A Simple and Reliable Method to Determine Mean Incident Light Flux Densities on Cylindrical Photoreactors and Photobioreactors from a Unique Fluence Rate Measurement

Abstract

A new method to determine the hemispherical incident light (photon) flux density onto cylindrical photoreactors or photobioreactors is presented. It applies to situations where the photo(bio)reactor is radially illuminated by surrounding artificial sources or solar light. It relies on the direct measurement of a fluence rate with a spherical sensor put at the center of the reactor. Theoretical relations leading to the calculation of the hemispherical incident light flux density from the fluence rate value are established, and a web application performing those calculations is made available. It relies on a view factor, the expression of which, established for the first time with any assumption of the angular distribution of light at the boundary, is given. This requires a proper definition of the degree of collimation for the incident radiation field. Two different and complementary experimental devices are used to validate the method. As a result, the proposed method appears to be simple and reliable; it even looks faster and more accurate than actinometry for this particular geometry.

A facile strategy to determine photon flux and effective optical path length in intensified continuous-flow photoreactors

“…This is because light sources come with unique emission distribution patterns, and factors like refraction, back reflection, and total internal reflection can alter the effective optical path length. 13,18,37 While spectro-radiometric measurements offer a way to delineate the system's path length, 38,39 their precision can be compromised in scenarios with uneven irradiation fields or when bulky light sensors are paired with micro-scaled (or intensified) reactors. 40 Furthermore, achieving accuracy becomes more challenging when interfaces of materials, each having distinct refractive indices, affect the local irradiation profile.…”