| Summary: | 碩士 === 淡江大學 === 機械工程學系 === 89 === Regarding the micro channel thermal analysis, in the past by using trapezoid, triangle, and rectangular micro-channel to study phase change, exclude circular one. Experimental tests and theoretical analysis were conducted to investigate the characteristics of fluid flow and phase change in micro stainless pipe in this thesis, especially in the mechanism of force convection bubble nucleation.
Distillated water was used as the working fluid and flowed through micro-pipes with different diameters ranging from 153-508 mm in the experiments. Wall temperature and picked-time relations were obtained at different heating power in different micro tubes. During the working fluid heated in the inlet until boiling, we found that there are some bubbles to be generated and flowed into micro-channels and accompanied with several sudden wall temperature drop shown in data acquisition curve. We believed that bubbles flowed through micro-channel to block radial heat transmission of the fluid and accompanied with wall temperature curve decreased rapidly, and the frequency of the sudden wall temperature drop increased with the heating power. It would be assumed that the bubble numbers were increased with the heating power. If the working fluid heated until dryout, the wall temperature will slowly close to the maximum value. The wall temperature no longer significantly varied.
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