Abstract Safety concerns due to the highly unstable nature of boiling during the transition from the nucleate to the film boiling regime has limited investigations on this topic. Here we perform simultaneous characterization of the thermal, acoustic, and the bubble visualization data during the transition boiling regime. We show that the key features missed due to the high latency in the thermal data are captured in the audio ( 0 - 2 k H z ) . We correlate the acoustic emissions with the high-speed visualization to elucidate the presence of an explosive boiling sub-regime, also referred to as the microbubble emission boiling (MEB). This regime is typically observed after the critical heat flux (CHF) and is characterized by numerous small sized bubbles ( ≈ 300 ± 50 μ m ) emanating from an unstable vapor film on the heater surface. We correlate this change in bubble behavior with the corresponding increase in the intensity and peak frequency of acoustic emissions up until the onset of a completely silent and stable film boiling regime. Conversely, MEB features are also observed during the transition from film boiling to the nucleate boiling regime in quenching experiments. We modify the heater surface and the boiling fluid, and vary the test conditions, to confirm the existence of MEB in all experiments over a wide range of subcoolings ranging from 2 ° C to 25 ° C . Our experiments suggest that the extent of the MEB increases with, (i) the increase in subcooling, (ii) the decrease in the surface tension of the boiling fluid, and (iii) the increase in surface roughness/wettability of the heater surface. We believe these unique acoustic features of the transition boiling regime can be used as a feedback to design measures to avoid catastrophic failures in boiling based energy and thermal management systems.

中文翻译：

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过渡沸腾状态的同时视听热表征

摘要 由于在从成核到薄膜沸腾状态的转变过程中沸腾的高度不稳定性质引起的安全问题对该主题的研究有限。在这里，我们在过渡沸腾状态下同时对热、声和气泡可视化数据进行表征。我们表明，由于热数据的高延迟而遗漏的关键特征在音频 (0-2 k H z) 中被捕获。我们将声发射与高速可视化相关联，以阐明爆炸性沸腾子机制的存在，也称为微泡发射沸腾 (MEB)。这种状态通常在临界热通量 (CHF) 之后观察到，其特征是从加热器表面上的不稳定蒸气膜发出的许多小尺寸气泡 (≈ 300 ± 50 μ m)。我们将气泡行为的这种变化与声发射的强度和峰值频率的相应增加相关联，直到完全安静和稳定的薄膜沸腾状态开始。相反，在淬火实验中从薄膜沸腾到核沸腾状态的转变过程中也观察到 MEB 特征。我们修改了加热器表面和沸腾流体，并改变了测试条件，以确认在从 2°C 到 25°C 的各种过冷度的所有实验中都存在 MEB。我们的实验表明，MEB 的程度随着（i）过冷度的增加，（ii）沸腾流体的表面张力的降低，以及（iii）加热器表面的表面粗糙度/润湿性的增加而增加。