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And Far-Field Radiative Heat Transfer

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And Far-Field Radiative Heat Transfer Photonic Engineering of Near- and Far-field Radiative Heat Transfer by Jonathan Kien-Kwok Tong Submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY June 2016 © Massachusetts Institute of Technology 2016. All rights reserved. Author…………………………………………………………………….. Department of Mechanical Engineering May 18, 2016 Certified by………………………………………………………………. Gang Chen Carl Richard Soderberg Professor of Power Engineering Thesis Supervisor Accepted by………………………………………………………............ Rohan Abeyaratne Chairman, Department Committee on Graduate Students 2 Photonic Engineering of Near- and Far-field Radiative Heat Transfer by Jonathan Kien-Kwok Tong Submitted to the Department of Mechanical Engineering on May 18, 2016, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Abstract Radiative heat transfer is the process by which two objects exchange thermal energy through the emission and absorption of electromagnetic waves. It is one of nature’s key fundamental processes and is ubiquitous in all facets of daily life from the light we receive from the Sun to the heat we feel when we place our hands near a fire. Fundamentally, radiative heat transfer is governed by the photonic dispersion, which describes all the electromagnetic states that can exist within a system. It can be modified by the material, the shape, and the environment. In this thesis, morphological effects are used to modify the photonic dispersion in order to explore alternative methods to spectrally shape, tune, and enhance radiative heat transfer from the near-field to the far-field regimes. We start by investigating the application of thin-film morphologies to different types of materials in the near-field regime using a rigorous fluctuational electrodynamics formalism. For thin-film semiconductors, trapped waveguide modes are formed, which simultaneously enhance radiative transfer at high frequencies where these modes are resonant and suppress radiative transfer at low frequencies where no modes are supported. This spectrally selective behavior is applied to a theoretical thermophotovoltaics (TPV) system where it is predicted the energy conversion efficiency can be improved. In contrast, thin-films of metals supporting surface plasmon polariton (SPP) modes will exhibit the opposite effect where the hybridization of SPP modes on both sides of the film will lead to a spectrally broadened resonant mode that can enhance near-field radiative transfer by over an order of magnitude across the infrared wavelength range. In order to observe these morphological spectral effects, suitable experimental techniques are needed that are capable of characterizing the spectral properties of near-field radiative heat transfer. To this end, we developed an experimental technique that consists of using a high index prism in an inverse Otto configuration to bridge the momentum mismatch between evanescent near-field radiative modes and propagation in free space in conjunction with a Fourier transform infrared (FTIR) spectrometer. Preliminary experimental results indicate that this method can be used to measure quantitative, gap-dependent near-field radiative heat transfer spectrally. While utilizing near-field radiative transfer remains a technologically challenging regime for practical application, morphological effects can still be used to modify the optical properties of materials in the far-field regime. As an example, we use polyethylene fibers to design an infrared transparent, visibly opaque fabric (ITVOF), which can provide personal cooling by allowing thermal radiation emitted by the human body to directly transmit to the surrounding environments while remaining visible opaque to the human eye. Thesis Supervisor: Gang Chen Title: Carl Richard Soderberg Professor of Power Engineering 3 4 Acknowledgments I was once told that to pursue a doctoral degree, the most important trait to have as a student is to be persistent. It is this undeniable stubbornness that can enable one to overcome the inevitable failures encountered when doing graduate level research. However, as I’ve come to learn from my own experience, persistence alone can only get you so far. There will often be times when despite considerable effort, samples continuously break, experiments won’t yield a signal, or calculations don’t converge and it may feel such research projects are simply insurmountable. It is in these moments that the people supporting you can enable you to push past these failures in order to ultimately find success. During my time at MIT, I was fortunate to have a number of people who did just that for me. I’d like to thank my advisor Prof. Gang Chen who gave me my first opportunity to conduct research in his lab back in the summer of 2008. Without his generosity, I never would have had the opportunity to attend graduate school at MIT. I’ve learned more than I ever could have imagined under his tutelage. I am also grateful for his guidance as he showed me that I was capable of far more than I ever thought possible. I would also like to thank my thesis committee members, Prof. Nicholas Fang and Prof. Marin Soljačić for their support, advice, and words of encouragement throughout my Ph.D. I also want to thank my colleagues in the NanoEngineering group. It was a real honor to be a member of such a talented, hardworking, and humble group of people. First, I’d like to thank my former colleagues Sheng Shen, Tony Feng, and Nitin Shukla who were not only true role models for me when I first started as a graduate student, but great friends as well. I would also like to specially thank my colleague Wei-Chun Hsu who has not only been an incredible colleague who I shared many wonderful discussions of ideas and concepts with over the years, but also a great friend who has always been there to pick me up whenever I was down. I also want to thank Svetlana Boriskina who has been a true mentor to me. She was not only the inspiration for much of my own work, but through her patience and encouragement I discovered the beauty of optics and all the possibilities it can lead to in research. I would also like to thank many of my other current and former colleagues who I shared many great memories with that would be far too many to list here. In no particular order, I’d like to thank Poetro Sambegoro, Anastassios Mavrokefalos, Brian Burg, Matthew Branham, Kimberlee Collins, Daniel Kraemer, Kenneth McEnaney, Maria Luckyanova, 5 Bo Qiu, Xiaopeng Huang, Jivtesh Garg, Selҫuk Yerci, Yongjie Hu, Sang Eon Han, Amador Guzman, Kazuki Ihara, Bolin Liao, Lingping Zeng, Yi Huang, Yoichiro Tsuramaki, Te-Huan Liu, George Ni, Yanfei Xu, Lee Weinstein, David Bierman, Kuang-Han Chu, Rong Xiao, and Tom Cooper. I’m sure I missed more people, but I hope you know who you are. I would also like to thank the support staff of the NanoEngineering group who have had the unenviable task of ensuring the administrative functions of the group are always properly maintained. I especially want to thank Ed Jacobson for his friendship and the many conversations we had about all manner of things in life from our favorite books to the best places to go grocery shopping. But most importantly, he was a constant source of encouragement to me especially as I became acclimated to life as a graduate student. I also want to thank Mai Hoang, Keke Xu, and Juliette Pickering for their support and for not batting an eye whenever I gave them a pile of receipts for purchases I made. I also want to thank the technicians that manage the shared facilities at MIT and Boston College, who I believe are one of the most valuable resources an aspiring experimentalist could ever have with their breadth and depth of knowledge. In particular, I want to thank Kurt Broderick at EML for his advice and patience in answering many of my deposition-related questions. I also want to thank Tim McClure at CMSE for his advice and constant encouragement on my near-field thermal emission experiments. I also want to thank my family for their enduring love and support over these many years. I will always cherish all the care packages sent to me, the many home-cooked meals, and most importantly the moments we all shared together as a family despite the fact we all live in different regions of the world. And last, but certainly not least, I want to thank my girlfriend, Sohae Kim, who has been an anchor for me in the truest sense of the word. I know for a fact I never would have it made this far if it wasn’t for her support. All the adventures we had and the many happy memories we shared together gave me the fortitude to push past the struggles of graduate school. I will forever be grateful to her. 6 7 8 Table of Contents 1 Introduction 29 1.1 Historical Development of Classical Radiative Heat Transfer . 30 1.2 Engineering Radiative Heat Transfer . 32 1.3 Organization of Thesis . 33 2 Morphological Modification of Near-field Radiative Heat transfer 35 2.1 Near-field Radiative Heat Transfer . 35 2.2 Morphological Effects on the Photonic Dispersion . 41 2.2.1 Thin-film Optical Waveguides . 42 2.2.2 Surface Polariton Waveguides . 43 2.3 Theoretical Model for Near-field Radiative Heat Transport . 45 2.3.1 Fluctuational Electrodynamics Formalism . 45 2.3.2 Formulation for Infinite 1D Multilayer Geometry . 49 2.3.3 Solutions for a Single Thin-film Supported by a Semi-Infinite Substrate . 51 2.4 Morphological Effects on Dielectrics . 57 2.4.1 Overview of Thermophotovoltaic Systems . 58 2.4.2 System Configuration . 59 2.4.3 Shaping Radiative Heat Transfer with Thermal Wells .
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