Bubble Growth Rates and Nucleation Site Densities in Saturated Pool Boiling of Water at High Pressures
Bubble Growth Rates and Nucleation Site Densities in Saturated Pool Boiling of Water at High Pressures
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饱和池高压水沸腾中的气泡生长速率和成核位点密度
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
H. Sakashita
中科院分区：
文献类型：
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作者：
H. Sakashita
在0.35 ~ 5 MPa压力范围内，对水在水平和垂直表面的沸腾行为进行了实验观察。在整个压力范围内t1/2的变化可以很好地描述初级气泡的生长曲线。初生气泡的生长速率与Jakob数的平方根成正比，符合Labuntsov与任意常数β = 3的相关性。泡沫增长率的传统相关性与雅各布数成正比，预测在更高的压力下，泡沫增长率会更慢。在垂直表面3.66 MPa下，测量了初级气泡的聚并行为。合并气泡由两个初级气泡合并而成，其生长速度与初级气泡相似。在同等热流条件下，在压力达到5mpa时，在垂直表面测得的成核位置密度成比例地增加，约为压力的1.5次方。成核位置密度对热流密度的依赖关系与在大气压力下得到的结果非常相似，在大气压力下，成核位置密度与热流密度的1.5次方成正比。在压力为0.35 ~ 5 MPa和热通量为0.05 ~ 0.35 mw /m2时测得的成核位密度与已有的相关关系相当吻合。
Experiments were carried out to observe boiling behaviors of water on horizontal and vertical surfaces at pressures from 0.35 to 5 MPa. The growth curves of the primary bubbles are well described by the t1/2 variation over the whole range of pressures. The growth rates of primary bubbles are proportional to the square root of the Jakob number, and agree with the correlation by Labuntsov with the arbitrary constant β = 3. The conventional correlations of bubble growth rates, which are directly proportional to the Jakob number, predict slower growth rates at higher pressures. The coalescence behaviors of the primary bubbles were also measured on the vertical surface at 3.66 MPa. The coalesced bubbles, which were formed by the coalescence of two primary bubbles, grow at rates similar to the rates of the primary bubbles. The nucleation site densities measured on the vertical surface at pressures up to 5 MPa increase in proportion to about the 1.5th power of the pressure under equivalent heat flux conditions. The dependence of the nucleation site densities on the heat flux is very similar to the results obtained near atmospheric pressure where the nucleation site density is proportional to the 1.5th power of the heat flux. The nucleation site densities measured in the range of pressures of 0.35 to 5 MPa and at heat fluxes of 0.05 to 0.35MW/m2 agree fairly well with the available correlations.