Research Interests

1) Heat Transfer in MicroElectroMechanical Systems (MEMS)

This research thrust aims at developing new MEMS-based cooling concepts (single-phase and boiling) and extending fundamental knowledge of vapor-liquid phase change in micro systems.  Systems that are studied include forced boiling flow in microchannels, and single-phase and boiling over micro scale pin fin heat sinks.  A range of geometrical, thermal and hydraulic conditions are being investigated.  Specific examples include experimental studies of boiling flow over specially designed reentrant cavities for enhanced heat transfer, and analytical/experimental studies of thermal and hydraulic performance of circular pin fin heat sinks with water and R123.  Engineering data measured include single and two-phase heat transfer coefficients, onset of nucleate boiling and critical heat flux conditions, total system thermal resistance, and friction factor.  Basic studies include identifying predominating heat transfer mechanisms, understanding bubble nucleation process (bubble inception, growth and detachment) during nucleate boiling and its effect on boiling inception, heat transfer coefficient and critical heat flux conditions. 

2) Cavitation in MEMS

This research endeavor aims at establishing a cavitation knowledge base pertinent to microsystems.  The current research effort is expected to greatly advance the exceedingly limited fundamental knowledge of cavitation in microsystems.  Additionally, this work will serve as a launching pad for future research in novel high-speed micro-hydraulic devices. A meticulous study of cavitating flows in rudimentary indispensable micro scale configurations such as micro scale orifices, venturis, valves, hydrofoils, and heat exchangers are being investigated.  Both fundamental as well as engineering understanding is being sought.  This research will generate a basic understanding of flow structures under various hydraulic conditions, and ameliorate the current understanding of scale effects instigated by a variety of parameters such as surface nuclei and stream nuclei size and population, Reynolds number, Weber number, inlet and exit pressures, velocity modulation, liquid wettability characteristics etc. Engineering data such as cavitation inception number and choking cavitation number, which have emerged from this research, will indubitably abet designers of high-velocity MEMS hydraulic machines.  

3) MEMS Design, Process and Fabrication Development

In support of the micro scale heat transfer, fluid flow and cavitation research an extensive effort to fabricate state-of-the-art MEMS devices are being carried out.