Prof. Zhixiong Guo

Department of Mechanical and Aerospace Engineering,

Rutgers University-New Brunswick, USA

Dr. Zhixiong “James” Guo is a Professor of Mechanical and Aerospace Engineering at Rutgers University-New Brunswick, NJ, USA. He received his B.S., M.S., and Doctorate, all in Engineering Physics, from Tsinghua University, Beijing in 1989, 1991, and 1995, respectively. Then he worked as a Research Fellow in KAIST, South Korea, and a Research Associate in Tohoku University, Japan. From 1999 to 2001, he worked as a research staff member in NYU-Tandon School of Engineering, where he completed his Ph.D. in Mechanical Engineering in the same time period. He joined the faculty at Rutgers in July 2001. He has supervised 17 PhD and 20 Master students and mentored 14 postdoctoral/visiting scholars. He received research funds from the NSF, NASA/NJSGC, USDA, ASEE/DOD, MTF, NIH, NJ Nanotechnology Consortium, Charles and Johanna Busch Memorial Funds, NNSFC, JSPS, and other sources.  He also received a teaching award from Rutgers Vice President Office for Undergraduate Education in 2002. He is the author or co-author of over 260 articles/editorials in archival journals and conference proceedings. He is the Editor-in-Chief for Journal of Enhanced Heat Transfer and a Managing Editor for journal Heat Transfer Research, and an editorial board member for Applied Thermal Engineering and Frontiers in Energy. Dr. Guo is an elected Fellow of ASME and ASTFE. He was the K-18 technical committee Chair of Heat Transfer Division in ASME during 2009-2015. He was the Technical Program Chair for the 6th International Symposium on Advances in Computational Heat Transfer (CHT-15). He was a conference Co-Chair for 2011, 2013, and 2015 International Workshops on Heat Transfer Advances for Energy Conservation and Pollution Control. Among many distinctions, he was awarded a JSPS Invitation Fellowship, a K.C. Wong Education Foundation Fellowship, and Rutgers the Board of Trustee’s Award for Excellence in Research, the university's highest honor for outstanding research contributions to a discipline or to society.

He is a recognized expert in heat transfer, with notable expertise in radiation transport, heat transfer enhancement, and nanoscale heat transfer. His discovery and solution for conserving scattered energy and scattering angle in radiation transfer modeling is of significant contribution to the advancement of radiative transfer computation. He is a pioneer in ultrafast laser radiation transport modeling and applications. He explored plasma-mediated ablation and developed it successfully to tissue grafting and decontamination. He conducted leading research on near-field radiation, addressing emerging technological applications such as MEMS/NEMS sensors, ultrafine measurement, and biological sensing at the molecular level.  Nowadays he explores innovative utilization of renewable solar energy and investigates fundamentals in interfacial heat transfer and boiling mechanisms at the molecular level. 

Title: Molecular Dynamics Studies of Pool Boiling and Solid-liquid Interfacial Heat Transfer

Abstract：Heat transfer on the micro- and nano-scales has quickly become an important area of research and development due to its implications for use in MEMS/NEMS devices and electronics cooling in the past decade. Micro-heat-sinks technology based on phase-change heat transfer could be a potential solution to this problem. By utilizing the latent heat capacity, liquid could efficiently remove heat at a stable temperature in the pool boiling process. As a more approachable method, molecular dynamics (MD) simulations are adopted to study the mechanism of nanoscale boiling and solid-liquid interfacial heat transfer.

Wettability and pitch size have shown effect on the maximum heat flux in evaporation and pool boiling process. For a given pitch, it shows an inverse relationship between the contact angle and the heat flux. The heat flux on a hydrophilic surface could be several times higher than on a hydrophobic surface. The maximum heat flux has a positive correlation with the pitch length. For pitches 65.1 Å and above, the temperature at which critical heat flux (CHF) occurs (and thus the degree of superheat) increases with increasing contact angle, and was also found to increase with pitch.

The effect of philic/phobic surface nano-patterning on pool boiling heat transfer was also investigated. In the nucleate boiling regime, heat flux and evaporation are most improved with the use of both a philic base wall and philic pillars, with a maximum instantaneous flux of ~5.1 × 108 W/m2. During explosive boiling, once again the All Philic case showed better performance than all other cases in terms of evaporation number and heat flux, with maximum instantaneous fluxes nearing 1 × 109 W/m2. An effect of cutoff radius on the calculation of heat flux was found, which a typical 2.5σ cutoff in MD simulations could underpredict heat flux by about 8.7 % in comparison with 8σ cutoff.

The effect of pristine graphene and defective graphene surface coating on pool boiling heat transfer was studied. The addition of single-layer pristine graphene greatly improves the through-plane thermal conductivity of Cu, Ni, Pt, and Si substrates during boiling, with increases in conductivity one to two orders of magnitude greater than that of the substrate alone. The single-layer pristine graphene coating increases the CHF, with a maximum increase of 14% on the copper substrate. However, among all the tested defective graphene coatings, the induced defects have not obviously altered the CHF value in comparison with the pristine graphene coating. The measured heat flux suggests that most of the tested defect graphene has higher initial heat flux value than the pristine graphene with isothermal heat source. The percentage of pentagon-heptagon defect in the graphene unit cell does not have a clear correlation with the boiling heat transfer performance.

A spectral analysis of heat flux was carried out across a modified solid diamond- liquid water surface to better understand the effect of surface nanopatterning. A nanochannel with various depths and widths was constructed on the computational domain of the diamond surface. It is found that the magnitude of the spectral heat flux generally has a positive correlation with the channel depth. The channel width nearly has no effect on the spectral heat flux when the channel depth is under five diamond lattice constants; but it has a negative effect when the depth is above five diamond lattice constants. Adding 2-D nanochannels on the solid surface mainly affected the in-plane spectral heat flux. The through-channel direction almost had no contribution to heat flux spectra, suggesting that 3-D nanostructure might perform better than 2-D structures.