In situ detailed fluence rate distributions in a UV reactor with multiple low-pressure lamps: Comparison of experimental and model results Mengkai Li a , Zhimin Qiang a,⇑ , James R. Bolton b,⇑ a State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing 100085, China b Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB, Canada T6G 2W2 highlights " In situ detailed FR distributions were measured in a multiple-lamp UV reactor. " FR distributions were determined along axial, radial and arc directions. " The measured FR data agreed reasonably well with the model predictions. " The effects of shadowing and reflection on FR distributions were clarified. graphical abstract article info Article history: Received 23 June 2012 Received in revised form 16 October 2012 Accepted 20 October 2012 Available online 27 October 2012 Keywords: In situ measurement Multiple-lamp UV reactor Fluence rate distribution Shadowing effect Reflection effect abstract Accurate and detailed in situ determination of fluence rate (FR) distributions in ultraviolet (UV) reactors with multiple lamps is important in validating mathematical models for the purpose of estimating the fluence (UV dose) delivery. In this study, the FR distributions in a practical multiple-lamp UV reactor were determined experimentally for waters with various transmittances (at 254 nm) using a micro-fluorescent silica detector. Three lamp configurations were investigated through detailed FR distribution measure- ments along the reactor axis, a radial direction, and a certain arc in a plane perpendicular to the reactor axis. The results showed that the mathematical model (UVCalc Ò versions 2A and 3) FR predictions agreed reasonably well with the experimental data. A shadowing effect was found not only in totally-blocked regions, but also in partially-blocked regions. Reflection from the reactor wall exhibited a strong influence when the UV lamps were placed near the reactor wall. In addition, certain effects were measured quan- titatively, such as a shadowing effect (the model over-predicted by about 8% in the shadow region) and a reflection effect from lamp/sleeve pairs (the model under-predicted by about 7–9% for the local FRs and about 2% for the radius-weighted average FR). A semi-closed ‘loop’ formed by the three lamps and their sleeves appeared to induce a reflection enhancement. This study has potential applications toward the improvement of mathematical models and the optimization of UV reactor design. Ó 2012 Elsevier B.V. All rights reserved. 1385-8947/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2012.10.024 ⇑ Corresponding authors. Tel.: +86 10 62849632; fax: +86 10 62923541 (Z. Qiang), tel.: +1 780 4394709; fax: +1 780 4397792 (J.R. Bolton). E-mail addresses: qiangz@rcees.ac.cn (Z. Qiang), jb3@ualberta.ca (J.R. Bolton). Chemical Engineering Journal 214 (2013) 55–62 Contents lists available at SciVerse ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej