Theory of Nucleate Pool Boiling Heat Transfer

本研究的目的是建立一个可靠的核池沸腾传热理论，该理论可用于预测从受热表面到液体的传热速率。本研究将探讨沸腾起始标准、气泡生长和沸腾过程中的传热机制。沸点将通过对固体表面微腔内成核过程的严格数学分析来研究。与沸腾起始有关的令人困惑的温度超调现象，将通过考察不溶性表面活性剂在液-气界面上形成的蒸发屏障的影响来加以阐明。气泡生长的分析将采用边界元法进行，并将考虑气泡底部薄微层的蒸发和表面变形。基于气泡颈在生长过程中形成的毛细不稳定性，提出了一种新的气泡脱离准则。将进行一项实验，以可视化20 μ m v型槽中的成核和生长过程，以增加所提出的微观现象学描述的可信度。尽管沸腾过程对许多高功率密度设备的现代工程应用具有重要意义，但仍然没有一个能够预测从固体表面到液体的热传递速率的综合理论。提出的研究将通过增加我们对单个成核位点中复杂的微尺度过程的理解来帮助发展这样一个理论。

The purpose of the proposed research is to develop a reliable theory of nucleate pool boiling heat transfer that can be used to predict the rate of heat transfer from a heated surface to a liquid. The research will examine boiling incipience criteria, bubble growth and heat transfer mechanisms in boiling. Boiling incipience will be studied by a rigorous mathematical analysis of the nucleation process in a microcavity on a solid surface. The bewildering temperature overshoot phenomenon, associated with boiling incipience, will be elucidated by examining the influence of an evaporative barrier which is formed on the liquid-vapor interface by insoluble surfactants. The analysis of bubble growth will be carried out by the boundary element method, and will account for evaporation of a thin microlayer at the bubble base and surface deformation. A new bubble detachment criterion will be introduced based on the capillary instability of the bubble neck which is formed during the growth process. An experiment will be conducted to visualize the nucleation and growth processes in a 20 um v-groove to add credence to the proposed microscopic phenomenalogical description. A comprehensive theory of boiling that can predict the rate of heat transfer from a solid surface to a liquid is still unavailable in spite of the importance of the process to many modern engineering applications to high power density equipment. The proposed research will aid the development of such a theory by increasing our understanding of the intricate microscale processes in a single nucleation site.