On heat transfer mechanism of nucleate boiling with MEMS sensors (2nd report, electrolysis triggering and heat transfer analysis)

The experimental approach to the heat transfer mechanism of nucleate boiling has been studied with a MEMS thermal sensor and a numerical analysis. The MEMS sensor includes gap electrode and eight micro thermocouple on a silicon or a glass substrate. The electrolysis of water by the gap electrode was used to trigger an isolated boiling bubble growth. The electrolysis trigger features low thermal influence and high repeatability in the bubble initiation, thus the temperature variation under a similar condition to the ordinary nucleate boiling can be measured. Moreover, the evaluation method of the heat transfer beneath the bubble has been developed through the transient heat conduction simulation of the heating wall. With the measured temperature data as an interface boundary condition, local heat flux, heat flow and transferred heat were derived for an isolated boiling bubble generation. It was demonstrated that the detailed information of the heat transfer beneath the boiling bubble can be evaluated quantitatively through the measurement with the MEMS sensor and the numerical analysis with the measured temperature data.