Superficial emission model

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... 

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). 

The lamp radiative flux, qg, can be calculated by using an extensive source superficial diffuse emission model (ESSDE) (Tsekov and Smirniotis, 1997). Figure 4.2 presents the qg.z.i distribution and the results of the ESSDE model at the radial positions, 3.1 and 4.5 cm from the lamp axis (or 1.9 and 3.2 cm from the lamp surface). As it can... 

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)...

Three-dimensional source with superficial diffuse emission. The E-SDE source model. 

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... 

In contrary, surface dielectric function model [38] suggests that photon emission of sized quantum dot (QD) depends on changes to dielectric function in the superficial skin rather than the entire dot as QC theory refers. The dielectric function in the core interior of a QD remains as that of the bulk material, but in a small dot, the differences are greater near the grain boundary. 

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