溶入氣體對萊氏現象之影響

The effects of dissolved gas on the Leidenfrost phenomenon

林巧琪(Chiao- Chi Lin)

指導教授 ： 黃振康

國立臺北科技大學/機電學院/機電整合研究所/碩士(2006年)

https://doi.org/10.6841/NTUT.2006.00326

摘要

液滴在高溫表面，因底部產生具隔絕作用之蒸汽層，而使得液滴呈較低的速度蒸發，此現象稱為萊氏現象。發生此現象之最低溫度稱為萊氏溫度。影響萊氏溫度出現的原因計有液滴尺寸大小、液體與加熱表面的熱性質、加熱表面的粗糙度、液體的表面張力等。於不同的表面溫度下，將液滴置於加熱的平板上，量測其蒸發時間後繪製蒸發曲線的實驗方法，稱為萊氏實驗。萊氏實驗除了能夠成功呈現池沸騰實驗無法得到的過渡沸騰區域外，亦能忠實模擬噴霧冷卻的物理機制。
本研究使用純水及兩種不同濃度之飽和二氧化碳水溶液、四種液滴大小，以及6061鋁合金、二氧化鈦鍍層、純鈦鍍層三種的加熱表面進行萊氏實驗，將結果繪製為蒸發曲線，並討論溶入氣體、液滴大小與鍍層對萊氏現象的影響。並嘗試利用固液界面接觸時瞬間產生的聲音，來判斷液滴的沸騰區域。

關鍵字

相變熱傳 ； 萊氏現象 ； 萊氏溫度

並列摘要

When the droplet is deposited on a hot enough surface, the bottom of droplet produces insulation vapor layer to cause the droplet evaporated slowly. This is called Leidenfrost Phenomenon. The lowest temperature occurring the Leidenfrost phenomenon is called the Leidenfrost temperature.
Some parameters affect the Leidenfrost temperature, such as size of droplet, thermal properties of liquid and heated surface, surface roughness of the heated surface, surface tension of the liquid, etc.
The experimentation, measuring evaporated time of the droplet and drawing evaporation curve beneath different temperature, is called Leidenfrost experiment. In addition to present transition boiling region successfully that we cannot attain through pool experiments, the Leidenfrost experiments better simulate the physical mechanism of spray cooling.
This investigation proceeds the Leidenfrost experiment with varied parameters, distilled water and saturated carbonated water of two kinds of concentration, four droplet sizes, and three kinds of heated surface material (6061 alloy aluminum, 6061 surface coating with Ti, 6061 surface coating with TiO2). According to the experimental results, evaporation curves are drawn, and the effects of dissolved gas, size of droplet, and surface coating are discussed.

並列關鍵字

Phase-change heat transfer ； Leidenfrost phenomenon ； Evaporation curve

參考文獻

[1] Leidenfrost, J.G., “On the Fixation of Water on Diverse Fire,” Int. J. Heat Mass Transfer, vol. 9, 1974, pp. 1209-1203.

[3] Bernardin, J. D. and Mudawar, I., “The Leidenfrost Point﹕Experimental Study and Assessment of Existing Models,” ASME J. Heat Transfer, vol. 40, no. 11, 1999, pp. 2579-2593.

[4] Baumeister, K.J. and Simon, F.F., “Leidenfrost Temperature- its correlation for liquid metal, cryogens, hydrocarbons, and water,” ASME J. Heat Transfer, vol. 95, 1973, pp. 166-173.

[5] Berenson, P.J., “Film-Boiling Heat Transition from a Horizontal Surface,” ASME J. Heat Transfer, vol. 83, 1961, pp. 351-358.

[6] Henry, R.E., “A Correlation for the Minimum Film Boiling Temperature,” Chem. Eng. Prog, 1974, pp. 81-90.