonon modes in large bundles are additional processes that substantially reduce thermal transport along nanotubes. Equivalent circuit simulations and an experimental self-heating 3{omega} technique were used to determine the peculiarities of anisotropic heat flow and thermal conductivity of single MWNTs, bundled MWNTs and aligned, free-standing MWNT sheets. The thermal conductivity of individual MWNTs grown by chemical vapor deposition and normalized to the density of graphite is much lower ({kappa}{sub MWNT} = 600 {+-} 100 W m{sup -1} K{sup -1}) than theoretically predicted. Coupling within MWNT bundles decreases this thermal conductivity to 150 W m{sup -1} K{sup -1}. Further decrease of the effective thermal conductivity in MWNT sheets to 50 W m{sup -1} K{sup -1} comes from tube-tube interconnections and sheet imperfections like dangling fiber ends, loops and misalignment of nanotubes. Optimal structures for enhancing thermal conductivity are discussed.

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)

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)

Ballistic heat conduction and mass disorder in one dimension.

Science.gov (United States)

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.

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

Intense radiative heat transport across a nano-scale gap

International Nuclear Information System (INIS)

Budaev, Bair V.; Ghafari, Amin; Bogy, David B.

2016-01-01

In this paper, we analyze the radiative heat transport in layered structures. The analysis is based on our prior description of the spectrum of thermally excited waves in systems with a heat flux. The developed method correctly predicts results for all known special cases for both large and closing gaps. Numerical examples demonstrate the applicability of our approach to the calculation of the radiative heat transport coefficient across various layered structures.

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

Analysis of the thermal performance of heat pipe radiators

Science.gov (United States)

Boo, J. H.; Hartley, J. G.

1990-01-01

A comprehensive mathematical model and computational methodology are presented to obtain numerical solutions for the transient behavior of a heat pipe radiator in a space environment. The modeling is focused on a typical radiator panel having a long heat pipe at the center and two extended surfaces attached to opposing sides of the heat pipe shell in the condenser section. In the set of governing equations developed for the model, each region of the heat pipe - shell, liquid, and vapor - is thermally lumped to the extent possible, while the fin is lumped only in the direction normal to its surface. Convection is considered to be the only significant heat transfer mode in the vapor, and the evaporation and condensation velocity at the liquid-vapor interface is calculated from kinetic theory. A finite-difference numerical technique is used to predict the transient behavior of the entire radiator in response to changing loads.

Adriamycin resistance, heat resistance and radiation response in Chinese hamster fibroblasts

International Nuclear Information System (INIS)

Wallner, K.; Li, G.

1985-01-01

Previous investigators have demonstrated synergistic interaction between hyperthermia and radiation or Adriamycin (ADR), using cell lines that are sensitive to heat or ADR alone. The authors investigated the effect of heat, radiation or ADR on Chinese hamster fibroblasts (HA-1), their heat resistant variants and their ADR resistant variants. Heat for ADR resistance did not confer cross resistance to radiation. Cells resistant to heat did show cross resistance to ADR. While cells selected for ADR resistance were not cross resistant to heat, they did not exhibit drug potentiation by hyperthermia, characteristic of ADR sensitive cells. Cytofluorometric measurement showed decreased ADR uptake in both heat and ADR resistant cells. The possibility of cross resistance between heat and ADR should be considered when designing combined modality trials

A new method for simultaneous measurement of convective and radiative heat flux in car underhood applications

International Nuclear Information System (INIS)

Khaled, M; Garnier, B; Peerhossaini, H; Harambat, F

2010-01-01

A new experimental technique is presented that allows simultaneous measurement of convective and radiative heat flux in the underhood. The goal is to devise an easily implemented and accurate experimental method for application in the vehicle underhood compartment. The new method is based on a technique for heat-flux measurement developed by the authors (Heat flow (flux) sensors for measurement of convection, conduction and radiation heat flow 27036-2, © Rhopoint Components Ltd, Hurst Green, Oxted, RH8 9AX, UK) that uses several thermocouples in the thickness of a thermal resistive layer (foil heat-flux sensor). The method proposed here uses a pair of these thermocouples with different radiative properties. Measurements validating this novel technique are carried out on a flat plate with a prescribed constant temperature in both natural- and forced-convection flow regimes. The test flat plate is instrumented by this new technique, and also with a different technique that is intrusive but very accurate, used as reference here (Bardon J P and Jarny Y 1994 Procédé et dispositif de mesure transitoire de température et flux surfacique Brevet n°94.011996, 22 February). Discrepancies between the measurements by the two techniques are less than 10% for both convective and radiative heat flux. Error identification and sensitivity analysis of the new method are also presented

Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble's dynamics

Science.gov (United States)

Mahdi, M.; Ebrahimi, R.; Shams, M.

2011-06-01

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with the experimental data and a good correspondence was observed. The dynamics of hydrofoil cavitation bubble were also investigated. It was concluded that the thermal radiation heat transfer rate strongly depended on the cavitation number, initial bubble radius and hydrofoil angle of attack.

Radiative heat exchange between surfaces

International Nuclear Information System (INIS)

Yener, Y.; Yuncu, H.

1987-01-01

The geometrical features of radiative heat exchange between surfaces are discussed first by developing various radiation shape factor relations. The governing equations for enclosures with diffusely emitting and diffusely reflecting surfaces, as well as the equations for enclosures with gray surfaces having specular component of reflectivity are introduced next. Finally, a simplified model for enclosures with isothermal surfaces under the assumption of uniform radiosity over the surfaces is discussed, and various working relations for different conditions are presented

Maximal near-field radiative heat transfer between two plates

Science.gov (United States)

Nefzaoui, Elyes; Ezzahri, Younès; Drévillon, Jérémie; Joulain, Karl

2013-09-01

Near-field radiative transfer is a promising way to significantly and simultaneously enhance both thermo-photovoltaic (TPV) devices power densities and efficiencies. A parametric study of Drude and Lorentz models performances in maximizing near-field radiative heat transfer between two semi-infinite planes separated by nanometric distances at room temperature is presented in this paper. Optimal parameters of these models that provide optical properties maximizing the radiative heat flux are reported and compared to real materials usually considered in similar studies, silicon carbide and heavily doped silicon in this case. Results are obtained by exact and approximate (in the extreme near-field regime and the electrostatic limit hypothesis) calculations. The two methods are compared in terms of accuracy and CPU resources consumption. Their differences are explained according to a mesoscopic description of nearfield radiative heat transfer. Finally, the frequently assumed hypothesis which states a maximal radiative heat transfer when the two semi-infinite planes are of identical materials is numerically confirmed. Its subsequent practical constraints are then discussed. Presented results enlighten relevant paths to follow in order to choose or design materials maximizing nano-TPV devices performances.

Measurement of Critical Heat Flux Using the Transient Inverse Heat Conduction Method in Spray cooling

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.

Measurement of Critical Heat Flux Using the Transient Inverse Heat Conduction Method in Spray cooling

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.

Heat transfer analysis in a calorimeter for concentrated solar radiation measurements

Energy Technology Data Exchange (ETDEWEB)

Estrada, C.A.; Jaramillo, O.A.; Arancibia-Bulnes, C.A. [Universidad Nacional Autonoma de Mexico, Centro de Investigacion en Energia, Privada Xochicalco S/N, Col. Centro. Temixco, Morelos 62580 (Mexico); Acosta, R. [Universidad de Quintana Roo, Boulevard Bahia s/n Esq. I. Comonfort, Chetumal Quintana Roo 77019 (Mexico)

2007-10-15

A calorimeter was built for measuring the concentrated solar power produced by a point focus solar concentrator that was developed at CIE - UNAM. In order to obtain a thermal characterization of the calorimeter a theoretical and experimental heat transfer study is carried out. This study addresses the heat transfer in the circular flat plate of the calorimeter, which acts as receiver for the concentrating system. Temperatures are measured at different points of this plate and fit with a theoretical model that considers heat conduction with convective and radiative boundary conditions. In particular, it is possible to calculate the temperature distribution on the irradiated surface. This allows to examine the validity of the assumptions of cold water calorimetry, which was the technique applied to this system in previous works. (author)

The effect of turbulence-radiation interaction on radiative entropy generation and heat transfer

International Nuclear Information System (INIS)

Caldas, Miguel; Semiao, Viriato

2007-01-01

The analysis under the second law of thermodynamics is the gateway for optimisation in thermal equipments and systems. Through entropy minimisation techniques it is possible to increase the efficiency and overall performance of all kinds of thermal systems. Radiation, being the dominant mechanism of heat transfer in high-temperature systems, plays a determinant role in entropy generation within such equipments. Turbulence is also known to be a major player in the phenomenon of entropy generation. Therefore, turbulence-radiation interaction is expected to have a determinant effect on entropy generation. However, this is a subject that has not been dealt with so far, at least to the extent of the authors' knowledge. The present work attempts to fill that void, by studying the effect of turbulence-radiation interaction on entropy generation. All calculations are approached in such a way as to make them totally compatible with standard engineering methods for radiative heat transfer, namely the discrete ordinates method. It was found that turbulence-radiation interaction does not significantly change the spatial pattern of entropy generation, or heat transfer, but does change significantly their magnitude, in a way approximately proportional to the square of the intensity of turbulence

Aerodynamic characteristics and heat radiation performance of sportswear fabrics

Science.gov (United States)

Koga, H.; Hiratsuka, M.; Ito, S.; Konno, A.

2017-10-01

Sports such as swimming, speed skating, and marathon are sports competing for time. In recent years, reduction of the fluid drag of sportswear is required for these competitions in order to improve the record. In addition, sweating and discomfort due to body temperature rise during competition are thought to affect competitor performance, and heat radiation performance is also an important factor for sportswear. The authors have measured fluid force drag by wrapping cloth around a cylinder and have confirmed their differences due to the roughness of the fabric surface, differences in sewing. The authors could be verified the drag can be reduced by the position of the wear stitch. This time, we measured the heat radiation performance of 14 types of cloths whose aero dynamic properties are known using cylinders which are regarded as human fuselages, and found elements of cloth with heat radiation performance. It was found to be important for raising the heat radiation performance of sportswear that the fabric is thin and flat surface processing.

Heat radiation approach for harnessing heat of the cook stove to generate electricity for lighting system and charging of mobile phone

Science.gov (United States)

Muñoz, Rodrigo C., Jr.; Manansala, Chad Deo G.

2018-01-01

This study is based on the potential of thermoelectric coupling such as the thermoelectric cooler module. A thermoelectric cooler converts the heat coming from the cook stove into electricity and store in a battery. A dc-dc boost converter will be used to produce enough voltage to light a minimum house dwelling or charge phone battery. This device will be helpful to those that faces a problem on electricity especially in the isolated areas. The study aims (1) to harness heat from the cook stove up to 110 °C (2) To automatically cool-off the system to protect the thermoelectric cooler from damage due to excessive heat using an electronic solenoid; (3) To store energy harnessed in the battery; (4) To amplify the output voltages of the battery using DC to DC boost converter for lighting system and charging of mobile phone battery. From various tests conducted, it can fully charge a mobile phone in 3 hours observing the unit’s battery voltage drop from 4.06V to 3.98V. In the testing it used different orientation of steel rod by conduction to transfer heat and by radiation through tubular steel with its different dimensions. Most recent testing proved that the 2x2x9 tubular steel by radiation had the best result. The temperature reached more than a hundred degree Celsius that met the objective. The test resulted of boosting the voltage of the battery output from 3.7V to 4.96V on the average. The boosted voltage decrease as the system’s cool-off mechanism operated when the temperature reached above 110 degree Celsius decreasing output voltage to 0.8V resulting the boosted voltage to drop to zero. Therefore, the proponents concluded that heat waste can be converted to electrical energy by harnessing heat through radiation, with the help of TEC that generates voltage for lighting and can be boosted to be used for mobile charging. Furthermore, the study proved that the excess heat can damaged the TEC which was prevented by using of cooling-off mechanism, making it more

Radiation drive in laser heated hohlraums

International Nuclear Information System (INIS)

Suter, L.J.; Kauffman, R.L.; Darrow, C.B.

1995-01-01

Nearly 10 years of Nova experiments and analysis have lead to a relatively detailed quantitative and qualitative understanding of radiation drive in laser heated hohlraums. Our most successful quantitative modelling tool is 2D Lasnex numerical simulations. Analysis of the simulations provides us with insight into the details of the hohlraum drive. In particular we find hohlraum radiation conversion efficiency becomes quite high with longer pulses as the accumulated, high Z blow-off plasma begins to radiate. Extensive Nova experiments corroborate our quantitative and qualitative understanding

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

Science.gov (United States)

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.

Experimental and numerical investigation of thermal radiator performances as a source of heat energy in design of dryer simulation

Science.gov (United States)

Wiryanta, I. K. E. H.; Adiaksa, I. M. A.

2018-01-01

The purposes of this research was to investigate the temperature performance of tube and fins car radiator experimentally and numerically. The experiment research was carried out on a simulation design consists of a reservoir water tank, a heater, pump to circulate hot water to the radiator and a cooling fan. The hot water mass flow rate is 0.486 kg/s, and the cooling air velocity of the fan is 1 m/s. The heat transfer rate and the effectiveness of radiator were investigated. The results showed that the exhaust heat transfer rate from the radiator tended to increase over time, with an average heat transfer rate of 3974.3 Watt. The maximum heat transfer rate was 4680 Watt obtained at 6 minutes. The effectiveness of the radiator (ε) over time tends to increase with an average of ε = 0.3 and the maximum effectiveness value was obtained at 12 minutes i.e. 0.35. The numerical research conducted using CFD method. The geometry and meshing created using ANSYS Workbench and the post processing using Fluent. The simulation result showed the similarity with the experimental research. The temperatures of air-side radiator are about 45°C.

Multiplied effect of heat and radiation in chemical stress relaxation

International Nuclear Information System (INIS)

Ito, Masayuki

1981-01-01

About the deterioration of rubber due to radiation, useful knowledge can be obtained by the measurement of chemical stress relaxation. As an example, the rubber coating of cables in a reactor containment vessel is estimated to be irradiated by weak radiation at the temperature between 60 and 90 deg C for about 40 years. In such case, it is desirable to establish the method of accelerated test of the deterioration. The author showed previously that the law of time-dose rate conversion holds in the case of radiation. In this study, the chemical stress relaxation to rubber was measured by the simultaneous application of heat and radiation, and it was found that there was the multiplied effect of heat and radiation in the stress relaxation speed. Therefore the factor of multiplication of heat and radiation was proposed to describe quantitatively the degree of the multiplied effect. The chloroprene rubber used was offered by Hitachi Cable Co., Ltd. The experimental method and the results are reported. The multiplication of heat and radiation is not caused by the direct cut of molecular chains by radiation, instead, it is based on the temperature dependence of various reaction rates at which the activated species reached the cut of molecular chains through complex reaction mechanism and the temperature dependence of the diffusion rate of oxygen in rubber. (Kako, I.)

Radiative Heating in MSL Entry: Comparison of Flight Heating Discrepancy to Ground Test and Predictive Models

Science.gov (United States)

Cruden, Brett A.; Brandis, Aaron M.; White, Todd R.; Mahzari, Milad; Bose, Deepak

2014-01-01

During the recent entry of the Mars Science Laboratory (MSL), the heat shield was equipped with thermocouple stacks to measure in-depth heating of the thermal protection system (TPS). When only convective heating was considered, the derived heat flux from gauges in the stagnation region was found to be underpredicted by as much as 17 W/sq cm, which is significant compared to the peak heating of 32 W/sq cm. In order to quantify the contribution of radiative heating phenomena to the discrepancy, ground tests and predictive simulations that replicated the MSL entry trajectory were performed. An analysis is carried through to assess the quality of the radiation model and the impact to stagnation line heating. The impact is shown to be significant, but does not fully explain the heating discrepancy.

Engine and radiator: fetal and placental interactions for heat dissipation.

Science.gov (United States)

Schröder, H J; Power, G G

1997-03-01

The 'engine' of fetal metabolism generates heat (3-4 W kg-1 in fetal sheep) which has to be dissipated to the maternal organism. Fetal heat may move through the amniotic/allantoic fluids to the uterine wall (conductive pathway; total conductance, 1.1 W degrees C-1 kg-1) and with the umbilical arterial blood flow (convective pathway) to the placenta. Because resistance to heat flow is larger than zero fetal temperature exceeds maternal temperature by about 0.5 degree C (0.3-1 degree C). Probably 85% of fetal heat is lost to the maternal organism through the placenta, which thus serves as the main 'radiator'. Placental heat conductivity appears to be extremely high and this may lead to impaired heat exchange (guinea-pig placenta). A computer simulation demonstrates that fetal temperature is essentially clamped to maternal temperature, and that fetal thermoregulatory efforts to gain thermal independence would be futile. Indeed, when the late gestational fetus in utero is challenged by cold stress, direct and indirect indicators of (non-shivering) thermogenesis (oxygen consumption, increase of plasma glycerol and free fatty acid levels) change only moderately. In prematurely delivered lambs, however, cold stress provokes summit metabolism and maximum heat production. Only when birth is imitated in utero (by cord clamping, external artificial lung ventilation and cooling) do thermogenic efforts approach levels typical of extra-uterine life. This suggests the presence of inhibitors of thermogenesis of placental origin, e.g. prostaglandins and adenosine. When the synthesis of prostaglandins is blocked by pretreatment with indomethacin, sheep fetuses react to intra-uterine cooling with vigorous thermogenic responses, which can be subdued by infusion of prostaglandin E2 (PGE2). Since the sheep placenta is known to produce sufficient amounts of PGE2, it seems that the placenta controls fetal thermogenic responses to some extent. This transforms the fetus into an ectothermic

Radiative heat transfer by the Monte Carlo method

CERN Document Server

Hartnett †, James P; Cho, Young I; Greene, George A; Taniguchi, Hiroshi; Yang, Wen-Jei; Kudo, Kazuhiko

1995-01-01

This book presents the basic principles and applications of radiative heat transfer used in energy, space, and geo-environmental engineering, and can serve as a reference book for engineers and scientists in researchand development. A PC disk containing software for numerical analyses by the Monte Carlo method is included to provide hands-on practice in analyzing actual radiative heat transfer problems.Advances in Heat Transfer is designed to fill the information gap between regularly scheduled journals and university level textbooks by providing in-depth review articles over a broader scope than journals or texts usually allow.Key Features* Offers solution methods for integro-differential formulation to help avoid difficulties* Includes a computer disk for numerical analyses by PC* Discusses energy absorption by gas and scattering effects by particles* Treats non-gray radiative gases* Provides example problems for direct applications in energy, space, and geo-environmental engineering

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

Science.gov (United States)

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.

Dry heat and radiation combination effects on Aspergillus flavus Link. infecting cocoa beans

International Nuclear Information System (INIS)

Amoako-Atta, B.; Meier, H.; Odamtten, G.T.

1981-01-01

The paper deals with the effect of heat and radiation combination treatments on the control of microbial spoilage of cocoa beans caused by toxigenic Aspergillus flavus Link. The heat and radiation sources were from dry air oven heat and 60 Co gammacell 220 irradiator, respectively. The radiation doses used were either 0, 50, 100, 150 or 200 krad, with combined heat temperatures of 30, 60 or 90 0 C. At each temperature level three different exposure time intervals of either 15 min, 30 min or 60 min respectively, were used. Two reversible sequential heat/radiation combination effects were evaluated. The first sequence involved cocoa beans inoculated with A. flavus spores exposed first to dry heat at pre-determined temperature heat exposure time, followed by radiation treatment, then retention of samples in a constant humidity environmental chamber set at 80% for daily observation up to forty days post-treatment. The second sequence involved exposure of the inoculated beans first to radiation, then to heat before retention under fixed RH for observation. From their results, the authors arrive at four conclusions: first, that there is a critical radiation/heat combination range (200, 150 and 100 krad/90 0 C for 15 min) that significantly decontaminates (less than 5% mouldiness) A. flavus infected cocoa beans even under high relative humidity (80% RH) environment; second, that a temperature level of 90 0 C combined with 200, 150 or 100 krad maximizes such effect but the heat exposure time is a major factor; third, that low heat temperature ranges of 30 or 60 0 C, combined with low radiation dosages of 150 krad or below, enhance the rate of A. flavus spoilage effects of cocoa beans; and, lastly, that the sequence of exposure of the inoculated cocoa beans to heat/radiation combination influenced the spore germination; exposure to heat before radiation would sensitize the spores (200 krad/90 0 C) but results in an increased radioresistance. (author)

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

Science.gov (United States)

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.

Radiation-induced conductivity of polynaphthoyl benzimidazole

Energy Technology Data Exchange (ETDEWEB)

Tiutnev, A P; Berlin, A M; Saenko, V S; Rusanov, A L; Korshak, V V

1985-01-01

The nonstationary radiation-induced conductivity of polynaphthoyl benzimidazole, synthesized by single-stage high-temperature catalytic polycondensation, is investigated experimentally. It is shown that the radiation-induced conductivity of this material is characterized by an anomalous (non-Gaussian) transfer of excess charge carriers. The activation energy of the delayed component (0.1 ms after pulse termination) is determined to be 0.12 eV; the volt-ampere characteristic of this component is nonlinear, with the coefficient of nonlinearity increasing with the intensity of the external electric field. Experimental results are interpreted on the basis of the phenomenological theory of jump conductivity proposed by Zviagin. 15 references.

Influence of radiative heat and mass transfer mechanism in system “water droplet-high-temperature gases” on integral characteristics of liquid evaporation

Directory of Open Access Journals (Sweden)

Glushkov Dmitrii O.

2015-01-01

Full Text Available Physical and mathematical (system of differential equations in private derivatives models of heat and mass transfer were developed to investigate the evaporation processes of water droplets and emulsions on its base moving in high-temperature (more than 1000 K gas flow. The model takes into account a conductive and radiative heat transfer in water droplet and also a convective, conductive and radiative heat exchange with high-temperature gas area. Water vapors characteristic temperature and concentration in small wall-adjacent area and trace of the droplet, numerical values of evaporation velocities at different surface temperature, the characteristic time of complete droplet evaporation were determined. Experiments for confidence estimation of calculated integral characteristics of processes under investigation - mass liquid evaporation velocities were conducted with use of cross-correlation recording video equipment. Their satisfactory fit (deviations of experimental and theoretical velocities were less than 15% was obtained. The influence of radiative heat and mass transfer mechanism on characteristics of endothermal phase transformations in a wide temperature variation range was established by comparison of obtained results of numerical simulation with known theoretical data for “diffusion” mechanisms of water droplets and other liquids evaporation in gas.

Radiators in hydronic heating installations structure, selection and thermal characteristics

CERN Document Server

Muniak, Damian Piotr

2017-01-01

This book addresses key design and computational issues related to radiators in hydronic heating installations. A historical outline is included to highlight the evolution of radiators and heating technologies. Further, the book includes a chapter on thermal comfort, which is the decisive factor in selecting the ideal heating system and radiator type. The majority of the book is devoted to an extensive discussion of the types and kinds of radiators currently in use, and to identifying the reasons for the remarkable diversity of design solutions. The differences between the solutions are also addressed, both in terms of the effects of operation and of the thermal comfort that needs to be ensured. The book then compares the advantages and disadvantages of each solution, as well as its potential applications. A detailed discussion, supported by an extensive theoretical and mathematical analysis, is presented of the computational relations that are used in selecting the radiator type. The dynamics of radiator hea...

Radiation heat transfer within an open-cycle MHD generator channel

Science.gov (United States)

Delil, A. A. M.

1983-05-01

Radiation heat transfer in an MHD generator was modeled using the Sparrow and Cess model for radiation in an emitting, absorbing and scattering medium. The resulting general equations can be considerably reduced by introducing simplifying approximations for the channel and MHD gas properties. The simplifications lead to an engineering model, which is very useful for one-dimensional channel flow approximation. The model can estimate thermo-optical MHD gas properties, which can be substituted in the energy equation. The model considers the contribution of solid particles in the MHD gas to radiation heat transfer, considerable in coal-fired closed cycle MHD generators. The modeling is applicable also for other types of flow at elevated temperatures, where radiation heat transfer is an important quantity.

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

Spectral tuning of near-field radiative heat transfer by graphene-covered metasurfaces

Science.gov (United States)

Zheng, Zhiheng; Wang, Ao; Xuan, Yimin

2018-03-01

When two gratings are respectively covered by a layer of graphene sheet, the near-field radiative heat transfer between two parallel gratings made of silica (SiO2) could be greatly improved. As the material properties of doped silicon (n-type doping concentration is 1020 cm-3, marked as Si-20) and SiO2 differ greatly, we theoretically investigate the near-field radiative heat transfer between two parallel graphene-covered gratings made of Si-20 to explore some different phenomena, especially for modulating the spectral properties. The radiative heat flux between two parallel bulks made of Si-20 can be enhanced by using gratings instead of bulks. When the two gratings are respectively covered by a layer of graphene sheet, the radiative heat flux between two gratings made of Si-20 can be further enhanced. By tuning graphene chemical potential μ and grating filling factor f, due to the interaction between surface plasmon polaritons (SPPs) of graphene sheets and grating structures, the spectral properties of the radiative heat flux between two parallel graphene-covered gratings can be effectively regulated. This work will develop and supplement the effects of materials on the near-field radiative heat transfer for this kind of system configuration, paving a way to modulate the spectral properties of near-field radiative heat transfer.

Tunable heat conduction through coupled Fermi-Pasta-Ulam chains

Science.gov (United States)

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.

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

Comparison of vibrational conductivity and radiative energy transfer methods

Science.gov (United States)

Le Bot, A.

2005-05-01

This paper is concerned with the comparison of two methods well suited for the prediction of the wideband response of built-up structures subjected to high-frequency vibrational excitation. The first method is sometimes called the vibrational conductivity method and the second one is rather known as the radiosity method in the field of acoustics, or the radiative energy transfer method. Both are based on quite similar physical assumptions i.e. uncorrelated sources, mean response and high-frequency excitation. Both are based on analogies with some equations encountered in the field of heat transfer. However these models do not lead to similar results. This paper compares the two methods. Some numerical simulations on a pair of plates joined along one edge are provided to illustrate the discussion.

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

Radiation heat transfer model for the SCDAP code

International Nuclear Information System (INIS)

Sohal, M.S.

1984-01-01

A radiation heat transfer model has been developed for severe fuel damage analysis which accounts for anisotropic effects of reflected radiation. The model simplifies the view factor calculation which results in significant savings in computational cost with little loss of accuracy. Radiation heat transfer rates calculated by the isotropic and anisotropic models compare reasonably well with those calculated by other models. The model is applied to an experimental nuclear rod bundle during a slow boiloff of the coolant liquid, a situation encountered during a loss of coolant accident with severe fuel damage. At lower temperatures and also lower temperature gradients in the core, the anisotropic effect was not found to be significant

Solar-Radiation Heating as a Possible Heat Source for Dehydration of Hydrous Carbonaceous Chondrites

Science.gov (United States)

Nakamura, T.; Golabek, G.; Ohtsuka, K.; Matsuoka, M.

2017-07-01

We have calculated time-dependent temperature profiles of near surface layers of primitive Near Sun Asteroid (3200) Phaethon and found that solar radiation heating is a possible heat source for dehydration of carbonaceous chondrites.

Coupling conduction radiation and convection phenomena in complex 2D and 3D geometries

International Nuclear Information System (INIS)

Rupp, I.; Peniguel, C.

1997-01-01

In many industrial applications, convection radiation and conduction participate simultaneously to the heat transfers. A numerical approach able to cope with such problems has been developed. The code SYRTHES is tackling conduction and radiation (limited to non participating medium) while the fluid part is solved by CFD codes like ESTET (Finite volumes) or N3S (Finite elements). SYRTHES relies on an explicit numerical scheme to couple all phenomena. No stability problems has been encountered. To provide further flexibility, the three phenomena are solved on independent grids. All data transfers being automatically taken care of by SYRTHES. Extending the development to multi-physics or multi-code problems it is fairly straightforward thanks to the explicit approach. Illustrating applications show how SYRTHES is managing problems for which several CFD codes are needed simultaneously with message passing tools like PVM and CALCIUM. (author)

Coupling conduction radiation and convection phenomena in complex 2D and 3D geometries

Energy Technology Data Exchange (ETDEWEB)

Rupp, I [SIMULOG, Guyancourt Cedex, (France); Peniguel, C [Electricite de France (EDF), 78 - Chatou (France). Direction des Etudes et Recherches

1998-12-31

In many industrial applications, convection radiation and conduction participate simultaneously to the heat transfers. A numerical approach able to cope with such problems has been developed. The code SYRTHES is tackling conduction and radiation (limited to non participating medium) while the fluid part is solved by CFD codes like ESTET (Finite volumes) or N3S (Finite elements). SYRTHES relies on an explicit numerical scheme to couple all phenomena. No stability problems has been encountered. To provide further flexibility, the three phenomena are solved on independent grids. All data transfers being automatically taken care of by SYRTHES. Extending the development to multi-physics or multi-code problems it is fairly straightforward thanks to the explicit approach. Illustrating applications show how SYRTHES is managing problems for which several CFD codes are needed simultaneously with message passing tools like PVM and CALCIUM. (author) 9 refs.

Radiative heat conduction and the magnetorotational instability

CERN Document Server

Araya-Gochez, R A; 10.1111/j.1365-2966.2004.08329.x

2004-01-01

A photon or a neutrino gas, semicontained by a non-diffusive particle species through scattering, comprises a rather peculiar magnetohydrodynamic fluid where the magnetic field is truly frozen only to the comoving volume associated with the mass density. Although radiative diffusion precludes a formal adiabatic treatment of compressive perturbations, we cast the energy equation in quasi- adiabatic form by assuming a negligible rate of energy exchange among species on the time-scale of the perturbation. This leads to a simplified dispersion relation for toroidal, non-axisymmetric magnetorotational modes when the accretion disc has comparable stress contributions from diffusive and non-diffusive components. The properties of the modes of fastest growth are shown to depend strongly on the compressibility of the mode, with a reduction in growth rate consistent with the results of Blaes & Socrates for axisymmetric modes. A clumpy disc structure is anticipated on the basis of the polarization properties of the ...

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....

EFFECT OF A RADIATION COOLING AND HEATING FUNCTION ON STANDING LONGITUDINAL OSCILLATIONS IN CORONAL LOOPS

Energy Technology Data Exchange (ETDEWEB)

Kumar, S.; Nakariakov, V. M.; Moon, Y.-J., E-mail: sanjaykumar@khu.ac.kr [School of Space Research, Kyung Hee University, Yongin, 446-701, Gyeonggi (Korea, Republic of)

2016-06-10

Standing long-period (with periods longer than several minutes) oscillations in large, hot (with a temperature higher than 3 MK) coronal loops have been observed as the quasi-periodic modulation of the EUV and microwave intensity emission and the Doppler shift of coronal emission lines, and they have been interpreted as standing slow magnetoacoustic (longitudinal) oscillations. Quasi-periodic pulsations of shorter periods, detected in thermal and non-thermal emissions in solar flares could be produced by a similar mechanism. We present theoretical modeling of the standing slow magnetoacoustic mode, showing that this mode of oscillation is highly sensitive to peculiarities of the radiative cooling and heating function. We generalized the theoretical model of standing slow magnetoacoustic oscillations in a hot plasma, including the effects of the radiative losses and accounting for plasma heating. The heating mechanism is not specified and taken empirically to compensate the cooling by radiation and thermal conduction. It is shown that the evolution of the oscillations is described by a generalized Burgers equation. The numerical solution of an initial value problem for the evolutionary equation demonstrates that different dependences of the radiative cooling and plasma heating on the temperature lead to different regimes of the oscillations, including growing, quasi-stationary, and rapidly decaying. Our findings provide a theoretical foundation for probing the coronal heating function and may explain the observations of decayless long-period, quasi-periodic pulsations in flares. The hydrodynamic approach employed in this study should be considered with caution in the modeling of non-thermal emission associated with flares, because it misses potentially important non-hydrodynamic effects.

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

Classical entropy generation analysis in cooled homogenous and functionally graded material slabs with variation of internal heat generation with temperature, and convective–radiative boundary conditions

International Nuclear Information System (INIS)

Torabi, Mohsen; Zhang, Kaili

2014-01-01

This article investigates the classical entropy generation in cooled slabs. Two types of materials are assumed for the slab: homogeneous material and FGM (functionally graded material). For the homogeneous material, the thermal conductivity is assumed to be a linear function of temperature, while for the FGM slab the thermal conductivity is modeled to vary in accordance with the rule of mixtures. The boundary conditions are assumed to be convective and radiative concurrently, and the internal heat generation of the slab is a linear function of temperature. Using the DTM (differential transformation method) and resultant temperature fields from the DTM, the local and total entropy generation rates within slabs are derived. The effects of physically applicable parameters such as the thermal conductivity parameter for the homogenous slab, β, the thermal conductivity parameter for the FGM slab, γ, gradient index, j, internal heat generation parameter, Q, Biot number at the right side, Nc 2 , conduction–radiation parameter, Nr 2 , dimensionless convection sink temperature, δ, and dimensionless radiation sink temperature, η, on the local and total entropy generation rates are illustrated and explained. The results demonstrate that considering temperature- or coordinate-dependent thermal conductivity and radiation heat transfer at both sides of the slab have great effects on the entropy generation. - Highlights: • The paper investigates entropy generation in a slab due to heat generation and convective–radiative boundary conditions. • Both homogeneous material and FGM (functionally graded material) were considered. • The calculations are carried out using the differential transformation method which is a well-tested analytical technique

The radiation and variable viscosity effects on electrically conducting fluid over a vertically moving plate subjected to suction and heat flux

Energy Technology Data Exchange (ETDEWEB)

Malekzadeh, P., E-mail: malekzadeh@pgu.ac.i [Department of Mechanical Engineering, Persian Gulf University, Bushehr 75168 (Iran, Islamic Republic of); Center of Excellence for Computational Mechanics, Shiraz University, Shiraz (Iran, Islamic Republic of); Moghimi, M.A. [Department of Mechanical Engineering, School of Engineering, Shaid Bahonar University, Kerman (Iran, Islamic Republic of); Nickaeen, M. [K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of)

2011-05-15

Research highlights: {yields} A new application of the differential quadrature method in thermo-fluid fields. {yields} Moving vertical plate with suction and heat flux is considered. {yields} Fluid with variable viscosity subjected to thermal radiation is studied. -- Abstract: In this paper, firstly, the applicability of the differential quadrature method (DQM) as an efficient and accurate numerical method for solving the problem of variable viscosity and thermally radiative unsteady magneto-hydrodynamic (MHD) flow over a moving vertical plate with suction and heat flux is investigated. The spatial as well as the temporal domains are discretized using the DQM. The fast rate of convergence of the method is demonstrated and for the cases that a solution is available, comparison is done. Then, effects of the temperature dependence of viscosity and different fluid parameters on the velocity and temperature of transient MHD flow subjected to the above mentioned boundary condition are studied.

Exergy applied to the heat conduction analysis in glass covers of a solar cooker box-type with internal and external reflectors

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)

In situ characterization of thermal conductivities of irradiated solids by using ion beam heating and infrared imaging

Energy Technology Data Exchange (ETDEWEB)

Mondrik, Nicholas; Gigax, Jonathan; Wang, Xuemei; Price, Lloyd [Department of Nuclear Engineering, Texas A and M University, College Station, TX 77843 (United States); Wei, Chaochen [Materials Science and Engineering Department, Texas A and M University, College Station, TX 77843 (United States); Shao, Lin, E-mail: lshao@tamu.edu [Department of Nuclear Engineering, Texas A and M University, College Station, TX 77843 (United States); Materials Science and Engineering Department, Texas A and M University, College Station, TX 77843 (United States)

2014-08-01

We propose a method to characterize thermal properties of ion irradiated materials. This method uses an ion beam as a heating source to create a hot spot on sample surface. Infrared imaging is used as a surface temperature mapping tool to record hot zone spreading. Since ion energy, ion flux, and ion penetration depth can be precisely controlled, the beam heating data is highly reliable and repeatable. Using a high speed infrared camera to capture lateral spreading of the hot zone, thermal diffusivity can be readily extracted. The proposed method has advantages in studying radiation induced thermal property changes, for which radiation damage can be introduced by using an irradiating beam over a relatively large beam spot and beam heating can be introduced by using a focused testing beam over a relatively small beam spot. These two beams can be switched without breaking vacuum. Thus thermal conductivity changes can be characterized in situ with ion irradiation. The feasibility of the technique is demonstrated on a single crystal quartz substrate.

In situ characterization of thermal conductivities of irradiated solids by using ion beam heating and infrared imaging

International Nuclear Information System (INIS)

Mondrik, Nicholas; Gigax, Jonathan; Wang, Xuemei; Price, Lloyd; Wei, Chaochen; Shao, Lin

2014-01-01

We propose a method to characterize thermal properties of ion irradiated materials. This method uses an ion beam as a heating source to create a hot spot on sample surface. Infrared imaging is used as a surface temperature mapping tool to record hot zone spreading. Since ion energy, ion flux, and ion penetration depth can be precisely controlled, the beam heating data is highly reliable and repeatable. Using a high speed infrared camera to capture lateral spreading of the hot zone, thermal diffusivity can be readily extracted. The proposed method has advantages in studying radiation induced thermal property changes, for which radiation damage can be introduced by using an irradiating beam over a relatively large beam spot and beam heating can be introduced by using a focused testing beam over a relatively small beam spot. These two beams can be switched without breaking vacuum. Thus thermal conductivity changes can be characterized in situ with ion irradiation. The feasibility of the technique is demonstrated on a single crystal quartz substrate

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.

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

Science.gov (United States)

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.

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.

Inactivation of ascaris lumbricoides eggs by heat, radiation, and thermoradiation

International Nuclear Information System (INIS)

Brannen, J.P.; Garst, D.M.; Langley, S.

1975-07-01

It is desirable to eliminate the public health hazards associated with land application of municipal sewage sludge as a fertilizer or soil conditioner. This report describes experimentation to determine the effects of heat, radiation, and thermoradiation on the suppression of embryonation of Ascaris lumbricoides ova, a parasite commonly found in sewage sludge. Heat effects were observed at a minimum temperature of 51 0 C and radiation effects at doses in excess of 15 krads of radiation. Thermoradiation at 47 0 C suppressed embryonation at less than half the total dose required by radiation alone. (U.S.)

Fundamental principles of heat transfer

CERN Document Server

Whitaker, Stephen

1977-01-01

Fundamental Principles of Heat Transfer introduces the fundamental concepts of heat transfer: conduction, convection, and radiation. It presents theoretical developments and example and design problems and illustrates the practical applications of fundamental principles. The chapters in this book cover various topics such as one-dimensional and transient heat conduction, energy and turbulent transport, forced convection, thermal radiation, and radiant energy exchange. There are example problems and solutions at the end of every chapter dealing with design problems. This book is a valuable int

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)

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.)

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...

Experimental Investigation of Heat Transfer Characteristics of Automobile Radiator using TiO2-Nanofluid Coolant

Science.gov (United States)

Salamon, V.; Senthil kumar, D.; Thirumalini, S.

2017-08-01

The use of nanoparticle dispersed coolants in automobile radiators improves the heat transfer rate and facilitates overall reduction in size of the radiators. In this study, the heat transfer characteristics of water/propylene glycol based TiO2 nanofluid was analyzed experimentally and compared with pure water and water/propylene glycol mixture. Two different concentrations of nanofluids were prepared by adding 0.1 vol. % and 0.3 vol. % of TiO2 nanoparticles into water/propylene glycol mixture (70:30). The experiments were conducted by varying the coolant flow rate between 3 to 6 lit/min for various coolant temperatures (50°C, 60°C, 70°C, and 80°C) to understand the effect of coolant flow rate on heat transfer. The results showed that the Nusselt number of the nanofluid coolant increases with increase in flow rate. At low inlet coolant temperature the water/propylene glycol mixture showed higher heat transfer rate when compared with nanofluid coolant. However at higher operating temperature and higher coolant flow rate, 0.3 vol. % of TiO2 nanofluid enhances the heat transfer rate by 8.5% when compared to base fluids.

The inaccuracy of heat transfer characteristics of insulated and non-insulated circular duct while neglecting the influence of heat radiation

International Nuclear Information System (INIS)

Hsien, T.-L.; Wong, K.-L.; Yu, S.-J.

2009-01-01

The non-insulated and insulated ducts are commonly applied in the industries and various buildings, because the heat radiation equation contains the 4th order exponential of temperature which is very complicate in calculations. Most heat transfer experts recognized from their own experiences that the heat radiation effect can be ignored due to the small temperature difference between insulated and non-insulated surface and surroundings. This paper studies in detail to check the inaccuracies of heat transfer characteristics non-insulated and insulated duct by comparing the results between considering and neglecting heat radiation effect. It is found that neglecting the heat radiation effect is likely to produce large errors of non-insulated and thin-insulated ducts in situations of ambient air with low external convection heat coefficients and larger surface emissivity, especially while the ambient air temperature is different from that of surroundings and greater internal fluid convection coefficients. It is also found in this paper that using greater duct surface emissivity can greatly improve the heat exchanger effect and using smaller insulated surface emissivity can obtain better insulation.

Applications of Radiative Heating for Space Exploration

Science.gov (United States)

Brandis, Aaron

2017-01-01

Vehicles entering planetary atmospheres at high speeds (6 - 12 kms) experience intense heating by flows with temperatures of the order 10 000K. The flow around the vehicle experiences significant dissociation and ionization and is characterized by thermal and chemical non-equilibrium near the shock front, relaxing toward equilibrium. Emission from the plasma is intense enough to impart a significant heat flux on the entering spacecraft, making it necessary to predict the magnitude of radiative heating. Shock tubes represent a unique method capable of characterizing these processes in a flight-similar environment. The Electric Arc Shock tube (EAST) facility is one of the only facilities in its class, able to produce hypersonic flows at speeds up to Mach 50. This talk will review the characterization of radiation measured in EAST with simulations by the codes DPLR and NEQAIR, and in particular, focus on the impact these analyses have on recent missions to explore the solar system.

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.

Enhancement of ionic conductivity in stabilized zirconia ceramics under millimeter-wave irradiation heating

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.

Homogenization of some radiative heat transfer models: application to gas-cooled reactor cores; Homogeneisation de modeles de transferts thermiques et radiatifs: application au coeur des reacteurs a caloporteur gaz

Energy Technology Data Exchange (ETDEWEB)

El Ganaoui, K

2006-09-15

In the context of homogenization theory we treat some heat transfer problems involving unusual (according to the homogenization) boundary conditions. These problems are defined in a solid periodic perforated domain where two scales (macroscopic and microscopic) are to be taken into account and describe heat transfer by conduction in the solid and by radiation on the wall of each hole. Two kinds of radiation are considered: radiation in an infinite medium (non-linear problem) and radiation in cavity with grey-diffuse walls (non-linear and non-local problem). The derived homogenized models are conduction problems with an effective conductivity which depend on the considered radiation. Thus we introduce a framework (homogenization and validation) based on mathematical justification using the two-scale convergence method and numerical validation by simulations using the computer code CAST3M. This study, performed for gas cooled reactors cores, can be extended to other perforated domains involving the considered heat transfer phenomena. (author)

Heat transfer in heterogeneous propellant combustion systems

International Nuclear Information System (INIS)

Brewster, M.Q.

1992-01-01

This paper reports that heat transfer plays an important role in several critical areas of heterogeneous, solid-propellant combustion systems. These areas include heat feedback to the propellant surface, heat transfer between burning aluminum droplets and their surroundings, heat transfer to internal insulation systems, and heat transfer to aft-end equipment. Gas conduction dominates heat feedback to the propellant surface in conventional ammonium perchlorate (AP) composite propellants, although particle radiative feedback also plays a significant role in combustion of metalized propellants. Particle radiation plays a dominant role in heat transfer to internal insulation, compared with that of convection. However, conduction by impingement of burning aluminum particles, which has not been extensively studied, may also be significant. Radiative heat loss plays an important role in determining the burning rate of molten aluminum particles due to a highly luminous, oxide particle-laden, detached flame envelope. Radiation by aluminum oxide smoke particles also plays a dominant role in heat transfer from the exhaust plume to aft-end equipment. Uncertainties in aluminum oxide particle-size distribution and optical properties still make it difficult to predict radiative plume heat transfer accurately from first principles

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.

Impact of melting heat transfer and nonlinear radiative heat flux mechanisms for the generalized Burgers fluids

Directory of Open Access Journals (Sweden)

Waqar Azeem Khan

Full Text Available The present paper deals with the analysis of melting heat and mass transfer characteristics in the stagnation point flow of an incompressible generalized Burgers fluid over a stretching sheet in the presence of non-linear radiative heat flux. A uniform magnetic field is applied normal to the flow direction. The governing equations in dimensional form are reduced to a system of dimensionless expressions by implementation of suitable similarity transformations. The resulting dimensionless problem governing the generalized Burgers is solved analytically by using the homotopy analysis method (HAM. The effects of different flow parameters like the ratio parameter, magnetic parameter, Prandtl number, melting parameter, radiation parameter, temperature ratio parameter and Schmidt number on the velocity, heat and mass transfer characteristics are computed and presented graphically. Moreover, useful discussions in detail are carried out with the help of plotted graphs and tables. Keywords: Generalized Burgers fluid, Non-linear radiative flow, Magnetic field, Melting heat transfer

The inaccuracy of heat transfer characteristics for non-insulated and insulated spherical containers neglecting the influence of heat radiation

International Nuclear Information System (INIS)

Wong, King-Leung; Salazar, Jose Luis Leon; Prasad, Leo; Chen, Wen-Lih

2011-01-01

In this investigation, the differences of heat transfer characteristics for insulated and non-insulated spherical containers between considering and neglecting the influence of heat radiation are studied by the simulations in some practical situations. It is found that the heat radiation effect cannot be ignored in conditions of low ambient convection heat coefficients (such ambient air) and high surface emissivities, especially for the non-insulated and thin insulated cases. In most practical situations when ambient temperature is different from surroundings temperature and the emissivity of insulation surface is different from that of metal wall surface, neglecting heat radiation will result in inaccurate insulation effect and heat transfer errors even with very thick insulation. However, the insulation effect considering heat radiation will only increase a very small amount after some dimensionless insulated thickness (such insulation thickness/radius ≥0.2 in this study), thus such dimensionless insulated thickness can be used as the optimum thickness in practical applications. Meanwhile, wrapping a material with low surface emissivity (such as aluminum foil) around the oxidized metal wall or insulation layer (always with high surface emissivity) can achieve very good insulated effect for the non-insulated or thin insulated containers.

Heat transfer augmentation of a car radiator using nanofluids

Science.gov (United States)

Hussein, Adnan M.; Bakar, R. A.; Kadirgama, K.; Sharma, K. V.

2014-05-01

The car radiator heat transfer enhancement by using TiO2 and SiO2 nanoparticles dispersed in water as a base fluid was studied experimentally. The test rig is setup as a car radiator with tubes and container. The range of Reynolds number and volume fraction are (250-1,750) and (1.0-2.5 %) respectively. Results showed that the heat transfer increases with increasing of nanofluid volume fraction. The experimental data is agreed with other investigator.

Anisotropic conducting films for electromagnetic radiation applications

Science.gov (United States)

Cavallo, Francesca; Lagally, Max G.; Rojas-Delgado, Richard

2015-06-16

Electronic devices for the generation of electromagnetic radiation are provided. Also provided are methods for using the devices to generate electromagnetic radiation. The radiation sources include an anisotropic electrically conducting thin film that is characterized by a periodically varying charge carrier mobility in the plane of the film. The periodic variation in carrier mobility gives rise to a spatially varying electric field, which produces electromagnetic radiation as charged particles pass through the film.

Radiation Effects in Dual Heat Sinks for Cooling of Concentrated Photovoltaics

Science.gov (United States)

2016-06-01

heat transfer out of a module is by radiation [7]. 1. Previous work Previous work in field has been focused on improving convection transfer via...LEFT BLANK 35 VII. CONCLUSION AND RECOMMENDATION A. CONCLUSION This thesis examined means to improve heat transfer out of a CPV module by... heat transfer by radiation to lower the operating temperature of the CPV system, and therefore increase the power output. Experimental and

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

Resolving the stratification discrepancy of turbulent natural convection in differentially heated air-filled cavities. Part III: A full convection–conduction–surface radiation coupling

International Nuclear Information System (INIS)

Xin, Shihe; Salat, Jacques; Joubert, Patrice; Sergent, Anne; Penot, François; Quéré, Patrick Le

2013-01-01

Highlights: ► Turbulent natural convection is studied numerically and experimentally. ► DNS of full conduction–convection–radiation coupling is performed. ► Spectral methods are combined with domain decomposition. ► Considering surface radiation improves strongly numerical results. ► Surface radiation is responsible for the weak stratification. -- Abstract: The present study concerns an air-filled differentially heated cavity of 1 m × 0.32 m × 1 m (width × depth × height) subject to a temperature difference of 15 K and is motivated by the need to understand the persistent discrepancy observed between numerical and experimental results on thermal stratification in the cavity core. An improved experiment with enhanced metrology was set up and experimental data have been obtained along with the characteristics of the surfaces and materials used. Experimental temperature distributions on the passive walls have been introduced in numerical simulations in order to provide a faithful prediction of experimental data. By means of DNS using spectral methods, heat conduction in the insulating material is first coupled with natural convection in the cavity. As heat conduction influences only the temperature distribution on the top and bottom surfaces and in the near wall regions, surface radiation is added to the coupling of natural convection with heat conduction. The temperature distribution in the cavity is strongly affected by the polycarbonate front and rear walls of the cavity, which are almost black surfaces for low temperature radiation, and also other low emissivity walls. The thermal stratification is considerably weakened by surface radiation. Good agreement between numerical simulations and experiments is observed on both time-averaged fields and turbulent statistics. Treating the full conduction–convection–radiation coupling allowed to confirm that experimental wall temperatures resulted from the coupled phenomena and this is another way to

21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Radiofrequency radiation for the heating of food... PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency radiation for the heating of food, including microwave frequencies. Radiofrequency radiation, including...

Gas Temperature and Radiative Heat Transfer in Oxy-fuel Flames

DEFF Research Database (Denmark)

Bäckström, Daniel; Johansson, Robert; Andersson, Klas

This work presents measurements of the gas temperature, including fluctuations, and its influence on the radiative heat transfer in oxy-fuel flames. The measurements were carried out in the Chalmers 100 kW oxy-fuel test unit. The in-furnace gas temperature was measured by a suction pyrometer...... on the radiative heat transfer shows no effect of turbulence-radiation interaction. However, by comparing with temperature fluctuations in other flames it can be seen that the fluctuations measured here are relatively small. Further research is needed to clarify to which extent the applied methods can account...

Chemical implications of heat and radiation damage to rock salt

International Nuclear Information System (INIS)

Pederson, L.R.

1984-11-01

Chemical changes induced in Palo Duro and Paradox Basin natural rock salts and in synthetic NaCl by heat and gamma radiation were investigated. Heating of unirradiated natural rock salts to 300 0 C resulted in HCl (most prevalent), SO 2 , CO 2 , and H 2 S evolution, and increased the base content of the remaining salt by not more than 10 microequivalents per gram; whereas, heating of synthetic NaCl gave no product. Gamma irradiation produced sodium colloids and neutral chlorine in amounts similar to the results of Levy and coworkers. When the irradiated salts were heated, three reactions were apparent: (1) radiation-induced defects recombined; (2) neutral chlorine was evolved; and (3) HCl, SO 2 , CO 2 , and H 2 S were evolved, similar to results for unirradiated salts. Because reaction (1) appeared to dominate over reaction (2), it is expected that the influence of radiation damage to salt on the near-field chemical environment will be minor. 4 figures, 1 table

Sandwich Core Heat-Pipe Radiator for Power and Propulsion Systems

Science.gov (United States)

Gibson, Marc; Sanzi, James; Locci, Ivan

2013-01-01

Next-generation heat-pipe radiator technologies are being developed at the NASA Glenn Research Center to provide advancements in heat-rejection systems for space power and propulsion systems. All spacecraft power and propulsion systems require their waste heat to be rejected to space in order to function at their desired design conditions. The thermal efficiency of these heat-rejection systems, balanced with structural requirements, directly affect the total mass of the system. Terrestrially, this technology could be used for thermal control of structural systems. One potential use is radiant heating systems for residential and commercial applications. The thin cross section and efficient heat transportability could easily be applied to flooring and wall structures that could evenly heat large surface areas. Using this heat-pipe technology, the evaporator of the radiators could be heated using any household heat source (electric, gas, etc.), which would vaporize the internal working fluid and carry the heat to the condenser sections (walls and/or floors). The temperature could be easily controlled, providing a comfortable and affordable living environment. Investigating the appropriate materials and working fluids is needed to determine this application's potential success and usage.

Modeling Radiative Heat Transfer and Turbulence-Radiation Interactions in Engines

Energy Technology Data Exchange (ETDEWEB)

Paul, Chandan [Pennsylvania State Univ., University Park, PA (United States); Sircar, Arpan [Pennsylvania State Univ., University Park, PA (United States); Ferreyro-Fernandez, Sebastian [Pennsylvania State Univ., University Park, PA (United States); Imren, Abdurrahman [Pennsylvania State Univ., University Park, PA (United States); Haworth, Daniel C [Pennsylvania State Univ., University Park, PA (United States); Roy, Somesh P [Marquette University (United States); Ge, Wenjun [University of California Merced (United States); Modest, Michael F [University of California Merced (United States)

2017-04-26

Detailed radiation modelling in piston engines has received relatively little attention to date. Recently, it is being revisited in light of current trends towards higher operating pressures and higher levels of exhaust-gas recirculation, both of which enhance molecular gas radiation. Advanced high-efficiency engines also are expected to function closer to the limits of stable operation, where even small perturbations to the energy balance can have a large influence on system behavior. Here several different spectral radiation property models and radiative transfer equation (RTE) solvers have been implemented in an OpenFOAM-based engine CFD code, and simulations have been performed for a full-load (peak pressure ~200 bar) heavy-duty diesel engine. Differences in computed temperature fields, NO and soot levels, and wall heat transfer rates are shown for different combinations of spectral models and RTE solvers. The relative importance of molecular gas radiation versus soot radiation is examined. And the influence of turbulence-radiation interactions is determined by comparing results obtained using local mean values of composition and temperature to compute radiative emission and absorption with those obtained using a particle-based transported probability density function method.

Storage chamber for container of radiation-contaminated material

International Nuclear Information System (INIS)

Takakura, Masahide.

1996-01-01

The present invention concerns a storage chamber for containing radiation-contaminated materials in containing tubes and having cooling fluids circulated at the outer side of the containing tubes. The storage chamber comprises a gas supply means connected to the inside of the container tube for supplying a highly heat-conductive gas and a gas exhaustion means for discharging the gas present in the container tube. When containing vessels for radiation-contaminated materials are contained in the container tube, the gases present inside of the container tube is exhausted by means of the gas exhaustion means, and highly heat conductive gases are filled from the gas supply means to the space between the container tube and the containing vessels for the radiation-contaminated materials. When the temperature of the highly heat conductive gas is elevated due to the heat generation of the radiation-contaminated materials, the container tube is heated, and then cooled by the cooling fluid at the outer side of the container tube. In this case, the heat of the radiation-contaminated material-containing vessels is removed by the heat conduction by the highly heat conductive gas to reduce temperature gradient between the containing vessels and the containing tube. This can enhance the cooling effect. (T.M.)

Large-time behavior of the motion of a viscous heat-conducting one-dimensional gas coupled to radiation

Czech Academy of Sciences Publication Activity Database

Ducomet, B.; Nečasová, Šárka

2012-01-01

Roč. 191, č. 2 (2012), s. 219-260 ISSN 0373-3114 R&D Projects: GA ČR GA201/08/0012 Institutional research plan: CEZ:AV0Z10190503 Keywords : compressible * viscous * heat-conducting Subject RIV: BA - General Mathematics Impact factor: 0.680, year: 2012 http://www.springerlink.com/content/0gw2j0311w430012/

Near-field radiative heat transfer between graphene-covered hyperbolic metamaterials

Science.gov (United States)

Hong, Xiao-Juan; Li, Jian-Wen; Wang, Tong-Biao; Zhang, De-Jian; Liu, Wen-Xing; Liao, Qing-Hua; Yu, Tian-Bao; Liu, Nian-Hua

2018-04-01

We propose the use of graphene-covered silicon carbide (SiC) nanowire arrays (NWAs) for theoretical studies of near-field radiative heat transfer. The SiC NWAs exhibit a hyperbolic characteristic at an appropriately selected filling-volume fraction. The surface plasmon supported by graphene and the hyperbolic modes supported by SiC NWAs significantly affect radiative heat transfer. The heat-transfer coefficient (HTC) between the proposed structures is larger than that between SiC NWAs. We also find that the chemical potential of graphene plays an important role in modulating the HTC. The tunability of chemical potential through gate voltage enables flexible control of heat transfer using the graphene-covered SiC NWAs.

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

Impact of cloud radiative heating on East Asian summer monsoon circulation

International Nuclear Information System (INIS)

Guo, Zhun; Zhou, Tianjun; Wang, Minghuai; Qian, Yun

2015-01-01

The impacts of cloud radiative heating on the East Asian Summer Monsoon (EASM) over southeastern China (105°–125°E, 20°–35°N) are addressed by using the Community Atmosphere Model version 5 (CAM5). Sensitivity experiments demonstrate that the radiative heating of clouds leads to a positive effect on the local EASM circulation over southeastern China. Without the radiative heating of clouds, the EASM circulation and precipitation would be much weaker than that in normal conditions. The longwave heating of clouds dominates the changes of EASM circulation. The positive effect of clouds on EASM circulation is explained by the thermodynamic energy equation, i.e. the different heating rate between cloud base and cloud top enhances the convective instability over southeastern China, which consequently enhances updraft. The strong updraft would further result in a southward meridional wind above the center of the updraft through Sverdrup vorticity balance. (letter)

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

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.

Comparison of DSMC and CFD Solutions of Fire II Including Radiative Heating

Science.gov (United States)

Liechty, Derek S.; Johnston, Christopher O.; Lewis, Mark J.

2011-01-01

The ability to compute rarefied, ionized hypersonic flows is becoming more important as missions such as Earth reentry, landing high mass payloads on Mars, and the exploration of the outer planets and their satellites are being considered. These flows may also contain significant radiative heating. To prepare for these missions, NASA is developing the capability to simulate rarefied, ionized flows and to then calculate the resulting radiative heating to the vehicle's surface. In this study, the DSMC codes DAC and DS2V are used to obtain charge-neutral ionization solutions. NASA s direct simulation Monte Carlo code DAC is currently being updated to include the ability to simulate charge-neutral ionized flows, take advantage of the recently introduced Quantum-Kinetic chemistry model, and to include electronic energy levels as an additional internal energy mode. The Fire II flight test is used in this study to assess these new capabilities. The 1634 second data point was chosen for comparisons to be made in order to include comparisons to computational fluid dynamics solutions. The Knudsen number at this point in time is such that the DSMC simulations are still tractable and the CFD computations are at the edge of what is considered valid. It is shown that there can be quite a bit of variability in the vibrational temperature inferred from DSMC solutions and that, from how radiative heating is computed, the electronic temperature is much better suited for radiative calculations. To include the radiative portion of heating, the flow-field solutions are post-processed by the non-equilibrium radiation code HARA. Acceptable agreement between CFD and DSMC flow field solutions is demonstrated and the progress of the updates to DAC, along with an appropriate radiative heating solution, are discussed. In addition, future plans to generate more high fidelity radiative heat transfer solutions are discussed.

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.

Best estimate radiation heat transfer model developed for TRAC-BD1

International Nuclear Information System (INIS)

Spore, J.W.; Giles, M.M.; Shumway, R.W.

1981-01-01

A best estimate radiation heat transfer model for analysis of BWR fuel bundles has been developed and compared with 8 x 8 fuel bundle data. The model includes surface-to-surface and surface-to-two-phase fluid radiation heat transfer. A simple method of correcting for anisotropic reflection effects has been included in the model

Numerical analysis of natural convection and radiation heat transfer from various shaped thin fin-arrays placed on a horizontal plate-a conjugate analysis

International Nuclear Information System (INIS)

Dogan, M.; Sivrioglu, Mecit; Yılmaz, Onder

2014-01-01

Highlights: • Optimum fin shape is determined for natural convection and radiation heat transfer. • Fin array with the optimum shape has a much greater average heat transfer coefficient. • The most important factors affecting the heat transfer coefficient are determined. - Abstract: Steady state natural convection and radiation heat transfer from various shaped thin fin-arrays on a horizontal base plate has been numerically investigated. A conjugate analysis has been carried out in which the conservation equations of mass, momentum and energy for the fluid in the two fin enclosure are solved together with the heat conduction equation in the fin and the base plate. Heat transfer by radiation is also considered in analysis. The heat transfer coefficient has been determined for each of the fin array considered in the present study at the same base and the same total area. The results of the analysis show that there are some important geometrical factors affecting the design of fin arrays. Taking into consideration these factors, an optimum fin shape that yields the highest average heat transfer coefficient has been determined

Comparison of CFD Natural Convection and Conduction-only Models for Heat Transfer in the Yucca Mountain Project Drifts

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

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

Graphene-assisted near-field radiative heat transfer between corrugated polar materials

International Nuclear Information System (INIS)

Liu, X. L.; Zhang, Z. M.

2014-01-01

Graphene has attracted great attention in nanoelectronics, optics, and energy harvesting. Here, the near-field radiative heat transfer between graphene-covered corrugated silica is investigated based on the exact scattering theory. It is found that graphene can improve the radiative heat flux between silica gratings by more than one order of magnitude and alleviate the performance sensitivity to lateral shift. The underlying mechanism is mainly attributed to the improved photon tunneling of modes away from phonon resonances. Besides, coating with graphene leads to nonlocal radiative transfer that breaks Derjaguin's proximity approximation and enables corrugated silica to outperform bulk silica in near-field radiation.

Numerical simulation of a TLD pulsed laser-heating scheme for determination of shallow dose and deep dose in low-LET radiation fields

International Nuclear Information System (INIS)

Kearfott, K.J.; Han, S.; Wagner, E.C.; Samei, E.; Wang, C.-K.C.

2000-01-01

A new method is described to determine the depth-dose distribution in low-LET radiation fields using a thick thermoluminescent dosimeter (TLD) with a pulsed laser-heating scheme to obtain TL glow output. The computational simulation entails heat conduction and glow curve production processes. An iterative algorithm is used to obtain the dose distribution in the detector. The simulation results indicate that the method can predict the shallow and deep dose in various radiation fields with relative errors less than 20%

Radiation hygienic assessment of centralized heat and hot water supply of Bilibino village from Bilibin central nuclear heating- and power plant

International Nuclear Information System (INIS)

Eremin, V.A.; Marej, A.N.; Nechiporenko, N.I.; Rasskazov, A.P.; Sayapin, N.P.; Soldatov, G.E.; Shcherbinin, A.S.

1983-01-01

The experience in using an atomic power plant for heat and hot water supply of the village of Bilibino is outlined. Particular attention is given to the population radiation safety. It has been demonstrated that radiation safety of the system is ensured by maintaining fixed pressure levels in the heating media and by the hermetic state of heat exchanges. Water in the heat and hot water supply network meets the requirements for drinking water. Radioactive corrosion products were not detected in the test water. Gamma-radiation dose rate from the surface of heating devices and pipe-lines in the test premises did not exceed the natural background, that is, U.U1-0.025 mrad

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

The Liquid Droplet Radiator - an Ultralightweight Heat Rejection System for Efficient Energy Conversion in Space

Science.gov (United States)

Mattick, A. T.; Hertzberg, A.

1984-01-01

A heat rejection system for space is described which uses a recirculating free stream of liquid droplets in place of a solid surface to radiate waste heat. By using sufficiently small droplets ( 100 micron diameter) of low vapor pressure liquids the radiating droplet sheet can be made many times lighter than the lightest solid surface radiators (heat pipes). The liquid droplet radiator (LDR) is less vulnerable to damage by micrometeoroids than solid surface radiators, and may be transported into space far more efficiently. Analyses are presented of LDR applications in thermal and photovoltaic energy conversion which indicate that fluid handling components (droplet generator, droplet collector, heat exchanger, and pump) may comprise most of the radiator system mass. Even the unoptimized models employed yield LDR system masses less than heat pipe radiator system masses, and significant improvement is expected using design approaches that incorporate fluid handling components more efficiently. Technical problems (e.g., spacecraft contamination and electrostatic deflection of droplets) unique to this method of heat rejectioon are discussed and solutions are suggested.

Forced convection heat transfer in rectangular ducts - general case of wall resistances and peripheral conduction for ventilation cooling of nuclear waste repositories [ heat transfer and nuclear disposal

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.

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

Temperature dependency of the thermal conductivity of porous heat storage media

Science.gov (United States)

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.

Thermosolutal MHD flow and radiative heat transfer with viscous ...

African Journals Online (AJOL)

This paper investigates double diffusive convection MHD flow past a vertical porous plate in a chemically active fluid with radiative heat transfer in the presence of viscous work and heat source. The resulting nonlinear dimensionless equations are solved by asymptotic analysis technique giving approximate analytic ...

Heat transfer in melt ponds with convection and radiative heating: observationally-inspired modelling

Science.gov (United States)

Wells, A.; Langton, T.; Rees Jones, D. W.; Moon, W.; Kim, J. H.; Wilkinson, J.

2016-12-01

Melt ponds have key impacts on the evolution of Arctic sea ice and summer ice melt. Small changes to the energy budget can have significant consequences, with a net heat-flux perturbation of only a few Watts per square metre sufficient to explain the thinning of sea ice over recent decades. Whilst parameterisations of melt-pond thermodynamics often assume that pond temperatures remain close to the freezing point, recent in-situ observations show more complex thermal structure with significant diurnal and synoptic variability. We here consider the energy budget of melt ponds and explore the role of internal convective heat transfer in determining the thermal structure within the pond in relatively calm conditions with low winds. We quantify the energy fluxes and temperature variability using two-dimensional direct numerical simulations of convective turbulence within a melt pond, driven by internal radiative heating and surface fluxes. Our results show that the convective flow dynamics are modulated by changes to the incoming radiative flux and sensible heat flux at the pond surface. The evolving pond surface temperature controls the outgoing longwave emissions from the pond. Hence the convective flow modifies the net energy balance of a melt pond, modulating the relative fractions of the incoming heat flux that is re-emitted to the atmosphere or transferred downward into the sea ice to drive melt.

Calculation of the fuel temperature field under heat release and heat conductance transient conditions

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

Shape Morphing Adaptive Radiator Technology (SMART) for Variable Heat Rejection

Science.gov (United States)

Erickson, Lisa

2016-01-01

The proposed technology leverages the temperature dependent phase change of shape memory alloys (SMAs) to drive the shape of a flexible radiator panel. The opening/closing of the radiator panel, as a function of temperature, passively adapts the radiator's rate of heat rejection in response to a vehicle's needs.

Rapidly curable electrically conductive clear coatings

Energy Technology Data Exchange (ETDEWEB)

Bowman, Mark P.; Anderson, Lawrence G.; Post, Gordon L.

2018-01-16

Rapidly curable electrically conductive clear coatings are applied to substrates. The electrically conductive clear coating includes to clear layer having a resinous binder with ultrafine non-stoichiometric tungsten oxide particles dispersed therein. The clear coating may be rapidly cured by subjecting the coating to infrared radiation that heats the tungsten oxide particles and surrounding resinous binder. Localized heating increases the temperature of the coating to thereby thermally cure the coating, while avoiding unwanted heating of the underlying substrate.

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

Science.gov (United States)

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).

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...

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

Local total and radiative heat-transfer coefficients during the heat treatment of a workpiece in a fluidised bed

International Nuclear Information System (INIS)

Gao, W.M.; Kong, L.X.; Hodgson, P.D.

2006-01-01

The heat-transfer coefficients around a workpiece immersed in an electrically heated heat treatment fluidised bed were studied. A suspension probe designed to simulate a workpiece of complex geometry was developed to measure local total and radiative heat-transfer coefficients at a high bed temperature. The probe consisted of an energy-storage region separated by insulation from the fluidised bed, except for the measuring surface, and a multi-thermocouple measurement system. Experiments in the fluidised bed were performed for a fluidising medium of 120-mesh alumina, a wide temperature range of 110-1050 deg. C and a fluidising number range of 1.18-4.24. It was found that the workpiece surface temperature has a more significant effect on heat transfer than the bed temperature. The total heat-transfer coefficient at the upper surface of the workpiece sharply decreased at the start of heating, and then steadily increased as heating progressed, while a sharp decrease became a rapid increase and then a slow increase for the radiative heat-transfer coefficient. A great difference in the heat-transfer coefficients around the workpiece was observed

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)

The radiation safety assessment of the heating loop of district heating reactors

International Nuclear Information System (INIS)

Liu Yuanzhong

1993-01-01

The district heating reactors are used to supply heating to the houses in cities. The concerned problems are whether the radioactive materials reach the heated houses through heating loop, and whether the safety of the dwellers can be ensured. In order to prevent radioactive materials getting into the heated houses, the district heating reactors have three loops, namely, primary loop, intermediate loop, and heating loop. In the paper, the measures of preventing radioactive materials getting into the heating loop are presented, and the possible sources of the radioactivity in the water of the intermediate loop and the heating loop are given. The regulatory aim limit of radioactive concentration in the water of the intermediate loop is put forward, which is 18.5 Bq/l. Assuming that specific radioactivity of the water of contaminated intermediate loop is up to 18.5 Bq/l, the maximum concentration of radionuclides in water of the heating loop is calculated for the normal operation and the accident of district heating reactor. The results show that the maximum possible concentration is 5.7 x 10 -3 Bq/l. The radiation safety assessment of the heating loop is made out. The conclusions are that the district heating reactors do not bring any harmful impact to the dwellers, and the safety of the dwellers can be safeguarded completely

Heat transfer study on convective–radiative semi-spherical fins with temperature-dependent properties and heat generation using efficient computational methods

International Nuclear Information System (INIS)

Atouei, S.A.; Hosseinzadeh, Kh.; Hatami, M.; Ghasemi, Seiyed E.; Sahebi, S.A.R.; Ganji, D.D.

2015-01-01

In this study, heat transfer and temperature distribution equations for semi-spherical convective–radiative porous fins are presented. Temperature-dependent heat generation, convection and radiation effects are considered and after deriving the governing equation, Least Square Method (LSM), Collocation Method (CM) and fourth order Runge-Kutta method (NUM) are applied for predicting the temperature distribution in the described fins. Results reveal that LSM has excellent agreement with numerical method, so can be suitable analytical method for solving the problem. Also, the effect of some physical parameters which are appeared in the mathematical formulation on fin surface temperature is investigated to show the effect of radiation and heat generation in a solid fin temperature. - Highlights: • Thermal analysis of a semi-spherical fin is investigated. • Collocation and Least Square Methods are applied on the problem. • Convection, radiation and heat generation is considered. • Physical results are compared to numerical outcomes.

Analysis of conduction–radiation heat transfer during phase change process of semitransparent materials using lattice Boltzmann method

International Nuclear Information System (INIS)

Maroufi, Arman; Aghanajafi, Cyrus

2013-01-01

This article deals with the analysis of solidification of a 2-D semitransparent material using the lattice Boltzmann method (LBM). Both conduction and radiation terms in governing energy equation were computed using the LBM. First, the LBM formulation regarding conduction component was validated and the results analyzed. Next, the results involving phase change or radiation term in the LBM were compared with the finite volume method (FVM). The results show good accuracy and less time consumption during LBM implementation. Finally, temperature distribution, the location of solid-liquid front, mushy zone thickness and the effects of heat transfer parameters were studied. -- Highlights: ► Solidification of 2-D semitransparent material is studied. ► Both conduction and radiation were computed using lattice Boltzmann method (LBM). ► LBM results validated by solving three benchmark problems. ► Effects of various parameters were studied on temperature distributions. ► Results show good accuracy and less time consumption during LBM implementation.

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

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

The combined effects of wall longitudinal heat conduction and inlet fluid flow maldistribution in crossflow plate-fin heat exchangers

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.)

Application of the finite element method to problems with heat radiation exchange

International Nuclear Information System (INIS)

Breitbach, G.; Altes, J.

1985-07-01

The calculation of temperature distributions for systems exchanging heat radiation requires in a first step the determination of the heat fluxes caused by radiation at its surfaces. In this paper the radiation transport equation is developed and it is shown, that it can be derived from a variational principle. The functional of the variational principle is the starting point of a numerical solution method. By using Finite Element Procedures a system of linear equations is derived, which supplies an approximation of the radiosity. Having the radiosity the heat flux at the surfaces, which governs as the boundary condition the temperature distribution in the structure, can be calculated. (orig.) [de

A heat transfer model for the analysis of transient heating of the slab in a direct-fired walking beam type reheating furnace

Energy Technology Data Exchange (ETDEWEB)

Kim, Man Young [School of Mechanical and Aerospace Systems Engineering, Research Center of Industrial Technology, Chonbuk National University, 664-14 Duckjin-Dong, Duckjin-Gu, Jeonju, Chonbuk 561-756 (Korea)

2007-09-15

A mathematical heat transfer model for the prediction of heat flux on the slab surface and temperature distribution in the slab has been developed by considering the thermal radiation in the furnace chamber and transient heat conduction governing equations in the slab, respectively. The furnace is modeled as radiating medium with spatially varying temperature and constant absorption coefficient. The steel slabs are moved on the next fixed beam by the walking beam after being heated up through the non-firing, charging, preheating, heating, and soaking zones in the furnace. Radiative heat flux calculated from the radiative heat exchange within the furnace modeled using the FVM by considering the effect of furnace wall, slab, and combustion gases is introduced as the boundary condition of the transient conduction equation of the slab. Heat transfer characteristics and temperature behavior of the slab is investigated by changing such parameters as absorption coefficient and emissivity of the slab. Comparison with the experimental work show that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace. (author)

Experimental study of effective thermal conductivity of stainless steel fiber felt

International Nuclear Information System (INIS)

Li, W.Q.; Qu, Z.G.

2015-01-01

An experimental apparatus was designed to measure the effective thermal conductivity of porous stainless steel fiber felt under different operating pressures. The total effective thermal conductivity was studied by analyzing matrix heat conduction, air natural convection, and matrix thermal radiation at ambient pressure. The contribution of air natural convection was experimentally obtained by changing the ambient pressure to vacuum condition and the solid matrix heat conduction was evaluated using a theoretical model. The ratios of the three mechanisms to the total effective thermal conductivity were approximately 40%, 37.9%, and 22.1%, respectively. In addition, the effects of fiber diameter and porosity on the three mechanisms and on the total effective thermal conductivity were studied. The air natural convection was found to gradually intensify when the operating pressure increases from vacuum condition (15 Pa) to ambient pressure (1.0 × 10 5  Pa). With an increase in fiber diameter under fixed porosity, the solid matrix heat conduction remained unchanged, and air natural convection and thermal radiation decreased, thereby resulting in reduced effective thermal conductivity. With an increase in porosity under fixed fiber diameter, the air natural convection was almost unchanged, and solid matrix heat conduction and thermal radiation were reduced, thereby resulting in reduced effective thermal conductivity. - Highlights: • Matrix conduction, radiation and air convection were in the same order of magnitude. • Air natural convection was suppressed by reducing operating pressure. • Intensity of air convection was more sensitive to fiber diameter than porosity. • Surface area and permeability was comparable in air convection as fiber diameter fixed. • Interfacial area exerted dominant role in radiation and air convection as porosity fixed

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

Combination Treatment of Spores of Cl. Botulinum with Heat plus Radiation

Energy Technology Data Exchange (ETDEWEB)

Grecz, N.; Upadhyay, J.; Tang, T. C.; Lin, C. A. [Illinois Institute of Technology, Chicago, IL (United States)

1967-11-15

Radiation resistance of spores of Cl. botulinum is strongly affected by the temperature during irradiation. Very low radiation resistance was consistently observed at 0 Degree-Sign C when samples were in the liquid state. Below 0 Degree-Sign C, the resistance of spores increased because the solidly frozen medium presumably decreased the diffusion of free radicals. As temperature increased above 0 Degree-Sign C processes of radiation protection occurred. When spores were subjected to low levels of radiation (0.6-0.8 Mrad) the heat resistance of the surviving spores was very remarkedly decreased. Experiments were designed to study what kind of radiation damage, i.e. direct hit or indirect action, is responsible for the loss of heat resistance of spores. Indirect effects were reduced by freezing the medium and lowering the temperature during irradiation down to -196 Degree-Sign C. Spores of Cl. botulinum 33A in phosphate buffer were irradiated to 0.6, 0.8 and 1.0 Mrad at irradiation temperatures ranging from +25 to -196 Degree-Sign C and subsequently heated at 99 Degree-Sign C. Survival curves revealed that all spores irradiated at +25 and 0 Degree-Sign C were highly sensitive to heat with D{sub 10} = 5.5 min (after 0.6 Mrad), D{sub 10} = 3.0 min (after 0.8 Mrad) and D{sub 10} = 2.3 min (after 1.0 Mrad). For nonTirradiated controls D10 was 23 min. Pre-irradiation at -25 through -196 Degree-Sign C resulted in a much smaller loss of heat resistance with D{sub 10} clustering around 17.4 min (after 0.6 Mrad), 13. 5 min (after 0.8 Mrad) and 11.5 min (after 1.0 Mrad). Loss of heat resistance after pre-irradiation at +25 and 0 Degree-Sign C was highly influenced by the liquid state of suspending medium whereas at -25 through -196 Degree-Sign C it depended primarily on radiation dose. The mechanism of heat sensitization of spores seems to be related primarily to migrating active free radicals at +25 and 0 Degree-Sign C and to random splitting of molecular bonds at -25 to -196

Heat conduction errors and time lag in cryogenic thermometer installations

Science.gov (United States)

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.

Modelling radiative heat transfer inside a basin type solar still

International Nuclear Information System (INIS)

Madhlopa, A.

2014-01-01

Radiative heat transfer inside a basin type solar still has been investigated using two models with (model 1) and without (model 2) taking into account optical view factors. The coefficient of radiative heat exchange (h r,w-gc ) between the water and cover surfaces of a practical solar still was computed using the two models. Simulation results show that model 1 yields lower values of h r,w-gc and the root mean square error than model 2. It is therefore concluded that the accuracy of modelling the performance of a basin-type solar still can be improved by incorporating view factors. - Highlights: • Radiative heat transfer in a basin type solar still has been investigated. • Two models with and without view factors were used. • The model with view factors exhibits a lower magnitude of root mean square error. • View factors affect the accuracy of modelling the performance of the solar still

Title Investigation of the influence of various factors on the power of heat exchange by radiation

Directory of Open Access Journals (Sweden)

Korolyov Alexander V.

2017-04-01

Full Text Available The issue of lack of knowledge of radiation heat transfer process has been repeatedly raised in various studies. Despite the fact that works on study of heat transfer by radiation covers a wide range of different industries, it should be noted the lack of materials on study of heat exchange processes by radiation in a core of a nuclear reactor. In this work, the fuel assemblies of the VVER-1000 reactor were used as the bodies under study. Aim: The aim of the research is to investigate the heat exchange process between heat transfer assemblies and to study of the effect of changing the distance between the fuel assemblies on their power taking into account the inter-radiating of assemblies. Materials and Methods: A general description of the process of heat transfer by radiation. A calculation study of the effect of geometric parameters on heat transfer in the close lattice of the reactor core is performed. The influence of heat transfer by radiation on the temperature change of the fuel assemblies surface of the VVER-1000 reactor at change in the cassette gap is studied. The change in the power of the fuel assemblies relative to the initial power with a change in the cassette gap was studied. Experimental measurements of the temperature at different distances from the radiation source were made with an obstacle in the path of radiation propagation in the form of glass and water of different levels. The heat radiation and convective heat transfer are calculated based on the obtained experimental data. The calculation of thermal radiation power and convective heat transfer based on the obtained experimental data is performed. Results: The calculation results show that in models that determine the temperature of the fuel assemblies in the core of the VVER-1000 reactor, the radiation heat transfer must be taken into account. In this case, the amount of transferred energy is the greater, the smaller the distance between objects. This is observed

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

Heat transfer enhancement of car radiator using aqua based magnesium oxide nanofluids

OpenAIRE

Ali Hafiz Muhammad; Azhar Muhammad Danish; Saleem Musab; Saeed Qazi Samie; Saieed Ahmed

2015-01-01

The focus of this research paper is on the application of water based MgO nanofluids for thermal management of a car radiator. Nanofluids of different volumetric concentrations (i.e. 0.06%, 0.09% and 0.12%) were prepared and then experimentally tested for their heat transfer performance in a car radiator. All concentrations showed enhancement in heat transfer compared to the pure base fluid. A peak heat transfer enhancement of 31% was obtained at 0.12 % vol...

Heat transfer from internally-heated molten UO2 pools

International Nuclear Information System (INIS)

Stein, R.P.; Baker, L. Jr.; Gunther, W.H.; Cook, C.

1978-01-01

Experimental measurements of heat transfer from internally heated pools of molten UO 2 have been obtained for two cell sizes: 10 cm x 10 cm and 20 cm x 20 cm. The experiments with the large cell have supported a previous conclusion from early small data that the measured downward heat fluxes are higher than would be expected on the basis of considerations of thermal convection. A convective model underpredicts the downward heat fluxes by a factor of 2.5 to 4.5 for all but one early experiment. Arbitrary assumptions of increased thermal conductivity do not account for the discrepancy. A single model based on internal thermal radiation heat transfer is able to account for the high values. The model uses the optically thick Rosseland approximation. Because of this, it is tentatively concluded that thermal radiation plays a dominant role in controlling the heat transfer from internally heated molted fuel

Heights integrated model as instrument for simulation of hydrodynamic, radiation transport, and heat conduction phenomena of laser-produced plasma in EUV applications.

Energy Technology Data Exchange (ETDEWEB)

Sizyuk, V.; Hassanein, A.; Morozov, V.; Sizyuk, T.; Mathematics and Computer Science

2007-01-16

The HEIGHTS integrated model has been developed as an instrument for simulation and optimization of laser-produced plasma (LPP) sources relevant to extreme ultraviolet (EUV) lithography. The model combines three general parts: hydrodynamics, radiation transport, and heat conduction. The first part employs a total variation diminishing scheme in the Lax-Friedrich formulation (TVD-LF); the second part, a Monte Carlo model; and the third part, implicit schemes with sparse matrix technology. All model parts consider physical processes in three-dimensional geometry. The influence of a generated magnetic field on laser plasma behavior was estimated, and it was found that this effect could be neglected for laser intensities relevant to EUV (up to {approx}10{sup 12} W/cm{sup 2}). All applied schemes were tested on analytical problems separately. Benchmark modeling of the full EUV source problem with a planar tin target showed good correspondence with experimental and theoretical data. Preliminary results are presented for tin droplet- and planar-target LPP devices. The influence of three-dimensional effects on EUV properties of source is discussed.

Experimental and numerical study on heat transfer enhancement of flat tube radiator using Al2O3 and CuO nanofluids

Science.gov (United States)

Alosious, Sobin; R, Sarath S.; Nair, Anjan R.; Krishnakumar, K.

2017-12-01

Forced convective heat transfer of Al2O3 and CuO nanofluids through flat tube automobile radiator were studied experimentally and numerically. Nanofluids of 0.05% volume concentrations were prepared with Al2O3 and CuO nanoparticles having diameter below 50 nm. The working fluid recirculates through an automobile flat tube radiator with constant inlet temperature of 90 °C. Experiments were conducted by using water and nanofluids by varying the Reynolds numbers from 136 to 816. The flat tube of the radiator with same dimensions were modeled and numerically studied the heat transfer. The model includes the thickness of tube wall and also considers the effect of fins in the radiator. Numerical studies were carried out for six different volume concentrations from 0.05% to 1% and Reynolds number varied between 136 and 816 for both nanofluids. The results show an enhancement in heat transfer coefficient and effectiveness of radiator with increase in Reynolds number and volume concentration. A maximum enhancement of 13.2% and 16.4% in inside heat transfer coefficient were obtained for 1% concentration of CuO and Al2O3 nanofluids respectively. However increasing the volume concentration causes an increase in viscosity and density, which leads to an increase in pumping power. For same heat rejection of water, the area of the radiator can be reduced by 2.1% and 2.9% by using 1% concentration of CuO and Al2O3 nanofluids respectively. The optimum values of volume concentration were found to be 0.4% to 0.8% in which heat transfer enhancement dominates pumping power increase. Al2O3 nanofluids gives the maximum heat transfer enhancement and stability compared to CuO nanofluids.

Free convection effects and radiative heat transfer in MHD Stokes ...

Indian Academy of Sciences (India)

... radiative heat transfer is useful for predicting the heat feedback to the burning surface ... petroleum technology, to study the movement of natural gas, oil and water ... (e.g. sea water, rain water, and sewage) past an impulsively started infinite ...

Fully coupled heat conduction and deformation analyses of nonlinear viscoelastic composites

KAUST Repository

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.

Heat loss from an open cavity

Energy Technology Data Exchange (ETDEWEB)

McDonald, C.G. [California State Polytechnic Univ., Pomona, CA (United States). Coll. of Engineering

1995-12-01

Cavity type receivers are used extensively in concentrating solar thermal energy collecting systems. The Solar Total Energy Project (STEP) in Shenandoah, Georgia is a large scale field test for the collection of solar thermal energy. The STEP experiment consists of a large field array of solar collectors used to supplement the process steam, cooling and other electrical power requirements of an adjacent knitwear manufacturing facility. The purpose of the tests, conducted for this study, was to isolate and quantify the radiative, conductive, and convective components of total heat loss, and to determine the effects of operating temperature, receiver angle, and aperture size on cavity heat loss. An analytical model for radiative heat loss was developed and compared with two other methods used to determine radiative heat loss. A proposed convective heat loss correlation, including effects of aperture size, receiver operating temperature, and receiver angle is presented. The resulting data is a source to evaluate the STEP measurements.

Radiative shocks with electron thermal conduction

International Nuclear Information System (INIS)

Borkowski, Kazimierz.

1988-01-01

The authors studies the influence of electron thermal conduction on radiative shock structure for both one- and two-temperature plasmas. The dimensionless ratio of the conductive length to the cooling length determines whether or not conduction is important, and shock jump conditions with conduction are established for a collisionless shock front. He obtains approximate solutions with the assumptions that the ionization state of the gas is constant and the cooling rate is a function of temperature alone. In the absence of magnetic fields, these solutions indicate that conduction noticeably influences normal-abundance interstellar shocks with velocities 50-100 km s -1 and dramatically affects metal-dominated shocks over a wide range of shock velocities. Magnetic fields inhibit conduction, but the conductive energy flux and the corresponding decrease in the post-shock electron temperature may still be appreciable. He calculates detailed steady-state radiative shock models in gas composed entirely of oxygen, with the purpose of explaining observations of fast-moving knots in Cas A and other oxygen-rich supernova remnants (SNRs). The O III ion, whose forbidden emission usually dominates the observed spectra, is present over a wide range of shock velocities, from 100 to 170 kms -1 . All models with conduction have extensive warm photoionization zones, which provides better agreement with observed optical (O I) line strengths. However, the temperatures in these zones could be lowered by (Si II) 34.8 μm and (Ne II) 12.8 μm cooling if Si and Ne are present in appreciable abundance relative to O. Such low temperatures would be inconsistent with the observed (O I) emission in oxygen-rich SNRs

Multiscale solutions of radiative heat transfer by the discrete unified gas kinetic scheme

Science.gov (United States)

Luo, Xiao-Ping; Wang, Cun-Hai; Zhang, Yong; Yi, Hong-Liang; Tan, He-Ping

2018-06-01

The radiative transfer equation (RTE) has two asymptotic regimes characterized by the optical thickness, namely, optically thin and optically thick regimes. In the optically thin regime, a ballistic or kinetic transport is dominant. In the optically thick regime, energy transport is totally dominated by multiple collisions between photons; that is, the photons propagate by means of diffusion. To obtain convergent solutions to the RTE, conventional numerical schemes have a strong dependence on the number of spatial grids, which leads to a serious computational inefficiency in the regime where the diffusion is predominant. In this work, a discrete unified gas kinetic scheme (DUGKS) is developed to predict radiative heat transfer in participating media. Numerical performances of the DUGKS are compared in detail with conventional methods through three cases including one-dimensional transient radiative heat transfer, two-dimensional steady radiative heat transfer, and three-dimensional multiscale radiative heat transfer. Due to the asymptotic preserving property, the present method with relatively coarse grids gives accurate and reliable numerical solutions for large, small, and in-between values of optical thickness, and, especially in the optically thick regime, the DUGKS demonstrates a pronounced computational efficiency advantage over the conventional numerical models. In addition, the DUGKS has a promising potential in the study of multiscale radiative heat transfer inside the participating medium with a transition from optically thin to optically thick regimes.

Design and Testing of an Active Heat Rejection Radiator with Digital Turn-Down Capability

Science.gov (United States)

Sunada, Eric; Birur, Gajanana C.; Ganapathi, Gani B.; Miller, Jennifer; Berisford, Daniel; Stephan, Ryan

2010-01-01

NASA's proposed lunar lander, Altair, will be exposed to vastly different external environment temperatures. The challenges to the active thermal control system (ATCS) are compounded by unfavorable transients in the internal waste heat dissipation profile: the lowest heat load occurs in the coldest environment while peak loads coincide with the warmest environment. The current baseline for this fluid is a 50/50 inhibited propylene glycol/water mixture with a freeze temperature around -35 C. While the overall size of the radiator's heat rejection area is dictated by the worst case hot scenario, a turn-down feature is necessary to tolerate the worst case cold scenario. A radiator with digital turn-down capability is being designed as a robust means to maintain cabin environment and equipment temperatures while minimizing mass and power consumption. It utilizes active valving to isolate and render ineffective any number of parallel flow tubes which span across the ATCS radiator. Several options were assessed in a trade-study to accommodate flow tube isolation and how to deal with the stagnant fluid that would otherwise remain in the tube. Bread-board environmental tests were conducted for options to drain the fluid from a turned-down leg as well an option to allow a leg to freeze/thaw. Each drain option involved a positive displacement gear pump with different methods of providing a pressure head to feed it. Test results showed that a start-up heater used to generate vapor at the tube inlet held the most promise for tube evacuation. Based on these test results and conclusions drawn from the trade-study, a full-scale radiator design is being worked for the Altair mission profile.

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

Thermal control system. [removing waste heat from industrial process spacecraft

Science.gov (United States)

Hewitt, D. R. (Inventor)

1983-01-01

The temperature of an exothermic process plant carried aboard an Earth orbiting spacecraft is regulated using a number of curved radiator panels accurately positioned in a circular arrangement to form an open receptacle. A module containing the process is insertable into the receptacle. Heat exchangers having broad exterior surfaces extending axially above the circumference of the module fit within arcuate spacings between adjacent radiator panels. Banks of variable conductance heat pipes partially embedded within and thermally coupled to the radiator panels extend across the spacings and are thermally coupled to broad exterior surfaces of the heat exchangers by flanges. Temperature sensors monitor the temperature of process fluid flowing from the module through the heat exchanges. Thermal conduction between the heat exchangers and the radiator panels is regulated by heating a control fluid within the heat pipes to vary the effective thermal length of the heat pipes in inverse proportion to changes in the temperature of the process fluid.

Fluctuation theory for transport properties in multicomponent mixtures: thermodiffusion and heat conductivity

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...

Effects of radiation and thermal diffusivity on heat transfer over a stretching surface with variable heat flux

International Nuclear Information System (INIS)

Seddeek, M.A.; Abdelmeguid, M.S.

2006-01-01

The effect of radiation and thermal diffusivity on heat transfer over a stretching surface with variable heat flux has been studied. The thermal diffusivity is assumed to vary as a linear function of temperature. The governing partial differential equations have been transformed to ordinary differential equations. The exact analytical solution for the velocity and the numerical solution for the temperature field are given. Numerical solutions are obtained for different values of variable thermal diffusivity, radiation, temperature parameter and Prandtl number

Research on high-temperature heat receiver in concentrated solar radiation system

Directory of Open Access Journals (Sweden)

Estera Przenzak

2017-01-01

Full Text Available The article presents the results of experimental and computer simulations studies of the high temperature heat receiver working in the concentrated solar radiation system. In order to study the radiation absorption process and heat exchange, the two types of computer simulations were carried out. The first one was used to find the best location for absorber in the concentrating installation. Ray Tracing Monte Carlo (RTMC method in Trace Pro software was used to perform the optical simulations. The results of these simulations were presented in the form of the solar radiation distribution map and chart. The data obtained in RTMC simulations were used as a second type boundary conditions for Computational Fluid Dynamics (CFD simulations. These studies were used to optimize the internal geometry of the receiver and also to select the most effective flow parameters of the working medium. In order to validate the computer simulations, high temperature heat receiver was tested in experimental conditions. The article presents the results of experimental measurements in the form of temperature, radiation intensity and power graphs. The tests were performed for varied flow rate and receiver location. The experimental and computer simulation studies presented in this article allowed to optimize the configuration of concentrating and heat receiving system.

A two-parameter nondiffusive heat conduction model for data analysis in pump-probe experiments

Science.gov (United States)

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.

Heat transfer in Rockwool modelling and method of measurement. The effect of natural convection on heat transfer in fibrous materials

Energy Technology Data Exchange (ETDEWEB)

Dyrboel, Susanne

1998-05-01

Fibrous materials are some of the most widely used materials for thermal insulation. In this project the focus of interest has been on fibrous materials for building application. Interest in improving the thermal properties of insulation materials is increasing as legislation is being tightened to reduce the overall energy consumption. A knowledge of the individual heat transfer mechanisms - whereby heat is transferred within a particular material is an essential tool to improve continuously the thermal properties of the material. Heat is transferred in fibrous materials by four different transfer mechanisms: conduction through air, conduction through fibres, thermal radiation and convection. In a particular temperature range the conduction through air can be regarded as a constant, and conduction through fibres is an insignificant part of the total heat transfer. Radiation, however, constitutes 25-40% of the total heat transfer in light fibrous materials. In Denmark and a number of other countries convection in fibrous materials is considered as non-existent when calculating heat transmission as well as when designing building structures. Two heat transfer mechanisms have been the focus of the current project: radiation heat transfer and convection. The radiation analysis serves to develop a model that can be used in further work to gain a wider knowledge of the way in which the morphology of the fibrous material, i.e. fibre diameter distribution, fibre orientation distribution etc., influences the radiation heat transfer under different conditions. The convection investigation serves to examine whether considering convection as non-existent is a fair assumption to use in present and future building structures. The assumption applied in practically is that convection makes a notable difference only in very thick insulation, at external temperatures below -20 deg. C, and at very low densities. For large thickness dimensions the resulting heat transfer through the

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.

Thermotronics: Towards Nanocircuits to Manage Radiative Heat Flux

Science.gov (United States)

Ben-Abdallah, Philippe; Biehs, Svend-Age

2017-02-01

The control of electric currents in solids is at the origin of the modern electronics revolution that has driven our daily life since the second half of 20th century. Surprisingly, to date, there is no thermal analogue for a control of heat flux. Here, we summarise the very last developments carried out in this direction to control heat exchanges by radiation both in near and far-field in complex architecture networks.

Thermotronics. Towards nanocircuits to manage radiative heat flux

International Nuclear Information System (INIS)

Ben-Abdallah, Philippe; Sherbrooke Univ., PQ; Biehs, Svend-Age

2017-01-01

The control of electric currents in solids is at the origin of the modern electronics revolution that has driven our daily life since the second half of 20 th century. Surprisingly, to date, there is no thermal analogue for a control of heat flux. Here, we summarise the very last developments carried out in this direction to control heat exchanges by radiation both in near and far-field in complex architecture networks.

Thermotronics. Towards nanocircuits to manage radiative heat flux

Energy Technology Data Exchange (ETDEWEB)

Ben-Abdallah, Philippe [Univ. Paris-Sud 11, Palaiseau (France). Lab. Charles Fabry; Sherbrooke Univ., PQ (Canada). Dept. of Mechanical Engineering; Biehs, Svend-Age [Oldenburg Univ. (Germany). Inst. fuer Physik

2017-05-01

The control of electric currents in solids is at the origin of the modern electronics revolution that has driven our daily life since the second half of 20{sup th} century. Surprisingly, to date, there is no thermal analogue for a control of heat flux. Here, we summarise the very last developments carried out in this direction to control heat exchanges by radiation both in near and far-field in complex architecture networks.

Effect of dose on radiation-induced conductivity in polymers

International Nuclear Information System (INIS)

Tyutnev, A.P.; Saenko, V.S.; Pozhidaev, E.D.; Ikhsanov, R.Sh.

2007-01-01

Numerical simulation of radiation-induced conductivity in polymers upon long-term irradiation on the basis of the generalized Rose-Fowler-Vaisberg model, which allows for both dipolar carrier transport and generation of radiation traps during irradiation, was performed. The unusual properties of radiation-induced conductivity, such as the appearance of a maximum on current transients, the absence of a steady state, and a substantial difference between these curves for the first and subsequent irradiation, are rationalized in terms of the formation of free radicals, the major feature of radiolysis in the chemical aspect. This interpretation does not require the involvement of degradation or crosslinking processes, unlike other interpretations that appear in the literature. With the use of low-density polyethylene as an example, it was shown that radiation-induced conductivity both upon pulse and continuous irradiation can satisfactorily be described with the unified set of parameters of the generalized Rose-Fowler-Vaisberg model [ru

ESTIMATION OF WORKING CONDITIONS OF FOUNDRY WORKERS BY INFRARED (HEAT RADIATION

Directory of Open Access Journals (Sweden)

A. M. Lazarenkov

2010-01-01

Full Text Available The description of infrared radiations, their influence on human organism is given. The results of investigation of infrared (heat radiation intensity on the workers in foundries are given.

Computer simulation of heating of biological tissue during laser radiation

International Nuclear Information System (INIS)

Bojanic, S.; Sreckovic, M.

1995-01-01

Computer model is based on an implicit finite difference scheme to solve the diffusion equation for light distribution and the bio-heat equation. A practical application of the model is to calculate the temperature distributions during thermal coagulation of prostate by radiative heating. (author)

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.

Influence of prehistory of polymer samples on radiation electric conductivity induced by ionizing radiation

Energy Technology Data Exchange (ETDEWEB)

Aleksanina, O S; Sichkar' , V P; Vajsberg, S Eh [Nauchno-Issledovatel' skij Fiziko-Khimicheskij Inst., Moscow (USSR)

1984-05-01

Radiation electric conductivity of PS films prepared from solutions in various solvents at various initial concentrations and temperatures and various power of absorbed dose (..gamma..-radiation of /sup 60/Co) has been measured. The results are compared with the change of density of films and existing theoretical concepts of the role of microvoids and free volume in electrical conductivity of a polymer.

Influence of prehistory of polymer samples on radiation electric conductivity induced by ionizing radiation

International Nuclear Information System (INIS)

Aleksanina, O.S.; Sichkar', V.P.; Vajsberg, S.Eh.

1984-01-01

Radiation electric conductivity of PS films prepared from solutions in various solvents at various initial concentrations and temperatures and various power of absorbed dose (γ-radiation of 60 Co) has been measured. The results are compared with the change of density of films and existing theoretical concepts of the role of microvoids and free volume in electrical conductivity of a polymer

Preliminary SP-100/Stirling heat exchanger designs

International Nuclear Information System (INIS)

Schmitz, P.; Tower, L.; Blue, B.; Dunn, P.

1994-01-01

Analytic modeling of several heat exchanger concepts to couple the SP-100 nuclear reactor lithium loop and the Space Stirling Power Convertor (SSPC) was performed. Four 25 kWe SSPC's are used to produce the required 100 kW of electrical power. This design work focused on the interface between a single SSPC and the primary lithium loop. Manifolding to separate and collect the four channel flow was not modeled. This work modeled two separate types of heat exchanger interfaces (conductive coupling and radiative coupling) to explore their relative advantages and disadvantages. The minimum mass design of the conductively coupled concepts was 18 kg or 0.73 kg/kWe for a single 25 kWe convertor. The minimum mass radiatively coupled concept was 41 kg or 1.64 kg/kWe. The direct conduction heat exchanger provides a lighter weight system because of its ability to operate the Stirling convertor evaporator at higher heat fluxes than those attainable by the radiatively coupled systems. Additionally the conductively coupled concepts had relatively small volumes and provide potentially simpler assembly. Their disadvantages were the tight tolerances and material joining problems associated with this refractory to superalloy interface. The advantages of the radiatively coupled designs were the minimal material interface problems

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.

Experimental analysis of heat conduction in a high diameter ratio annular gap filled with a rarefied gas

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.

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.

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.

Heat transfer including radiation and slag particles evolution in MHD channel-I

International Nuclear Information System (INIS)

Im, K.H.; Ahluwalia, R.K.

1980-01-01

Accurate estimates of convective and radiative heat transfer in the magnetohydrodynamic channel are provided. Calculations performed for a base load-size channel indicate that heat transfer by gas radiation almost equals that by convection for smooth walls, and amounts to 70% as much as the convective heat transfer for rough walls. Carbon dioxide, water vapor, and potassium atoms are the principal participating gases. The evolution of slag particles by homogeneous nucleation and condensation is also investigated. The particle-size spectrum so computed is later utilized to analyze the radiation enhancement by slag particles in the MHD diffuser. The impact of the slag particle spectrum on the selection of a workable and design of an efficient seed collection system is discussed

Drying characteristics of rough rice by far-infrared radiation heating

International Nuclear Information System (INIS)

Matsuoka, T.

1990-01-01

The relationship between the heat radiation characteristics of a far-infrared radiation heater and the drying characteristics of rough rice was investigated to determine the basic data required for utilization of far-infrared rays for drying rough rice. Results of investigations are discussed in detail

Scrape-off layer radiation and heat load to the ASDEX Upgrade LYRA divertor

International Nuclear Information System (INIS)

Kallenbach, A.; Kaufmann, M.; Coster, D.P.

1999-01-01

In 1997 the new 'LYRA' divertor went into operation at ASDEX Upgrade and, in parallel, the neutral beam heating power was increased to 20 MW by installation of a second injector leading to a P/R value of 12 MW/m. Experiments have shown that the ASDEX Upgrade LYRA divertor is capable of handling such high heating powers. There is an overall reduction of the maximum heat flux in the LYRA divertor by about a factor of 2 compared with the previous open divertor Div I. This reduction is mainly due to increased radiative losses inside the divertor region, which are caused by an effective reflection of hydrogen neutrals into the hot separatrix region. The main channel of radiative loss is carbon radiation, which cools the divertor plasma down to a few electronvolts, where hydrogen radiation losses become significant. The radiative losses preferentially reduce the power flux at the separatrix, leading to early detachment around the strike point position. With increasing density, the detached region extends upwards on the vertical target. The power fraction radiated in the LYRA divertor is around 45% and nearly independent of the heating power. This value is a factor of 2 higher than the typical radiation fraction in Div I. B2-EIRENE modelling of the performed experiments supports the experimental finding and refines the understanding of loss processes in the divertor region. (author)

Environmental microbiology as related to planetary quarantine. [synergetic effect of heat and radiation

Science.gov (United States)

Pflug, I. J.

1973-01-01

The mechanistic basis of the synergetic effect of combined heat and radiation on microbial destruction was analyzed and results show that radiation intensity, temperature, and relative humidity are the determining factors. Dry heat resistance evaluation for selected bacterial spore crops indicates that different strains of Bacillus stearothermophilus demonstrate marked differences in resistance. Preliminary work to determine the effects of storage time, suspending medium, storage temperature and spore crop cleaning procedures on dry heat survival characteristics of Bacillus subtilis var. Niger, and dry heat resistance of natural microflora in soil particles is also reported.

Information filtering via weighted heat conduction algorithm

Science.gov (United States)

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.

Radiation and convective heat transfer, and burnout in oxy-coal combustion

Energy Technology Data Exchange (ETDEWEB)

J.P. Smart; P. O' Nions; G.S. Riley [RWE npower, Swindon (United Kingdom)

2010-09-15

Measurements of radiative and convective heat transfer, and carbon-in-ash have been taken on the RWEn 0.5 MWth combustion test facility (CTF) firing two different coals under oxy-fuel firing conditions. The two coals fired were a Russian Coal and a South African Coal. Recycle ratios were varied within the range of 65-75% dependent on coal. Furnace exit O{sub 2} values were maintained at 3% and 6% for the majority of tests. Air firing tests were also performed to generate baseline data. The work gives a comprehensive insight into the effect of oxy-fuel combustion on both radiative and convective heat transfer, and carbon-in-ash compared to air under dry simulated recycle conditions. Results have shown peak radiative heat flux values are inversely related to the recycle ratio for the two coals studied. Conversely, the convective heat flux values increase with increasing recycle ratio. It was also observed that the axial position of the peak in radiative heat flux moves downstream away from the burner as recycle ratio is increased. A 'working range' of recycle ratios exists where both the radiative and convective heat fluxes are comparable with air. Carbon-in-ash (CIA) was measured for selected conditions. For air firing of Russian Coal, the CIA for follows and expected trend with CIA decreasing with increasing furnace exit O{sub 2}. The CIA data for the two recycle ratios of 72% and 68% for the same coal show that the CIA values are lower than for air firing for corresponding furnace exit O{sub 2} levels and vary little with the value of furnace exit O{sub 2}. CIA measurements were taken for the South African Coal for a range of recycle ratios at 3% and 6% furnace exit O{sub 2} levels. Results indicate that the CIA values are lower for higher furnace exit O{sub 2}. 32 refs., 11 figs., 1 tab.

Numerical simulation of heat transfer process in solar enhanced natural draft dry cooling tower with radiation model

International Nuclear Information System (INIS)

Wang, Qiuhuan; Zhu, Jialing; Lu, Xinli

2017-01-01

Graphical abstract: A 3-D numerical model integrated with a discrete ordinate (DO) solar radiation model (considering solar radiation effect in the room of solar collector) was developed to investigate the influence of solar radiation intensity and ambient pressure on the efficiency and thermal characteristics of the SENDDCT. Our study shows that introducing such a radiation model can more accurately simulate the heat transfer process in the SENDDCT. Calculation results indicate that previous simulations overestimated solar energy obtained by the solar collector and underestimated the heat loss. The cooling performance is improved when the solar radiation intensity or ambient pressure is high. Air temperature and velocity increase with the increase of solar radiation intensity. But ambient pressure has inverse effects on the changes of air temperature and velocity. Under a condition that the solar load increases but the ambient pressure decreases, the increased rate of heat transferred in the heat exchanger is not obvious. Thus the performance of the SENDDCT not only depends on the solar radiation intensity but also depends on the ambient pressure. - Highlights: • A radiation model has been introduced to accurately simulate heat transfer process. • Heat transfer rate would be overestimated if the radiation model was not introduced. • The heat transfer rate is approximately proportional to solar radiation intensity. • The higher the solar radiation or ambient pressure, the better SENDDCT performance. - Abstract: Solar enhanced natural draft dry cooling tower (SENDDCT) is more efficient than natural draft dry cooling tower by utilizing solar radiation in arid region. A three-dimensional numerical model considering solar radiation effect was developed to investigate the influence of solar radiation intensity and ambient pressure on the efficiency and thermal characteristics of SENDDCT. The numerical simulation outcomes reveal that a model with consideration of

Design and Fabrication of a Composite Morphing Radiator Panel Using High Conductivity Fibers

Science.gov (United States)

Wescott, Matthew T.; McQuien, J. Scott; Bertagne, Christopher L.; Whitcomb, John D.; Hart, Darren J.; Erickson, Lisa R.

2017-01-01

Upcoming crewed space missions will involve large internal and external heat loads and require advanced thermal control systems to maintain a desired internal environment temperature. Radiators with at least 12:1 turndown ratios (the ratio between the maximum and minimum heat rejection rates) will be needed. However, current technologies are only able to achieve turndown ratios of approximately 3:1. A morphing radiator capable of altering shape could significantly increase turndown capabilities. Shape memory alloys offer qualities that may be well suited for this endeavor; their temperature-dependent phase changes could offer radiators the ability to passively control heat rejection. In 2015, a morphing radiator prototype was constructed and tested in a thermal vacuum environment, where it successfully demonstrated the morphing behavior and variable heat rejection. Newer composite prototypes have since been designed and manufactured using two distinct types of SMA materials. These models underwent temperature cycling tests in a thermal vacuum chamber and a series of fatigue tests to characterize the lifespan of these designs. The focus of this paper is to present the design approach and testing of the morphing composite facesheet. The discussion includes: an overall description of the project background, definition of performance requirements, composite materials selection, use of analytic and numerical design tools, facesheet fabrication, and finally fatigue testing with accompanying results.

Effects of variable properties on MHD heat and mass transfer flow near a stagnation point towards a stretching sheet in a porous medium with thermal radiation

International Nuclear Information System (INIS)

Salem, A. M.; Fathy, Rania

2012-01-01

The effect of variable viscosity and thermal conductivity on steady magnetohydrodynamic (MHD) heat and mass transfer flow of viscous and incompressible fluid near a stagnation point towards a permeable stretching sheet embedded in a porous medium are presented, taking into account thermal radiation and internal heat genberation/absorbtion. The stretching velocity and the ambient fluid velocity are assumed to vary linearly with the distance from the stagnation point. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing fundamental equations are first transformed into a system of ordinary differential equations using a scaling group of transformations and are solved numerically by using the fourth-order Rung—Kutta method with the shooting technique. A comparison with previously published work has been carried out and the results are found to be in good agreement. The results are analyzed for the effect of different physical parameters, such as the variable viscosity and thermal conductivity, the ratio of free stream velocity to stretching velocity, the magnetic field, the porosity, the radiation and suction/injection on the flow, and the heat and mass transfer characteristics. The results indicate that the inclusion of variable viscosity and thermal conductivity into the fluids of light and medium molecular weight is able to change the boundary-layer behavior for all values of the velocity ratio parameter λ except for λ = 1. In addition, the imposition of fluid suction increases both the rate of heat and mass transfer, whereas fluid injection shows the opposite effect. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Studi Eksperimen Pengaruh Variasi Kecepatan Udara Terhadap Performa Heat Exchanger Jenis Compact Heat Exchanger (Radiator) Dengan Susunan Tube Inline Sebagai Pemanas Pada Sistem Pengeringan Batubara

OpenAIRE

Irvan Paramananda; Prabowo Prabowo

2014-01-01

Pengeringan yang dilakukan pada batu bara dengan memanfaatkan udara panas menggunakan konsep heat exchanger. Salah satu heat exchanger yang sering digunakan adalah heat exchanger dengan tipe single row-fin tube yaitu radiator. Radiator ini akan dimanfaatkan sebagai penghasil udara panas dari air panas yang mengalir dan dihembuskan oleh kipas radiator. Penelitian ini difokuskan pada effectiveness dari komponen radiator fungsi dari kecepatan udara mulai dari kecepatan 1 m/s, 2 m/s, 3 m/s, 4 m/s...

Analytical heat transfer modeling of a new radiation calorimeter

Energy Technology Data Exchange (ETDEWEB)

Obame Ndong, Elysée [Department of Industrial Engineering and Maintenance, University of Sciences and Technology of Masuku (USTM), BP 941 Franceville (Gabon); Grenoble Electrical Engineering Laboratory (G2Elab), University Grenoble Alpes and CNRS, G2Elab, F38000 Grenoble (France); Gallot-Lavallée, Olivier [Grenoble Electrical Engineering Laboratory (G2Elab), University Grenoble Alpes and CNRS, G2Elab, F38000 Grenoble (France); Aitken, Frédéric, E-mail: frederic.aitken@g2elab.grenoble-inp.fr [Grenoble Electrical Engineering Laboratory (G2Elab), University Grenoble Alpes and CNRS, G2Elab, F38000 Grenoble (France)

2016-06-10

Highlights: • Design of a new calorimeter for measuring heat power loss in electrical components. • The calorimeter can operate in a temperature range from −50 °C to 150 °C. • An analytical model of heat transfers for this new calorimeter is presented. • The theoretical sensibility of the new apparatus is estimated at ±1 mW. - Abstract: This paper deals with an analytical modeling of heat transfers simulating a new radiation calorimeter operating in a temperature range from −50 °C to 150 °C. The aim of this modeling is the evaluation of the feasibility and performance of the calorimeter by assessing the measurement of power losses of some electrical devices by radiation, the influence of the geometry and materials. Finally a theoretical sensibility of the new apparatus is estimated at ±1 mW. From these results the calorimeter has been successfully implemented and patented.

Analytical heat transfer modeling of a new radiation calorimeter

International Nuclear Information System (INIS)

Obame Ndong, Elysée; Gallot-Lavallée, Olivier; Aitken, Frédéric

2016-01-01

Highlights: • Design of a new calorimeter for measuring heat power loss in electrical components. • The calorimeter can operate in a temperature range from −50 °C to 150 °C. • An analytical model of heat transfers for this new calorimeter is presented. • The theoretical sensibility of the new apparatus is estimated at ±1 mW. - Abstract: This paper deals with an analytical modeling of heat transfers simulating a new radiation calorimeter operating in a temperature range from −50 °C to 150 °C. The aim of this modeling is the evaluation of the feasibility and performance of the calorimeter by assessing the measurement of power losses of some electrical devices by radiation, the influence of the geometry and materials. Finally a theoretical sensibility of the new apparatus is estimated at ±1 mW. From these results the calorimeter has been successfully implemented and patented.

Modeling Loss-of-Flow Accidents and Their Impact on Radiation Heat Transfer

Directory of Open Access Journals (Sweden)

Jivan Khatry

2017-01-01

Full Text Available Long-term high payload missions necessitate the need for nuclear space propulsion. The National Aeronautics and Space Administration (NASA investigated several reactor designs from 1959 to 1973 in order to develop the Nuclear Engine for Rocket Vehicle Application (NERVA. Study of planned/unplanned transients on nuclear thermal rockets is important due to the need for long-term missions. In this work, a system model based on RELAP5 is developed to simulate loss-of-flow accidents on the Pewee I test reactor. This paper investigates the radiation heat transfer between the fuel elements and the structures around it. In addition, the impact on the core fuel element temperature and average core pressure was also investigated. The following expected results were achieved: (i greater than normal fuel element temperatures, (ii fuel element temperatures exceeding the uranium carbide melting point, and (iii average core pressure less than normal. Results show that the radiation heat transfer rate between fuel elements and cold surfaces increases with decreasing flow rate through the reactor system. However, radiation heat transfer decreases when there is a complete LOFA. When there is a complete LOFA, the peripheral coolant channels of the fuel elements handle most of the radiation heat transfer. A safety system needs to be designed to counteract the decay heat resulting from a post-LOFA reactor scram.

Heat transfer enhancement of car radiator using aqua based magnesium oxide nanofluids

Directory of Open Access Journals (Sweden)

Ali Hafiz Muhammad

2015-01-01

Full Text Available The focus of this research paper is on the application of water based MgO nanofluids for thermal management of a car radiator. Nanofluids of different volumetric concentrations (i.e. 0.06%, 0.09% and 0.12% were prepared and then experimentally tested for their heat transfer performance in a car radiator. All concentrations showed enhancement in heat transfer compared to the pure base fluid. A peak heat transfer enhancement of 31% was obtained at 0.12 % volumetric concentration of MgO in basefluid. The fluid flow rate was kept in a range of 8-16 liter per minute. Lower flow rates resulted in greater heat transfer rates as compared to heat transfer rates at higher flow rates for the same volumetric concentration. Heat transfer rates were found weakly dependent on the inlet fluid temperature. An increase of 8°C in inlet temperature showed only a 6% increase in heat transfer rate.

Solid state radiative heat pump

Science.gov (United States)

Berdahl, P.H.

1984-09-28

A solid state radiative heat pump operable at room temperature (300 K) utilizes a semiconductor having a gap energy in the range of 0.03-0.25 eV and operated reversibly to produce an excess or deficit of change carriers as compared equilibrium. In one form of the invention an infrared semiconductor photodiode is used, with forward or reverse bias, to emit an excess or deficit of infrared radiation. In another form of the invention, a homogenous semiconductor is subjected to orthogonal magnetic and electric fields to emit an excess or deficit of infrared radiation. Three methods of enhancing transmission of radiation the active surface of the semiconductor are disclosed. In one method, an anti-refection layer is coated into the active surface of the semiconductor, the anti-reflection layer having an index of refraction equal to the square root of that of the semiconductor. In the second method, a passive layer is speaced trom the active surface of the semiconductor by a submicron vacuum gap, the passive layer having an index of refractive equal to that of the semiconductor. In the third method, a coupler with a paraboloid reflecting surface surface is in contact with the active surface of the semiconductor, the coupler having an index of refraction about the same as that of the semiconductor.

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

Thermal-hydraulic analysis of the improved TOPAZ-II power system using a heat pipe radiator

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wenwen; Zhang, Dalin, E-mail: dlzhang@mail.xjtu.edu.cn; Tian, Wenxi; Qiu, Suizheng; Su, G.H.

2016-10-15

Highlights: • The system thermal-hydraulic model of the improved space thermionic reactor is developed. • The temperature reactivity feedback effects of the moderator, UO2 fuel, electrodes and reflector are considered. • The alkali metal heat pipe radiator is modeled with the two dimensional heat pipe model. • The steady state and the start-up procedure of the system are analyzed. - Abstract: A system analysis code coupled with the heat pipe model is developed to analyze the thermal-hydraulic characteristics of the improved TOPAZ-II reactor power system with a heat pipe radiator. The core thermal-hydraulic model, neutron physics model, and the coolant loop component models (including pump, volume accumulator, pipes and plenums) are established. The designed heat pipe radiator, which replaces the original pumped loop radiator, is also modeled, including two-dimensional heat pipe analysis model, fin model and coolant transport duct model. The system analysis code and the heat pipe model is coupled in the transport duct model. Steady state condition and start-up procedure of the improved TOPAZ-II system are calculated. The results show that the designed radiator can satisfy the waste heat rejection requirement of the improved power system. Meanwhile, the code can be used to obtained the thermal characteristics of the system transients such as the start-up process.

Microwave Heating of a Liquid Stably Flowing in a Circular Channel Under the Conditions of Nonstationary Radiative-Convective Heat Transfer

Science.gov (United States)

Salomatov, V. V.; Puzyrev, E. M.; Salomatov, A. V.

2018-05-01

A class of nonlinear problems of nonstationary radiative-convective heat transfer under the microwave action with a small penetration depth is considered in a stabilized coolant flow in a circular channel. The solutions to these problems are obtained, using asymptotic procedures at the stages of nonstationary and stationary convective heat transfer on the heat-radiating channel surface. The nonstationary and stationary stages of the solution are matched, using the "longitudinal coordinate-time" characteristic. The approximate solutions constructed on such principles correlate reliably with the exact ones at the limiting values of the operation parameters, as well as with numerical and experimental data of other researchers. An important advantage of these solutions is that they allow the determination of the main regularities of the microwave and thermal radiation influence on convective heat transfer in a channel even before performing cumbersome calculations. It is shown that, irrespective of the heat exchange regime (nonstationary or stationary), the Nusselt number decreases and the rate of the surface temperature change increases with increase in the intensity of thermal action.

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

Science.gov (United States)

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.

Dynamic simulation of space heating systems with radiators controlled by TRVs in buildings

Energy Technology Data Exchange (ETDEWEB)

Xu, Baoping; Fu, Lin; Di, Hongfa [Department of Building Science, School of Architecture, Tsinghua University, Beijing 100084 (China)

2008-07-01

The objective of this paper is to develop a model for simulating the thermal and hydraulic behavior of space heating systems with radiators controlled by thermostat valves (TRVs) in multi-family buildings. This is done by treating the building and the heating system as a complete entity. Sub-models for rooms, radiators, TRVs, and the hydraulic network are derived. Then the suggested sub-models are combined to form an integrated model by considering interactions between them. The proposed model takes into account the heat transfer between neighboring rooms, the transport delay in the radiator, the self-adjusting function of the TRV, and the consumer's regulation behavior, as well as the hydraulic interactions between consumers. To test the model, two space heating systems in Beijing and Tianjin were investigated, and the model was validated under three operation modes. There was good agreement between the measured and simulated values for room temperature, return water temperature, and flow rate. A modeling analysis case was given based on an existing building and heating system. It was found that when the set value of the TRVs were kept on 2-3, about 12.4% reduction of heat consumption could be gained, compared with the situation in which the TRVs were kept fully open. The water flow rate was an important index that truly reflected the heat load change. It was also noted that if the flow rate or supply water temperature changed much during the transport delay time in the radiator, ignoring the transport delay would introduce an obvious deviation of the simulation results. Additionally, when an apartment stopped using the heating system during a heating season, the heat consumption of its neighboring apartments would be increased about 6-14%. (author)

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

Science.gov (United States)

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.

Effect of thermal radiation and suction on convective heat transfer of nanofluid along a wedge in the presence of heat generation/absorption

Energy Technology Data Exchange (ETDEWEB)

Kasmani, Ruhaila Md; Bhuvaneswari, M. [Centre for Foundation Studies in Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Sivasankaran, S.; Siri, Zailan [Institute of Mathematical Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2015-10-22

An analysis is presented to find the effects of thermal radiation and heat generation/absorption on convection heat transfer of nanofluid past a wedge in the presence of wall suction. The governing partial differential equations are transformed into a system of ordinary differential equations using similarity transformation. The resulting system is solved numerically using a fourth-order Runge–Kutta method with shooting technique. Numerical computations are carried out for different values of dimensionless parameters to predict the effects of wedge angle, thermophoresis, Brownian motion, heat generation/absorption, thermal radiation and suction. It is found that the temperature increases significantly when the value of the heat generation/absorption parameter increases. But the opposite observation is found for the effect of thermal radiation.

Introduction to heat transfer

CERN Document Server

SUNDÉN, B

2012-01-01

Presenting the basic mechanisms for transfer of heat, Introduction to Heat Transfer gives a deeper and more comprehensive view than existing titles on the subject. Derivation and presentation of analytical and empirical methods are provided for calculation of heat transfer rates and temperature fields as well as pressure drop. The book covers thermal conduction, forced and natural laminar and turbulent convective heat transfer, thermal radiation including participating media, condensation, evaporation and heat exchangers.

Performance analysis and optimization of radiating fins with a step change in thickness and variable thermal conductivity by homotopy perturbation method

Science.gov (United States)

Arslanturk, Cihat

2011-02-01

Although tapered fins transfer more rate of heat per unit volume, they are not found in every practical application because of the difficulty in manufacturing and fabrications. Therefore, there is a scope to modify the geometry of a constant thickness fin in view of the less difficulty in manufacturing and fabrication as well as betterment of heat transfer rate per unit volume of the fin material. For the better utilization of fin material, it is proposed a modified geometry of new fin with a step change in thickness (SF) in the literature. In the present paper, the homotopy perturbation method has been used to evaluate the temperature distribution within the straight radiating fins with a step change in thickness and variable thermal conductivity. The temperature profile has an abrupt change in the temperature gradient where the step change in thickness occurs and thermal conductivity parameter describing the variation of thermal conductivity has an important role on the temperature profile and the heat transfer rate. The optimum geometry which maximizes the heat transfer rate for a given fin volume has been found. The derived condition of optimality gives an open choice to the designer.

Measurement of heat transfers in cryogenic tank with several configurations

International Nuclear Information System (INIS)

Khemis, O.; Bessaieh, R.; Ait Ali, M.; Francois, M.X.

2004-01-01

The work presented here concerns the measurement of heat transfer in a cryogenic tank with several configurations. The experimental test incorporates the conductive heat in the neck, the convection heat transfers between the inner wall of the neck and the ascending vapor resulting from boiling, and the radiation heat transfers between the external envelope and the tank through a vacuum of 10 -8 mm Hg. An experimental prototype was produced in collaboration with the nuclear center of Orsay in France according to a didactic design, which takes into account the Wexler effect and the importance of the radiation compared to the conduction-convection heat transfer. The addition of a screen radiative ventilated with variable position on the neck (which can effectively replace several tens of floating screens), in order to find the optimal position, which minimizes the radiation flux, is presented in this paper

Radiation budget, soil heat flux and latent heat flux at the forest floor in warm, temperate mixed forest

International Nuclear Information System (INIS)

Tamai, K.; Abe, T.; Araki, M.; Ito, H.

1998-01-01

Seasonal changes in the radiation budget and soil heat flux of a forest floor were measured in a mixed forest located in Kyoto, Japan. The basal area at breast height in the survey forest was about 15·82 m 2 ha −1 , for evergreen trees, and 12·46 m 2 ha −1 , for deciduous trees. The sky view factor was 16 and 22% at the survey site in the foliate and defoliate seasons, respectively. The small difference between the sky view factor in the two seasons was reflected in the seasonal change in the radiation budget of the forest floor. Namely, the net long-wave radiation changed rapidly in leafing and falling days, and the rate of net short-wave radiation was highest in April. The distinctive characteristic of the radiation budget was that the rates of available radiation in the daytime and at night were almost equal in September and October. Latent heat flux at the forest floor was estimated to be around 94 MJ m −2 annually, from our measurement with the simulation model. (author)

Radiation losses and global energy balance for Ohmically heated discharges in ASDEX

International Nuclear Information System (INIS)

Mueller, E.R.; Behringer, K.; Niedermeyer, H.

1982-01-01

Global energy balance, radiation profiles and dominant impurity radiation sources are compared for Ohmically heated limiter and divertor discharges in the ASDEX tokamak. In discharges with a poloidal stainless-steel limiter, total radiation from the plasma is the dominant energy loss channel. The axisymmetric divertor reduces this volume-integrated radiation to 30-35% of the heating power and additional Ti-gettering halves it again to 10-15%. Local radiation losses in the plasma centre, which are mainly due to the presence of iron impurity ions, are reduced by about one order of magnitude. In high-current (Isub(p) = 400 kA) and high-density (nsub(e)-bar = 6 x 10 13 cm -3 ) ungettered divertor discharges, up to 55% of the heating power is dumped into a cold-gas target inside the divertor chambers. The bolometrically detected volume power losses in the chambers can mainly be attributed to neutral hydrogen atoms with kinetic energies of a few eV. In this parameter range, the divertor plasma is dominated by inelastic molecular and atomic processes, the main process being Franck-Condon dissociation of H 2 molecules. (author)

Ocean heat content and Earth's radiation imbalance. II. Relation to climate shifts

International Nuclear Information System (INIS)

Douglass, D.H.; Knox, R.S.

2012-01-01

In an earlier study of ocean heat content (OHC) we showed that Earth's empirically implied radiation imbalance has undergone abrupt changes. Other studies have identified additional such climate shifts since 1950. The shifts can be correlated with features in recently updated OHC data. The implied radiation imbalance may possibly alternate in sign at dates close to the climate shifts. The most recent shifts occurred during 2001–2002 and 2008–2009. The implied radiation imbalance between these dates, in the direction of ocean heat loss, was −0.03±0.06 W/m 2 , with a possible systematic error of [−0.00,+0.09] W/m 2 . -- Highlights: ► Ocean heat content (OHC) slope discontinuities match similar Earth climate features. ► OHC slopes between climate shifts give most of the implied radiation balance (IRI). ► IRI often alternates in sign at dates close to the climate shifts. ► IRI between climate shifts of 2001–2002 and 2008–2009 was −0.03±0.06 W/m 2 . ► Geothermal flux is relevant to analyses of radiation imbalance.

Analytical minimization of overall conductance and heat transfer area in refrigeration and heat pump systems and its numerical confirmation

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

Ocean heat content and Earth's radiation imbalance

International Nuclear Information System (INIS)

Douglass, David H.; Knox, Robert S.

2009-01-01

Earth's radiation imbalance is determined from ocean heat content data and compared with results of direct measurements. Distinct time intervals of alternating positive and negative values are found: 1960-mid-1970s (-0.15), mid-1970s-2000 (+0.15), 2001-present (-0.2 W/m 2 ), and are consistent with prior reports. These climate shifts limit climate predictability.

Hydromagnetic nonlinear thermally radiative nanoliquid flow with Newtonian heat and mass conditions

Directory of Open Access Journals (Sweden)

Muhammad Ijaz Khan

Full Text Available This paper communicates the analysis of MHD three-dimensional flow of Jeffrey nanoliquid over a stretchable surface. Flow due to a bidirectional surface is considered. Heat and mass transfer subject to volume fraction of nanoparticles, heat generation and nonlinear solar radiation are examined. Newtonian heat and mass transportation conditions are employed at surface. Concept of boundary layer is utilized to developed the mathematical problem. The boundary value problem is dictated by ten physical parameters: Deborah number, Hartman number, ratio of stretching rates, thermophoretic parameter, Brownian motion parameter, Prandtl number, temperature ratio parameter, conjugate heat and mass parameters and Lewis number. Convergent solutions are obtained using homotopic procedure. Convergence zone for obtained results is explicitly identified. The obtained solutions are interpreted physically. Keywords: Hydromagnetic flow, Viscoelastic nanofluid, Thermophoretic and Brownian moment, Nonlinear thermal radiation, Heat generation

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

Science.gov (United States)

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.

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.

Effect of radiative transfer of heat released from combustion reaction on temperature distribution: A numerical study for a 2-D system

International Nuclear Information System (INIS)

Zhou Huaichun; Ai Yuhua

2006-01-01

Both light and heat are produced during a chemical reaction in a combustion process, but traditionally all the energy released is taken as to be transformed into the internal energy of the combustion medium. So the temperature of the medium increases, and then the thermal radiation emitted from it increases too. Chemiluminescence is generated during a chemical reaction and independent of the temperature, and has been used widely for combustion diagnostics. It was assumed in this paper that the total energy released in a combustion reaction is divided into two parts, one part is a self-absorbed heat, and the other is a directly emitted heat. The former is absorbed immediately by the products, becomes the internal energy and then increases the temperature of the products as treated in the traditional way. The latter is emitted directly as radiation into the combustion domain and should be included in the radiation transfer equation (RTE) as a part of radiation source. For a simple, 2-D, gray, emitting-absorbing, rectangular system, the numerical study showed that the temperatures in reaction zones depended on the fraction of the directly emitted energy, and the smaller the gas absorption coefficient was, the more strong the dependence appeared. Because the effect of the fraction of the directly emitted heat on the temperature distribution in the reacting zones for gas combustion is significant, it is required to conduct experimental measurements to determine the fraction of self-absorbed heat for different combustion processes

Surface temperatures in New York City: Geospatial data enables the accurate prediction of radiative heat transfer.

Science.gov (United States)

Ghandehari, Masoud; Emig, Thorsten; Aghamohamadnia, Milad

2018-02-02

Despite decades of research seeking to derive the urban energy budget, the dynamics of thermal exchange in the densely constructed environment is not yet well understood. Using New York City as a study site, we present a novel hybrid experimental-computational approach for a better understanding of the radiative heat transfer in complex urban environments. The aim of this work is to contribute to the calculation of the urban energy budget, particularly the stored energy. We will focus our attention on surface thermal radiation. Improved understanding of urban thermodynamics incorporating the interaction of various bodies, particularly in high rise cities, will have implications on energy conservation at the building scale, and for human health and comfort at the urban scale. The platform presented is based on longwave hyperspectral imaging of nearly 100 blocks of Manhattan, in addition to a geospatial radiosity model that describes the collective radiative heat exchange between multiple buildings. Despite assumptions in surface emissivity and thermal conductivity of buildings walls, the close comparison of temperatures derived from measurements and computations is promising. Results imply that the presented geospatial thermodynamic model of urban structures can enable accurate and high resolution analysis of instantaneous urban surface temperatures.

Tumor necrosis factor alpha selectively sensitizes human immunodeficiency virus-infected cells to heat and radiation

International Nuclear Information System (INIS)

Wong, G.H.; McHugh, T.; Weber, R.; Goeddel, D.V.

1991-01-01

We report here that infection of the human T-cell line HUT-78 with human immunodeficiency virus (HIV) increases its sensitivity to heat and radiation toxicity. A possible explanation for this result may be the reduced expression of manganous superoxide dismutase (MnSOD) in HIV-infected cells compared to uninfected cells. Tumor necrosis factor alpha (TNF-alpha) further sensitizes HIV-infected cells but not uninfected cells to heat and radiation. This is consistent with the ability of TNF-alpha to induce the expression of MnSOD in uninfected but not in HIV-infected cells. HIV-infected HUT-78 cell lines engineered to overexpress MnSOD are more resistant to heat and radiation than HIV-infected cells that do not overexpress MnSOD. However, treatment with TNF-alpha still sensitizes these cells to heat and radiation

Human local and total heat losses in different temperature.

Science.gov (United States)

Wang, Lijuan; Yin, Hui; Di, Yuhui; Liu, Yanfeng; Liu, Jiaping

2016-04-01

This study investigates the effects of operative temperature on the local and total heat losses, and the relationship between the heat loss and thermal sensation. 10 local parts of head, neck, chest, abdomen, upper arm, forearm, hand, thigh, leg and foot are selected. In all these parts, convection, radiation, evaporation, respiration, conduction and diffusion heat losses are analyzed when operative temperature is 23, 28, 33 and 37 °C. The local heat losses show that the radiation and convection heat losses are mainly affected by the area of local body, and the heat loss of the thigh is the most in the ten parts. The evaporation heat loss is mainly affected by the distribution of sweat gland, and the heat loss of the chest is the most. The total heat loss of the local body shows that in low temperature, the thigh, leg and chest have much heat loss, while in high temperature, the chest, abdomen, thigh and head have great heat loss, which are useful for clothing design. The heat losses of the whole body show that as the operative temperature increases, the radiation and convection heat losses decrease, the heat losses of conduction, respiration, and diffusion are almost constant, and the evaporation heat loss increases. By comparison, the heat loss ratios of the radiation, convection and sweat evaporation, are in agreement with the previous researches. At last, the formula about the heat loss ratio of convection and radiation is derived. It's useful for thermal comfort evaluation and HVAC (heating, ventilation and air conditioning) design. Copyright © 2016 Elsevier Inc. All rights reserved.

Heat transfer analysis of the waste-container sleeve/salt configuration

International Nuclear Information System (INIS)

Callahan, G.D.; Ratigan, J.L.; Russell, J.E.; Fossum, A.F.

1975-01-01

Prior to this investigation, the heat transport considered was only that of straight conduction. The waste container, air gap, and sleeve arrangement was considered to be a single, consistent, time-dependent, heat-generating unit in intimate contact with the salt. The conduction model does not accurately model the heat transfer mechanisms available. Thus radiation and combined radiation and convection must also be considered in the determination of the temperature field. As would be expected, the canister temperatures are higher for the case of radiation across the airgap than those that result from conduction when the canister is in intimate contact with the salt. For the radiation case, the canister temperatures rise rapidly to a temperature of approximately 1,140 0 F and maintain an almost steady state condition for one year whereafter the temperatures slowly decrease. The far field temperatures, near the pillar centerline, are essentially equivalent for all cases. As time proceeds, the far field temperatures of the conduction models are about 15% different

Unsteady Hydromagnetic Flow of Radiating Fluid Past a Convectively Heated Vertical Plate with the Navier Slip

Directory of Open Access Journals (Sweden)

O. D. Makinde

2014-01-01

Full Text Available This paper investigates the unsteady hydromagnetic-free convection of an incompressible electrical conducting Boussinesq’s radiating fluid past a moving vertical plate in an optically thin environment with the Navier slip, viscous dissipation, and Ohmic and Newtonian heating. The nonlinear partial differential equations governing the transient problem are obtained and tackled numerically using a semidiscretization finite difference method coupled with Runge-Kutta Fehlberg integration technique. Numerical data for the local skin friction coefficient and the Nusselt number have been tabulated for various values of parametric conditions. Graphical results for the fluid velocity, temperature, skin friction, and the Nusselt number are presented and discussed. The results indicate that the skin friction coefficient decreases while the heat transfer rate at the plate surface increases as the slip parameter and Newtonian heating increase.