Topic
Thermal radiation
About: Thermal radiation is a research topic. Over the lifetime, 12290 publications have been published within this topic receiving 197186 citations. The topic is also known as: heat radiation.
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TL;DR: In this article, the MHD two-dimensional flow of Eyring-Powell fluid with thermophoresis and Brownian motion is studied and the velocity, temperature and concentration gradients are also evaluated.
80 citations
01 Jan 1984
TL;DR: In this article, the authors proposed an approach to calculate the effective photon path length of clouds in the presence of visible and ultraviolet light, based on the spectral properties of clouds and their optical properties.
Abstract: I. Cloud Structures and Optical Characteristics of Clouds.- 1. Spatial Structure of Clouds.- 1.1. Cloud frequencies.- 1.2. Structure of stratiform clouds.- 1.2.1. Definitions.- 1.2.2. Height distribution of clouds.- 1.2.3. Horizontal extent.- 1.3. Clouds of vertical extent.- 1.3.1. Definitions.- 1.3.2. Shapes and typical sizes.- 1.3.3. Degree of sky cover and cloud duration.- 1.4. Regional peculiarities of clouds in the Arctic, Antarctic and tropics.- 2. Physical Characteristics of Clouds.- 2.1. Temperature and phase.- 2.1.1. Temperature characteristics of clouds.- 2.1.2. Cloud phase.- 2.2. Cloud water content.- 2.2.1. Definitions.- 2.2.2. Relation of water content to temperature.- 2.2.3. Water content of convective clouds.- 2.2.4. Spatial variability.- 2.3. Droplet-size distribution.- 2.4. Crystals in clouds.- 2.4.1. Shapes of cloud crystals.- 2.4.2. Crystal size and concentration.- 2.5. Microstructural features of polar and tropical clouds.- 3. Space-Time Statistical Structure of a Cumulus Field.- 3.1. A theoretical-experimental model of the statistical structure.- 3.1.1. Mean characteristics of cumulus cloudiness.- 3.1.2. Statistics of cumulus parameters.- 3.1.3. Correlation and spectral characteristics of cumulus fields.- 3.1.4. The use of eigenvectors to describe the cloud cover of alrrrucantars.- 3.2. An empirical model.- 4. Optical Properties of Clouds.- 4.1. Spectrum of optical parameters.- 4.2. An approximate calculation method.- 4.3. Optical parameters of an inhomogeneous cloud for a bimodal droplet-size distribution.- 4.4. Measurements of attenuation of visible light in clouds.- 4.5. Optical characteristics of ice clouds.- 4.5.1. Attenuation coefficient.- 4.5.2. Scattering function.- 4.6. An evaluation of aerosol absorption in clouds.- 4.7. Spectral transmission of thin clouds.- 4.8. Variability of optical thickness for stratiform clouds.- 4.9. Spatial inhomogeneity of optical parameters of clouds.- 5. An Optical Model of the Atmosphere.- 5.1. A model of a cloudless atmosphere.- 5.2. An aerosol model of the atmosphere.- 5.3. Transmission functions of solar radiation in water-vapor absorption bands. Integral transmission function.- 5.4. Transmission function of thermal radiation.- II. Photon Paths in Clouds.- 6. Calculations for Various Cloud Types.- 6.1. Photon-path distribution, mean and effective path lengths in an isolated stratiform cloud.- 6.2. Photon-path distribution and mean lengths in two-layer clouds, taking underlying surface into account.- 6.3. Photon-path distribution and mean path lengths in cumulus clouds.- 6.4. Equivalent trajectories in clouds exhibiting nonuniform absorption.- 7. Experimental Determination of Effective Photon Path Lengths.- 7.1. Measuring effective photon path lengths using a weak absorption band.- 7.2. Results of determining effective photon path lengths.- III. Fluxes of Solar Radiation.- 8. Visible and Ultraviolet Radiation.- 8.1. Methods of calculating albedo, transmission, and absorption.- 8.1.1 Asymptotic methods.- 8.1.2. The Monte-Carlo method.- 8.1.3. Two-stream approximation.- 8.1.4. An improved transport approximations.- 8.2. Albedo and transmittance of homogeneous cloud layers.- 8.3. Radiation properties of ice clouds.- 8.4. Effect of aerosol on radiation characteristics of clouds.- 9. Integral Solar Radiation.- 9.1. Infrared albedo and absorptivity of cloud layers.- 9.2. Integral albedo and absorptivity of cloud layers.- 9.3. Simplified method for calculating fluxes of infrared solar radiation in a cloudy atmosphere.- 9.4. Fluxes and influxes of infrared solar radiation in a cloudy atmosphere.- 10. Experimental Aircraft Studies of Solar Fluxes in the Presence of Stratiform Clouds.- 10.1. Regime of integral solar radiation for St-Sc clouds.- 10.2. Experimental model of "average" St-Sc cloud.- 10.3. Spectral and integral radiation characteristics of stratiform clouds.- 10.4. Radiation properties of urban clouds.- 10.5. Comparison of calculations with data of aircraft measurements.- 11. Solar Fluxes in the Presence of Cumulus Clouds.- 11.1. Radiation regime of isolated cumulus cloud.- 11.2. Statistical structure of fluxes for broken cloudiness.- 11.2.1. Direct radiation.- 11.2.2. Scattered radiation.- 11.2.3. Total radiation.- 11.3. Parametrization of radiation regime of cumulus field using experimental aircraft data.- 11.4. Variability of fluxes of short-wave radiation for broken cloudiness.- 11.5. A comparison of calculated and experimental radiation characteristics of a cumulus field.- 11.5.1. The Monte-Carlo method.- 11.5.2. The analytical method.- IV. Thermal Radiation of a Cloudy Atmosphere.- 12. Methods of Calculating Radiation.- 12.1. Fundamental relations and use of integral transmission function.- 12.2. Thermal radiation of a cloudy atmosphere.- 12.3. Semiempirical methods.- 12.4. Algorithm for models of general circulation.- 12.5. Radiation calculations in cloud-formation models.- 13. Experimental Studies of the Thermal Radiation of a Cloudy Atmosphere.- 13.1. Actinometric radiosonde observations of atmosphere.- 13.2. Actinometric model of the atmosphere.- 13.3. Aircraft studies of thermal radiation of a cloudy atmosphere.- 13.4. Characteristics of an "average" stratiform cloud.- 13.5. Dependence of calculation results on accuracy of measuring atmospheric parameters.- 13.6. Comparison of measurements and calculations under specific conditions.- 14. Effect of Optical Properties of Clouds on Thermal Radiation.- 14.1. Flux distribution inside a cloud layer. Estimates of error of "blackbody" approximation.- 14.2. Thermal albedo of clouds.- 14.3. Emissivity of clouds.- 14.4. Effect of "nonb1ackness" of clouds.- V. Regional Features of the Radiation Regime of a Cloudy Atmosphere.- 15. The Polar Regions.- 15.1. Structural features of the atmosphere.- 15.2. Mean data on radiation regime of cloudless atmosphere.- 15.3. Effect of cloudiness on regime of solar radiation.- 15.4. Effect of cloudiness on regime of thermal radiation.- 16. Radiation Regime of the Tropical Central Atlantic.- 16.1. Fluxes of solar radiation in water-adjacent layer under cloudy and cloudless conditions.- 16.2. Classification of fluxes of thermal radiation.- 16.3. Fluxes of thermal radiation and radiative cooling of a cloudy or cloudless atmosphere.- References.
80 citations
TL;DR: A new numerical code has been developed which describes hydrodynamics in two spatial dimensions and radiation transport along rays in three dimensions with the 4 π solid angle discretized in direction, which allows to propagate sharply edged beams without ray tracing, though at the price of some lateral diffusion.
80 citations
TL;DR: In this paper, the authors investigated the heat augmentation and hydromagnetic flow of water-based carbon nanotubes (CNTs) inside a partially heated rectangular fin-shaped cavity, where a thin heated rod was placed within the cavity to create a resistance or to provide a source for heat transfer.
Abstract: This study investigates the heat augmentation and hydromagnetic flow of water-based carbon nanotubes (CNTs) inside a partially heated rectangular fin-shaped cavity. A thin heated rod is placed within the cavity to create a resistance or to provide a source for heat transfer. The obstacle is tested for the heated case, while the right side of the horizontal tip is tested for three different temperatures (adiabatic, cold, and heated). The left vertical side of the cavity is partially heated with temperature Th, and the rest of the sides are kept cold at temperature Tc except the right tip. Two different thermal boundary conditions (prescribed temperature and adiabatic) are employed on the fin tip. The CNTs and water are assumed to be in thermal equilibrium with no-slip velocity. The magnetic field and thermal radiation are introduced in the momentum and energy equations, respectively. The governing equations are obtained in dimensionless form by means of dimensionless variables. The numerical computation is performed via the finite element method using the Galerkin approach. The substantial effects of emerging parameters on the streamlines, isotherms, dimensionless velocities, and temperature are reported graphically and discussed. In the case of a cold or adiabatic fin-tip, a drop to minimum is found in the dimensionless temperature. The components of velocity are perceived maximum at a vertical corner while minimum at the horizontal corner. It is demonstrated that the local Nusselt numbers are increased by introducing both solid volume fraction of CNTs and radiation effects, while the Nusselt number noticed maximum at the corners.
80 citations
TL;DR: In this paper, the thermodynamics and kinetics of the carbothermic reduction of ZnO are examined over the temperature range 400−1600 K. The model involves solving, by the finite-volume technique, a 1D unsteady-state energy equation that couples heat transfer to the chemical kinetics for a shrinking packed bed exposed to thermal radiation.
Abstract: The thermodynamics and kinetics of the carbothermic reduction of ZnO are examined over the temperature range 400−1600 K. Above 1340 K, the equilibrium composition of the stoichiometric chemical system consists of an equimolar gas mixture of Zn (vapor) and CO. Assuming a first-order rate constant for the surface reaction kinetics between ZnO(s) and CO and further applying a shrinking spherical particle model with an unreacted core, the apparent activation energy obtained by linear regression of the thermogravimetric data is EA = 201.5 kJ/mol. A numerical model is formulated for a solar chemical reactor that uses concentrated solar radiation as the energy source of process heat. The model involves solving, by the finite-volume technique, a 1D unsteady-state energy equation that couples heat transfer to the chemical kinetics for a shrinking packed bed exposed to thermal radiation. Validation is accomplished by comparison with experimentally measured temperature profiles and Zn production rates as a function ...
80 citations