Synergistic heat transfer enhancement characteristics due to electric field and macro-structured surface during thin film boiling

doi:10.11949/0438-1157.20241233

Abstract

Abstract:

The synergistic enhancement of thin liquid film boiling heat transfer by electric field and macrostructure is expected to break through the bottleneck of high heat flux heat dissipation of electronic devices. In this study, six distinct macro-structured surfaces are designed and fabricated to systematically investigate the effects of liquid film thickness, structural parameters, and applied voltage on the boiling heat transfer performance with ethanol as the working medium. High-speed imaging and precise heat transfer measurements are employed to evaluate the boiling characteristics, providing insights into the underlying mechanisms driving the observed enhancements. The dynamics of boiling bubbles are found to significantly influence the enhancement of critical heat flux (CHF). When a 4 kV voltage is applied, the bubble departure frequency increases by up to 80%, while the bubble departure diameter decreases by 28% as compared to 0 kV, resulting in a CHF enhancement of approximately 20%. CHF is positively correlated with liquid film thickness and rib height, but exhibits a negative correlation with rib spacing, achieving an increase of up to 139% in CHF under optimal conditions. Further analysis of the CHF enhancement ratio reveals that liquid film thickness exerts the greatest influence on CHF improvement (0.37), followed by rib spacing (0.24) and applied voltage (0.20).

Key words: thin film boiling, electric field, macro-structured surface, bubble, heat transfer, gas-liquid flow

摘要：

利用电场与宏观结构协同强化薄液膜沸腾传热，有望突破电子器件高热通量散热瓶颈。以乙醇为工质，设计并加工了6种宏观结构表面，通过高速摄像可视化和沸腾传热测量，系统分析了液膜厚度、结构参数以及荷电电压对薄液膜沸腾传热特性的影响规律。实验结果表明，气泡动力学特性调控是临界热通量（CHF）增强的关键。与不施加电场相比，施加4 kV荷电电压时，宏观结构表面的气泡脱离频率最高可提升80%，气泡脱离直径减小了28%，从而使CHF提升了20%。CHF随着液膜厚度和肋高的增大而增大，随肋间距的增大而减小。在最优条件下，CHF提升幅值可达139%。通过定义CHF增强比发现，液膜厚度对CHF的提升贡献最大（0.37），其次是肋间距（0.24）和荷电电压（0.20）。

关键词: 薄液膜沸腾, 电场, 宏观结构表面, 气泡, 传热, 气液两相流

CLC Number:

TK 124

Changqiu HE, Jiameng TIAN, Yiqi CHEN, Yuchen ZHU, Xin LIU, Hai WANG, Zhentao WANG, Junfeng WANG, Zhifu ZHOU, Bin CHEN. Synergistic heat transfer enhancement characteristics due to electric field and macro-structured surface during thin film boiling[J]. CIESC Journal, 2025, 76(6): 2589-2602.

何昌秋, 田加猛, 陈义齐, 朱宇琛, 刘鑫, 王海, 王贞涛, 王军锋, 周致富, 陈斌. 电场-宏观结构表面协同强化薄液膜沸腾传热特性[J]. 化工学报, 2025, 76(6): 2589-2602.

Figures/Tables 16

Fig.1 Experiment system of thin film boiling

Table 1 Physical properties of ethanol （20℃， 1 atm）［25-26］

物理性质	数值
密度/(g/cm³)	0.79
热导率/(W/(m·K))	0.17
黏度/(mPa·s)	1.1
表面张力/(N/m)	21.97×10^-3
电导率/(S/m)	5.10×10^-5
相对介电常数	25.30

Fig.2 Bubble visualization system

Fig.3 Cubic-pin-fin structured surface

Table 2 Cubic-pin-fin structural parameters

表面类型	肋数/个	基底面积/mm²	结构面积/mm²	总面积A_tot/mm²
s2.5-h0.5	16	96	20	116
s2.5-h1.5	16	96	52	148
s2.5-h2.5	16	96	84	180
s1.5-h0.5	36	91	45	136
s1.5-h1.5	36	91	117	208
s1.5-h2.5	36	91	189	280

Fig.4 Bubbles image processing

Fig.5 Temperature measurements by IR camera

Fig.6 Variations of surface heat flux with wall temperature on different structured surfaces under electrical field

Fig.7 Variations of surface heat transfer coefficient with wall temperature on different structured surfaces under electrical field

Fig.8 Behavior of boiling bubbles at different wall temperatures

Fig.9 Variations of triple-phase contact line length and wetted area with wall temperature under electrical field

Fig.10 Boling bubble diameter distributions under electrical field (Ts=95℃, h=0.5 mm)

Fig.11 Variations of bubble detachment frequency with applied voltage (Ts=95℃)

Fig.12 Critical heat flux under different conditions

Fig.13 Enhancement ratio η of critical heat flux at different conditions

Fig.14 Averaged critical heat flux enhancement ratios with different parameters

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