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SUMMARY:IMX Colloquium - Surface engineering for phase change heat and mas
 s transfer: controlling nucleation and bubble dynamics
DTSTART:20260413T131500
DTEND:20260413T141500
DTSTAMP:20260502T063613Z
UID:5a26a41f26d4eda9f4729608c0c3c191dc1ed2b7218dedb960e0e868
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Zhengmao Lu\, EPFL\nBoiling is one of the most efficien
 t modes of heat transfer\, underlying many energy-intensive processes. Adv
 ancements in surface engineering have enabled significant enhancement of b
 oiling heat transfer. However\, performance gains rarely transfer across c
 onditions or geometries. Two challenges illustrate why: bubble nucleation 
 behavior is poorly reproducible\; and increasing nucleating density to rai
 se the heat transfer coefficient typically lowers the system’s maximum a
 chievable heat flux. This talk presents our efforts in addressing each cha
 llenge by identifying the governing mechanism and designing for it.\nIn th
 e first part\, micro-engineered silicon surfaces isolate two governing len
 gth scales: the hydrodynamic boundary layer thickness\, which controls nuc
 leation stability through inter-site shielding\, and the bubble departure 
 diameter\, which governs vapor removal after full activation. We experimen
 tally show that nucleation stability responds to the former length scale (
 ~0.24 mm)\; heat transfer in the activated regime responds to the latter l
 ength scale (~2.5 mm).\nThe second study addresses the high-heat-flux limi
 t\, where large vapor structures block liquid return. Capillary wicking th
 rough copper inverse opals (~10 μm pores) supplies liquid beneath the vap
 or. Crucially\, the pore cavities are themselves the nucleation sites\, so
  wicking capacity and nucleation density derive from the same structure. F
 urther\, CuO nanograss on the pore walls suppresses vapor penetration into
  the porous layer\, enabling thicker structures and greater capillary head
 . The result is simultaneous enhancement of heat transfer coefficients and
  maximum heat fluxes.\nTogether\, the two works show that mechanism-target
 ed surface design yields gains that empirical topography optimization does
  not. They point toward a broader design principle: that nucleation and in
 terfacial transport\, treated as controllable rather than given\, offer a 
 promising path to engineering phase change processes across applications.\
 n\nhttps://dx.doi.org/10.1021/acsami.9b20520?ref=pdf\nhttps://doi.org/10.1
 038/s41467-019-10209-w \n\nBio: Zhengmao Lu is a Tenure Track Assistant P
 rofessor of Mechanical Engineering at EPFL. Prior to joining EPFL\, Zhengm
 ao was a postdoctoral scholar in the Department of Materials Science and E
 ngineering at MIT with Prof. Jeffrey Grossman. He received his Ph.D. and M
 .S. in Mechanical Engineering from MIT\, both advised by Prof. Evelyn Wang
 . At EPFL\, Zhengmao leads the Energy Transport Advances Laboratory (η-La
 b)\, aiming to deepen our understanding of phase change phenomena and deve
 lop more sustainable energy and water technologies by optimizing interfaci
 al transport. Zhengmao is a recipient of the ERC Starting Grant\, MicroFIP
 S Outstanding Early Career Award\,  Keck Travel Award in Thermal Sciences
 \, and the Outstanding Graduate Research Award from MIT Mechanical Enginee
 ring.
LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201
STATUS:CONFIRMED
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