Western Michigan University ScholarWorks at WMU Master's Theses Graduate College 12-2016 Optimal Design of Automotive Exhaust Thermoelectric Generator (AETEG) Hassan Fagehi Follow this and additional works at: https://scholarworks.wmich.edu/masters_theses Part of the Aerospace Engineering Commons, and the Mechanical Engineering Commons Recommended Citation Fagehi, Hassan, "Optimal Design of Automotive Exhaust Thermoelectric Generator (AETEG)" (2016). Master's Theses. 764. https://scholarworks.wmich.edu/masters_theses/764 This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. OPTIMAL DESIGN OF AUTOMOTIVE EXHAUST THERMOELECTRIC GENERATOR (AETEG) by Hassan Fagehi A thesis submitted to the Graduate College in partial fulfillment of the requirements for the degree of Master of Science in Engineering (Mechanical) Mechanical and Aerospace Engineering Western Michigan University December 2016 Thesis Committee: HoSung Lee, Ph.D., Chair Bade Shrestha, Ph.D. Chris Cho, Ph.D. OPTIMAL DESIGN OF AUTOMOTIVE EXHAUST THERMOELECTRIC GENERATOR (AETEG) Hassan Fagehi, M.S.E. Western Michigan University, 2016 A consumption of energy continues to increase at an exponential rate, especially in terms of automotive spark ignitions vehicles. About 40% of the applied fuel into a vehicle is lost as waste exhaust to the environment. The desire for improved fuel efficiency by recovering the exhaust waste heat in automobiles has become an important subject. The thermoelectric generator (TEG) has the potential to convert exhaust waste heat into electricity as long as it is improving fuel economy. The remarkable amount of research being conducted on TEGs indicates that this technology will have a bright future in terms of power generation. The current study discusses the optimal design of the automotive exhaust thermoelectric generator (AETEG). The work investigates the effect of leg length and ceramic plate materials on the performance of the thermoelectric module. A new design is conducted analytically based on the idea of leg length and the ceramic plate materials effect, giving a significant improvement in terms of power density. Experimental work is conducted to verify the model that used the ideal (standard) equations along with effective material properties. The model is reasonably verified by experimental work, which is mainly due to the utilization of the effective material properties. Hence, the thermoelectric module that was used in the experiment is optimized by using a newly developed optimal design theory (dimensionless analysis technique). © 2016 Hassan Fagehi ACKNOWLEDGEMENTS Foremost, I would like to especially thank my advisor Prof. HoSung Lee for his encouragement and patience throughout my work. Without his support and guidance this work would not have been possible. I’m very lucky and thankful to have Dr. Lee as my advisor, who is always trying to improve his student’s knowledge. I would also like to extend my thanks to my committee members, Prof. Bade Shrestha and Prof. Chris Cho, for their guidance and suggestions to improve the quality of this work. I wish to thank the government of Saudi Arabia who believed in me and provided me with a generous scholarship. I would also like to thank my family, especially my mother, my wife, and my daughter for their support and patience. Their support is a big part of my accomplishment. Also, I thank all my friends and classmates for their support and helpful comments. Hassan Fagehi ii TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................................................................ ii LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ......................................................................................................... viii NOMENCLATURE ......................................................................................................... xii 1 BACKGROUND OF THERMOELECTRIC .......................................................... 1 1.1 Thermoelectric Effects ......................................................................................... 1 1.1.1 Seebeck Effect .............................................................................................. 2 1.1.2 Peltier Effect ................................................................................................. 3 1.1.3 Thomson Effect ............................................................................................. 3 1.1.4 The Figure of Merit ....................................................................................... 4 1.2 Thermoelectric Ideal (Standard) Equations.......................................................... 5 1.2.1 General Governing Equations ....................................................................... 5 1.2.2 Thermoelectric Couple Equations................................................................. 7 1.2.3 Thermoelectric Generators Equations ......................................................... 12 1.3 Contact Resistance for Thermoelectric Generator ............................................. 19 1.4 Thermoelectric Generator System ...................................................................... 23 1.4.1 Basic Equations of Thermoelectric Generator System ............................... 24 iii Table of Contents—Continued 1.4.2 Heat Sink Design and Optimization ........................................................... 25 1.4.3 Power Density ............................................................................................. 27 1.5 Chapter Conclusion ............................................................................................ 27 2 LITERATURE SURVEY AND OBJECTIVES OF THE CURRENT STUDY ... 29 2.1 Background ........................................................................................................ 29 2.1.1 Hot Side Heat Exchanger ............................................................................ 29 2.1.2 Coolant System ........................................................................................... 30 2.1.3 Bypass System ............................................................................................ 31 2.2 Literature Survey of Automotive Exhaust Thermoelectric Generator (AETEG) . ............................................................................................................................ 32 2.2.1 AETEG System ........................................................................................... 32 2.2.2 Numerical And Experimental Work of AETEG ......................................... 32 2.3 Motivation .......................................................................................................... 38 2.4 Objectives of Current Study ............................................................................... 39 3 MODELING OF (AETEG) .................................................................................. 40 3.1 Modeling of Module Tests ................................................................................. 40 3.2 Calculating the Effective Material Properties .................................................... 41 3.3 Dimensional Analysis Method ........................................................................... 43 iv Table of Contents—Continued 3.4 Heat Sink Optimization ...................................................................................... 47 3.5 Offset Strip-Fin Heat Exchanger (OSF) ............................................................. 49 3.6 Exhaust Mass Flow Rate Calculations ............................................................... 50 3.7 Pressure Drop Calculations ................................................................................ 51 3.8 Chapter Conclusion ............................................................................................ 52 4 EXPERIMENTAL WORK ...................................................................................... 53 5 RESULTS AND DISCUSSION .............................................................................. 61 5.1 GM Project ......................................................................................................... 61 5.1.1 Module Test Validation .............................................................................. 61 5.1.2 AETEG Test Validation .............................................................................. 65 5.1.3 Optimizing and Improving GM System (New Design) .............................. 71 5.2 Applying the New Design of AETEG System for 400 Kw Engine ................... 84 5.2.1 Choosing of 400 Kw Diesel Engine ........................................................... 84 5.2.2 Exhaust Mass Flow Rate Calculation ......................................................... 85 5.2.3 Estimation of Power Output for 400 Kw Engine ....................................... 86 5.3 Experimental Results.......................................................................................... 87 5.3.1 Effective Material Properties Results ......................................................... 88 5.3.2 Experimental Results Comparing with Analytical Model .......................... 91 v Table of Contents—Continued