Graduate Thesis Or Dissertation
 

Application of infrared thermography for temperature measurement in microscale internal and external flows

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/qv33s0977

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  • Infrared (IR) thermography is applied to estimate heat transfer rates in external and internal microscale convective flows. The technique and analysis are developed in the context of external jet impingement flow and internal single-phase liquid flows. A heated-thin-foil thermography technique is applied to perform surface temperature visualization on a submerged 125-[mu]m circular microscale jet impingement. Microscale jets flows are associated with low exit Reynolds number (Re) due to the small characteristic length of the nozzle, but correspondingly high exit velocities, and hence, a high subsonic Mach number. Detailed distributions of heated and adiabatic wall temperature, and local and average Nusselt number (Nu) variations are presented for a single 125-[mu]m diameter air jet impingement for five laminar exit Re in the range of 690 to 1770 at three nozzle-to-surface spacing of 2, 4, and 6 times the nozzle diameter. The corresponding jet exit Mach numbers vary between 0.26 and 0.63. Lateral heat conduction along the impingement surface is significant and warrants inclusion in the calculation of heat transfer coefficient. Results indicate that the adiabatic surface temperature distribution is relatively insensitive to nozzle-to-surface spacing within the parameter range studied. With an increase in Re, the adiabatic surface temperature decreases significantly near the stagnation point. The average Nu is higher compared to the turbulent macroscale Martin's correlation for large Re. A technique for quantitative temperature visualization of single-phase liquid flows in silicon (Si) microchannels using infrared thermography is presented. This technique offers a new way to measure, non-intrusively, local variations in wall temperature, or fluid temperature at the fluid-wall interface, in a microchannel fabricated entirely of silicon. The experimental setup and measurement procedure required to obtain high signal-to-noise ratio is elaborated. A single 13-mm long, 50 [mu]m wide by 135 [mu]m deep Si microchannel was used in this study. Experiments were performed with a constant electrical heat input rate to the heat sink surface for four fluid flow rates between 0.6 g/min and 1.2 g/min, corresponding to a Re range from 200 to 300. The estimated experimental fully developed Nu compares reasonably well with the solution provided in literature for laminar flows. Results indicate that axial non-uniformity can be significant for the large Peclet number flows.
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