Heat and mass transfer characteristics of binary droplets in acoustic levitation
Heat and mass transfer characteristics of binary droplets in acoustic levitation
复制标题
DOI：
10.1063/1.5144396
复制
发表时间：
2020-07-01
影响因子：
4.6
通讯作者：
Abe, Y.
中科院分区：
文献类型：
--
作者：
Sasaki, Y.;Hasegawa, K.;Abe, Y.
研究了声悬浮液滴蒸发过程中流场与传热现象之间的复杂关系。为了解释这些相关性，使用乙醇和水的二元液滴作为测试流体。液滴悬浮后，液滴外部流场方向立即朝向液滴，在液滴表面附近形成循环涡流。随着蒸发的进行，外部流动向相反的方向过渡，而循环涡扩大。为了更好地理解液滴热边界层的转捩过程，假设乙醇和水二元液滴的转捩过程分为3个阶段：（1）乙醇优先蒸发;（2）转捩（乙醇蒸发和水冷凝）;（3）水蒸发和冷凝，计算了传热系数的时间序列变化。最后，通过对流场和热边界转变的比较，分析了蒸发声悬浮液滴流动结构和传热现象的转变机理。我们的实验和分析结果提供了更深层次的物理见解非接触流体操纵，并建议潜在的未来应用，如在声镊和微反应器。
The complex relationships between the flow field and heat transfer phenomena of acoustically levitated droplets under evaporation were investigated. To explain these correlations, binary droplets of ethanol and water were used as test fluids. Immediately after droplet levitation, the droplet external flow field direction was toward the droplet, with a circulating vortex forming near the droplet surface. As evaporation progressed, the external flow transitioned toward the opposite direction, while the circulation vortex expanded. To better understand the transition process of the droplet thermal boundary layer, the heat transfer coefficient time series changes were calculated by assuming that the transitions of the ethanol and water binary droplets occurred in three stages: (1) preferential evaporation of ethanol, (2) transition (evaporation of ethanol and condensation of water), and (3) evaporation and condensation of water. Finally, by comparing the flow field and thermal boundary transitions, the transition mechanism for flow structures and heat transport phenomena of acoustically levitated droplets with evaporation was considered. Our experimental and analytical results provide deeper physical insights into noncontact fluid manipulation and suggest potential future applications, such as in acoustic tweezers and microreactors.