Showing papers on "Thermal radiation published in 1979"

Radiative processes in astrophysics

Abstract: Chapter 1 Fundamentals of Radiative Transfer 1.1 The Electromagnetic Spectrum Elementary Properties of Radiation 1.2 Radiative Flux Macroscopic Description of the Propagation of Radiation Flux from an Isotropic Source-The Inverse Square Law 1.3 The Specific Intensity and Its Moments Definition of Specific Intensity or Brightness Net Flux and Momentum Flux Radiative Energy Density Radiation Pressure in an Enclosure Containing an Isotropic Radiation Field Constancy of Specific Intensity Along Rays in Free Space Proof of the Inverse Square Law for a Uniformly Bright Sphere 1.4 Radiative Transfer Emission Absorption The Radiative Transfer Equation Optical Depth and Source Function Mean Free Path Radiation Force 1.5 Thermal Radiation Blackbody Radiation Kirchhoff's Law for Thermal Emission Thermodynamics of Blackbody Radiation The Planck Spectrum Properties of the Planck Law Characteristic Temperatures Related to Planck Spectrum 1.6 The Einstein Coefficients Definition of Coefficients Relations between Einstein Coefficients Absorption and Emission Coefficients in Terms of Einstein Coefficients 1.7 Scattering Effects Random Walks Pure Scattering Combined Scattering and Absorption 1.8 Radiative Diffusion The Rosseland Approximation The Eddington Approximation Two-Stream Approximation Problems References Chapter 2 Basic Theory of Radiation Fields 2.1 Review of Maxwell's Equations 2.2 Plane Electromagnetic Waves 2.3 The Radiation Spectrum 2.4 Polarization and Stokes Parameters 62 Monochromatic Waves Quasi-monochromatic Waves 2.5 Electromagnetic Potentials 2.6 Applicability of Transfer Theory and the Geometrical Optics Limit Problems References Chapter 3 Radiation from Moving Charges 3.1 Retarded Potentials of Single Moving Charges: The Lienard-Wiechart Potentials 3.2 The Velocity and Radiation Fields 3.3 Radiation from Nonrelativistic Systems of Particles Larmor's Formula The Dipole Approximation The General Multipole Expansion 3.4 Thomson Scattering (Electron Scattering) 3.5 Radiation Reaction 3.6 Radiation from Harmonically Bound Particles Undriven Harmonically Bound Particles Driven Harmonically Bound Particles Problems Reference Chapter 4 Relativistic Covariance and Kinematics 4.1 Review of Lorentz Transformations 4.2 Four-Vectors 4.3 Tensor Analysis 4.4 Covariance of Electromagnetic Phenomena 4.5 A Physical Understanding of Field Transformations 129 4.6 Fields of a Uniformly Moving Charge 4.7 Relativistic Mechanics and the Lorentz Four-Force 4.8 Emission from Relativistic Particles Total Emission Angular Distribution of Emitted and Received Power 4.9 Invariant Phase Volumes and Specific Intensity Problems References Chapter 5 Bremsstrahlung 5.1 Emission from Single-Speed Electrons 5.2 Thermal Bremsstrahlung Emission 5.3 Thermal Bremsstrahlung (Free-Free) Absorption 5.4 Relativistic Bremsstrahlung Problems References Chapter 6 Synchrotron Radiation 6.1 Total Emitted Power 6.2 Spectrum of Synchrotron Radiation: A Qualitative Discussion 6.3 Spectral Index for Power-Law Electron Distribution 6.4 Spectrum and Polarization of Synchrotron Radiation: A Detailed Discussion 6.5 Polarization of Synchrotron Radiation 6.6 Transition from Cyclotron to Synchrotron Emission 6.7 Distinction between Received and Emitted Power 6.8 Synchrotron Self-Absorption 6.9 The Impossibility of a Synchrotron Maser in Vacuum Problems References Chapter 7 Compton Scattering 7.1 Cross Section and Energy Transfer for the Fundamental Process Scattering from Electrons at Rest Scattering from Electrons in Motion: Energy Transfer 7.2 Inverse Compton Power for Single Scattering 7.3 Inverse Compton Spectra for Single Scattering 7.4 Energy Transfer for Repeated Scatterings in a Finite, Thermal Medium: The Compton Y Parameter 7.5 Inverse Compton Spectra and Power for Repeated Scatterings by Relativistic Electrons of Small Optical Depth 7.6 Repeated Scatterings by Nonrelativistic Electrons: The Kompaneets Equation 7.7 Spectral Regimes for Repeated Scattering by Nonrelativistic Electrons Modified Blackbody Spectra y"1 Wien Spectra y"1 Unsaturated Comptonization with Soft Photon Input Problems References Chapter 8 Plasma Effects 8.1 Dispersion in Cold, Isotropic Plasma The Plasma Frequency Group and Phase Velocity and the Index of Refraction 8.2 Propagation Along a Magnetic Field Faraday Rotation 8.3 Plasma Effects in High-Energy Emission Processes Cherenkov Radiation Razin Effect Problems References Chapter 9 Atomic Structure 9.1 A Review of the Schrodinger Equation 9.2 One Electron in a Central Field Wave Functions Spin 9.3 Many-Electron Systems Statistics: The Pauli Principle Hartree-Fock Approximation: Configurations The Electrostatic Interaction LS Coupling and Terms 9.4 Perturbations, Level Splittings, and Term Diagrams Equivalent and Nonequivalent Electrons and Their Spectroscopic Terms Parity Spin-Orbit Coupling Zeeman Effect Role of the Nucleus Hyperfine Structure 9.5 Thermal Distribution of Energy Levels and Ionization Thermal Equilibrium: Boltzmann Population of Levels The Saha Equation Problems References Chapter 10 Radiative Transitions 10.1 Semi-Classical Theory of Radiative Transitions The Electromagnetic Hamiltonian The Transition Probability 10.2 The Dipole Approximation 10.3 Einstein Coefficients and Oscillator Strengths 10.4 Selection Rules 10.5 Transition Rates Bound-Bound Transitions for Hydrogen Bound-Free Transitions (Continuous Absorption) for Hydrogen Radiative Recombination - Milne Relations The Role of Coupling Schemes in the Determination of f Values 10.6 Line Broadening Mechanisms Doppler Broadening Natural Broadening Collisional Broadening Combined Doppler and Lorentz Profiles Problems References Chapter 11 Molecular Structure 11.1 The Born-Oppenheimer Approximation: An Order of Magnitude Estimate of Energy Levels 11.2 Electronic Binding of Nuclei The H2+ Ion The H2 Molecule 11.3 Pure Rotation Spectra Energy Levels Selection Rules and Emission Frequencies 11.4 Rotation-Vibration Spectra Energy Levels and the Morse Potential Selection Rules and Emission Frequencies 11.5 Electronic-Rotational-Vibrational Spectra Energy Levels Selection Rules and Emission Frequencies Problems References Solutions Index

Macroscopic parity violating effects: neutrino fluxes from rotating black holes and in rotating thermal radiation

Abstract: Two macroscopic effects of parity nonconservation are considered. (i) Particle emission by rotating black holes is shown to be asymmetric. In particular, neutrinos are emitted preferentially in the direction opposite to the hole's angular momentum. (ii) It is shown that in a rotating thermal radiation there exist equilibrium neutrino and antineutrino currents parallel to the angular velocity vector.

Techniques for reducing thermal conduction and natural convection heat losses in annular receiver geometries

Abstract: An effective device for the collection of solar energy which has received widespread attention is the so called parabolic-cylindrical solar collector. In this design a circular receiver tube, with a suitable selective coating, is enclosed by a concentric glass envelope and situated along the focal line of a parabolic trough reflector. The heat transfer processes which occur in the annular space between the receiver tube and the glass envelope are important in determining the overall heat loss from the receiver tube. In typical high temperature receiver tube designs the rate of energy loss by combined thermal conduction and natural convection is of the same order of magnitude as that due to thermal radiation, and can amount to approximately 6 percent of the total rate at which energy is absorbed by the solar collector. The elimination of conduction and natural convection losses can significantly improve the performance of a large collector field. Several techniques useful for the reduction of energy loss by thermal conduction and natural convection are considered. The receiver configuration chosen for study is typical of those used in the Solar Total Energy System at Sandia Laboratories. The receiver tube has a ''black chrome'' selective coating and is 2.54 more » cm in outside diameter. The inside diameter of the glass envelope is approximately 4.4 cm. Typical operating temperatures of the receiver tube and glass envelope are approximately 300/sup 0/C and 100/sup 0/C, respectively. « less

Optical absorption and radiative heat transport in olivine at high temperature

Abstract: Results are presented of measurements of the optical absorption spectra (300-8000 nm) of olivine as a function of temperature (300-1700 K) under conditions of controlled and known oxygen fugacity within the stability field of the samples. The absorption spectra are used to calculate the temperature-dependent radiative transfer coefficient of olivine and to numerically study the accuracy of the method. The present absorption measurements in olivine under oxidizing conditions known to be within the olivine stability field indicate that the effective radiative conductivity K(R) is lower than that obtained in previous studies under different experimental conditions. The lower value of K(R) makes it more likely that some of the earth's internal heat is removed by convection and less likely that thermal models involving conduction and radiation alone will satisfactorily explain thermal conditions in the earth's mantle.

A Study of Climate Sensitivity Using a Simple Energy Balance Model

Abstract: The results of simple zonal energy balance climate models are rather sensitive to the parameterizations used to calculate the fluxes of solar radiation absorbed, thermal radiation emitted and energy transported by the atmosphere and oceans. For this reason results are examined for North's (1975a) constant coefficient diffusion model using climatologically consistent radiation parameterizations. With these radiation parameterizations, the calculated climate is less sensitive to changes in the incident solar radiation than was previously found using other parameterizations. In addition, how the model's results are influenced by the biofeedback mechanism recently proposed by Cess (1978) is studied. This feedback accounts for changes in the surface albedo caused by changes in the vegetation that might accompany climate change. Based on the model results, this feedback could be an important link between the climate and the earth's orbit around the sun.

A stationary thermal model for smooth air-gap rotating electric machines

Abstract: A steady state heat transfer model applicable to rotating electrical machines with non salient poles is presented. Several cooling options are accounted for, ranging from the totally enclosed machine running in a high vacuum to the open ventilated one with axial and radial ducts. Sophisticated cooling systems, such as gas or water cooled windings, are not considered. The model includes such unusual levels of detail as radiation heat exchanges and prediction of the actual hot spot temperatures of the iron and windings. Peripheral results are the temperatures at other representative points and complete maps of the conduction, convection and radiation heat exchanges. The resultant computer program may be used either to check the temperature rise constraints for a given design, or as a tool to analyze the performance of the cooling system of an actual machine or proposed design. Parametric studies can be easily performed, showing the sensitivity of the temperature rises and heat exchanges to variatio...

Generalized Computations of the Gray Body Shape Factor for Thermal Radiation from a Rectangular U-Channel

Abstract: Gray body shape factors are computed for radiation exchange between the interior of rectangular fin structures and a nonreflecting ambient. The shape factors are derived from an equivalent thermal circuit using emissivity-dependent resistance elements between each black body potential and corresponding radiosity node. Geometric-shape-factor-dependent resistance elements connect interacting radiosities. Several curves are plotted to aid the heat sink designer to assess the radiative heat transfer for n variety of heat sink dimensions and emissivities. These results show that gross errors exist in some of the previously published data and prediction methods in common usage throughout the electronics industry.

Method and device for converting thermal images into secondary images, e. g. visible images

Abstract: A converter and method of converting thermal images into secondary images, e.g. visible images. The infrared radiation emitted by an object is focused by an optical system to form a thermal image on the free surface of a thermal radiation absorbing layer to one side of a liquid-liquid interface which has low surface tension and is a mixture of two liquid partially miscible at operating temperature and pressure. To convert the thermal image to a visible a parallel beam of light or a beam of light from a point source in the visible range is directed to the other side of the interface and, depending on the selected indices of the interface liquids and whether a prism is used or not; is either transmitted or reflected. The emerging transmitted or reflected beam is then received on a screen or in a detection system where variations of the optical properties of the emerging beam are observed.

Influence of Thermal Radiation on the Temperature Distribution in a Semi-Transparent Solid

Abstract: The importance of radiation on the temperature distribution in a semi-transparent solid is reported. The first-order differential approximation of radiation is combined with conduction analysis to investigate the temperature profiles in a plane slab and a rectangular region. The coupled nonlinear partial differential equations are solved numerically by either a standard implicit or an implicit alternating direction method. Results obtained for opaque boundaries are in good agreement with exact formulations found in the literature. An extension to partially transparent boundaries is made and results presented

Emissivity correction for interpreting thermal radiation from a terrestrial surface

Abstract: A general method of accounting for emissivity in making temperature determinations of graybody surfaces from radiometric data is presented. The method differs from previous treatments in that a simple blackbody calibration and graphical approach is used rather than numerical integrations which require detailed knowledge of an instrument's spectral characteristics. Also, errors caused by approximating instrumental response with the Stephan-Boltzman law rather than with an appropriately weighted Planck integral are examined. In the 8-14 micron wavelength interval, it is shown that errors are at most on the order of 3 C for the extremes of the earth's temperature and emissivity. For more practical limits, however, errors are less than 0.5 C.

Thermal Parameters as a Function of Thickness for Combined Radiation and Conduction Heat Transfer in Low-Density Insulation:

Abstract: Approximate expressions are obtained for the apparent ther mal conductivity and thermal resistance, in the case of combined conduc tive and radiative heat transfer through low-density insulation. These ex pressions are obtained in the regimes of intermediate and large optical depth, and they depend on only two parameters to be determined by experiment, namely the "conduction" thermal conductivity, kc, and the extinction coefficient, β. An expression is obtained for the apparent ther mal resistance of an insulation consisting of layers with distinct densities. The applicability of these expressions to the interpretation of experimental results and to the improvement of ASTM Test Methods is discussed.

Molecular gas radiation in the thermal entrance region of a duct

Abstract: The effect of molecular gas radiation upon the thermal development downstream from a step change in wall temperature is examined for both laminar and turbulent flow in a black-walled flat-plate duct. The exponential-tailed band model is used to represent spectral variations in gas absorption and emission. Values of total and radiative Nusselt numbers, cold-wall-layer transmission factors, and dimensionless bulk temperatures are reported for several dimensionless axial locations and for various sets of the dimensionless controlling parameters. Even in the entrance region, self absorption by wall layer gas blocks significantly the radiation exchange between the gas core and wall. An approximate correlation is proposed for both plane-duct and pipe turbulent entrance flows.

Inconsistency between the boltzmann distribution for relativistic free particles and the rayleigh-jeans law for thermal radiation within classical electrodynamics

Abstract: The classical electrodynamic model introduced by Einstein and Hopf of a massive free particle containing an electric dipole oscillator in interaction with random classical radiation is extended to relativistic particle velocities. The equilibrium distribution of classical particle velocities enforced by the Rayleigh-Jeans law of thermal radiation is found to be different from the Boltzmann distribution for relativistic free particles at the same temperature. Thus apparently there is an inconsistency within classical theory between the relativistic Boltzmann particle distribution and the Rayleigh-Jeans law for thermal radiation.

Radiation from Burning Hydrocarbon Clouds

Abstract: This paper reports on the measurement and analysis of time resolved thermal radiation from combustion of methane, ethane, and propane clouds formed from laboratory scale vapor samples initially contained within a soap bubble. The time scale of the radiant heat pulse was found to be the same as that of the fluid mechanical motion (Fay and Lewis, 1976). The time-integrated radiant energy flux, expressed as a fraction of the initial fuel heating value, was between 0.09 and 0.15 for these fuels, with some dependence on initial fuel volume. The radiation was correlated by a grey gas model, which assumed a uniform time-dependent temperature in a spherical cloud and a time-independent absorption coefficient. The grey gas temperature decreased monotonically during and after the period of combustion. The absorption coefficient was found to be a function of the initial fuel volume and fuel type; it was between 10−3 and 10−2 cm−1 and decreased slightly with increasing initial fuel volume.

Heat radiation deflectors within an EFG crucible

Abstract: The thermal profile at the top of an EFG die is improved by including heat radiation deflectors within the crucible to change the level of radiation heating experienced by at least some portions of the die.

Effects of precursor heating on radiative and chemically reacting viscous flow around a Jovian entry body

Abstract: The influence of change in the precursor region flow properties on the entire shock layer flow phenomena around a Jovian entry body was investigated. The flow in the shock layer was assumed to be steady, axisymmetric, and viscous. Both the chemical equilibrium and the nonequilibrium composition of the shock layer gas were considered. The effects of transitional range behavior were included in the analysis of high altitude entry conditions. Realistic thermophysical and radiation models were used, and results were obtained by employing the implicit finite difference technique in the shock layer and an iterative procedure for the entire shock layer precursor zone. Results obtained for a 45 degree angle hyperboloid blunt body entering Jupiter's atmosphere at zero angle of attack indicates that preheating the gas significantly increases the static pressure and temperature ahead of the shock for entry velocities exceeding 36 km/sec. The nonequilibrium radiative heating rate to the body is found to be significantly higher than the corresponding equilibrium heating. The precursor heating generally increases the radiative and convective heating of a body. That increase is slightly higher for the nonequilibrium conditions.

Wärmestrahlung in dispersen Feststoffsystemen

Abstract: Heat radiation in packed solids. The term packed solids embraces fixed beds and all other, sometimes less rigidly fixed, arrangements of solids particles of any shape in a gaseous environment. Cell and quasihomogeneous models have been developed for determining heat radiation in such systems and their predictions compared with one another and especially with available experimental data. Since fixed beds of spherical particles have been considered most frequently so far, they receive the greatest attention in this article. Topics such as radiation components in insulation systems, in chemical fixed bed reactors, in porous particles, and the effect of radiation on the wall heat transfer coefficient are mentioned only briefly.

Optically Pumped Carbon Dioxide Laser Mixtures

Abstract: This work explores the concept of blackbody radiation pumping of CO2 gas as a step toward utilization of solar radiation as a pumping source for laser action. To demonstrate this concept, an experiment was performed in which laser gas mixtures were exposed to 1500 K thermal radiation for brief periods of time. A gain of 2.8 x 10 to the -3rd reciprocal centimeters has been measured at 10.6 microns in a CO2-He gas mixture of 1 Torr pressure. A simple analytical model is used to describe the rate of change of energy of the vibrational modes of CO2 and to predict the gain. Agreement between the prediction and experiment is good.

Scattering of emitted radiation from inhomogeneous and nonisothermal layers

Abstract: A parametric study is performed for the exiting monochromatic intensities scattered from finite plane-parallel inhomogeneous layers that are driven solely by a distribution of thermal sources. Intensities are obtained by invariantly imbedding the standard and thermal scattering functions. The single-scattering albedo and the Henyey-Greenstein phase-function parameter are varied independently, and both linear and exponential profiles are considered. Linear temperature profiles are used, including temperature inversions. The resulting intensities, as a function of the direction cosine of propagation, are discussed from a remote-sensing point of view. For an isothermal and homogeneous medium, the gross characteristics of the exiting intensity, represented by its overall slope, mean value (magnitude), and an interior maximum value, can be related to the total optical depth, single-scattering albedo, and phase function, respectively. For a homogeneous medium, linearly decreasing (in the line of sight) temperature profiles tend to obscure the phase-function information and decrease the apparent optical depth. On the other hand, linearly increasing temperature profiles tend to retain phase-function information and increase the apparent optical depth. Temperature inversion profiles give intensities very similar to those for purely linear profiles.

Thermostat system for radiant room heating

Abstract: A receiver of thermal radiation of thin film deposit material of high temperature coefficient of electrical resistance having surface absorptive characteristics.

Swashhplate type compressor

Abstract: PURPOSE:To effectively perform heat radiation and cooling and elongate the life of a compressor by applying copper plating onto the surface of a swash plate, a thrust surface, an outer surface etc., and transmitting the friction heat between a slipper and swash plate surface to others speedily. CONSTITUTION:Onto the whole surface of a swash plate 1, mainly onto the swash- plate surface 101, copper plating is applied in thickness of about 1-10mum. Copper plating is applied onto the whole of a swash plate surface 101, thrust surface 102, outer surface 103, shaft-force-fitting surface 104, and the outer surface part 105 for a boss. When a shaft 2 is driven by an outside power, the swash plate 1 is revolved, and the slipper which is arranged onto the swash plate is slidably moved with the swash plate surface 101, and the movement of the piston is converted to the movement in the axial direction. At this time, the friction heat between the swash plate surface 101 and the slipper is transmitted to a wide area due to copper having a high heat conductivity, and heat radiation effect is improved. Thus, lubricating effect and wear resistance are improved, and the life of a compressor can be elongated.

Numerical results for the thermal scattering functions

Abstract: A recent formulation in radiative transfer defined the thermal scattering functions that characterize radiative transfer from a general plane-parallel finite medium driven solely by an internal distribution of thermal sources. Exiting diffuse intensities are expressed as space convolutions of the thermal scattering functions with any thermal source distribution. A parametric study is presented to obtain the basic structure of these scattering functions. The independent variables of these azimuthally independent functions are the direction cosine and source location, while the parameters are the single-scattering albedo, total optical depth, and the asymmetry factor in the Henyey-Greenstein phase function. The basic functional trends are discussed by using various parametric plots, and selected results are given to allow numerical checks. The computational method is invariant imbedding.