IN SITU TEMPERATURE MEASUREMENT OF EVAPORATION IN MICROPILLAR WICK STRUCTURES USING MICRO-RAMAN SPECTROSCOPY Conference Paper uri icon

abstract

  • 2018 International Heat Transfer Conference. All rights reserved. Micro and nanostructures to enhance liquid-to-vapor phase change heat transfer for cooling high-performance electronics have attracted significant attention owing to their ability to generate capillary flow and thin-film area. Typically, heat transfer measurements are performed remotely (i.e., away from the three-phase contact line) due to limitations of conventional contact-mode temperature sensors such as thermocouples and resistance temperature detectors (RTDs), or averaged over an area of 20-50 m with infrared cameras. However, as evaporation mainly occurs in the thin-film region near the three-phase contact line, fundamental understanding of the enhancement mechanism requires a microscopic measurement technique capable of probing temperature near the contact line with high spatial resolution. Here, we report a novel platform using micro-Raman spectroscopy to perform in situ temperature measurement of micropillar structures during thin-film evaporation. We built a custom micro-Raman spectroscopy with a spatial resolution of 1.5 m. We calibrated the Stokes peak positions of silicon with its temperature and observed a linear relationship and an uncertainty of approximately 0.9 oC, which agrees well with literature. We fabricated silicon micropillar arrays (diameters of 20 m, heights of 50 m and pitches of 40-100 m) and built a thermo-fluidic test block to house the sample and to interface with the micro-Raman system. De-gassed and de-ionized water was used as the test fluid. We measured temperature on the top of silicon micropillars near the liquid-vapor interface at various locations on the sample and heat flux conditions. The results indicate that the local wall temperature reduced as the pitch of micropillars reduced, which is a result of increased thin-film area. The experimental results provide a guideline for optimizing the wick structures to increase evaporation heat transfer coefficient. The local, in situ temperature measurement platform presented in this study serves as a new tool to aid mechanistic understanding of phase change heat transfer.

name of conference

  • International Heat Transfer Conference 16

published proceedings

  • International Heat Transfer Conference 16

author list (cited authors)

  • Zhang, L., Zhu, Y., Rao, S. R., Bagnall, K. R., Antao, D. S., Leroy, A., ... Wang, E. N.

citation count

  • 0

complete list of authors

  • Zhang, Lenan||Zhu, Yangying||Rao, Sameer Raghavendra||Bagnall, Kevin R||Antao, Dion S||Leroy, Arny||Zhao, Lin||Bhatia, Bikram||Kelsall, Colin C||Wang, Evelyn N

publication date

  • January 1, 2018 11:11 AM