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Showing papers on "Thermal radiation published in 1976"


Journal ArticleDOI
TL;DR: A heat transfer analysis of animals is presented which lies between detailed thermal energy budget analysis and the simplified “Newton's Law of cooling” approach, and it is possible to make direct measurements of Te, K0, Tes, and M∗ with taxidermic models of the animal.

345 citations


Book ChapterDOI
TL;DR: In this article, a nongray radiation heat transfer analysis for problem situations involving molecular gases with infrared vibration rotation bands when the gaseous mixture is in a state corresponding to thermodynamic equilibrium at the local thermodynamic state variables: pressure, temperature, and composition.
Abstract: Publisher Summary Radiation heat transfer involving molecular gases is the desirable effect in fossil-fuel or waste-fired steam generators for power production or process steam supply and in industrial heat-treating, melting, or enameling furnaces Heat radiation from gases may be utilized as a means of heat transfer and also of information transfer Information on the location, extent, composition, and temperature of a volume of molecular gases can be inferred from thermal radiation measurements The information obtained can be used by process control, fire and air pollution warning and monitoring systems, and by weapon and brush-fire-suppressant targeting or guidance systems This chapter examines how to make a nongray radiation heat transfer analysis for problem situations involving molecular gases with infrared vibration rotation bands when the gaseous mixture is in a state corresponding to thermodynamic equilibrium at the local thermodynamic state variables: pressure, temperature, and composition The special circumstances under which total emissivity and total absorptivity appear as useful quantities are derived, and approximations extending their utility are discussed The chapter examines how the more general and difficult problem of a nonisothermal gas is treated Some particular solutions for the parallel-plate duct are described, both to illustrate nonisothermal gas analysis and to obtain wall-layer transmission factors to extend the utility of engineering models employing an isothermal gas volume concept The chapter provides a brief description of the experimental knowledge of molecular gas behavior and a review of the fundamental ideas of radiation transfer The spectral band nature of gas radiation is briefly described and correlations for working calculations of gas radiation properties are presented

291 citations


Journal ArticleDOI
TL;DR: To characterize the properties of heat-mirror films for solar-energy collection, the parameters alpha(eff), the effective solar absorptivity, and epsilon(eff, the effective ir emissivity are defined and comparable to the values of alpha/epsilon reported for the leading selective absorbers.
Abstract: Transparent heat-mirror films, which transmit solar radiation but reflect ir thermal radiation, have potentially important applications in solar/thermal/electric conversion, solar heating, solar photovoltaic conversion, and window insulation. We have used rf sputtering to prepare two types of films: TiO2/Ag/TiO2 and Sn-doped In2O3. To characterize the properties of heat-mirror films for solar-energy collection, we define the parameters αeff, the effective solar absorptivity, and ∊eff, the effective ir emissivity. For our Sn-doped In2O3 films, αeff/∊eff is comparable to the values of α/∊ reported for the leading selective absorbers. Even higher values of αeff/∊eff are obtained for the TiO2/Ag/TiO2 films.

233 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of an impulse and adiabatic manipulation on the dynamics of a sphere were studied from atmospheric pressure down to ∼10−6 Torr, and the calculated time for an oscillating particle to decay to half-amplitude due to the intrinsic optical damping at zero pressure is ∼0.7 years.
Abstract: Optical levitation of highly transparent particles has been observed in the high‐vacuum regime where viscous damping and thermal conductivity are small, the particle is cooled only by thermal radiation, and radiometric forces are negligible. The effects of an impulse and adiabatic manipulation on the dynamics of a sphere were studied from atmospheric pressure down to ∼10−6 Torr. The calculated time for an oscillating particle to decay to half‐amplitude due to the intrinsic optical damping at zero pressure is ∼0.7 years.

219 citations


Journal ArticleDOI
22 Apr 1976-Nature
TL;DR: In this article, the existence of continuum radiation from just beyond the plasmapause was revealed by Cerenkov radiation coupling to the O mode of radiation, which can propagate in low density plasmas.
Abstract: Observations from satellites have revealed the existence of continuum radiation from just beyond the plasmapause. I propose here that this is generated by Cerenkov radiation coupling to the O mode of radiation, which can propagate in low density plasmas. The observations are interpreted on the basis of this theory.

128 citations


Journal ArticleDOI
TL;DR: In this article, a general theory for applying the doubling method to spatially inhomogeneous radiation sources whose angular and spatial variations separate is given, and the doubling rules for a linear-in-optical-depth source (which may approximate a source of thermal radiation) and for an exponential-inoptical depth source are derived as special cases.
Abstract: This paper gives a general theory for applying the doubling method to spatially inhomogeneous radiation sources whose angular and spatial variations separate. In particular, inhomogeneous sources of thermal radiation may be efficiently treated by the methods herein, as well as direct and specularly-reflected beams of radiation which do not lie along a quadrature direction for the intensity. Doubling rules for a linear-in-optical-depth source (which may approximate a source of thermal radiation) and for an exponential-in-optical-depth source are derived as special cases.

83 citations


Journal ArticleDOI
TL;DR: In this paper, an apparatus for the measurement of the thermal conductivity of non-conducting liquids under their saturation vapour pressure is described, which is based upon the transient hot wire principle.
Abstract: The paper describes an apparatus for the measurement of the thermal conductivity of non-conducting liquids under their saturation vapour pressure. The instrument, which is based upon the transient hot wire principle, has been designed so that the measuring element conforms as closely as possible to an infinite line source of heat in an infinite fluid. Under these conditions the thermal conductivity of the liquid can be determined from the slope of a plot of the temperature rise of the heating element against the logarithm of time. The measurement system has been arranged so as to provide as many as 60 points on this plot for any particular thermodynamic state of the fluid under investigation. The reproducibility of the instrument is of the order of 0.03% and the precision of the measurements is estimated as +or-0.1%. Owing to a lack of a suitable theory for the effects of radiative heat transfer, the accuracy of the thermal conductivity values cannot be defined unequivocally, but a reasoned upper bound is +or-0.3%. Preliminary results are presented for n-heptane at three temperatures in the range 20 to 30 degrees C.

80 citations


Journal ArticleDOI
TL;DR: In this article, an account of the mechanism of the emission of blackbody radiation from an incipient (about-to-be-formed) black hole, which results from the gravitational collapse of a star, is given.
Abstract: On the basis of the phenomenon of zero-point energy an account is given of the mechanism of the emission of blackbody radiation from an incipient (about-to-be-formed) black hole, which results from the gravitational collapse of a star. The account is given in terms of three related points of view: (1) the emitted blackbody radiation results from a Fourier spectrum analysis of the zero-point fluctuations on the surface of the collapsing star; (2) the radiation results from a parametric amplification by a time-dependent potential of waves emerging from the collapsing surface of the star; (3) the radiation results from the star passing continually through states of resonance mutual to the natural modes internal and those external to the star. These three points of view are related by virtue of the underlying principle that explains the blackbody radiation mechanism: the nonadiabatic red-shift process operating on the randomly correlated zero-point fluctuation modes. The picture that emerges from these analyses is that all zero-point oscillation modes emerging from the star give rise to statistically identical blackbody radiation packets. Their only difference lies in their time of emission. The packets are emitted in a time sequential order and each is created during a limited time interval at the surface of the star: those packets caused by low-frequency zero-point modes first, those caused by high-frequency modes later. The blackbody radiation continuously drains away the irreducible mass of the black hole at an ever increasing rate. The lifetime of the incipient black hole is therefore finite. Consequently, the total number of zero-point fluctuation modes taking part in the emission of blackbody radiation packets is finite. The logarithm of this number (multiplied by Boltzmann's constant) equals the entropy of a black hole. This suggests that the internal microscopic states (in the statistical-mechanical sense) of a macroscopic black hole, i.e., the "hairs" lost by the black hole, are to be identified with those degrees of freedom that are capable of and will be causing the emission of blackbody radiation. The statistical fluctuation spectrum of the emitted energy is exhibited and found to be identical to that associated with a blackbody, showing thereby that radiation emitted from a black hole is thermal radiation in the precise sense of the term. The relevance of these statistical fluctuations to the formation of a black hole is discussed briefly. Brief mention is made of the sense in which a radiating incipient black hole lends support to Sakharov's idea that gravitation is a manifestation of the alteration of the zero-point fluctuations of space. The formulation of the radiation mechanism in terms of successively amplified zero-point radiation modes allows us to conclude that a star can never pass through its instantaneous $r=2M$ surface. In view of the fact that the evaporation and the final demise of an incipient black hole are visible to a distant observer, it is necessary to reformulate the classical version of the issue of the final state of gravitational collapse. A qualitative account of the evolution of a classical incipient black hole is given. The issue of the final state of stellar gravitational collapse is restated in the form of a question: What is the ground state of an incipient black hole?

72 citations


Journal ArticleDOI
TL;DR: More than 300 publications have been revised for studying the thermal conductivity and the thermal radiation properties of UO2, and most of them are investigating the radiation transport through solid fuel.
Abstract: More than 300 publications have been revised for studying the thermal conductivity and the thermal radiation properties of UO2. The temperature, the porosity, the uranium to oxygen ratio and irradiation effects have an important influence on the thermal conductivity. The thermal conductivity of stoichiometric UO2 with nearly theorectical density is well known up to the melting point with a maximum uncertainity of ± 15%. Relations can be established to calculate the conductivity of porous UO2. The correlation between the conductivity and the Ö/U ratio could not be described analytically but the qualitative dependence is evident. Only a few publications could be found on thermal radiation properties of UO2; most of them are investigating the radiation transport through solid fuel. Emittance data are therefore quite speculative. The total emittance and the spectral emittance might be approximately 0.9, and not significantly dependent on temperature and porosity or surface roughness.

60 citations


Patent
08 Apr 1976
TL;DR: In this article, a transparent thermal insulating system with controllable transmissivity to visible radiation was proposed, comprising a first layer generally transparent to visible, a second layer generally opaque to visible and spaced from the first layer, partition means for separating the space between the layers into compartments; a thermal radiation suppression device for suppressing thermal radiation transmission; and variable transparency thermal control device for controlling transmisson of visible radiation as a function of temperature.
Abstract: A transparent thermal insulating system having controllable transmissivity to visible radiation comprising a first layer generally transparent to visible radiation, a second layer generally transparent to visible radiation and spaced from the first layer; partition means for separating the space between the layers into compartments; a thermal radiation suppression device for suppressing thermal radiation transmission; and a variable transparency thermal control device for controlling transmisson of visible radiation as a function of temperature.

56 citations


Journal ArticleDOI
S. Rea, S. West1
TL;DR: In this paper, an accurate straightforward technique is presented to compute thermal radiation from finned heat sinks, and a set of graphs is included to aid in the computational procedure, which compares favorably with experimental data.
Abstract: An accurate straightforward technique is presented to compute thermal radiation from finned heat sinks. A set of graphs is included to aid in the computational procedure. The analytical approach presented compares favorably with experimental data.

Book ChapterDOI
TL;DR: In this paper, it was shown that spontaneous emission is independent of the environmental radiation field, and therefore, Kirchhoff's law still holds in the case of nonequilibrium, provided that the distribution of the material states of the sample is the equilibrium distribution.
Abstract: Publisher Summary Kirchhoff's law of heat radiation states that the emissivity of radiating bodies is equal to their absorptivity. Kirchhoff's law seems to remain valid in the case of nonequilibrium if induced emission is considered as negative absorption as was first shown for freely radiating weakly absorbing bodies. Absorptivity is redefined as induced absorption minus induced emission, whereas emissivity is understood as being due to spontaneous emission only. In addition, from studying the original concepts of Kirchhoff, it can be inferred that the quantities compared in Kirchhoff's law are the spontaneous emission and the net absorption. The emissivity is exclusively due to spontaneous emission and is consequently independent of the environmental radiation field. Therefore, one expects Kirchhoff's law to hold as well for freely radiating bodies, provided that the distribution of the material states of the sample is the equilibrium distribution.

Journal ArticleDOI
TL;DR: In this article, the authors show that the desorption efficiency of the absorbed 300-k radiant energy is approximately 7×10−6 for most of the 20 bakeable cryosurfaces tested.
Abstract: Hydrogen molecules, physisorbed or condensed on cryosurfaces at liquid‐helium temperatures, can be desorbed by thermal radiation. The probability of the process depends on the nature of the cryosurface, the degree of H2 coverage, and the spectrum of the radiation. For a given spectrum the desorption rate is proportional to radiation intensity, and, with a few exceptions, to the absorptivity of the cryosurface. The desorption efficiency of the absorbed 300‐K radiant energy is approximately 7×10−6 for most of the 20 bakeable cryosurfaces tested. A decrease of radiation temperature below 130 K causes a progressive reduction of the desorption efficiency which amounts to a factor of three at 80 K. This variation of efficiency can be fitted to a curve obtained by assuming that a threshold wavelength for desorption exists in the radiation spectrum at 45 μm. The energy carried by a photon of this threshold wavelength is about three times that required for the desorption of a condensed H2 molecule. Precondensed su...

Journal ArticleDOI
TL;DR: In this article, the fundamental thermal radiation laws are valid only if the dimensions of the cavity are everywhere large compared to the wavelengths, and the theoretical results for the refined density of states are emphasized.

Journal ArticleDOI
TL;DR: In this paper, a four-stream, multi-layered radiative transfer model was developed to treat the problem of the transfer of infrared radiation in an atmosphere containing both scatterers and absorbers.
Abstract: A four-stream, multi-layered radiative transfer model has been developed to treat the problem of the transfer of infrared radiation in an atmosphere containing both scatterers and absorbers. Each atmospheric layer is isothermal and contains a uniform concentration of scatterers and absorbers. To facilitate the computations, the infrared spectrum was divided into four bands. In each band empirical transmission functions were fitted by a series of exponential functions. Test calculations of the infrared cooling rate were made using the empirical transmission functions and the fitted transmission functions. The resulting cooling rate profiles exhibit good agreement with each other. A model of a typical urban aerosol was developed using recent experimental results on the spectral dependence of the complex refractive index and the size distributions of aerosols. Atmospheric cooling rates as a function of height were computed on a band by band basis, with and without aerosols, in order to compare the e...


Patent
09 Jan 1976
TL;DR: In this paper, the authors proposed a structure for providing shelter at low cost by reflecting a high fraction of the optical and thermal radiation incident on the walls from the outside, or by reflecting an additional high fraction on the wall from inside.
Abstract: This invention comprises structures for providing shelter at low cost by reflecting a high fraction of the optical and thermal radiation incident on the walls from the outside, or by reflecting a high fraction of the thermal radiation incident on the walls from inside. The structures are composed of translucent container modules attached to a framework, said container modules holding a translucent liquid, foam or gel medium with a dispersion of microparticles which can reflect or absorb the spectrum of radiation impinging on it. These containers incorporate into themselves thermal insulators for minimizing thermal conduction and means for minimizing thermal convection.

Patent
13 Feb 1976
TL;DR: In this paper, a solar appliance apparatus for utilizing solar thermal radiation to supply heat to a heating and cooking surface is described, which includes a housing permanently stationed inside a residential structure and the like.
Abstract: This invention relates to a solar appliance apparatus for utilizing solar thermal radiation to supply heat to a heating and cooking surface. The apparatus includes a housing permanently stationed inside a residential structure and the like. The housing contains a heat transfer medium and a radiation receiver carried in heat exchange contact with the medium. A heating and cooking surface is carried by the housing in heat exchange relationship with the heat transfer medium. A radiation pipe extends through the exterior wall of the building structure to deliver a concentrated beam of solar radiation rays to the radiation receiver.

Journal ArticleDOI
TL;DR: In this paper, the energy balance among the energy absorbed from solar and planetary radiation fields, the energy radiated by the particles, and the sensible heat exchanged through collisions with the ambient gas is established.
Abstract: A previous analysis (Fiocco et al., 1975) of the energetic equilibrium of small particles in the earth's upper atmosphere is extended to the 0–60 km region. The analysis is based on establishing a balance among the energy absorbed from solar and planetary radiation fields, the energy radiated by the particles, and the sensible heat exchanged through collisions with the ambient gas. The planetary radiation field is calculated as a function of altitude and includes radiation from the surface as well as emission and absorption by the infrared bands of CO2, O3, and H2O The various energy term change as a function of radius and altitude of the particles, season, time of day and the earth's albedo. Thus aerosols may beat or cool the atmosphere and their temperature may. differ from the ambient gas temperature. Maximum and average values for the heating rates induced by the particles into the ambient gas are computed for summer and winter 45°N conditions.

Journal ArticleDOI
01 Jun 1976
TL;DR: In this article, the radiative heat transfer, in a bed of negligible interparticle axial heat conduction, was measured by means of an original developed apparatus, which was taken over a temperature range of 350 K to 930 K. The experimental results support a previously published (and here improved) theory.
Abstract: The radiative heat transfer, in a bed of negligible interparticle axial heat conduction, was measured by means of an original developed apparatus. The measurements were taken over a temperature range of 350 K to 930 K, in a bed packed with spherical particles of negligible heat resistance. The experimental results support a previously published (and here improved) theory, which was developed for the calculation of radiative heat transfer in terms of the radiative properties and the geometry of the packing material. The results are valid for particles of high heat conductivity.

Journal ArticleDOI
TL;DR: In this article, a local stability analysis is used to determine the stability of disturbances generated at each point along a nozzle of variable area ratio for a one-dimensional flow heated by laser radiation entering from the upstream direction.
Abstract: A local stability analysis is utilized to determine the stability of disturbances generated at each point along a nozzle of variable area ratio for a one-dimensional flow heated by laser radiation entering from the upstream direction. The governing equations for the quasi-one-dimensional flow without viscous dissipation, diffusion, and thermal conduction but including radiative heat transfer are given. The governing equations are combined to yield a relationship which governs the Mach number variation through the nozzle. The complete steady-state solution can be calculated from knowledge of the Mach number profile, the inlet conditions, and the laser power. The local stability analysis permits obtaining contour (or contours) of neutral stability. Solutions have been obtained for various nozzle configurations, but only one set of example calculations is presented. The results obtained indicate that the analysis serves as an important indicator as to where potential absorption wave phenomena may be initiated.



Journal ArticleDOI
TL;DR: In this article, the influence of the peak wavelength on the performance of thermal imaging systems is analyzed, and the radiation function is used in the analysis since it contains the wavelength-dependent portion of the figures of merit for thermal imaging system such as the noise equivalent temperature difference (NETD) and the minimum resolvable temperature (MRT).


Journal ArticleDOI
01 Jun 1976
TL;DR: In this article, the radiative heat transfer, in a bed of negligible interparticle axial heat conduction, was measured by means of an original developed apparatus, which was taken over a temperature range of 350 K to 930 K. The experimental results support a previously published (and here improved) theory.
Abstract: The radiative heat transfer, in a bed of negligible interparticle axial heat conduction, was measured by means of an original developed apparatus. The measurements were taken over a temperature range of 350 K to 930 K, in a bed packed with spherical particles of negligible heat resistance. The experimental results support a previously published (and here improved) theory, which was developed for the calculation of radiative heat transfer in terms of the radiative properties and the geometry of the packing material. The results are valid for particles of high heat conductivity.


Journal ArticleDOI
TL;DR: In this article, the inversion of observed thermal infrared spectra of Jupiter to obtain temperature structures is reviewed and an ambiguity is noted when the 7.8 $mu$ band of CH$sub 4$ is used and alternative temperature structures are obtained.
Abstract: Defects in the inversion of observed thermal infrared spectra of Jupiter to obtain temperature structures are reviewed. An ambiguity is noted when the 7.8 $mu$ band of CH$sub 4$ is used and alternative temperature structures are obtained. (AIP)

Journal ArticleDOI
TL;DR: In this paper, the distribution function as well as the fluctuation spectrum of the radiation emitted from a spherically symmetric black hole are derived within the basic framework of statistical mechanics from the fact that it is an entity endowed with a densely spaced quantum level spectrum.
Abstract: The distribution function as well as the fluctuation spectrum of the radiation emitted from a spherically symmetric black hole is derived within the basic framework of statistical mechanics from the fact that it is an entity endowed with a densely spaced quantum level spectrum. The fluctuation spectrum of the emitted radiation is thus found to exhibit deviations from that of pure thermal radiation. (AIP)

Journal ArticleDOI
TL;DR: The time dependence of thermal radiation emitted from aerosol particles heated with pulses from a TEA laser is shown to be related to the size of individual particles and to the distribution of sizes within an aerosol.
Abstract: Some effects arising from the interaction of TEA CO2 laser pulses with individual aerosol particles are described. The time dependence of thermal radiation emitted from aerosol particles heated with pulses from a TEA laser is shown to be related to the size of individual particles and to the distribution of sizes within an aerosol. Charge and mass changes have been determined for single particles on absorption of 10.6-μm CO2 laser radiation. The predominant charging effect at low intensities (≃ 105 W/cm2) involves a loss of positive charge. Splitting of particle aggregates has also been observed.