Heat Radiation

A transient two-dimensional computational model of combined natural convection, conduction, and radiation in a cavity with an aspect ratio of one, containing air as a laminar and non-participating fluid, is presented. The cavity has two opaque adiabatic horizontal walls, one opaque isothermal vertical wall, and an opposite semitransparent wall, which consists of a 6-mm glass sheet with a solar control coating of SnS-CuxS facing the cavity. The semitransparent wall also exchanges heat by convection and radiation from its external surface to the surroundings and allows solar radiation pass through into the interior of the cavity. The momentum and energy equations in the transient state were solved by finite differences using the alternating direction implicit (ADI) technique. The transient conduction equation and the radiative energy flux boundary conditions are coupled to these equations. The results in this paper are limited to the following conditions: 104Gr106, an isothermal vertical cold wall of 21°C, outside air temperatures in the range 30°CT040°C and incident solar radiation of AM2 (750 W m-2) normal to the semitransparent wall. The model allows calculation of the redistribution of the absorbed component of solar radiation to the inside and outside of the cavity. The influences of the time step and mesh size were considered. Using arguments of energy balance in the cavity, it was found that the percentage difference was less than 4 per cent, showing a possible total numerical error less than this number. For Gr=106 a wave appeared in the upper side of the cavity, suggesting the influence of the boundary walls over the air flow inside the cavity. A Nusselt number correlation as a function of the Rayleigh number is presented. Copyright

We report an experiment that extends the concept of two-photon probability amplitude to the general case of independent photons. The experiment also shows interesting practical applications regarding high resolution interference patterns with thermal sources.

Rydberg state lifetimes in the singly ionized lithium atom were calculated using an inward integration approach and a Hartree-Slater potential to represent the ionic core. The calculated oscillator strengths for the s-p and p-d transitions compare favorably with high accuracy calculations using Hylleraas-type wavefunctions for the limited number of states for which such results are available. Comparison with the also sparse experimental studies of lifetimes is good overall and our predictions indicate specific revisions of some experimental determinations. The effects due to black-body radiation were explicitly included, but found to be insignificant for the states with n < 11, even at temperatures of 600 K.

Thermal (or pseudo-thermal) radiation has been recently proposed for imaging and interference types of experiments to simulate entangled states. We report an experimental study on the momentum correlation properties of a pseudo-thermal field in the photon counting regime. The characterization and understanding of such a light source in the context of two photon physics, especially its similarities and differences compared to entangled two-photon states, is useful in gaining knowledge of entanglement and may help us to assess the real potential of applications of chaotic light in this context.

Mineral dust radiative effects and feedbacks upon Saharan boundary layer meteorology are estimated by means of regional dust simulations for a one-week period in May 2006. The regional dust model system LM-MUSCAT is used, which allows online interaction of the computed dust load with the solar and thermal radiation and consequently with the model dynamics. For the Bodélé depression, a mechanism is proposed that describes positive and negative dust radiative feedbacks on surface wind speeds and dust emission in dependence on atmospheric stratification, dust-induced stabilization, and baroclinity. These effects are attributed to the formation and breakdown of the low-level jet (LLJ), which is a common phenomenon in the Bodélé. However, such processes are likely also relevant for other Saharan regions.

Abstract—Mobile communication is where signal is transferred via electromagnetic wave through radio frequency and microwave signals. This signal produced electromagnetic radiation in the form of thermal radiation that consists of harmful ionizing radiation and harmless non-...

Manufacturers of PV-modules usually give a warranty for at least 20 years. There is still only little knowledge about the lifetime of newly developed modules, however. How do they cope with snow, desert-climate or tropical humidity? In order to answer this question the ...

This article describes the application of a feedback linearization technique for control of a distributed solar collector field using the energy from solar radiation to heat a fluid. The control target is to track an outlet temperature reference by manipulating the fluid flow rate through the solar field, while attenuating the effect of disturbances (mainly radiation and inlet temperature). The proposed control scheme is very easy to implement, as it uses a numerical approximation of the transport delay and a modification of the classical control scheme to improve startup in such a way that results compared with other control structures under similar conditions are improved while preserving short commissioning times. Experiments in the real plant are also described, demonstrating how operation can be started up efficiently.