Thermal performance of multi-loop flat loop heat pipes

doi:10.11949/0438-1157.20240961

Abstract

Abstract:

To solve the heat dissipation problem of high heat flux electronic components, a novel multi-loop flat-type loop heat pipe with a size of 200 mm×150 mm×30 mm was prepared. The heat pipe adopts a design that couples an array of pin-fins on the evaporation surface with multiple gas-liquid pipelines, which can improve heat transfer efficiency in a limited space. The effects of heat flux, filling ratio, and working fluid properties on the thermal performance of loop heat pipe, and the startup characteristics of loop heat pipe under different heat load were studied. The heat performance of loop heat pipe under single and multi-source heating conditions was compared. The results show that the new loop heat pipe starts quickly, with a startup time of only 52 s at 300 W heat power, and the surface temperature fluctuation of the heat source after steady state is less than 0.3℃. When heated by three heat sources simultaneously with a total heat load of 388.8 W (the heat flux of main heat source can reach 133 W/cm²), the heating surface temperature is less than 85℃, and no dry burning occurs in the evaporator, effectively satisfy the heat dissipation requirements of high-power and high heat flux electronic devices.

Key words: loop heat pipe, pin-fin, phase change, heat transfer, gas-liquid two-phase flow

摘要：

为解决高热通量电子元器件的散热问题，制备了一款尺寸为200 mm×150 mm×30 mm的新型多回路平板式环路热管，该热管采用多气液管路与微针肋阵列蒸发板耦合的设计，能够在有限空间内提高热量传输效率。研究了热通量、充液比和工质物性对环路热管传热特性的影响，测试了不同功率下环路热管的启动特性，并对单热源和多热源环境下的热性能进行了比较。结果显示：该新型环路热管启动迅速，300 W功率下启动时间仅为52 s，稳态后热源表面温度波动小于0.3℃。在3个热源同时加热，总输入功率为388.8 W（主热源热通量可达133 W/cm²）时，加热面的温度低于85℃，蒸发器内没有出现干烧现象，有效满足了大功率高热通量散热需求。

关键词: 环路热管, 针肋, 相变, 传热, 气液两相流

CLC Number:

TK 172.4

Yiming ZHANG, Peng YANG, Xianbing JI, Jixing REN, Lei ZHANG, Zheng MIAO. Thermal performance of multi-loop flat loop heat pipes[J]. CIESC Journal, 2025, 76(3): 1018-1028.

张亦鸣, 杨鹏, 纪献兵, 任纪星, 张磊, 苗政. 多回路平板式环路热管热性能[J]. 化工学报, 2025, 76(3): 1018-1028.

Figures/Tables 10

Fig.1 Experimental system1—steel based heating sheet; 2—heating rod; 3—heating copper; 4—liquid injection pipe; 5—voltage regulator; 6—power display; 7—data acquisition instrument; 8—computer; 9—evaporator; 10—condenser

Table 1 Loop heat pipe and pin-fin structure parameters

部件	参数	数值
蒸发器	腔体尺寸	65.0 mm×65.0 mm×25.0 mm；δ=2.0 mm
	加热面	90.0 mm×90.0 mm×2.0 mm
	铜肋针	φ=2.17 mm；d=4.0 mm；h=20.0 mm
	顶盖（石英玻璃）	65.0 mm×65.0 mm×3.0 mm
蒸气通道	长内/外径	78.0 mm 5.0 mm/6.0 mm
液体通道	长内/外径	130.0 mm 4.0 mm/5.0 mm
冷凝器	腔体尺寸	200.0 mm×20.0 mm×10.0 mm；δ=1.5 mm

Fig.2 (a) Physical diagram of pin-fin evaporation base plate; (b) Structure diagram of pin-fin evaporation base plate; (c) Working principle and thermocouple distribution

Fig.3 Effect of filling ratio on thermal performance of loop heat pipes (single heat source environment)

Fig.4 Start-up characteristics of loop heat pipes at different powers (η=40%, working fluid is deionized water, single heat source environment)

Table 2 Physical property parameters of working fluid

工质	常压下沸点/℃	汽化潜热/(kJ/kg)	热导率/(W/(m∙K))	表面张力/(mN/m)	黏度/(mPa·s)
FCM-47	49.0	121.7	0.221	12.20	1.2
无水乙醇	78.2	962.5	0.1625	22.40	1.2
去离子水	100.0	2257.2	0.614	71.97	1.00
丙酮	57.0	520.6	0.1514	18.80	0.31
R1233zd	18.7	183.5	0.0769	15.10	0.47

Fig.5 Boiling phenomena of different working fluids in the evaporator at 300 W (η=40%)

Fig.6 Variation curve of bubble detachment diameter with temperature for different working fluids

Fig.7 Influence of working fluid on thermal performance of loop heat pipes (single heat source environment)

Fig.8 Relationship between surface temperature and input power under single heat source and multi-heat source heating condition

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