System level thermal hydraulic performance of water-based and PAO-based alumina nanofluids

Date of Award


Degree Name

M.S. in Mechanical Engineering


Department of Mechanical and Aerospace Engineering


Advisor: Robert J. Wilken


Current and future military aircraft have a critical need for improved avionics heat removal. A drop-in replacement is sought for the existing heat transfer fluid, poly-alpha-olefin (PAO). Nanofluids have been considered for this application due reports of increases in thermal conductivity higher than predicted by conventional theory. In this study, a coolant loop apparatus was designed and built to evaluate the laminar and turbulent heat transfer performance of water-based and PAO-based alumina nanofluids in a flowing system. Alumina/water solutions showed an increase in pressure drop with particle loading which caused the heat transfer coefficient (HTC) at equal pumping power to be lower than at equal flowrates. In turbulent heat transfer, the alumina/water nanofluids show a 1-5% increase in HTC at equal flowrates. At equal pumping power, the nanofluid HTC is lower than water. In laminar flow at equal flowrates the HTC is decreased, which is not predicted. The alumina/PAO nanofluid showed similar pressure drop performance to the pure PAO base fluid. In turbulent flow at equal flowrates and equal pumping power, the HTC increase is only 1-3%. In laminar flow, a similar increase of 1-3% was observed. This increase is too small to warrant further testing of these fluids. In addition, particle settling was observed after only a few hours, which leads to questions about the long term stability of these nanofluids in a continuously flowing system. Overall, the fluids tested showed only marginal enhancement to the heat transfer coefficient. There were no significant (i.e. order of magnitude) increases observed between the results and conventional theory as have been reported elsewhere. The results of this work show that coolant loop apparatus is a valuable system-level screening tool for the U.S. Air Force to evaluate new single-phase coolants for avionics cooling.


Nanofluids Thermal properties Testing, Jet engines Cooling, Airplanes Motors Cooling

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Copyright © 2011, author