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Enhanced pool boiling heat transfer on freeze-casted surfaces

机译：增强池沸腾热传递在冷冻铸造表面上

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摘要

Distinct from monoporous structures with only one characteristic pore size, biporous structures are characterized by two distinguished pore sizes. In this paper, novel double-layered biporous coatings consisting of a biporous top layer and a monoporous base layer are fabricated by freeze casting from aqueous nickel slurry, where the particle size (D_(50)) is 400 nm. The biporous layer of the freeze-casted coating is characterized by lamellar vertical large pores formed by templating ice crystals and small pores formed by particle accumulation. The sizes of the large pores are in the order of 10-100 μm depending on coating thicknesses and freezing temperatures, while the sizes of small pores are in the order of -1 μm. Pool boiling heat transfer performances of freeze-casted double-layered biporous coatings are investigated. For comparison purposes, saturated pool boiling experiments under the same conditions are also carried out on a slurry-evaporation-deposited surface as well as on a smooth surface. Experimental results indicate that freeze-casted coatings enhance boiling heat transfer performance significantly by increasing nucleate site density, decreasing bubble departure diameter, increasing departure frequency, and enhancing surface wickability. Compared to a smooth surface, the inception temperature on a freeze-casted surface is significantly reduced from about 10 K to less than 5 K while the heat transfer coefficient (HTC) and the critical heat flux (CHF) are improved by 180% and 67%, respectively. It is found that there is an optimum coating thickness to maximum HTC due to a tradeoff between nucleation site density and vapor removal efficiency. In addition, liquid slurry frozen at low supercoolings has better boiling heat transfer performance since the pore size is bigger as a result of larger ice crystal size.
机译：与只有一种特征孔径的单孔结构不同，双孔结构的特征在于两个杰出的孔径。在本文中，由双层顶层和单孔基层组成的新型双层双层涂层通过从含镍浆料的冷冻浇铸来制造，其中粒径（D_（50））为400nm。冷冻铸造涂层的双层的特征在于通过模板凝冰形成的层状垂直大孔和通过颗粒积聚形成的小孔。根据涂层厚度和冷冻温度，大孔的尺寸为10-100μm，而小孔的尺寸为-1μm。研究了池沸腾的热传递冻铸双层双层双层涂层的性能。为了比较目的，在相同条件下的饱和池沸腾实验也在浆料蒸发沉积的表面以及光滑的表面上进行。实验结果表明，通过增加成核位点密度，降低泡沫脱离直径，增加的脱离频率，提高表面清晰度，冻结涂层显着提高沸腾传热性能。与光滑的表面相比，冷冻铸造表面上的初始温度从约10k显着降低至小于5 k，而传热系数（HTC）和临界热通量（CHF）得到180％和67 ％， 分别。发现由于成核位点密度和蒸汽去除效率之间的折衷，存在最佳涂层厚度至最大HTC。此外，在低过冷下冷冻的液体浆料具有更好的沸腾传热性能，因为由于冰晶尺寸较大，孔径较大。

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  • 来源
    《International Journal of Heat and Mass Transfer》 |2020年第6期|119622.1-119622.11|共11页
  • 作者

    Tao Lin; Xiaojing Ma; Xiaojun Quan; P. Cheng; Gang Chen;

  • 作者单位

    MOE Laboratory for Power Machinery and Engineering School of Mechanical Engineering Shanghai Jiao-Tong University Shanghai 200240 PR China;

    MOE Laboratory for Power Machinery and Engineering School of Mechanical Engineering Shanghai Jiao-Tong University Shanghai 200240 PR China;

    MOE Laboratory for Power Machinery and Engineering School of Mechanical Engineering Shanghai Jiao-Tong University Shanghai 200240 PR China;

    MOE Laboratory for Power Machinery and Engineering School of Mechanical Engineering Shanghai Jiao-Tong University Shanghai 200240 PR China;

    Shanghai Institute of Satellite Engineering Shanghai 200000 PR China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Pool boiling; Freeze casting; Biporous; Multiscale;

    机译：池沸腾;冷冻铸造;bipope;多尺度;

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