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Experimental and Numerical Investigations on the Flow Characteristics within Hydrodynamic Entrance Regions in Microchannels

National Key Laboratory of Science and Technology on Aero Engines Aero-thermodynamics, The Collaborative Innovation Middle for Advanced Aero-Engine of China, School of Energy and Power Engineering, Beihang University, Beijing 100191, China
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Micromachines 2019, 10(5), 317; https://doi.org/10.3390/mi10050317
Received: 19 March 2019 / Revised: 23 April 2019 / Accepted: 5 May 2019 / Published: 11 May 2019
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Abstract

Flow characteristics within entrance regions in microchannels are important due to their effect on heat and mass transfer. However, relevant research is limited and some conclusions are controversial. In order to reveal flow characteristics within entrance regions and to provide empiric correlation estimating hydrodynamic entrance length, experimental and numerical investigations were conducted in microchannels with square cross-sections. The inlet configuration was elaborately designed in a more common pattern for microdevices to diminish errors caused by separation flow near the inlet and fabrication faults so that conclusions which were more applicable to microchannels could be drawn. Three different microchannels with hydraulic diameters of 100 μm, 150 μm, and 200 μm were investigated with Reynolds (Re) number ranging from 0.5 to 50. For the experiment, deionized water was chosen as the working fluid and microscopic particle image velocimetry (micro-PIV) was adopted to record and analyze velocity profiles. For numerical simulation, the test-sections were modeled and incompressible laminar Navier–Stokes equations were solved with commercial software. Strong agreement was achieved between the experimental data and the simulated data. According to the results of both the experiments and the simulations, new correlations were proposed to estimate entrance length. Re numbers ranging from 12.5 to 15 was considered as the transition region where the relationship between entrance length and Re number converted. For the microchannels and the Reynolds number range investigated compared with correlations for conventional channels, noticeable deviation was observed for lower Re numbers (Re < 12.5) and strong agreement was found for higher Re numbers (Re > 15). View Full-Text
Keywords: microchannel; velocity profile; microscopic particle image velocimetry (micro-PIV); entrance length microchannel; velocity profile; microscopic particle image velocimetry (micro-PIV); entrance length
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Li, H.; Huang, B.; Wu, M. Experimental and Numerical Investigations on the Flow Characteristics within Hydrodynamic Entrance Regions in Microchannels. Micromachines 2019, 10, 317.

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