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[en] A simple undergraduate experiment designed to study cooling purely by radiation and cooling by a combination of convection and radiation is described. Results indicate that the contribution from radiative cooling in normal laboratory experiments is more significant than students often realize, even in the case of forced cooling
[en] An arrangement of plates was built using two minerals, calcite and hematite, deposited on glass (slides). The plates were placed in Chilapa de Alvarez city, in the southeast of Mexico. The goal of this work is to prove that mineral plates perform better than glass in nocturnal radiative cooling phenomena. The results obtained are that the glass/hematite plate collected 1.2-1.5 x 10-3 l of water and the glass/calcite plate only 0.71-0.75 x 10-3 l; meanwhile dew was not observed on a glass plate without minerals
[en] The present paper studies the role of radiative cooling on natural convection in a square cavity. Radiative cooling of the air sets up convection. The interaction depends on multitude of parameters such as Planck number, optical length and the length scale of the enclosure. Both gray and non-gray gases have been considered for the study.
[en] Although the total radiated power in the Tokamak Fusion Test Reactor is often as high as 70% of the heating power, most of the radiation is concentrated near the surface of the plasma, and the interior loss is almost negligible. Fractional radiation loss declines during neutral beam heating. Under most interesting plasma conditions, the radiation profiles are dominated by asymmetrical peaks, which indicate locally intense edge radiation. As the high-density limit is approached, under most conditions, a bright band of radiation (a marfe) appears on the inner side of the plasma column. Marfe location is affected by toroidal field direction, neutral beam direction, and nearness to the high-density limit. Marfes have been observed to drift under the plasma column to the lower outside plasma edge. Marfes naturally develop into detached plasmas. In enhanced confinement discharges (supershots), an unexplained peculiar bright band, distinct from a marfe, appears in the lower outside part of the vacuum vessel, outside of the limiter radius. In high-density pellet-fueled discharges, there is a central peak that shows evidence for inward impurity convection
[en] We introduce a general approach to radiatively lower the temperature of a structure, while preserving its color under sunlight. The cooling effect persists in the presence of considerable convective and conductive heat exchange and for different solar absorptances
[en] The authors examine the validity of the differential equations used to describe ionization cooling. They find that the simple heating term due to multiple scattering given by D. Neuffer is a good approximation to the expression obtained from a more rigorous derivation
[en] This work examines the influences of relative dispersion (the ratio of the standard deviation to the mean radius of the cloud droplet size distribution) on cloud albedo and cloud radiative forcing, derives an analytical formulation that accounts explicitly for the contribution from droplet concentration and relative dispersion, and presents a new approach to parameterize relative dispersion in climate models. It is shown that inadequate representation of relative dispersion in climate models leads to an overestimation of cloud albedo, resulting in a negative bias of global mean shortwave cloud radiative forcing that can be comparable to the warming caused by doubling CO2 in magnitude, and that this dispersion bias is likely near its maximum for ambient clouds. Relative dispersion is empirically expressed as a function of the quotient between cloud liquid water content and droplet concentration (i.e., water per droplet), yielding an analytical formulation for the first aerosol indirect effect. Further analysis of the new expression reveals that the dispersion effect not only offsets the cooling from the Twomey effect, but is also proportional to the Twomey effect in magnitude. These results suggest that unrealistic representation of relative dispersion in cloud parameterization in general, and evaluation of aerosol indirect effects in particular, is at least in part responsible for several outstanding puzzles of the aerosol-cloud conundrum: for example, overestimation of cloud radiative cooling by climate models compared to satellite observations; large uncertainty and discrepancy in estimates of the aerosol indirect effect; and the lack of interhemispheric difference in cloud albedo.
[en] It has been shown that the fundamental results obtained in the works by Levine–Polevoi–Rytov (1980) and Rytov (1990) adequately describe the rate of radiative heat exchange and frictional force in a system of two thick parallel plates in relative motion, in full agreement with the results obtained by other authors later. A numerically calculated friction force for Drude metals turns out to be higher by a factor of 107 than the early result obtained by Polevoi. In addition, the friction force significantly increases with increasing the conductivity of the plates or increasing the relaxation time of electrons with decreasing temperature.