ポーラスマイクロチャンネルを用いた相変化除熱に関する研究

Abstract

The critical heat flux (CHF), heat transfer coefficient, and pressure loss were measured systematically for water subcooled flow boiling. A small rectangular channel containing a porous metal plate was used as the test channel (this was called “porous-microchannel” in this work). In the normal rectangular channel that did not contain the porous plate, large bubbles were produced at sufficiently high heat flux. In some experimental conditions, the formation of large bubbles immediately led to the onset of CHF condition. It was hence considered that the CHF value was deteriorated by the formation of large bubbles. Whist, in the porous-microchannel, the mixing effect associated with the complicated channel geometry prevented the formation of large bubbles to enhance the CHF value. The occurrence of flow instability was also mitigated. The effects of the material and the pore size of the porous metal were also investigated. Silver and nickel were selected as the high and low thermal conductivity materials, respectively. It was found that the CHF value was not influenced significantly by the material, but it was dependent noticeably on the pore size. These results supported the hypothesis that the CHF enhancement in the porous-microchannel can mainly be attributed to the mixing effect caused by the complicated channel geometry.