不同加热方式下环路热管蒸发器补偿器的可视化

doi:10.16085/j.issn.1000-6613.2020-1221

摘要/Abstract

摘要：

为了探索不同加热方式对环路热管的启动及稳定运行性能的影响，对环路热管的蒸发器补偿器进行了可视化试验研究。环路热管以R245fa为工质，充液率为50%，分别采用了三种不同的热负载施加方法：蒸发器顶部加热、蒸发器上下同时加热、蒸发器底部加热。根据启动过程中蒸发器空腔内的主要相变模式不同，对应地分为3种启动模式：蒸发启动模式、蒸发沸腾混合启动模式、沸腾启动模式。结果发现：在5W启动过程中，蒸发沸腾混合模式和沸腾模式下的启动速度最快，并在蒸发器空腔气体槽道出口处伴有气泡溢出，分别历时760s、1180s，远小于蒸发启动模式的2370s。分析可知，环路热管的启动速度与蒸发器空腔内的初始液面及其平均液体消失速度密切相关。另外，为研究蒸发器空腔内液相工质的沸腾，对不同的启动模式下空腔内的气泡生长进行了探索。在稳定工况中，同热负载下不同加热方式的环路热管的热阻及补偿器液面高度都不相同，其中底部加热方式的环路热管热阻最小。经分析发现，同热负载下不同加热方式会影响蒸发器内液相工质的蒸发效率，同时也会改变补偿器液面高度和蒸发器向补偿器的漏热，进而影响环路热管性能。

关键词: 环路热管, 蒸发, 可视化, 启动模式, 相变, 传热

Abstract:

A visualization study of the evaporator and compensator for the loop heat pipe (LHP) was conducted to explore the influence of different heating methods on the startup and stability characteristics of the LHP. The performance of an R245fa charged LHP with 50% liquid filling rate under three methods of heat load application was investigated: heating at the top of evaporator, heating at the bottom of evaporator, and heating both the top and bottom of evaporator at the same time. According to the main phase change modes in the cavity of the evaporator during the startup process, three startup modes were characterized: evaporation startup mode, evaporation-boiling mixed startup mode, and boiling startup mode. The results showed that the startup process in the latter two startup modes was faster when 5W of heat load was applied, and there were bubbles overflowing from capillary vapor channels of the evaporator cavity. The startup time was 760s and 1180s, respectively, far less than 2370s for the evaporation startup mode. The startup time of LHP was closely related to initial liquid level and the average liquid disappearance rate in the evaporation cavity. Additionally, the bubble growth in the cavity under different starting modes was explored. With the same heat load, the thermal resistances of the LHPs and the liquid height in the compensator under different heating methods were different. The LHP with the bottom heating method had the smallest thermal resistance. It is found that different heating methods affect the evaporation efficiency of liquid working in the evaporator. Meanwhile, it also could change the liquid height in the compensator and the heat leakage from the evaporator to the compensator, thus affecting the performance of the LHP.

Key words: loop heat pipe, evaporation, visualization, startup mode, phase change, heat transfer

中图分类号:

TK172.4

刘超, 谢荣建, 李南茜, 徐光明, 董德平. 不同加热方式下环路热管蒸发器补偿器的可视化[J]. 化工进展, 2021, 40(5): 2401-2415.

LIU Chao, XIE Rongjian, LI Nanxi, XU Guangming, DONG Deping. Visualization of compensator and evaporator of a loop heat pipe under different heating methods[J]. Chemical Industry and Engineering Progress, 2021, 40(5): 2401-2415.

图/表 18

参考文献 14

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蒸发器（石英玻璃）	补偿器（石英玻璃）	蒸发器内毛细芯（氧化锆）	液体管线（316L）	气体管线（316L）	冷凝器（316L）	加热片	气体槽道
长度90mm	长度83mm	长度80mm	长度800mm	长度500mm	长度303.2mm	长度50mm	长度75mm
外径42mm	外径50mm	外径20mm	外径6mm	外径6mm	外径6mm	宽度50mm	宽度1mm
内径24mm	内径32mm	内径8mm	内径4mm	内径4mm	内径4mm	阻值20Ω	高度1mm
				孔径1.75μm	工质R245fa	水冷机温度293.15K	数量12
				孔隙率67.6
				渗透率1.26×10^-12m²
				盲孔深度75mm

蒸发器（石英玻璃）	补偿器（石英玻璃）	蒸发器内毛细芯（氧化锆）	液体管线（316L）	气体管线（316L）	冷凝器（316L）	加热片	气体槽道
长度90mm	长度83mm	长度80mm	长度800mm	长度500mm	长度303.2mm	长度50mm	长度75mm
外径42mm	外径50mm	外径20mm	外径6mm	外径6mm	外径6mm	宽度50mm	宽度1mm
内径24mm	内径32mm	内径8mm	内径4mm	内径4mm	内径4mm	阻值20Ω	高度1mm
				孔径1.75μm	工质R245fa	水冷机温度293.15K	数量12
				孔隙率67.6
				渗透率1.26×10^-12m²
				盲孔深度75mm

启动模式	初始液面	热负载施加540s后		热负载施加732s后		环路热管稳定后
启动模式	初始液面	518.24s	540s	710.24s	732s	环路热管稳定后
蒸发启动	16.82					0
蒸发沸腾混合启动	15.42	8.15	7.98			0
沸腾启动	17.7	14.23	12.28	6.61	6.27	0

启动模式	初始液面	热负载施加540s后		热负载施加732s后		环路热管稳定后
启动模式	初始液面	518.24s	540s	710.24s	732s	环路热管稳定后
蒸发启动	16.82					0
蒸发沸腾混合启动	15.42	8.15	7.98			0
沸腾启动	17.7	14.23	12.28	6.61	6.27	0

气体槽道位置	758.24~764.25s		771.45~772.52s		778.04~780s
气体槽道位置	平均生长周期 /s	单位时间内气泡数 /个·s^-1	平均生长周期 /s	单位时间内气泡数 /个·s^-1	平均生长周期 /s	单位时间内气泡数 /个·s^-1
合计	0.0428	4.65	0.0412	8.76	0.0428	13.34
正下方	0.0406	1.66	0.0403	3.57	0.0429	4.76
右下方1	0.0426	2.16	0.0396	4.22	0.0431	5.72
右下方2	0.0490	0.50	0.0508	0.97	0.0407	0.95
左下方1	0.0453	0.33	0.0415	1.30	0.0426	1.91