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 paper, the authors analyzed the properties of thermal radiation in photonic crystals and showed that the spectral energy density, the spectral intensity, and the spectral hemispherical power are only limited by the total number of available photonic states and their propagation characteristics.
Abstract: We analyze the properties of thermal radiation in photonic crystals and show that the spectral energy density, the spectral intensity, and the spectral hemispherical power are only limited by the total number of available photonic states and their propagation characteristics. In addition, we show that the central quantity that determines these thermal radiation characteristics is the area of the isofrequency surfaces and not the photonic density of states as it is generally assumed. Through the presence of partial or complete photonic band gaps and the associated spectral and angular redistribution of photonic states, it is possible to have spectral regions over which the thermal radiation intensity is enhanced relative to the free space blackbody limit and propagation directions along which thermal photon focusing effects appear.
53 citations
TL;DR: In this paper, the effect of nanofluid and thermal radiation on MHD Williamson fluid over a stretching cylinder in the presence of convective boundary conditions is analyzed and the variable thermal conductivity is considered during the formulation of energy equation.
Abstract: The effect of nanofluid and thermal radiation on MHD Williamson fluid over a stretching cylinder in the presence of convective boundary conditions is analyzed. The variable thermal conductivity is considered during the formulation of energy equation. Nonlinear ordinary differential equations are attained by proposing relevant similarity transformations on partial differential equations. These non-dimensional ordinary differential equations are then converted to the system of first order ODEs and solved numerically by shooting method. Results are further compared by using bvp 4 c , a MATLAB built-in function. The results obtained from MATLAB codes are compared with previously published results of the same nature in limiting case. Numerical results of skin-friction coefficient, local Nusselt and Sherwood numbers are systematized in the form of tables. The effect of prominent parameters on velocity, temperature and concentration is displayed by using graphs. It is observed that velocity profile diminishes for the higher values of Weissenberg number but a reverse relation is noticed for the temperature profile.
53 citations
TL;DR: In this paper, an exact analysis is carried out to study the radiation effects on an unsteady natural convective flow of a nanofluid past an impulsively started infinite vertical plate.
Abstract: An exact analysis is carried out to study the radiation effects on an unsteady natural convective flow of a nanofluid past an impulsively started infinite vertical plate. The nanofluids containing nanoparticles of aluminium oxide, copper, titanium oxide and silver with nanoparticle volume fraction range less than or equal to 0.04 are considered. The partial differential equations governing the flow are solved by Laplace transform technique. The influence of various parameters on velocity and temperature profiles, as well as Nusselt number and skin-friction coefficient, are examined and presented graphically. An increase in radiation parameter and time leads to fall in temperature of the fluid. The presence of nanoparticles and thermal radiation increases the rate of heat transfer and skin friction. The effect of heat transfer is found to be more pronounced in silver water nanofluid than in the other nanofluids. It is observed that the fluid velocity increases with an increase in Grashof number and time. E...
53 citations
TL;DR: In this article, the authors used the REM2 method for radiative heat transfer in three-dimensional inhomogeneous, nongray and anisotropically scattering media, and the results were verified by benchmark comparisons against the solutions of Monte Carlo and YIX methods.
53 citations
TL;DR: In this paper, a converging-thermal-wave technique is described for the measurement of thermal diffusivity in bulk or thin-sheet materials, where an annular-shaped area is heated by a pulsed laser beam focused on the material's surface through a combination of spherical and conical lenses.
Abstract: A converging-thermal-wave technique is described for the measurement of thermal diffusivity in bulk or thin-sheet materials. An annular-shaped area is heated by a pulsed laser beam focused on the material's surface through a combination of spherical and conical lenses, and the surface temperature is monitored by an infrared detector focused on the center of the annulus. The converging action of the thermal flux results in a high amplitude of the detected signal with little overheating of the irradiated material. An analysis of such a technique is presented, as well as some experimental results obtained on heterogeneous materials. Several aspects relevant to the practical implementation of such a technique in an industrial environment, such as the effect of surface losses and different noise sources, are discussed.
52 citations