Study of Isolated Mixing Regions using Newtonian Fluids in Mechanically Stirred Vessels A Thesis Submitted for the Degree of Master of Engineering by WEI MING YEK School of Civil, Environmental and Chemical Engineering RMIT University Melbourne, Australia September, 2010 1 DECLARATION I, Wei Ming Yek, hereby declare that the work presented in this thesis, unless otherwise acknowledged is my own original work and has not been previously submitted, in whole or in part to qualify for any other academic award. I also declare that the content of the research project was carried out by me since the official commencement date of the approved research program at the School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne, Australia. Wei Ming Yek 2 ACKNOWLEGDEMENTS This master thesis concludes a major chapter of my life. I had walked through the toughest and most challenging journey. The working knowledge and research experience which I have gained from this journey is invaluable. This would not been done without the guidance and support of these following people who I would like to acknowledge for their contribution during the course of this research study. Dr. Raj. Parthasarathy, my primary RMIT supervisor: His undivided attention, understanding and constant guidance have led to the success of my research project. His enthusiasm towards science and technology inspired me to work as a researcher in fluid engineering. I would like to thank him for his kind understanding especially during the difficult periods that I have experienced with my family issues. Professor Satinath Bhattacharya, my secondary RMIT supervisor. His expertise in fluid rheology led me in exploring wide array of research area in fluid engineering. I would like to show my appreciation for his positive guidance and support given during external conferences. Dr. Jie Wu, my external CSIRO supervisor. I would like to thank him for giving the opportunity to use the experimental facilities and mixing rigs in CSIRO. I appreciate him for providing his expertise in fluid mixing. Dr. Nabil Noui Mehidi, Dr. Lachlan J. Graham and Bon Nguyen, CSIRO Staff. I would like to thank all of them for their warm and tender help given to me during my hardship of my experiments. I would like to specially thank Dr Nabil and Bon for helping me to set up the mixing rig in CSIRO. Ms. Sharon Taylor. my RMIT administrative officer. I would also like to thank her for being helpful in a number of administrative matters throughout the course of this research study. In addition, she also gave her kindness and compassion during my times of difficulties. 3 Fellow postgraduate students. I would like to send my regards especially Torika Oshadie Kumanayaka and Maryam Rezaei for their wonderful ideas and comments given during my coursework. I also enjoy numerous joyful moments and good times spent with them. My family members. I am grateful for their love and support given to me throughout the most difficult course of my life and also helping to take care of my mom when I am not around with her. 4 PUBLICATIONS The following publications have resulted from the research performed in the present study. Journal Papers W. M. Yek, R. Parthasarathy, M. N. Noui-Mehidi, S. N. Bhattacharya and J. Wu, 2009, ―Enhanced Mixing of Newtonian Fluids in a Stirred Vessel Using Impeller Speed Modulation,‖ Can. J. Chem. Eng. 87(6), 839-846. W. M. Yek, R. Parthasarathy and M. N. Noui-Mehidi, 2009, ―Intensification of Flow Characteristics using Modified Impeller Designs in a Laminar Flow Stirred Tank,‖ J. Chem. Eng. Japan, 43(1), 13-16. Conference Proceedings (Peer-Reviewed) W. M. Yek, R. Parthasarathy, S. N. Bhattacharya and J. Wu, ―Investigation of Impeller Type and Baffle Effects on Isolated Mixing Regions in a Laminar Stirred Tank‖ Proceedings of CHEMECA, Paper No 355, Perth, Australia, 2009. W. M. Yek, R. Parthasarathy, M. N. Noui-Mehidi, S. N. Bhattacharya and J. Wu, ―Effect of Speed Modulation on Isolated Mixing Regions in Stirred Vessel‖ Proceedings of CHEMECA, Paper No 74, Newcastle, Australia, 2008. 5 TABLE OF CONTENTS ACKNOWLEGDEMENTS ....................................................................................................... 3 PUBLICATIONS ....................................................................................................................... 5 TABLE OF CONTENTS ........................................................................................................... 6 LIST OF FIGURES ................................................................................................................... 8 LIST OF TABLES ................................................................................................................... 12 NOMENCLATURE ................................................................................................................ 13 SUMMARY ............................................................................................................................. 15 CHAPTER 1 INTRODUCTION ................................................................................................................... 17 1.1 Introduction ............................................................................................................... 18 1.2 Overview of the thesis ............................................................................................... 19 1.3 Outline of the thesis................................................................................................... 19 CHAPTER 2 LITERATURE REVIEW ........................................................................................................ 21 2.1 Introduction to laminar mixing ................................................................................. 22 2.2 Mixing equipment ..................................................................................................... 22 2.3 Types of impellers ..................................................................................................... 24 2.4 Flow patterns in agitated tanks .................................................................................. 27 2.5 Baffles ....................................................................................................................... 29 2.6 Fluid rheology ........................................................................................................... 31 2.7 Two dimensional laminar mixing and IMR structures in stirred tanks ..................... 33 2.8 Conclusions ............................................................................................................... 37 CHAPTER 3 EXPERIMENTAL ................................................................................................................... 38 3.1 Introduction ............................................................................................................... 39 3.2 Mixing vessels ........................................................................................................... 39 3.3 Impeller types ............................................................................................................ 41 3.4 Baffles ....................................................................................................................... 50 3.5 Liquids used in this work .......................................................................................... 52 3.6 Preparation of acid and base solution ........................................................................ 53 3.7 Mixing characteristics and impeller speed measurement .......................................... 53 6 3.8 Speed modulation protocols ...................................................................................... 54 3.9 Flow visualisation technique of IMRs ...................................................................... 55 3.10 Estimation of IMR volume ........................................................................................ 57 CHAPTER 4 CHARACTERTISTICS OF IMR STRUCTURES ................................................................. 58 4.1 Introduction ............................................................................................................... 59 4.2 Evolution of IMR Structures using steady-state impeller speed ............................... 59 4.3 Dynamic perturbation of IMR structures .................................................................. 61 4.4 Evolution of IMR structures using square wave modulation .................................... 63 4.5 Evolution of IMR Structures using sine wave modulation ....................................... 70 4.6 Conclusions ............................................................................................................... 72 CHAPTER 5 STUDY OF IMR STRUCTURES USING DIFFERENT IMPELLER TYPES AND BAFFLED CONDITIONS ...................................................................................................... 73 5.1 Introduction ............................................................................................................... 74 5.2 Effect of different type of impellers on IMR structures ............................................ 74 5.3 Evolution of IMR structures using impeller speed modulation ................................ 76 5.4 Effect of standard wall baffles on IMR structures .................................................... 78 5.5 Effect of modified baffles on IMR structures ..........................................................