Abstract:

The effect of initial quenching temperature on the transient boiling has been little discussed in depth, especially the mechanism of its effect on the quenching on surfaces with different wettability is still lacking. In this paper, nanoparticle deposition was used to prepare hydrophobic surfaces, and the influence of initial quenching temperature on the boiling heat transfer characteristics of hydrophobic surfaces was investigated experimentally. The evolution of critical heat flux (CHF), minimum heat flux (MHF), and transition heat flux (THF) as well as the corresponding temperature and time were quantitatively analyzed. The results show that the enhanced hydrophobicity shifts the quenching curve to the right, the boiling curve shifts to the left, the CHF and MHF and corresponding temperature decrease, and the quenching time increases. The above trends became less pronounced when the initial quenching temperature increased. This indicates that the increase of hydrophobicity deteriorates the heat transfer in general, while the increase of initial quenching temperature can relatively enhance the heat transfer. At the same time, it was found that the sub-regimes of the transition boiling stage increased with increasing initial quenching temperature, and the critical transition point (CTP) was also affected accordingly. The heat transfer coefficient exhibits a similar change to the boiling curve, with its maximum value occurring near the deviation from nucleation boiling (DNB) point.

Key words: quenching, nanoparticle, surface, initial temperature, hydrophobicity, heat transfer

摘要：

实验研究了不同淬火初温下疏水性对沸腾传热特性的影响规律，定量分析了临界热通量(CHF)、最小热通量(MHF)和转变热通量(THF)以及对应的温度、时间的演变规律。结果表明，疏水性增强使淬火曲线右移，沸腾曲线向左下偏移，CHF和MHF和对应的温度减小，淬火时间增加；淬火初温提高，上述变化趋势逐渐变得不明显。说明疏水性增强总体恶化了淬火沸腾传热，而淬火初温提高可相对强化淬火沸腾传热。同时发现，过渡沸腾阶段分亚区情况随淬火初温提高而增多，临界过渡点(CTP)也受到相应影响；传热系数最大值发生在偏离核态沸腾(DNB)点附近。

关键词: 淬火沸腾, 纳米粒子, 表面, 淬火初温, 疏水性, 传热