Cylindrical lamps are usually equipped in the tubular UV reactor to offer UV radiation. This paper describes the axisymmetric characteristics of UV radiation from the cylindrical UV lamp. Axisymmetric lamp emission models are developed in a two‐dimensional axisymmetric space for the line source, the superficial source and the volumetric source. The present axisymmetric lamp emission models are easy to understand and of simple mathematical expressions. The experimental data in literature is used to validate the present axisymmetric lamp emission models. Good agreements have been obtained between the experimental data and the computations. A comparison show that the present models obtain the identical results as previous models.
The flow and tracer transport in an ozone contactor is simulated by using computational fluid dynamics. The standard k- model, RNG k- model, Realizable k- model and SST k- model are used to describe turbulence. A step change method is used to simulate the residence time distribution. The residence time and cumulative residence time are compared with laboratory experiments. All turbulence models can capture the feature of the residence time distribution and cumulative residence time distribution. The residence time distribution in the initial period is sensitive to the used turbulence model, which can affect the value of MDI. The standard k- model behaves better among four turbulence models.
Introduction: Photocatalytic oxidation of gaseous pollutants in differential reactors is simulated using computational fluid dynamics.
Materials and methods: The momentum equation and pollutant transport are solved by using ANSYS Fluent. The SIMPLE algorithm is used to treat the pressure-velocity coupling. The laminar flow and low Reynolds k−ε models are used to describe turbulence.
Results: Velocity field distribution and degradation efficiency of different models at various flow rates were obtained and compared with the experimental data. The simulation results of degradation efficiency under different models are basically consistent.
Conclusion: Although low Reynolds k-ε models have better simulation results for high inlet flow rates, in terms of computation complexity, laminar flow is recommended for simulation.
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