UV Disinfection between Concentric Cylinders

Show full item record

Please use this identifier to cite or link to this item: http://hdl.handle.net/1853/14641

Title: UV Disinfection between Concentric Cylinders
Author: Ye, Zhengcai
Abstract: Outbreaks of food-born illness associated with the consumption of unpasteurized juice and apple cider have resulted in a rule published by the U.S. Food and Drug Administration (FDA) in order to improve the safety of juice products. The rule (21 CFR120) requires manufacturers of juice products to develop a Hazard Analysis and Critical Control Point (HACCP) plan and to achieve a 5-log reduction in the number of the most resistant pathogens. Ultraviolet (UV) disinfection is one of the promising methods to reach this 5-log reduction of pathogens. The absorption coefficients of juices typically vary from 10 to 40 1/cm and can be even higher depending on brand and processing conditions. Thin film reactors consisting of two concentric cylinders are suitable for inactivating pathogens in juices. When the two concentric cylinders are fixed, the flow pattern in the gap can be laminar Poiseuille flow or turbulent flow depending on flow rates. If the inner cylinder is rotating, and the rotating speed of the inner cylinder exceeds a certain value, the flow pattern can be either laminar or turbulent Taylor-Couette flow. UV disinfection between concentric cylinders in laminar Poiseuille flow, turbulent flow and both laminar and turbulent Taylor-Couette flow was investigated experimentally and numerically. This is the first systematic study done on UV disinfection between concentric cylinders in all three flow patterns. The present work provides new experimental data for pathogen inactivation in each of the three flow patterns. In addition, the present study constitutes the first systematic numerical CFD predictions of expected inactivation levels. Proper operating parameters and optimum gap widths for different flow patterns are suggested. It is concluded that laminar Poiseuille flow provides inferior (small) inactivation levels while laminar Taylor-Couette flow provides superior (large) inactivation levels. The relative inactivation levels are: laminar Poiseuille flow < turbulent flow < laminar Taylor-Couette flow.
Type: Dissertation
URI: http://hdl.handle.net/1853/14641
Date: 2007-01-10
Publisher: Georgia Institute of Technology
Subject: UV disinfection
Computational fluid dynamics
Numerical modeling
Taylor-Couette flow
Turbulent flow
Escherichia coli
Yersinia pseudotuberculosis
Disinfection and disinfectants
Ultraviolet radiation
Fruit juices
Taylor vortices
Hazard Analysis and Critical Control Point (Food safety system)
Department: Chemical Engineering
Advisor: Committee Chair: Forney, Larry; Committee Member: Agrawal, Pradeep; Committee Member: Breedveld, Victor; Committee Member: Pavlostathis, Spyros; Committee Member: Pierson, John
Degree: Ph.D.

All materials in SMARTech are protected under U.S. Copyright Law and all rights are reserved, unless otherwise specifically indicated on or in the materials.

Files in this item

Files Size Format View
ye_zhengcai_200705_phd.pdf 5.276Mb PDF View/ Open

This item appears in the following Collection(s)

Show full item record