Showing papers on "Thermal radiation published in 1970"

Radiation Heat Transfer

Abstract: 1. Fundamentals of thermal radiation 2. View factors 3. Heat exchange between black surfaces 4. Heat exchange between grey surfaces 5. Emission and absorption by gases 6. Radiative heat transfer in furnaces 7. Combined modes of heat transfer 8. Measurement of temperature 9. Radiation from flames Further reading

Experimental Investigation of Radiative Transfer Between Metallic Surfaces at Cryogenic Temperatures

Abstract: Radiative heat flux between two parallel copper disks at cryogenic temperature, showing dependence on emitter temperature and spacing

A point explosion in a cold exponential atmosphere. Part 2. Radiating flow

Abstract: : The problem considered is that of a strong shock propagating from a point energy source into a cold exponential atmosphere with radiative heat transfer in the flow behind the shock. The radiation mean free path is taken to be small compared to the shock radius so that the shock may be treated as discontinuous and the radiative heat flux represented by the Rosseland diffusion approximation. The solution obtained is an approximate one based upon the 'local radiality' assumption and integral method previously utilized by the authors for the case of adiabatic flow. A radiation parameter is developed which provides an index as to when the effects of radiation may be neglected and the flow taken to be adiabatic. The physical interpretation of this parameter is that of the ratio of a characteristic radiation energy flux to a characteristic kinetic energy flux. It is shown that when the radiation mean free path varies as a power of the temperature (T to the nth power), where n = - 17/6, the infinity of solutions for various polar angles can be transformed into two distinct solutions thereby essentially eliminating the parametric dependence on the polar angle and the atmospheric scale height. (Author)

Airborne Observations of Contrail Effects on the Thermal Radiation Budget

Abstract: Direct infrared and solar radiometric observations were made to analyse the effects on the environment of any alterations in the radiation budget in regions of heavy jet traffic. The observations, made from the NASA Convair 990 jet laboratory, were coupled with Mie scattering and absorption theory calculations to analyze any inadvertent alterations in the natural atmospheric thermal radiation budget. It was found that a 500 m thick contrail sheet increases the infrared emission below the sheet by 21% but decreases the solar power below the sheet by 15%. The infrared increase cannot make up for the solar depiction, resulting in a net available incoming power depletion at the base of the sheet of 12%. Such a change at altitude results in a 7% reduction in the net total available thermal power at the earth's surface, which, in turn, results in a 5.3C decrease in the surface temperature, if we assume contrail persistence. The actual temperature decrease is ∼0.15C with 5% contrail persistence.

Infrared spectra and radiative thermal conductivity of minerals at high temperatures

Abstract: Minerals radiative thermal conductivity at high temperatures from IR measurement of absorption coefficient and refractive index

Thermal Radiation Properties and Thermal Conductivity of Lunar Material

Abstract: The thermal radiation properties were measured for lunar fines and chips from three different lunar rocks. Measurements for the fines were made at atmospheric pressure and at a pressure of 10(-5) torr or lower. The directional reflectance was obtained over a wavelength range of 0.5 to 2.0 microns for angles of incidence up to 60 degrees. The bidirectional reflectance-the distribution of reflected light-was measured for white light angles of illumination up to 60 degrees. The thermal conductivity was measured over a temperature range 200 to 400 degrees K under vacuum conditions.

The Interaction of Thermal Radiation and M-2 Double-Base Solid Propellant

Abstract: This paper reports the results of experimental and theoretical investigations into the effects of thermal radiation upon ignition and deflagration of M-2 double-base solid propellant. The values of the heat of reaction, the frequency factor and the activation energy in the Arrhenius expression describing the chemical reactions in the solid are determined by matching the numerical solutions of the mathematical model with three sets of experimental data. The effect of thermal radiation upon the propellant is only thermal. Theoretically the effect of thermal radiation on the burning rate is shown to be equivalent to an increase in initial temperature of the propellant only when the radiation absorption coefficient is small. For M-2 propellant, thermal radiation has insignificant effect upon the burning rate for a range of fluxes from 0 to 1.5 cal/cm2-sec.

Apparent radiation properties of a rough surface

Abstract: Apparent thermal radiation properties for one dimensionally rough surface, discussing variance with property models employed in engineering analysis of radiant transfer

On the detectabillity limit of coherent optical signals in thermal radiation

Abstract: The problem of detecting a completely known coherent optical signal in a thermal background radiation is considered. The problem is a quantum mechanical analog of detection of a known signal in Gaussian noise. The quantum detection counterpart is formulated in terms of a pair of density operators and a solution is shown to exist. A perturbation solution is obtained by making use of a reproducing kernel Hilbert space of entire functions. The solution is particularly applicable to optical frequencies, where the effect of thermal radiation is small, and it is shown to converge to known results at zero thermal radiation. Curves are generated showing the detectability limit at optical frequencies. Also considered is the problem of finding an operator that maximizes a signal-to-noise ratio, defined for quantum detection in analogy with the classical theory. For a coherent signal with random phase, the operator that maximizes the signal-to-noise ratio is identicial to the one obtained by applying the Neyman Pearson criterion, thereby establishing a complete analogy with the classical detection theory. For a signal with known phase, however, the analogy breaks down in the limit of zero thermal radiation. In that case, it is shown that an operator that maximizes the “classical” signal-to-noise ratio does not exist.

Temperature rise of specimen due to electron irradiation.

Abstract: A rise in specimen temperature due to electron irradiation was directly measured by using a microthermocouple composed of evaporated gold and palladium films. The temperature rise with an increase in electron current density was explained referring to the thermal conduction and thermal radiation effects. The experimental results obtained by varying irradiated areas and film thicknesses were compared with Leisegang's theory. The thermal conductivity and thermal emissivity values for metallic films as well as the energy loss value that contributes to the temperature rise were estimated.

Thermal network correction techniques

Abstract: Correction techniques for thermal network lumped parameter inaccuracies with conduction and radiation coupling, considering temperature control system

Optimizing thermal and radiation effects for bacterial inactivation

Abstract: The temperatures required for dry-heat spacecraft sterilization have been known to degrade heat-sensitive components. Thermoradiation, the simultaneous application of dry heat and gamma radiation, can provide the same degree of microbial inactivation as dry heat alone while substantially reducing component degradation. This is made possible by the synergistic effects produced when relatively low levels of these agents (e.g., 90 to 350 krads and 60° to 105°C) are applied simultaneously, thus permitting the use of lower temperatures and a reduced duration of heat exposure. The effects of temperature, radiation dose rate, and relative humidity on microbial inactivation during thermoradiation exposure have been established.

The nernst detector: fast thermal radiation detection

Abstract: A thermal radiation detector based on the Nernst effect is capable of relatively high‐speed operation without loss of responsivity or detectivity (D*) over its low‐frequency values. The effective decoupling of the responsivity and thermal time constant is the result of the specific characteristics of the Nernst effect. Results are presented for materials having optimum properties for operation at room temperature (Bi), as well as lower temperatures (Bi97Sb3).

1. Precision Radiometry and Its Significance in Atmospheric and Space Physics

Abstract: Publisher Summary Radiation is the transfer of energy by either emitted waves or particles In this chapter, the discussion is limited to the type of energy that travels in the form of electromagnetic waves from some material substance excited by heat, electrical discharge, or other means, and is finally absorbed by another material substance This electromagnetic spectrum is a continuum consisting of the ordered arrangement of energy according to wavelength or frequency The electromagnetic spectrum extends from waves as short as a few angstroms (ie, of the order of a millionth of a millimeter) to those of many kilometers in length at the other end of the scale The chapter focuses on the electromagnetic spectrum extending from 2000 A (200 nanometers—nm) at the ultraviolet end to about 100 micrometers (μm) in the infrared The infrared radiation generally comprises the greatest portion of the thermal emission by bodies at normally encountered temperatures and thus (with the shorter wavelength radiation) plays a considerable role in heat transfer processes The measurement of this radiation is intimately related to the establishment of the temperature scale and thus to practical methods of temperature determination The measurement of thermal radiation involves the choice of detectors Such detectors have to be designed for exposure to not only the natural sources (ie, sun, sky, atmosphere, and ground) but also artificial sources such as blackbody radiators, tungsten-filament lamps, and arc systems Another aspect involved in radiation measurements is the treatment of the medium intervening between source and detector

On the Possibility of Determining the Nature of the Surface Material of Mars From its Radio Emission

Abstract: As is known, the study of the moon's thermal radiation provides a rather complete picture of the thermal behavior of its surface and also information on some of its other physical properties [e.g. Troitskii 1967]. The phase variation of the thermal radiation provides most of the information for such an analysis, and the method may also be applied to investigate the surfaces of Venus [Troitskii, 1964] and Mercury [Vetukhnovskaya et al., 1968]. For Mars, however, we cannot observe from the earth sufficiently large phase variations. In practice, it is only really possible to observe the more or less completely illuminated side of Mars.

The Apparent Temperature and Emissivity of Natural Surfaces at Microwave Frequencies.

Abstract: : The effect of surface roughness on the emissivity of natural surfaces has attained considerable importance in the fields of passive microwave remote sensing of environment and planetary surface emissions. Between the plane surface model and the Lambert surface model, which describe the two extreme cases of a perfectly flat surface and a very rough surface respectively, two statistical surface models have recently been considered: the geometric optics type surface and the physical optics type surface. The paper examines the behavior of the microwave emissivity of some natural surfaces as a function of nadir angle and polarization. This examination includes a comparison between measured and calculated values of the apparent temperature of the ocean surface at 19.4 and 37 GHz.

Thermal, radiation and mechanical analysis of cylindrical oxide fuel elements of fast reactor in unsteady state

Abstract: Cheng, Chi-kang, "Thermal, radiation and mechanical analysis of cylindrical oxide fuel elements of fast reactor in unsteady state " (1970). Retrospective Theses and Dissertations. Paper 4218. 1970 Signature was redacted for privacy.

Absorption and scattering of thermal radiation by a cloud of small particles

Abstract: An experimental investigation was made of the absorption and scattering of thermal radiation by a cloud of small, spherical, micronsized, aluminum oxide particles in a plane-parallel enclosure. By using carbon tetrachloride and carbon disulphide as suspendign media, transmission measurements were made with collimated and diffuse sources for wavelengths from 2 to 11μ. By employing a two-flux diffuse model, the data were correlated to obtain absorption and back-scattering cross sections. From the diffuse and collimated data, a backscattering coefficient was found which varied linearly with relative refractive index. With the developed coefficients, the absorptivities of the cloud of particles were determined.

Prediction of radiation from rocket exhaust gases

Abstract: Rocket exhaust gases radiant heat transfer prediction, using band models with computer program

6. Blackbodies as Absolute Radiation Standards

Abstract: Publisher Summary All matter, by the reason of its temperature, continuously emits and absorbs electromagnetic energy in the form of thermal radiation—so called because it originates from the thermal excitations of the constituent atoms and molecules. The fact that there is an intimate relationship between the reciprocal processes of emission and absorption is expressed by Kirchhoff's law, which states that the ratio of the spectral radiant emittance H (λ) (radiant power emitted per unit area per unit wavelength interval at wavelength λ) to the spectral absorptivity α(λ) (fraction of the total incident radiant power per unit wavelength interval at wavelength λ, which is absorbed) is the same for all thermal radiators at the same temperature. Of all possible thermal radiators, this chapter directs its attention to an ideal case—that of a body (called a blackbody), which completely absorbs all radiation incident upon it. Absolute blackbody radiometry may be defined as the measurement in absolute magnitude of the total or spectral radiant flux or radiant flux density from a blackbody. The principles of absolute total blackbody radiometry are discussed. The extent to which the accuracy of radiation measurements is determined by temperature measurements falls into three categories—that is, precision, surface temperature, and thermodynamic temperature scale. The total energy radiated by a blackbody is governed directly by the Stefan–Boltzmann constant. A low-temperature blackbody is presented as an absolute standard of total radiation. Experimental difficulties in the transfer of a total radiation scale to secondary devices are dealt with. Finally, the accuracy of total irradiance standards is checked in the chapter.

Passive temperature sensor

Abstract: A passive temperature sensor for controlling a thermostat or the like. The sensor reacts to the temperature of the air and also to thermal radiation in order to control a thermostat in such a manner to give optimum personal comfort despite relative changes over a period of time between the room air temperature and thermal radiation effects in the room.

Gas core nuclear rockets

Abstract: Nuclear light bulb and coaxial flow gaseous core nuclear rocket reactors based on energy transfer via thermal radiation