Radiation Transmission Modeling

FIGURE 4.1. Macroscopic radiation balances around the catalyst suspension and the reactor inner wall. (Reprinted from Chem. Eng. ScL, 59, M. Salaices, B. Serrano and H.l. de Lasa, Photocatalytic conversion of phenolic compounds in slurry reactor s, 3-15, Copyright 2004 with permission from Elsevier). 

The various rates involved in the right side of equation (4-1) can be calculated as follows  

Rate of Photons Reaching the Inner Reactor Surface Application of equation (4-1) requires the determination of the rate of photons reaching the inner reactor surface, Pi t). Consequently, the estimation of Pi t), according to equation (4-2), requires the estimation of the rate of emission of photons by the UV lamp, P/(t), and the rate of absorption of photons in the inner glass tube wall, Pa-wall iO- 

Rate of Emission of Photons by the UV Lamp The rate of emission of photons by the lamp, so-called lamp characterization can be developed in the LTU, as described in Chapter III. In the LTU, a radiometer is placed at a fixed distance form the lamp s axis. A radiomenter correction factor of 1.41 (equation 3-1) is used which relates the tnie absolute reading to the lamp emission spectrum and the radiometer normalized spectral response. Thus the radiometric measurement allowed for the determination of the spatial distribution of the lamp radiative flux, qe y i. 

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Salaices M., 2002, Photocatalysis in Slimy Reactors Radiation, Transmission and Kinetic Modeling. PhD Dissertation, University of Western Ontario. 

Radiation transmission throughout heterogeneous dilute Ti02 suspensions can be modeled using the Beer-Lambert s Law as represented by equation (4-18),... 

A mercury poroskneter (Micromeritics model 9305) was used to determine pore size distribution. A Quantasorb adsorption unit (Quantachrome Corporation, USA) was used for BET surface area measurements. Pharma test model PTB 300 equipment was used to measure the side crushing strength of the alumina extrudates. X-ray diffraction patterns were obtained using a Phillips PW 1410 x-ray spectrometer operated at 30 kV and 20 mA with Cu Kq radiation. Transmission electron micrographs were made with JEM-1200 EX microscope. 

From this equation it can be seen that the depth of penetration depends on the angle of incidence of the infrared radiation, the refractive indices of the ATR element and the sample, and the wavelength of the radiation. As a consequence of lower penetration at higher wavenumber (shorter wavelength), bands are relatively weaker compared to a transmission spectrum, but surface specificity is higher. It has to be kept in mind that the refractive index of a medium may change in the vicinity of an absorption band. This is especially the case for strong bands for which this variation (anomalous dispersion) can distort the band shape and shift the peak maxima, but mathematical models can be applied that correct for this effect, and these are made available as software commands by some instrument manufacturers. 

Zerefos C.S., Factors influencing the transmission of solar ultraviolet irradiance through the Earth s atmosphere, in Solar Ultraviolet Radiation, Modelling, Measurements and Effects, edited by C.S. Zerefos and A.F. Bais, pp. 133-142, NATO-ASI Series, vol.52, Springer Verlag, 1997. 

In the model pump, a LHe cryopanel (90 cm x 90 cm) made of silver-plated stainless steel is shielded at the rear by a parallel LN2-cooled wall, polished on the panel side and, facing the vacuum system, by a LN2-cooled chevron baffle (with a gas transmission of 20%). The He cryopanel is supplied from a stainless steel LHe reservoir (A = 1.75 m2), wrapped in A1 foil and protected by a LN2 radiation shield of equal area. 

FIGURE 2. (a) Schematic energy scale for electronic ground (r) and exited (yj) states of a neutral molecule M, its radical cation M e generated by ionization or oxidation and its radical anion M e and dianion M" resulting from electron insertion. Representative measurement methods used in many investigations are NMR, IR, UV, PE, ESR and ENDOR spectroscopy as well as cyclic voltammetry (CV). (b) Qualitative molecular-state model, (c) Schematic time scale for molecular states and their changes (in seconds, the time unit intermediate between the duration of a human heart-beat and the transmission of stimuli by the eye)10 0 Radiation frequencies and 0 measurement methods and information obtained... 

The clear plus gray WSGG spectral model also readily leads to values for gas absorptivity and transmissivity, with respect to some appropriate surface radiation source at temperature 7, for example,... 

For different rainout rates we have calculated widely different transmission of solar radiation through the atmosphere. For slow rainout rates, the transmission may remain below 10% for a whole month (see Figure 2), which means that sunlight transmission would be less than 1%, if twice the amount of aerosol were to be dumped in the atmosphere. Because of the uncertain analysis of the amounts of fuels burnt and particulate matter formed from different materials, and considering also the simplicity of the model adopted in this study, this possibility may not be discounted. A prolonged stay of aerosol particles in the atmosphere would occur if much particulate matter rapidly reached the stratosphere because of the intense solar heating of the smoke clouds. 

Fig. 6 Model calculations (employing the Lorentzian ocillator approximation and a three layer optical model) of AR/R for RAIRS on semiconducting or insulating (isotropic and nonabsorbing) substrates (ss=3) for P- and S-polarised radiation. Calculations are shown for two values of incident angle (<( ), below and above (pe- The adsorbate layer is assumed isotropic (e x=E y=s z) with e /e=0.5, v=2100cm, y=5cm . The convention AR=R-R ds is used, so that positive resonances correspond to absorption bands, and negative values transmission bands.

IR Spectra. The IR spectra of the SOG film were obtained with a Perkin Elmer Model 683 Infrared Spectrophotometer in transmission mode by passing radiation through the film coated on a single crystal silicon wafer. In order to enhance the spectral signal, three layers... 

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