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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Decoding Fundamental Boiling Processes in Micro Domains – Experimental Challenges and Opportunities

Get access (open in a dialog) DOI: 10.1615/IHTC15.kn.000011
pages 204-220

Аннотация

Flow boiling in microchannels has been extensively studied since the mid-1990. Accurate measurements at the micro scale are very demanding, and as a result, fundamental knowledge pertinent to boiling heat transfer in diminishing length scales is severely lacking. The main obstacles include significant conjugate conduction/convection processes and the lack of high frequency synchronized temperature/flow visualization measurements. Here we report on a new hybrid numerical-experimental method that overcomes major obstacles inhibiting progress pertinent to this important field. A new parameter, termed the S coefficient, which allows accounting for the conduction process, and therefore, isolating the convection process, is introduced and numerically calculated. It is then demonstrated on three high speed experimental measurements. Surface temperature with micron size thermistors are obtained at high frequencies (O(10kHz)); boiling events are simultaneously visualized and used in conjunction with transient temperature measurements and the S coefficient to infer processes controlling heat transfer in a microchannel. It was shown that high thermal conductivity substrates typically used to form microchannels, such as silicon and copper, are not suitable for elucidating fundamental transient processes in microchannels. Low thermal conductivity materials, such as Pyrex and Benzocyclobutene (BCB), are more applicable. However, this can only be done through careful numerical analysis of the conduction heat transfer within the solid structure used to form the microchannel.