Radiation modeling of ultraviolet light-emitting diode (UV-LED) for water treatment

Abstract

Determination of the profile of radiant energy is essential for the design and optimization of ultraviolet reactors. To simulate the distribution of radiation, the ultraviolet (UV) source geometry and its characteristics, the propagation of rays through different media and the reflection from relevant surfaces need to be considered. UV Light Emitting Diodes (UV-LEDs) have recently emerged as a new source of UV energy. As they are small, operate at low power and voltage, and can be turned on and off instantly, UV-LEDS are likely an excellent source of UV for water disinfection systems. However, existing UV-lamp radiation models cannot be directly applied to this model as UV-LEDs are a directional radiation source with various radiation profiles. Therefore, in this study, a general method is proposed for modeling the radiant energy field within a UV-LED reactor by considering multiple factors, including the UV-LED profile, refraction/reflection through/from different media, and reflection from internal wall surfaces. The propagation of the UV rays were calculated by solving a simplified form of the radiation transfer equation, assuming negligible thermal radiation and scattering in the media. Four UV-LEDs with different radiant powers and peak wavelengths, in the range of 265nm–275 nm, were chosen for the study. In order to holistically assess this numerical approach, photoluminescence processes were used to visualize UV patterns; the captured photons, a function of the intensity, were used against the model predictions. Further, irradiance was measured using a spectroradiometer inside the reactor to quantitatively evaluate the model predictions. Overall, the developed radiation model showed close agreement with the experimental data. The proposed radiation model along with hydrodynamic and kinetic models can be integrated into a general-purpose computational software to simulate overall performance of a UV-LED reactor.