Honors and Awards

• Best Paper Award at the 1st ASME Micro/Nanoscale Heat Transfer International Conference, Tainan, Taiwan, January 6-9, 2008
• Junior Bose Award for Excellence in Teaching, School of Engineering, 2007
• PAI Outstanding Teaching Award (presented by the student chapter of the American Nuclear Society), 2006 and 2007
• The Ruth and Joel Joel Spira Award for Distinguished Teaching, 2006
• Graduate Teaching Award, 2005
• Norman C. Rasmussen Career Development Chair, 2004
• ANS Mark Mills Award, 2001
• Best Technical Paper Award, Thermal-Hydraulic Track at the 8th International Conference on Nuclear Engineering (ICONE-8), 2000
• Manson Benedict Fellowship for Outstanding Academic Achievements, 2000
• Martin Society Fellow, 1999
• Alpha Nu Sigma Honor Society Member, 1999
• Best NED Teaching Assistant Award, 1998 and 1999

Publications (pdf)

Research Interests

Multi-phase flow and heat transfer; advanced reactor design; reactor thermal-hydraulic, neutronic and structural analysis.

Investigation of Nanofluids for Nuclear Applications

My research efforts have been directed primarily to the investigation of fundamental transport phenomena in colloidal suspensions of nanoparticles (known as nanofluids) with the ultimate goal of exploring their applications in nuclear systems, such as fission reactors, accelerator targets and fusion reactors.  The research program is in collaboration with the MIT Nuclear Reactor Laboratory, and sponsored by AREVA, the Idaho National Laboratory (INL), the Department of Energy and the Electric Power Research Institute (EPRI). 

The program emphasis is on elucidation of the mechanisms of mass, momentum and heat transfer enhancement that has been observed experimentally.  This entails (i) measurements and theoretical predictions of the thermophysical properties (thermal conductivity and viscosity above all) and single-phase convective heat transfer coefficient and pressure drop, (ii) evaluation of the colloidal stability of the nanoparticles under irradiation and in chemistries representative of the reactor environment, and (iii) measurements of the Critical Heat Flux (CHF) in both pool and flow boiling.  This last area has been the source of very exciting results lately.  Our experiments indicate that significant CHF enhancement is possible with nanofluids at modest concentrations (Fig. 1) and this enhancement was proven to occur for the first time also in a flow system. 

Since the performance of all water-cooled nuclear systems is CHF limited, the use of nanofluids could afford considerable economic and safety gains.  The work performed in our lab has also cast considerable light on the mechanism of CHF enhancement in nanofluids.  Briefly, buildup of a porous layer of nanoparticles on the heater surface was observed during nucleate boiling, and it was shown that this layer significantly improves the surface wettability, which in turn increases greatly the CHF.

(a) Pure water (1 MW/m2)	(b) Nanofluid (1 MW/m2)
Figure 1.  Pool boiling of pure water (a) and 0.01%v alumina nanofluid (b) at the same heat flux on a stainless steel wire.  Note that while the wire has experienced CHF in pure water, it is still well within the nucleate boiling regime in the nanofluid.

Among the possible nuclear applications of nanofluids that we have been exploring one has proven particularly promising so far, i.e., mitigation of postulated severe accidents during which the core melts and relocates to the bottom of the reactor vessel.  In such accidents it is desirable to retain the molten fuel within the vessel by removing the decay heat through the vessel wall.  This process is limited by the occurrence of CHF on the vessel outer surface.  Our analysis indicates that using a nanofluid vs water as the coolant can improve the in-vessel retention capabilities of nuclear reactors by as much as 30-40%.