Droplet and Bubble Dynamics in Saturated FC-72 Spray Cooling on a Smooth Surface
Droplet and Bubble Dynamics in Saturated FC-72 Spray Cooling on a Smooth Surface
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DOI：
10.1115/1.2953237
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发表时间：
2008-10
影响因子：
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通讯作者：
Ruey-Hung Chen;D. S. Tan;Kuo-Chi Lin;L. Chow;A. Griffin;D. Rini
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文献类型：
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作者：
Ruey-Hung Chen;D. S. Tan;Kuo-Chi Lin;L. Chow;A. Griffin;D. Rini
采用数值模拟方法研究了饱和FC-72喷雾冷却过程中液滴和气泡的动力学及核态传热。模拟的喷雾冷却系统由三个液滴通量冲击在一个光滑的加热器，其中二次核数量超过表面核。使用实验观察到的气泡生长速率在光滑的金刚石加热器上，子模型假设基于物理推理的碰撞液滴夹带的二次核的数量，碰撞液滴的气泡穿刺，气泡合并，和二次核的空间分布。预测的核传热与实验结果一致。根据模拟结果，讨论了实验上难以观察到的液滴和气泡的动力学特性及其强化核态传热的能力。这些方面包括气泡合并、撞击液滴对气泡的穿刺、二次成核、气泡尺寸分布和穿刺处的气泡直径。简单地增加次级核的数量在增强核传热方面不如当它还与通过撞击液滴增加的气泡穿刺频率相结合时有效。为了增强传热，希望具有尽可能多的小气泡和尽可能高的气泡密度。
Droplet and bubble dynamics and nucleate heat transfer in saturated FC-72 spray cooling were studied using a simulation model. The spray cooling system simulated consists of three droplet fluxes impinging on a smooth heater, where secondary nuclei outnumber the surface nuclei. Using the experimentally observed bubble growth rate on a smooth diamond heater, submodels were assumed based on physical reasoning for the number of secondary nuclei entrained by the impinging droplets, bubble puncturing by the impinging droplets, bubble merging, and the spatial distribution of secondary nuclei. The predicted nucleate heat transfer was in agreement with experimental findings. Dynamic aspects of the droplets and bubbles, which had been difficult to observe experimentally and their ability in enhancing nucleate heat transfer were then discussed based on the results of the simulation. These aspects include bubble merging, bubble puncturing by impinging droplets, secondary nucleation, bubble size distribution, and bubble diameter at puncture. Simply increasing the number of secondary nuclei is not as effective in enhancing nucleate heat transfer as when it is also combined with increased bubble puncturing frequency by the impinging droplets. For heat transfer enhancement, it is desirable to have as many small bubbles and as high a bubble density as possible.