Radiant thermal energy

The rate of radiant thermal energy transfer between two bodies is described by the Stefan-Boltzmann law. Originally proposed in 1879 by Joseph Stefan and verified in 1884 by Ludwig Boltzmann, the Stefan-Boltzmann law states thatthe emission of thermal radiative energy is proportional to the fourth power of the absolute temperature (Kelvin or Rankine) ... 

The third mechanism of heat transfer is thermal radiation that can be defined as radiant energy emitted by a medium by virtue of its temperature. The wavelengths of thermal radiation produced by emitting bodies fall roughly between 0.1 and 100 pm, which includes portions of the ultraviolet, visible, and infrared spectra. The net exchange of radiant thermal energy between two surfaces can be characterized by the following relationship... 

Substances can emit various forms of radiant energy such as X-rays. However, the only form produced by virtue of temperature is thermal radiation. At temperatures near or below room temperature this mode of heat transfer is not important. However, at temperatures in the range of 1(XX), the radiant thermal energy can be significant. 

Arc vapor deposition processes are used for vaporizing all forms of conductive materials with low radiant thermal energy from cathodic arc deposition. Non-conductive materials cannot be processed. However, the process is effective in depositing high-wear, corrosion and erosion-resistant thin-film coatings on precision parts. Pure metals, metal nitrides, carbides and carbo-nitrides, for example, can be deposited as a monolayer, multilayer, graded, or alloy film. 

Radiometry. Radiometry is the measurement of radiant electromagnetic energy (17,18,134), considered herein to be the direct detection and spectroscopic analysis of ambient thermal emission, as distinguished from techniques in which the sample is actively probed. At any temperature above absolute zero, some molecules are in thermally populated excited levels, and transitions from these to the ground state radiate energy at characteristic frequencies. Erom Wien s displacement law, T = 2898 //m-K, the emission maximum at 300 K is near 10 fim in the mid-ir. This radiation occurs at just the energies of molecular rovibrational transitions, so thermal emission carries much the same information as an ir absorption spectmm. Detection of the emissions of remote thermal sources is the ultimate passive and noninvasive technique, requiring not even an optical probe of the sampled volume. 

In practice, solar cells may only convert about 10% of the radiant energy into electricity. The other 90% of the sunlight is converted into thermal energy. 

Reactions (1) and (2) essentially convert solar radiant energy into thermal energy. The parameters which determine the rate of ozone formation (UV photon flux, atomic and molecular oxygen number density and the total gas number density) are not constant with altitude and so the ozone concentration and hence Tg varies with altitude. The net result is that Tg increases thoughout the stratosphere until a maximum is reached at the stratopause whence Tg begins to decrease again. 

In this instance the irradiation G may originate from a special source, such as the sun, or from other surfaces to which the surface of interest is exposed. A portion, or all, of the irradiation may be absorbed by the surface, thereby increasing the thermal energy of the material. Since the rate at which radiant energy is absorbed per unit area is evaluated in terms of the surface radiative property termed the absorptivity a, we get ... 

Solar cells may also use lenses or parabolic concentrators to convert more of the radiant energy into thermal-energy. The lens increases the brightness of the light and converts some of the photon-energy into thermal-energy. 

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