11 a.m. - 12 p.m. Location: ECSS 3.503
"Near-field Radiative Energy, Entropy and Momentum Transfer in Fluctuational Electrodynamics" by Mr. Yi Zheng (Department of Mechanical Engineering, Columbia University, New York, NY)
Abstract: The ability to control the radiative properties of objects is of great interest in diverse areas like solar and thermophotovoltaic energy conversion, selective thermal emission and absorption, and camouflage in military applications. Thermal radiation at the nanometer scale is significantly different from classical or macroscopic radiative energy transport since near-field effects such as interference, diffraction, and tunneling of surface waves play a significant role.
The talk will focus mainly on small-scale energy, entropy and momentum transfer via electromagnetic waves, especially due to thermal and quantum fluctuations. A dyadic Green’s function formalism has been developed to determine near-field radiative energy and momentum transfer between objects of arbitrary shapes and sizes. Momentum transfer due to electromagnetic fluctuations is responsible for van der Waals and Casimir forces, which are important in many different fields such as adhesion and stiction of materials, bioengineering, and phase change heat transfer. I will talk about how we model van der Waals forces, and show how my work provides a new interpretation, and a better understanding, of this historical problem. In addition, entropy associated with near-field radiative transfer has been studied for the first time. It can be used to determine the maximum work that can be extracted and a thermodynamic limit of energy conversion efficiency that can be obtained in near-field thermal radiation. Experimental investigation will focus on the thermal and optical properties of 2D or 3D nanostructured materials, and it leads to new types of thermophotovoltaic solar cells and selective thermal emitters using metamaterials and nanoparticles. Small-scale thermal transport has shown great potential and applications for use in manipulating macroscale energy systems and energy harvesting.
Bio: Mr. Yi Zheng is a PhD candidate in Micro/Nanoscale Thermal Transport Lab at Columbia University, and research associate at Columbia Optics and Quantum Electronics Center. He received his B.S. in Mechanical Engineering from Tsinghua University, China, in 2009, and M.S. in Mechanical Engineering from Columbia University, in 2011. His research interests are the theoretical, computational and experimental investigations on nanoscale thermal transport phenomena, and their applications in energy conversion and storage devices. He has served as reviewer for over 30 peer-reviewed papers for 4 journals and 5 conferences and as a session chair for “Fundamentals of Nanoscale Heat Transport” session at ASME 2013 Summer Heat Transfer Conference.