Showing papers on "Thermal radiation published in 1982"

The chemical potential of radiation

Abstract: In a thermodynamic treatment electromagnetic radiation of any kind is described. The difference between thermal and non-thermal radiation is accounted for by introducing the chemical potential of photons. Instead of an effective temperature all kinds of radiation have the real temperature of the emitting material. As a result Planck's law for thermal radiation is extended to radiation of any kind. The concept of the chemical potential of radiation is discussed in detail in conjunction with light-emitting diodes, two-level systems, and lasers. It allows the calculation of absorption coefficients, of emission spectra of luminescent materials, and of radiative recombination lifetimes of electrons and holes in semiconductors. Theoretical emission spectra are compared with experimental data on GaAs light-emitting diodes and excellent agreement is obtained.

A parameterization of effective soil temperature for microwave emission

Abstract: A parameterization of effective soil temperature is discussed, which when multiplied by the emissivity gives the brightness temperature in terms of surface (T sub o) and deep (T sub infinity) soil temperatures as T = T sub infinity + C (T sub o - T sub infinity). A coherent radiative transfer model and a large data base of observed soil moisture and temperature profiles are used to calculate the best-fit value of the parameter C. For 2.8, 6.0, 11.0, 21.0 and 49.0 cm wavelengths. The C values are respectively 0.802 + or - 0.006, 0.667 + or - 0.008, 0.480 + or - 0.010, 0.246 + or - 0.009, and 0,084 + or - 0.005. The parameterized equation gives results which are generally within one or two percent of the exact values.

Thermal Fluctuations in Resonant Motion of Fluxons on a Josephson Transmission Line: Theory and Experiment

Abstract: The radiation emission from long and narrow Josephson tunnel junctions dc-current biased on zero-field steps has been ascribed to resonant motion of fluxons on the transmission line. Within this dynamic model a theoretical expression for the radiation linewidth is derived from a full statistical treatment of thermal fluctuations in the fluxon velocity. The result appears to be very general and is corroborated by experimental determination of linewidth and frequency of radiation emitted from overlap Nb-$I$-Pb junctions.

Calculating heat transfer through windows

Abstract: To calculate the energy performance of buildings, one must know the heat-transfer characteristics of the windows as functions of environmental variables, such as temperature and wind speed. Window designs are becoming more complex in response to the need for energy conservation. In this paper, we develop a general procedure for calculating the net energy flux through the glazed area of a window composed of an arbitrary number of solid layers. These layers, which may have thin-film coatings, can have any specified solar and thermal radiation properties and enclosed spaces between solid layers can contain either air or other gases. We verified our results by comparing them with experimental measurements of heat flow using a calibrated hot-box.

Internal gravity waves in the solar atmosphere. II. Effects of radiative damping

Abstract: In the solar photosphere, temperature fluctuations associated with acoustic-gravity waves may be rapidly smoothed by the transfer mechanism of radiation between hotter and cooler regions. The present investigation of the radiative effects on internal gravity waves takes into account the parameterization of the radiative energy, employing the Newtonian cooling approximation. A linear analysis of the propagation of internal gravity waves is carried out in a model of the solar atmosphere which is taken to be homogeneous in the horizontal coordinates. Linear wave properties both with and without radiative cooling are summarized, and the variation with height of energy fluxes and of nonlinearities in the waves is discussed. Attention is given to the significance of the obtained results in terms of energy balance in the chromosphere and in relation to spectral line observations.

A laser radiometer

Abstract: The present invention concerns an unique laser radiometer capable of accurately measuring the radiation temperature of a radiant surface and independently measuring the surface's emissivity. A narrow-band radiometer is combined with a laser reflectometer to measure concurrently radiance and emissivity of a remote, hot surface. Together, radiance and emissivity yield the true surface temperature of the remote target. A narrow receiver bandwidth is attained by one of two methods; (a) heterodyne detection or (b) optical filtering. A direct measurement of emissivity is used to adjust the value obtained for the thermal radiation signal to substantially enhance the accuracy of the temperature measurement for a given subject surface. The technique provides substantially high detection sensitivity over a very narrow spectral bandwidth.

Microscopy of Si films during laser melting

Abstract: By using an optical microscope to directly observe thin Si films as they are melted with a cw argon laser beam, the crystallization process can be better understood. In an environment containing oxygen, stable filaments of solid silicon precipitate from the molten pool at low laser power. The surrounding melt may contain dissolved oxygen which reduces the melting point, allowing the liquid and solid to coexist. As laser power is increased a uniform molten pool is achieved. In emitted light the pool is dark compared to the surrounding solid due to the melt’s low emissivity. The spectrum of this emitted thermal radiation accurately fits the Planck law at 1740 °K, confirming the temperature of the melt.

Method of curing adhesive

Abstract: A method is provided for rapidly and thoroughly curing a heat curable adhesive substance by application of radiation heat energy without excessive temperature elevation of the adhesive substance. The method comprises the controlled application of radiation heat energy to the adhesive substance for elevating the exposed surface of the adhesive substance to a predetermined maximum temperature level. The radiation heat energy is then alternately removed from the adhesive substance to allow the exposed surface to cool partially, and resupplied to the adhesive substance to reheat the exposed surface to the predetermined maximum temperature level. This alternating controlled application of the radiation heat energy produces a thermal oscillation within the adhesive substance resulting in a rapid temperature rise and corresponding rapid cure time of portions of the adhesive substance not directly exposed to the radiation heat energy.

Microwave simmer pot

Abstract: A microwave cooking system comprising a thermally insulated holder for food bodies having a thermally reflective shield for reflecting thermal radiation from the food bodies to thereby reduce the loss of heat by radiation through the thermal insulation layer while providing for propagation of microwave energy into the food body through the thermal insulating portion of the food holder.

Thermal target display system

Abstract: A thermal target display system and method is disclosed by which thermal radiation patterns simulating the thermal "signature" of selected "real-scene" objects such as vehicles, buidings, and personnel, can be readily generated. The system utilizes a plurality of individually controlled, active heat-radiating thermal elements disposed in an array to form a thermal screen or target. The thermal screen is interfaced with a video system and is energized in response to a video image representing the real-scene object in the infrared spectrum. In the preferred embodiment, the gray scale representations of the individual video image pixels are converted into signals which define desired temperature differentials of each of the individual radiating elements of the thermal screen or target, these signals controlling the energization of the thermal elements so that the thermal screen generates a radiation pattern which corresponds to a particular video frame. The thermal radiation pattern, representative of the thermal signature of the real-scene object, can be enhanced and manipulated through conventional video processing techniques.

Scaling Laws of Plasma Ablation by Thermal Radiation

Abstract: Ablation of a plasma by thermal radiation is investigated within a framework of the diffusion approximation for the radiative transfer. The ablation pressure, mass ablation rate and hydrodynamic efficiency are obtained as functions of radiation intensity. The results show great improvement over laser driven ablation.

Prediction of the flow, reaction, and heat transfer in a glass furnace

Abstract: The paper describes the computation of the flow, reaction, and heat transfer in the combustion chamber region of a typical industrial glass producing furnace. The economy of the computation is considerably enhanced by the use of special grids; by the separate calculation of the burner and bulk combustion chamber regions in a manner which takes into account the differing physical nature of their flows; and by a novel technique for the handling of the thermal radiation. Predictions which demonstrate the value of such computations to furnace designers are shown for a range of operating parameters.

Non luminous gas radiation: approximate emissivity models

Abstract: The main sources of non-luminous gas radiation in furnaces are carbon dioxide and water vapor Approximation of the standard emissivities of water vapor and of carbon dioxide by mixed gray-gas model is studied The model developed for carbon dioxide standard emi s si vi ti es covers a range of temperature of 3DO-1BOOK and a partial-pressure-length product range of 001 to 10 m atm A mixture of six gray gases was adequate to cover the whole range For the water vapor thermal radiation two models were developed to approximate the standard water ~apor emissi~ities In the first model water ~apor is approximated by a mixture of four gray-gases and can be used in the temperature range of 300-700K and the partial-pressure-length range of 001 to 2 m atm The second model is a piece-wise one in which one gray gas is used to cover the pL range 05-2 m and a second gray gas covered the range of 005-05 m The model may be used in the temperature range of 700-l500K and has an error range of -23 to 37~

Heat Transfer in a Parallelogram Shaped Enclosure : 3rd Report, Combined Free Convection and Radiation Heat Transfer

Abstract: As the previous report has indicated, the main cause of the disagreement between calculated and experimental values is the effect of the radiation. In this report, the effect of the radiation on the convective heat transfer is investigated numerically. The same physical situation as the 2nd report is used for the calculation. Calculations are carried out by using the conditions of the experiments of the 2nd report and results are closely coincident with the experimental values. Calculations are also performed for aspect ratios 0.5 and 1, oblique angle π/3, distance between the hot and cold walls 0.01 to 0.04 m. The effects of the radiation on the convective heat transfer and the radiative heat transfer rate are made clear.

Thermal expansion 7

Abstract: Session 1 High and Low Temperature Measurements.- Measurement of Thermal Expansion and Volume Changes in Partially Stabilized Zirconia.- Thermal Expansion of Nickel to 2300 K.- Thermal Expansion of FeF2 Crystals.- Exfoliation of Graphite.- Thermal Expansion Studies of High-Damping Mn-Cu Alloys.- Session 2 Measurement Techniques.- Development of a Laser Interferometric Dilatometer.- A Low Temperature (4.2 to 350 K) Differential Dilatometer.- Session 3 ITCC/ITES Plenary Session.- The International Thermophysics Congress - Report on Recent Developments and Future Plans.- Session 4 Composite Materials.- Differential Thermal Expansion Studies of Graphite Reinforced Glass Matrix Composites.- Isotropic Zero CTE Materials.- Session 5 Theory and Correlations.- Role of Thermal Expansion in Thermal Stress Resistance of Semi-Absorbing Brittle Materials Subjected to Severe Thermal Radiation.- An Analysis of Thermal Expansion and Melting in Alkali Halides.- Calculation of Thermal Expansion in Insulating and Ceramic Materials.- Pressure and Temperature Behavior of Framework Silicates and Nitrides.- Session 6 Miscellaneous Materials/Applications.- High Pressure and High Temperature Studies on Mercurous Chloride.- Enhancement of Thermal Expansion Anomaly in Fe-B Amorphous Invar Alloys by Cold Rolling.- Thermal Expansion Behavior of Porous Rocks under Stress.- Thermal Expansion and Magnetic Properties of Fe-Pd Invar Alloys Containing Carbon.- Analysis of Thermally Generated Microstresses in Polycrystalline Be Due to the Presence of BeO Inclusions.- Appendix: List of Contributions to the Symposium for Which Manuscripts Were Not Published.- List of Authors.

Effective Conversion Method between Gas Enthalpy and Thermal Radiation and Its Application to Industrial Furnaces

Abstract: 適度の光学的厚さをもつ多孔性の通気性大層を高温の作動ガスが横切って流れるとき大きなエンタルピ落差が生じ, ふく射エネルギに変換され, その主要部が流れの上流方向に伝般する新しい伝熱系に関し理論解析と基礎実験を実施した. 本原理は応用範囲も広く, 工業用路に適用すると設計の基本概念を変革するほどの大きな効果が期待でき, 小型金属加熱炉の実験を行った結果, 60%もの燃費節減ができた.

The Measurement of Longwave Radiation Properties upon Plastic Films Used in Greenhouses

Abstract: Due to the rising cost of heating oils in recent years, the subject of heat conservation on a greenhouse has become more important. In this aspect, the plastic films used for reducing heat losses must have low transmittance property for longwave radiation, also need to have low emissivity. The properties of plastic films which affect on the transfer of energy are important.The paper discusses the measurements of reflectance, transmittance, and emissivity of longwave radiation (thermal radiation) upon various plastic films used for crop protection in agriculture, particularly in a greenhouse.New measuring methods for reflectance and emissivity were presented, and the previous transmittance calculations (Hagiwara and Horiguchi, 1972) were improved by using newly obtained reflectance values. The transmittance values obtained from the present study are about 2-5 percent larger than the values obtained from the previous study. The reason for the discrepancy may be due to the negligence of the reflectance term in the previous calculation.