Size-Dependent Bubble Dynamics in a Microchannel Heat Sink

L.S.L. Cheung, Y.-K. Lee, M. Wong and Y. Zohar

The height effect on bubble dynamics in a microchannel is experimentally studied. We reported that the critical size for a nucleation site to be active increases linearly with the channel height. However, once a bubble is formed, its evolution from incipience to departure can also be channel-size dependent. Thus, various microchannel heat sinks have been fabricated, about 5-10µm in height, with integrated temperature sensors utilizing Si-to-glass anodic bonding technology. Nucleation sites have been formed on the microchannels bottom silicon surface in order to ensure regular bubble formation, while the sensors allow continuous monitoring of the wall temperature. The microchannels are capped by a glass wafer; hence, it is possible to record the bubble activity using video equipment. The three aspects of bubble dynamics: growth rate, departure size and release frequency have been characterized experimentally, and proper control parameters have been identified.

ACKNOWLEDGEMENTS

This work is supported by Hong Kong Research Grant Council through grant HKUST6134/04E.

REFERENCES

[1] X. F. Peng & B. X. Wang, Int. J. Heat Mass Transfer, Vol. 36, pp. 3421-3427, 1993.

[2] L. Jiang, M. Wong & Y. Zohar, JMEMS, Vol. 8, pp. 358-365, 1999.

[3] L. Jiang, M. Wong & Y. Zohar, JMEMS, Vol. 10, pp. 80-87, 2001.

[4] L. Zhang, E. N. Wang, J. M. Koo, L. Jiang, K. E. Goodson, J. G. Santiago & T. W. Kenny, JMEMS, Vol. 11, pp. 12-19, 2002.

[5] M. Lee, L.S.L. Cheung, Y.-K. Lee, M. Wong & Y. Zohar, Proc. MEMS’04, pp.300-303, 2004.

[6] M. Lee, Y. Y. Wong, M. Wong & Y. Zohar, J. Micromech. Microeng, Vol. 13, pp. 155-164, 2003.

[7] V.K. Dhir, Int. J. Heat and Fluid Flow, Vol. 12, pp.290-314, 1991.

[8] S. Levy, Int. J. Heat Mass Transfer, Vol. 10, pp.951-965, 1967.

[9] H. J. Ivey, Int. J. Heat Mass Transfer, Vol. 10, pp.1023-1040, 1967.