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首页> 外文学位 >An experimental study of flow boiling heat transfer enhancement in minichannels with porous mesh heating wall.
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An experimental study of flow boiling heat transfer enhancement in minichannels with porous mesh heating wall.

机译：多孔网状加热壁微通道内流动沸腾传热增强的实验研究。

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摘要

A unique channel surface enhancement technique via diffusion-bonding a layer of conductive fine wire mesh onto the heating wall was developed and used to experimentally study flow boiling enhancement in parallel microchannels. Each channel was 1000 mum wide and 510 mum high. A dielectric working fluid, HFE 7000, was used during the study. Two fine meshes as well as two mesh materials were investigated and compared. According to the flow boiling curves for each channel, the amount of wall superheat was greatly reduced for all the mesh channels at four stream-wise locations; and the critical heat fluxes (CHF) for mesh channels were significantly higher than that for a bare channel in the low vapor quality region. According to the plots of local flow boiling heat transfer coefficient h versus vapor quality, a consistent increasing trend for h with vapor quality was observed for all the tested channels until the vapor quality reached approximately 0.4. However, the three mesh channels showed much higher values of h than the bare channel, with the 100 mesh copper performing the best. Visualization using a high-speed camera was performed thereafter to provide some insights to this enhancement mechanism. A significant increase in nucleation sites and bubble generation was observed, and departure rates inside the mesh channels were attributed to the flow boiling enhancement. A sudden increase of h for mesh channels can also be attributed to the characteristics of nucleate boiling and indicates that nucleate boiling was the dominant heat transfer mode. Another interesting point observed was that the 100 mesh bronze outperformed the 200 mesh bronze for most of the studies. This suggests that nucleations happened inside the mesh openings, instead of on the mesh openings. In addition, an optimal mesh size should exist for HFE 7000 flow boiling.
机译：开发了一种独特的通道表面增强技术，该技术通过将一层导电细金属丝网扩散粘合到加热壁上来开发，并用于实验研究平行微通道中的流动沸腾增强。每个通道的宽度为1000毫米，高度为510毫米。在研究期间使用了HFE 7000介电工作液。研究并比较了两个细网孔和两种网孔材料。根据每个通道的流动沸腾曲线，在四个流向位置，所有网状通道的壁过热量都大大减少了；在低蒸汽质量区域，网状通道的临界热通量（CHF）明显高于裸露通道的临界热通量。根据局部流动沸腾传热系数h与蒸汽质量的关系图，在所有测试通道中观察到h随蒸汽质量的一致增加趋势，直到蒸汽质量达到约0.4为止。但是，三个网格通道的h值比裸通道高得多，其中100网格铜的性能最佳。此后，使用高速相机进行可视化，以提供对该增强机制的一些见解。观察到成核位置和气泡的产生显着增加，并且网孔内的离开速率归因于流动沸腾的增强。网状通道的h突然增加也可归因于核沸腾的特征，这表明核沸腾是主要的传热模式。观察到的另一个有趣的观点是，在大多数研究中，100目青铜的性能优于200目青铜。这表明成核发生在网孔内而不是网孔上。此外，对于HFE 7000流动沸腾，应存在最佳筛孔尺寸。

著录项

  • 作者

    Wang, Hailei.;

  • 作者单位

    Oregon State University.;

  • 授予单位 Oregon State University.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 178 p.
  • 总页数 178
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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