Heat flux partitioning and macrolayer observation in pool boiling of water on a surface with artificial nucleation sites
Heat flux partitioning and macrolayer observation in pool boiling of water on a surface with artificial nucleation sites
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人工成核位点表面水池沸腾的热通量分配和大分子层观察
DOI：
10.1016/j.ijheatmasstransfer.2022.122924
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发表时间：
2022
影响因子：
5.2
通讯作者：
Yabuki Tomohide
中科院分区：
文献类型：
--
作者：
Yajima Shota;Io Nanako;Miyazaki Koji;Yabuki Tomohide
本文利用高速红外摄像机，研究了控制成核位密度（NSD）的蓝宝石传热表面上池饱和沸水的传热机理。采用超疏水剂喷墨打印的方法将人工成核位点布置在壁面上，NSD在24 ~ 318个位点/cm2之间。通过热流分配分析，评价了各基本传热过程的传热特性及其对总传热的贡献。增加NSD对传热的强化有一个上限。沸腾换热系数（HTC）不随NSD的增加而单调增加，在NSD为89 ~ 130 sites/cm2时达到最大值。当NSD过大时，气泡-气泡相互作用抑制了微层的形成。微层蒸发对壁面换热的贡献也减小，导致沸腾HTC降低。在所有测试的nsd中，与裸露表面的情况一样，液相传热主要是壁面传热。面积较小的微层蒸发对壁面总换热的贡献小于35%。在高热流密度区，成功地观察到聚并气泡底部的巨层，即液体运动受到抑制的液体层。
In this study, the heat transfer mechanisms in pool saturated boiling of water on a sapphire heat transfer surface with a controlled nucleation site density (NSD) were observed using a high-speed infrared camera. Artificial nucleation sites were arranged on the wall surface by ink-jet printing of a superhydrophobic agent, and NSD was varied between 24 and 318 sites/cm2. The heat transfer characteristics of each fundamental heat transfer process and its contribution to the total wall heat transfer were evaluated through the heat flux partitioning analysis. There was an upper limit to the heat transfer enhancement by increasing the NSD. The boiling heat transfer coefficient (HTC) did not increase monotonically with increasing NSD but had a maximum value at an NSD between 89 and 130 sites/cm2. When NSD was increased excessively, the microlayer formation was inhibited by bubble–bubble interaction. The contribution of the microlayer evaporation to the wall heat transfer also decreased, resulting in a decrease in the boiling HTC. At all tested NSDs, liquid-phase heat transfer dominated the wall heat transfer, as in the case of the bare surface. The contribution of the microlayer evaporation that occupies a small area to the total wall heat transfer was less than 35%. In the high heat flux region, the macrolayer, a liquid layer with suppressed liquid motion, was successfully observed at the bottom of the coalesced bubble.