Faculty of Engineering and Natural Sciences
Flow Boiling in Complex Microchannels with Non-Uniform Wall Temperatures
In this talk, we will present the fabrication of a three layer microchannel with various shapes and features and an experimental study of flow boiling in non-uniform microchannels, demonstrating the ability to provide a stable flow of evaporated fluid for energy conversion and chip cooling applications. Microchannels presented here are designed so that the onset of boiling will be fixed at a prescribed location along the shaped microchannel as the liquid vaporizes. Previous investigations of two-phase flow have mostly focused on straight, uniform cross-section area microchannels and have identified multiple undesirable phenomena, such as bubble formations, flow oscillations, and incomplete vaporization of the exiting fluid.
A silicon wafer is anodically bonded to a glass wafers with previously machined holes, which serve as the exit holes for the fluid in the microchannels. Shaped microchannels are etched in the bonded silicon wafers using deep reactive ion etching (DRIE) and capped by anodic bonding of a glass cover wafer. A metered flow rate of pressurized DI water is fed through the chip using a syringe pump, while it is heated with a cartridge heater on the exit side of the three layer chip. The qualitative nature of the two-phase flow along the shaped features is observed through the glass cover wafer, for different flow rates and wall temperatures. The objective of these investigations is to identify the most beneficial combination of mechanisms, leading to the development of adequate two-phase flow micro heat exchangers.
Two mechanisms are proposed to stabilize the internal flow boiling. The first of the stabilizing mechanisms is to get a temperature gradient across the channel to separate the room temperature inlet fluid from the steam exit flow. The second mechanism is to change the direction of the surface forces acting on the meniscus to fix its position along the channel. Experiments have been conducted using two different fluids, different heating conditions, and different flow supply approaches. As a result, evaporation of the fluid was observed from a meniscus without the presence of bubbles for these different scenarios. This talk will present the meniscus behavior along the channel, for the range of operating conditions explored.
Selin Arslan studied Mechanical Engineering at
Turkey, and received her B.S. degree in June 2000. Subsequently, she joined the graduate program in the Mechanical and Aerospace Engineering Department at
NJ, where she received an M.S. degree in July 2002. She is working towards her Ph.D. degree at The Fu Foundation School of Engineering & Applied Science at
NY. Ms. Arslan is the recipient of two “Best Teaching Assistant” awards at
University. She is currently on a Research Associate assignment at the University of Sherbrooke, Quebec, Canada. Her research interests include applications of microfluidics, two-phase flow in non-uniform microchannels, micro-power generation, microelectromechanical systems (MEMS), vortex tubes and advanced energy systems.
July 16, 2009, 14:40, FENS L055