Abo Bibliothek: Guest

ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

IN SITU TEMPERATURE MEASUREMENT OF EVAPORATION IN MICROPILLAR WICK STRUCTURES USING MICRO-RAMAN SPECTROSCOPY

Get access (open in a dialog) DOI: 10.1615/IHTC16.bae.023152
pages 763-771

Abstrakt

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 µm 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 µm. We calibrated the Stokes peak positions of silicon with its temperature and observed a linear relationship and an uncertainty of approximately ±0.9 °C, which agrees well with literature. We fabricated silicon micropillar arrays (diameters of 20 µm, heights of 50 µm and pitches of 40-100 µm) 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.