複合式溝槽/銅網毛細平板熱管之可視化實驗

本研究使用可視化平板熱管，以水為工作流體，量測並觀察雙層200目銅網毛細、溝槽毛細與複合式溝槽/銅網毛細三種熱管的操作特性。在燒結雙層200目銅網的情況下其最大熱傳量為24W，而溝槽毛細熱管的最大熱傳量為14W。採用複合式溝槽/銅網毛細時，蒸發過程在不同加熱量範圍呈現不同模態，熱阻值也呈階段式上升。最大熱傳量可以提高到66W，並且在小於44W時，蒸發熱阻值僅有0.05~0.07 Kcm2/W。更進一步增加傾角至45°及90°時，最大熱傳量仍達44W，而熱阻值與水平擺放時差異不大，如此顯示此種複合式熱管可以大幅提升熱管性能。可視化觀察顯示複合式燒結溝槽/銅網毛細可以提供更多的毛細交接處，使其能夠在水平操作下維持在部分乾化卻穩定蒸發的階段。在蒸發區動態行為的表現上較相近於溝槽熱管，工作流體的聚光性端部彼此間具有獨立性。另外，在本文中的所有不同毛細實驗中，皆未觀察到核沸騰的現象。

關鍵字

熱管；複合式毛細結構；可視化

並列摘要

This work presents visualization and measurement of the evaporation resistance for operating flat-plate heat pipes with composite groove/mesh wicked. For comparison, experiments are also conducted for heat pipes with a groove or a mesh wick. The performances of these heat pipes are compared under different inclination angles. The parallel, U-shaped grooves with a width of 0.18 mm and a depth of 0.1 mm are sintered with a layer of 200 mesh copper screen covering the top of the grooves. With stepwise increase of heat load Q, the behavior of the working fluid in the groove/mesh wicked was visualized and the evaporator and condenser resistances were measured. Horizontally, different stages are identified with increasing heat load. For Q < 44 W, the evaporator can be fully wetted and the evaporator resistance ranges between 0.05~0.07 Kcm2/W; for 44 W < Q < 66 W, partial dryout appears in the evaporator, with the evaporator resistances jump to about 0.3 Kcm2/W; for Q > 66 W, the evaporator fully dries out with runaway evaporator resistances. At inclination angle of 45°, 60°, or 90°, Qmax could remain at about 44 W. In contrast, Qmax is 14 W for the groove wicked heat pipe and 24 W for the 2 × 200 mesh heat pipe under the horizontal orientation. The results show that the composite groove/mesh wick provides strong capillary force yet low flow resistance to yield high Qmax even for high inclination angles. In addition, no boiling is observed in all present tests.

並列關鍵字

Heat pipe

參考文獻

[1] K.-T. Lin, S.-C. Wong, Performance degradation of flattened heat pipes, Appl. Therm. Eng. 50 (2013) 46–54.

[3] S.W. Chi, Heat Pipe Theory and Practice, McGraw-Hill, 1976.

[4] R.H. Nilson , S.W. Tchikanda, S.K. Griffiths, M.J. Martinez, Steady evaporating flow in rectangular microchannels, Int. J. Heat Mass Transfer 49 (2006) 1603–1618.

[5] K. Park, K.S. Lee, Flow and heat transfer characteristics of the evaporating extended meniscus in a micro-capillary channel, Int. J. Heat Mass Transfer 46 (2003) 4587–4594.

[6] S.-C. Wong, C.-W. Chen, Visualization and evaporator resistance measurement for a groove-wicked flat-plate heat pipe, Int. J. Heat Mass Transfer 55 (2012) 2229-2234.

國際替代計量

複合式溝槽/銅網毛細平板熱管之可視化實驗

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