[CCoE Notice] Zoom Webinar: Materials Engineering for Advanced Energy Storage Systems * Online * 10:30 am, Friday, April 3, 2020 * Hadi Ghasemi * University of Houston *

[Knudsen, Rachel W]

***** Seminar *****
Department of Electrical and Computer Engineering
Materials Engineering Program
Center for Integrated Bio and Nano Systems
  10:30 a.m., April 3, 2020
Join Zoom Meeting
https://zoom.us/j/845619943?pwd=QlZvYUV6M2dxNDkvNWxBd3F2YzdJZz09

Meeting ID: 845 619 943
Password: 016104

Liquid-vapor phase change from nano to molecular scale
Hadi Ghasemi
Department of Mechanical Engineering
The University of Houston
Abstract:. Advancement in high-performance photonics/electronics devices has boosted generated thermal energy, making thermal management a bottleneck for accelerated innovation in these disciplines. Although various methods have been used to tackle the thermal management problem, evaporation with nanometer fluid thickness is one of the most promising approaches for future technological demands. Here, we discuss fundamentals of evaporation at nanoscale and implementation of these underpinnings for extreme heat dissipation in photonic/electronics.
Evaporative mass flux is governed by the interfacial state of liquid and vapor phases. For closely similar pressures and mass fluxes of liquid water into its own vapor, the discontinuity between interfacial liquid and vapor temperatures in the range of 0.14−28 K is reported. This controversial discontinuity has resulted in an obstacle to understanding and theoretical modeling of evaporation. Here, through the study of vapor transport by the Boltzmann transport equation solved through the direct simulation Monte Carlo Method, we demonstrated that the measured discontinuities were strongly affected by boundary conditions on the vapor side of the interface and do not reflect the interfacial state. The temperature discontinuity across the evaporating interface is ≤0.1 K for all of these studies. To accurately capture the interfacial state, the vapor heat flux should be suppressed.
We studied thin-film evaporation in nanochannels under absolute negative pressure and demonstrated that thin-film evaporation in nanochannels can be a bubble-free process even at temperatures higher than boiling temperature, providing high reliability in thermal management systems. In steady-state condition, unprecedented average interfacial heat flux of 11 ± 2 kW cm−2 is achieved in the nanochannels, which corresponds to liquid velocity of 0.204 m s−1.
Short Bio: Hadi Ghasemi is Cullen Associate Professor in the Department of Mechanical Engineering at the University of Houston and director of Nanotherm research group. He received his PhD degree in 2011 from the University of Toronto. He continued his studies as a Postdoctoral Associate at Massachusetts Institute of Technology (MIT) from 2012 to 2014. He is the recipient of the several awards in the field of heat transfer and surface physics including Early Innovator Award, AFOSR Young Investigator Award, top three innovator award of NASA iTech, University Research Excellence Award and Russel Reynolds award in Thermodynamics. He was selected as one of the finalists for World Technology Award in the energy category in 2014. His research works are highlighted in Nature, Economists and Popular Science among others. His current research interests are in nanotechnology, surface physics and heat transfer.
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