Study on Nucleation Site Density of Surfaces Modified by Femtosecond Laser
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摘要: 以不锈钢材料为实验件，采用飞秒激光技术加工有序微纳结构来制备改性表面，并以去离子水为工质开展池沸腾核化点密度实验研究，获取了不同热工参数条件下3种不同实验表面（常规表面、改性表面1、改性表面2）的核化点密度实验数据，定量分析了核化点密度随壁面过热度的变化规律，并以李权模型为基础拟合得到改进核化点密度模型。研究发现，3种实验表面的核化点密度均随壁面过热度的升高而增大，且相同热工参数下改性表面的核化点密度显著大于常规表面；改进模型优化了核化点密度的预测值，且预测值与实验数据吻合较好。Abstract: Using stainless steel as the experimental piece, femtosecond laser technology is used to fabricate ordered micro-nano structures to prepare modified surfaces. The pool boiling nucleation site density experiment is carried out with deionized water as the working medium, and the nucleation site density experimental data of three different experimental surfaces (conventional surface, modified surface 1, and modified surface 2) under different thermal parameters are obtained. The variation law of nucleation site density with wall superheat degree is quantitatively analyzed, and an improved nucleation site density model is obtained by fitting on the basis of the Liquan model. It is found that the nucleation site density of the three experimental surfaces increases with the increase of wall superheat degree, and the nucleation site density of the modified surface is significantly higher than that of the conventional surface under the same thermal parameters.The improved model optimizes the predicted value of nucleation site density, and the predicted value is in good agreement with the experimental data.
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Key words:
- Nucleation site density /
- Pool boiling /
- Femtosecond laser /
- Modified surface /
- Improved model
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图 2 实验表面扫描电镜图像（放大250倍）
Figure 2. SEM Images of Experimental Surface (Magnified 250 Times)
图 4 相同壁面过热度时不同实验表面核化点密度图像
Figure 4. Nucleation Site Density Images of Different Experimental Surfaces under the Same Wall Superheat Degree
图 5 各实验表面核化点密度与壁面过热度的关系
Figure 5. Relationship between Nucleation Site Density and Wall Superheat Degree of Each Experimental Surfaces
图 7 改进模型预测值与实验数据对比情况
Figure 7. Comparison between the Predicted Value of the Improved Model and the Experimental Data
表 1 实验表面特性参数
Table 1. Characteristic Parameters of the Experimental Surfaces
表面类型 面粗糙度
（Sa）/μm表面接触角
（θ）空穴直径
（d）/μm空穴间距
（w）/μm常规表面 0.2615 62.51° — — 改性表面1 18.7165 109.49° 18.27 28.42 改性表面2 14.576 100.06° 30.13 45.82 “—”表示无数据 
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表 2 实验工况及统计数据
Table 2. Experimental Conditions and Statistical Data
工况
编号表面类型 q
/(kW·m−2)ΔTw/℃ Na/m−2 1 常规表面 18.7 3.5 7.50×103 2 常规表面 27.8 5.2 3.25×104 3 常规表面 34.6 6.3 4.00×104 4 常规表面 42.3 7.2 7.00×104 5 改性表面1 19.9 1.6 9.29×103 6 改性表面1 24.5 3.1 1.42×105 7 改性表面1 32.7 3.7 3.59×105 8 改性表面1 41.7 4.3 7.00×105 9 改性表面2 11.9 1.0 3.21×105 10 改性表面2 17.2 2.1 1.42×106 11 改性表面2 21.5 4.0 1.64×106
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