Superficial emission

Other emission models for photochemical reactors include the extense source with superficial emission (ESSE) model in which the light source is assumed to be a surface [119], and the equivalent extense source with diffuse superficial emission (ESDSE) model which has been developed to calculate the radiant power profile generated by several superficial light sources [120], Radiation field modelling for photochemical reactors has been extensively reviewed by Cassano et al. [121, 122],... 

To solve Equation (11) one can resort to the three-dimensional source with superficial emission model (Cassano ef al., 1995) and the ray tracing technique (Siegel and Howell, 2002). The integration limits depend on the geometry and dimensions of the reacting system and the set of the 14 employed lamps (Figures 5 and 6). 

Incident radiation at the wall Operation Measured by actinometry (potassium ferrioxalate) 100% (without filters) 7.55 X 10 Einstein cm s (at each window) Calculated with a superficial emission model... 

This book does not aim to treat semiconductors in any detail. However, wc have several reasons to mention, at least superficially, emission from semiconductors. These are ... 

Two main types of models for tubular lamps (the most widely used) will be described. There are lamps that produce an arc that emits radiation and, consequently, photons come out directly from such an arc. Emission is made by the whole lamp volume. We call this process Voluminal Emission. There are other types of lamps in which the discharged arc between electrodes induces an emission produced by some particular substance that has been coated on the lamp surface. We call this process Superficial Emission. Voluminal emission may be safely modeled as an isotropic emission in this case the specific intensity associated with each bundle of radiation originated in some element of volume of the lamp is independent of direction, and the associated emitted energy (per unit time and unit area) is also isotropic (Figure 6.6). On the other hand, it seems that superficial emission can be better modeled by a diffuse type of emission that is also known as one that follows the Lambert s cosine law of emission in this case the emitted intensity is independent of direction but the emitted energy depends on the surface orientation and follows the cosine law equation (Figure 6.7). The following assumptions are made (Irazoqui etal., 1973) ... 

Figure 6.7 The extended source with the superficial emission model for the lamp. Adapted from Cassano etal. (1995)...

According to equations 6.34, 6.35, and 6.37, the boundary condition when a lamp with superficial emission is used is given by... 

Limits of integration for the 3D emission models. When a lamp with superficial emission is used, according to equation 6.38, a constant value must be incorporated as a boundary condition. Conversely, when lamps with voluminal emission are used, according to equation 6.51, the boundary condition infioduces a function of x, 0, and . The limits of integration for the annular reactor with the tubular lamp were derived by Irazoqui etal. (1973) and systematically described by Cassano etal. (1995). They are... 

It is not possible for me to fit your interesting data by eye, but very superficially I would say that your measured rate is too slow as compared to the predictions of the theory based on thermionic emission. 

This assertion of experimental fact is not extracted simply from superficial examination of experimental evidence. Emission yields do vary considerably, but the effects can usually be associated with quenching by other solute molecules in condensed systems. Since a variety of common solvents do not function as quenchers in this sense, the quenching phenomenon is usually associated with special effects. The commonest explanations are transfer of electronic excitation to the quencher and some kind of chemical reaction. However, other more subtle quenching action has also been observed. 

It has been known for some time that the color of fabrics and the types of dyes used can be important factors in determining the solar reflectance of fabrics (15., l6). However, color of fabrics in apparel has no effect on the loss of body heat since the color of a fabric has a small effect on its surface emittance (16). Other factors such as fiber orientation and length, yarn twist, and fabric structure also influence the infrared and visible reflection properties of various fabrics (17). In a recent study, the various radiant properties of textiles measured at the peak emission wavelength of sunlight (0.6 urn), were found to approach constant values of absorptivity (0.67), absorptance (0.33), transmissivity (0.0), and reflectivity (0.33) at infinite superficial density (3.) ... 

At this point we note that the overall form of the absorption, fluorescence emission and excitation profiles for Agx, Ag + and AgP+ for AgxNaX and AgxNaY is superficially reminiscent of those observed for Ag°, Ag2 0, and Ag3 ° entrapped in rare gas solids (4-10). However, a number of important differences are also apparent. These details are discussed for each silver guest as a necessary prelude to the subject of metal-support interactions. 

The radiation flux af fhe wall of radiation entrance (Figure 22) was determined by actinometric measurements (Zalazar et al., 2005). Additionally, the boundary condition for fhis irradiafed wall (x = 0) was obtained using a lamp model with superficial, diffuse emission (Cassano et al., 1995) considering (i) direct radiation from fhe two lamps and (ii) specularly reflected radiation from fhe reflectors (Brandi et al., 1996). Note that the boundary conditions at the irradiated and opposite walls consider the effect of reflection and refraction at the air-glass and glass-liquid interfaces, as well as the radiation absorption by the glass window at low wavelengths (the details were shown for fhe laboratory reactor). The radiation model also assumes that no radiation arrives from fhe top and bottom reactor walls (x-y plane at z = 0 and z = Zr). 

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