Pushing the Limits of Thermal Transport for Electronics, Energy, and Climate
Date: 2022/09/16 - 2022/09/16
Academic Seminar: Pushing the Limits of Thermal Transport for Electronics, Energy, and Climate
Speaker: Xiulin Ruan,Professor at School of Mechanical Engineering and Birck Nanotechnology Center Purdue University, USA
Time: 10:00 - 11:30, September 16, 2022 (Beijing Time)
Location: CIMC Auditorium（Room 300）, JI Long Bin Building; ZOOM Meeting ID: 674 018 5276, Passcode: 115789
Abstract
This talk will overview our recent efforts in pushing the limits of thermal transport to address challenges in electronics thermal management, energy savings, and climate crisis. The first part of the talk will introduce four-phonon scattering as a significant intrinsic mechanism beyond three-phonon scattering, in governing thermal conductivity of high thermal conductivity materials, low thermal conductivity materials, and 2D materials at room temperature as well as nearly all materials at high temperature. For complex crystals at high temperature, the conventional phonon mean free path concept is insufficient, and we propose a dual-phonon transport theory to better describe their thermal transport. We further show that machine learning can be used to dramatically accelerate the predictive design of thermal nanomaterials. The second part of the talk will describe our invention of ultrawhite BaSO4-acrylic and CaCO3-acrylic radiative cooling paints, which show remarkable below-ambient cooling under direct sunlight. The solar reflectance and sky window emissivity are as high as 98.1% and 0.96 respectively. Field tests show a net cooling power up to 117 W/m2. Such high performance is enabled by synergistically pushing a few factors to the extremes: the use of wide bandgap pigments, appropriate particle size similar to solar photon wavelength, a broad particle size distribution, and high particle concentration. Radiative cooling paints can have broad implications from saving energy to mitigating climate crisis. The talk will close by exploring future opportunities.
Biography
Dr. Xiulin Ruan is a professor in the School of Mechanical Engineering and Birck Nanotechnology Center at Purdue University. He received his B.S. and M.S. in Engineering Thermophysics at Tsinghua University, in 2000 and 2002 respectively. He then received an M.S. in electrical engineering in 2006 and Ph.D. in mechanical engineering in 2007 from the University of Michigan at Ann Arbor. Subsequently he joined Purdue faculty. His research and teaching interests are in predictive simulations, scalable manufacturing, and multiscale characterizations of thermal transport materials and systems. Notably, his recent fundamental work has established a new research area of higher-order phonon scattering, and his recent applied work on ultrawhite radiative cooling paints has earned a Guinness World Record and been featured by more than 2,000 news reports globally, including BBC, CNN, Wall Street Journal, Washington Post, and Scientific American. He received the NSF CAREER Award, Air Force Summer Faculty Fellowship, ASME Heat Transfer Division Best Paper Award, the inaugural School of Mechanical Engineering Outstanding Graduate Student Mentor Award, and was named a University Faculty Scholar of Purdue University and an ASME Fellow, among his honors. He currently serves as an associate editor for ASME Journal of Heat Transfer.