Photon absorption in a hybrid slurry photocatalytic reactor: Assessment of differential approximations

Abstract

Radiative transfer inside a slurry photocatalytic reactor with hybrid illumination from both solar radiation and lamps is examined. The local volumetric rate of photon absorption is evaluated. For this purpose, the P1 and the modified differential approximations (MDAs) are used, and results compared to a solution by the Monte Carlo method. It is found that significant differences may arise between the predictions of the above approximations and the exact results provided by the Monte Carlo simulations. The P1 approximation is very inaccurate near to the radiation entrance for the partially collimated solar radiation, although it improves, as optical depth increases. As expected, the MDA improves the results near to the boundary. Surprisingly, it turns out to be much worse than the P1 approximation at medium and large optical depths. In the case of lamp irradiation, the behavior of the MDA is the opposite; it works better at small optical depths. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3256–3265, 2012

Insights into the hydrodynamic properties of slurry flow in a tubular photocatalytic reactor by PIV combined with LSIA

“…According to many previous studies, when the particle distribution is known, one must solve the radiative transfer equation (RTE) to obtain the radiation distribution in the photoreactor (Orozco et al, 2012). In consideration of the many random factors in light transmission such as scattering, absorption and reflectance, the Monte Carlo method is one of the most widely utilized methods because of its characteristics of accuracy, highefficiency and low computation resource requirements (Cao et al, 2014).…”

“…However, it is also a time-consuming method. In this study, our main target is to qualitatively explain how important a role the particle size distribution plays in the resultant light distribution, therefore the modified differential approximation (MDA) is adopted (Orozco et al, 2012). A series of typical CPC parameters was selected to be simulated according to our previous work (Jing et al, 2010), with the maximum acceptance half angle, truncation angle and incident angle of the CPC set to 40°, 60°and 0°, respectively.…”

Computer Simulations of Photocatalytic Reactors

“…This assumption is important in the view of the scattering phenomenon because it is possible to eliminate the directional behavior (from the radiation field) that originated from its sources [29]. This method has also been applied in photoreactor simulations [28][29][30].…”

“…This equation depends on the specific geometry of the photocatalytic reactor and the type of light source [22,23]. The RTE solution requires the application of a proper mathematical model, such as the statistical Monte Carlo method [24][25][26][27] or approximation approach-P1 model [28][29][30]. Another important procedure is the discrete ordination method (DOM), which is recognized as an accurate and flexible procedure [19,22,[31][32][33][34][35][36][37][38].…”

On the engineering of a laboratory LED‐based photocatalytic reactor for radiative and kinetic studies

“…[ 11–15 ] Regarding kinetics, there are two types of studies: those neglecting the effect of fluid dynamics and mass transport on kinetics and those accounting for it but by following a pseudo extrinsic approach. [ 8,15–19 ] These two types of contributions have led to the determination of experimental reaction rates with important uncertainties to be used during the development of a kinetic model. Concerning radiative transfer, its characterization still presents some limitations since the key variable relating the interaction between kinetics and radiative transfer, the local volumetric rate of energy absorption (LVREA), lacks reliability due to the uncertainty on the determination of the effective optical parameters such as the specific extinction coefficient (β*) which is used, along with other parameters, to describe the radiative field by the radiative transfer equation (RTE).…”