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Under the direction of Dr. Daniel K. Harris this laboratory conducts research in advanced cooling solutions and thermal management strategies for applications ranging from micro-scale electronics up to macro scale systems. Recent contributions have centered upon advancing heat pipe technology using micro-fibrous metal felts wicks. Heat pipes are closed passive phase change devices that can achieve very high thermal conductance values. Microfibrous metal felts are a unique and unexplored wicking medium that give heat pipes the ability to be flat, conformal, and bendable. Work on using micro-fibrous metal felt wicks continues to advance fabrication techniques and performance testing for bendable and conformal heat pipes. Shape Memory Alloy heat pipes are also being developed for miniature actuator designs and medical applications. Miniature scale heat pipes etched in silicon work is underway in an effort to commercialize the practice at the wafer level of fabrication. Work has recently begun on using MEMS metal build-up fabrication techniques to generate micro channels for micro heat pipes and micro-fluidics channel passages within common materials used as substrates in electronics packaging.
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A theoretical and experimental research program has been developed which is investigating the important topic of particle formation and dynamics in flames. Although the emission of combustion-generated particles into the atmosphere has negative environmental consequences, the presence of particles in flames is actually beneficial to the combustion process. Particles are effective radiators of heat, and thus can contribute significantly to the transfer of thermal energy from hot combustion gases to heat exchanger surfaces. The research at Auburn is focused on two related aspects with regard to particles in flames. First, an experimental program is underway which is examining the factors governing particle growth. The information provided by the experiments will be valuable in predicting whether a particle will either completely oxidize in a flame or be released into the atmosphere. The second aspect of the research program involves the prediction of the radiative properties of combustion-generated particles. Results here will be useful in assessing the contribution of particles to the overall heat release from a flame, and in determining the effect on heat transfer from particle fouling of heat exchanger surfaces.
This facility is directed towards the cooling of microelectronic components. Modern-day supercomputers are cooled by direct liquid immersion cooling due to the high power-densities of the circuits used. Knowledge gained from liquid-cooled supercomputers is now being applied to portable computers. Research carried out thus far in this laboratory has focused on pool boiling characteristics of micro-configured cavities etched into silicon heat sinks. A novel technique has been developed to create re-entrant cavities in silicon that have proven to have excellent vapor trapping ability. Current directions of research include the interaction of multiple heat source-sink combinations, two-phase heat transfer in vertical channels, and the fundamental phenomenological understanding of the mechanism of enhancement of nucleate pool boiling from microscopic cavities formed in silicon. All current experimental studies are carried out in ozone-safe dielectric fluids. These studies will lead to the development of effective methods of cooling the next generation of liquid-immersion cooled multi-chip microelectronic packages.
The laboratory is equipped with several pool boiling rigs, advanced temperature sensors, thin film heat sources, power supplies, a dissolved gas sensor, a distillation unit, and vacuum pumps. Microelectronics fabrication facilities are available on campus at the Alabama Microelectronics Science and Technology Center.
Current research activity focuses on development of improved cooling methods for turbo machinery components to ensure reliable operation at the elevated temperatures anticipated in advanced gas turbine cycles.
Facilities in the laboratory include hot-wire anemometry, laser-sheet flow visualization, 3-D flow measurement, turbine flow meters, pressure sensors, data acquisition equipment, large blowers, and an elaborate turbo machinery simulation rig.
The thermal radiation measurements lab is set up to measure spatial, directional, and spectral distributions of radiation intensity for the purposes of: quantification of radiation surface and bulk material properties; experimental determination of radiation arriving at or leaving a surface; and measurement of intensity distributions in radiatively participating media for comparison to numerical/analytical calculations.
The equipment in the thermal radiation measurements lab includes: parabolic mirrors for concentrating radiation, gold-coated to improve thermal wavelength reflection; a monochromator with a wide selection of gratings and filters for selection of a single wavelength component; pyroelectric radiation detection devices; a 1 nanowatt (sensitivity) radiometer, locked in to a noise-filtering beam chopper; a 1000 K radiating cavity blackbody source, for calibration; assorted positioning and heating equipment for sample surfaces and materials. With these items, the thermal radiation measurements lab is equipped for both basic research and applied studies of radiation heat transfer.