核沸騰熱伝達機構研究用MEMSセンサ(<小特集>第1回マイクロ・ナノ工学シンポジウム)

概要

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The objective of this study is to investigate heat transfer mechanism of pool nucleate boiling with MEMS (Micro-Electro-Mechanical systems) sensor fabricated for boiling research. Temperature variation beneath an isolated bubble under nucleate boiling condition of saturated water was measured with the sensor. Measured temperature data presents microlayer evaporation and expansion of dry-out area in bubble growth process and rewetting of the dry-out area in bubble departure process. Heat transfer from the heated surface was evaluated by calculating local heat flux by transient heat conduction simulation with the measurement data as a boundary condition. It is shown that high heat flux, induced by the microlayer evaporation, on the order of MW/m^2 was observed in the local heat flux distribution. The heat transfer enhancement by the microlayer evaporation was much larger than that by the rewetting, microlayer evaporation contributed mainly to the heat transfer from the heated surface to the boiling liquid and vapor phase. From the evaluation of the total surface heat transfer, transferred heat from the surface corresponded to about half of the latent heat of vaporization in the bubble.
2010-08-25