Using 3D LIF to investigate and improve performance of a multichamber ozone contactor

Abstract

Three‐dimensional laser‐induced fluorescence (3D LIF) was applied to visualize and quantitatively analyze hydrodynamics and mixing in a multichamber ozone contactor, the most widely used design for water disinfection. Results suggested that mixing was characterized by extensive short‐circuiting between chambers, internal recirculation within the chambers, and dead zones at the chamber centers. Because of these nonideal mixing behaviors, the hydrodynamics in the entire reactor showed greater dispersion than a series of completely mixed reactors. These flow patterns could be diminished by decreasing the channel width, whereas the effects of the flow rate and baffle gap were negligible within the range investigated. Accordingly, reactive transport model simulations suggested that overall reactor performance could be significantly improved by preventing these flow behaviors. The 3D LIF technique developed and presented in this study is expected to provide a novel tool for reactor diagnosis, retrofitting to improve performance, and new reactor design.

Unified Analysis of Multi-Chamber Contact Tanks and Mixing Efficiency Evaluation Based on Vorticity Field. Part II: Transport Analysis

“…The comparisons of the predicted residence time indexes are in good agreement with the previously reported experimental and numerical results that are given in the literature [7][8][9]12]. [9] 0.334 0.875 1.762 LES [12] 0.325 0.857 1.902 RANS [7] 0.322 0.860 1.949 The RTD analysis of the tracer is performed at the end of each chamber, as well as inside the chambers using the volumetric efficiency definitions given below.…”

“…Sc is the Schmidt number which is chosen as 0.7 for RANS and 1000 for LES [7,8], in order to be consistent with experimental studies [9,10].…”

“…[9] 0.334 0.875 1.762 LES [12] 0.325 0.857 1.902 RANS [7] 0.322 0.860 1.949 The RTD analysis of the tracer is performed at the end of each chamber, as well as inside the chambers using the volumetric efficiency definitions given below.…”

Unified Analysis of Multi-Chamber Contact Tanks and Mixing Efficiency Based on Vorticity Field. Part I: Hydrodynamic Analysis

“…The Reynolds number of the flow corresponds to the same flow configuration in the previously reported experimental [23] and numerical studies [6,10].…”

“…As seen in this figure, water enters the inlet of the tank on the left with constant discharge Q and emerges from the tank at the outlet on the right to maintain an approximately constant water level of H inside the tank. Experimental studies were also conducted in [23] for the same flow configuration in a tank with 12 chambers. In the present study, numerical simulations were performed on the truncated version of the physical domain, applying periodic boundary conditions at the inlet and outlet to reduce the computational time and exclude the turbulence intensity effects at the inlet, which are generally cumbersome to prescribe for the simulation of turbulent flows.…”