tailieunhanh - solar collectors and panels theory and applications Part 5

Tham khảo tài liệu 'solar collectors and panels theory and applications part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 112 Solar Collectors and Panels Theory and Applications positively charged helium nuclei and iii beta particles rapidly moving electrons. The artificial radioactive elements are formed by bombardment with high energy particles such as helium nuclei. The most of the radiation in ultraviolet region of radiation spectrum is absorbed by the ozone in the upper atmosphere whilst part of the radiation in the shortwave region of the radiation spectrum is scattered by air molecules for communication of blue colour appearance of sky to our eyes. The strength of the absorption of solar energy varies with wavelength and absorption bands are formed at regions of strong absorption. The important atmospheric gases forming part of absorption bands are ozone O3 water vapour H2O carbon dioxide CO2 oxygen O2 methane CH4 chlorofluorocarbons CFC and nitrogen dioxide NO2 . The scope of the chapter is to present detailed theoretical aspects of solar energy absorbers their radiation properties radiation sources diffraction and measurement of radiation sources. The importance of selection of roughness factors based on fluid flow is pointed out. The human environmental health is presented for metabolism of your body to intense solar radiation and heat. Mathematical analysis of a solar thermosyphon and experimental results for applications of solar collectors to the environment human health and buildings are elaborated later in the chapter. 2. Theory The rate of electromagnetic radiation emitted at a rate Ex from the surface of a solar energy absorber is given by the Stefan-Boltzmann equation as follows Ex eoT4 1 Where Ex is exitance of a solar energy absorber T is temperature in K o is Stefan-Boltzmann constant x 108 W and e is hemispherical emittance for a surface of solar energy absorber. The theoretical maximum value of hemispherical emittance possible from the surface of a solar energy absorber is . The radiation emitted from the surface of a solar energy absorber for e .

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