University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Dissertations, Theses, & Student Research in Food Science and Technology Food Science and Technology Department 4-2011 Electromagnetic and Heat Transfer Modeling of Microwave Heating in Domestic Ovens Krishnamoorthy Pitchai University of Nebraska at Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/foodscidiss Part of the Bioresource and Agricultural Engineering Commons, and the Food Processing Commons Pitchai, Krishnamoorthy, "Electromagnetic and Heat Transfer Modeling of Microwave Heating in Domestic Ovens" (2011). Dissertations, Theses, & Student Research in Food Science and Technology. 38. https://digitalcommons.unl.edu/foodscidiss/38 This Article is brought to you for free and open access by the Food Science and Technology Department at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Dissertations, Theses, & Student Research in Food Science and Technology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. ELECTROMAGNETIC AND HEAT TRANSFER MODELING OF MICROWAVE HEATING IN DOMESTIC OVENS by Krishnamoorthy Pitchai A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science Major: Agricultural and Biological Systems Engineering Under the Supervision of Professor Jeyamkondan Subbiah Lincoln, Nebraska May, 2011 ELECTROMAGNETIC AND HEAT TRANSFER MODELING OF MICROWAVE HEATING IN DOMESTIC OVENS KRISHNAMOORTHY PITCHAI, MS University of Nebraska, 2011 Adviser: Jeyamkondan Subbiah Microwave (MW) heating is fast and convenient, but is highly non-uniform. When a food product contains raw or partially cooked food components, non-uniform heating can result in inadequate cooking, leading to a microbiologically unsafe product. A mathematical model of microwave heating helps to understand non-uniform temperature distribution in domestic microwave ovens and a useful tool for food product developers and microwave oven manufacturers. The objective of this study was to develop a mathematical model to predict spatial and temporal variations in temperature of a model food during microwave heating. A mathematical model was developed by solving coupled Maxwell‘s electromagnetic and Fourier's heat transfer equations using finite-difference time-domain (FDTD) method in QuickWave v7.5 software. The model was used to describe the heating of a gellan gel cylinder for 30 s in a 700 W domestic microwave oven. The model domain included the magnetron, typical waveguide, cavity and turntable. Optimization of modeling parameters such as computational meshing size, heating time step, frequency, and electric field strength was performed to increase accuracy of the prediction of the temperature profile. The model was validated by conducting microwave heating experiments to observe time-temperature and spatial- temperature profiles using fiber optic thermocouples and thermal imaging camera, respectively. A good qualitative agreement between simulation and experimental temperature profiles was observed. Results of quantitative analysis of point measurement of time-temperature profile showed that average root-mean squared error of the 12 locations was 2.02°C. Keywords: Modeling, heat transfer, non-uniform heating, temperature variation. i ACKNOWLEDGEMENTS It is my great pleasure to thank Dr. Jeyamkondan Subbiah for providing me excellent advice and guidance to conduct this research. Throughout the program, he gave me a lot of courage and enthusiasm to lead the research independently. Even on hard times, he was there in the path to give immense support to lift me and my research to peaks of all. His encouragement and support led me to participate in various professional activities and international conferences. I sincerely appreciate him for showing extra care on my career and professional developments. I was fortunate to have him as my adviser. I would like to thank my graduate committee members, Dr. David D. Jones, Department of Biological Systems Engineering, Dr. Harshavardhan Thippareddi, Department of Food Science and Technology, Dr. Deepak R. Keshwani, Department of Biological Systems Engineering, for giving me wonderful ideas and comments on my research work. Their technical guidance, ideas, and insights helped me in many ways to improve the research day by day. I salute all of them. I also immensely thank Dr. Sohan Birla, Department of Biological Systems Engineering, for being part of this research to lead me all the time. His persistent advice and technical inputs paved the way to understand many facets of research. Thanks to Dr. Anne Parkhurst, Department of Statistics, for helping me in designing statistical models. My sincere appreciation goes to Brent Hanson, Edel Victor, and Armando Garcia for lending their hands on conducting experiments at various stages. I would like to say my gratitude to Govindarajan Konda Naganathan (KN), Govindarajan Suresh Babu (SG), and Valli Kannan for giving me an immense care and hospitality throughout my study. ii I take this space as an opportunity to thank all the faculty and staff members of Department of Biological Systems Engineering for their cooperation and help. I am obliged to thank my parents and younger brother for providing confidence and encouragement to achieve this new height in my life. Without their sacrifice and blessings, I would not have become as a professional graduate. I am honored for having them as my loved ones. My heart and soul will be always with them. iii TABLE OF CONTENTS CHAPTER I: INTRODUCTION ..................................................................................1 Objectives ....................................................................................................................3 Thesis Format ..............................................................................................................3 References ...................................................................................................................5 CHAPTER II: REVIEW OF LITERATURE ..............................................................7 Introduction .................................................................................................................7 Electromagnetic Waves ............................................................................................. 10 Fundamentals of Microwave Heating ......................................................................... 11 Dielectric Properties .................................................................................................. 12 Electromagnetic Field Equations ................................................................................ 14 Lambert’s law ........................................................................................................ 14 Maxwell’s equations .............................................................................................. 15 Factors Influencing Microwave Heating .................................................................... 17 Physical properties ................................................................................................ 17 Chemical composition ............................................................................................ 19 System and process factors .................................................................................... 20 Improving Heating Uniformity .................................................................................. 22 Modeling of Microwave Heating ............................................................................... 25 Necessity of Modeling ............................................................................................... 27 iv Challenges in Microwave Heating Modeling.............................................................. 27 Electromagnetic Field Models.................................................................................... 27 Heat Transfer Models ................................................................................................ 29 Coupled Electromagnetic and Thermal Models .......................................................... 31 Numerical Methods ................................................................................................... 33 Available Software .................................................................................................... 34 Microwave Heating Modeling Approach ................................................................... 35 Cornell University ................................................................................................. 36 Warsaw University of Technology .......................................................................... 37 Optimization of Modeling .......................................................................................... 38 Summary ................................................................................................................... 40 References ................................................................................................................. 41 CHAPTER III: COUPLED ELECTROMAGNETIC AND HEAT TRANSFER MODEL FOR MICROWAVE HEATING IN DOMESTIC OVENS ....................... 68 Abstract ....................................................................................................................