Radiative Heat Transfer
We have focused on the turbulent fluid mechanics, the chemical reactions, and the interactions between these two aspects of combustion and gasification. In this chapter we change emphasis and briefly examine the dominant heat-transfer mechanism in coal-fired combustors and gasifiers; namely, radiative heat transfer. Radiation is electromagnetic energy in transport. A photon of energy interacts with an individual molecule to excite it to increased energy states. As the molecule relaxes to lower-energy levels, different photons are emitted. Radiation can be transmitted at wavelengths anywhere from 1 nm to 1 km corresponding to x-ray radiation and radiowave radiation, respectively. Of interest to heat-transfer calculations is thermal radiation within the range of 0.1–100 μm in wavelength. In combustion and gasification processes, the most significant contributions to thermoenergy arrive from radiation having wavelengths between 0.5 and 10μm.
KeywordsPhase Function Radiative Heat Transfer Soot Particle Scatter Cross Section Coal Particle
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