Spontaneous nucleation and resulting explosive evaporation of liquid impinging on a hot surface with a high speed

当高温液体与挥发性低温液体接触并且接触界面温度超过低温液体的临界温度时，可能发生自发成核和由此产生的蒸气爆炸。在本研究中，液体与高温固体的接触和由此产生的气泡成核现象进行了研究，使用快速加热的方法。一个小的铂膜加热器浸在乙醇中，由一个矩形脉冲具有两个或三个阶段。聚结气泡的崩溃，这是形成作为由第一阶段的高脉冲的加热器表面上的自发成核的结果，导致固液再接触。改变第二阶段的脉冲功率，以控制接触处的加热器温度。采用电阻测温法测量了加热器表面温度。第三阶段的可忽略功率使接触过程中的表面温度测量。在接触过程中出现细小气泡，当加热器温度在液体的均质成核温度附近时，气泡数量达到最大。在较高的温度下，即使合并的气泡破裂后，蒸汽膜仍保留在整个表面上。

When a high temperature liquid contacts with a volatile low temperature liquid and the contact interface temperature is beyond the superheat limit of the low temperature liquid, spontaneous nucleation and resulting vapor explosion may occur. In the present study, the contact of liquid with a high temperature solid and the resulting bubble nucleation phenomenon were investigated using a rapid heating method. A small platinum film heater immersed in ethyl alcohol was powered by a rectangular pulse having two or three-stages. The collapse of a coalesced bubble, which is formed as the result of spontaneous nucleation over the heater surface by high pulse of the first stage, causes the solid-liquid re-contact. The pulse power of the second stage was changed in order to control the heater temperature at the contact. The heater surface temperature was measured by means of the resistance thermometry. The third stage of negligible power enabled the surface temperature measurement during the contact. Fine bubbles appeared during the contact and its number becomes maximal when the heater temperature was around the homogeneous nucleation temperature of the liquid. At higher temperatures, the vapor film remained on the entire surface even after the collapse of the coalesced bubble.