MARANGONI EFFECT ON BOILING OF MIXTURES

1.基于弯液面模型的气泡生长分析建立了数值模拟方案来分析泡核沸腾中的气泡生长以及微层蒸发对气泡生长的影响。假设气泡生长的热量通过泡罩通过对流提供，通过弯液面通过传导提供。使用基于四边形单元的二维任意拉格朗日-欧拉有限元法求解瞬态纳维-斯托克斯和能量方程。结果表明，该方案提供了一种在不假设气泡形状的情况下研究气泡生长过程的有用方法，并且能够定量描述生长气泡周围的流场和温度场。得出结论：微层蒸发对气泡生长起主导作用，因此在沸腾传热中可能发挥重要作用。 2．蒸发弯月面中的流动和传热薄膜蒸发在与相变相关的传热过程中非常重要。为了弄清楚这一点，使用马赫-曾德激光干涉仪测量了部分浸入液体中的倾斜加热铜板上形成的弯液面膜的稳态温度分布。采用水、乙醇、乙二醇及其混合物作为测试流体，研究马兰戈尼对流对蒸发弯月面传热的影响。还进行了数值分析，以阐明本征弯液面区域和相邻蒸发薄膜区域的热和流动特性。研究发现，无论混合物是正的还是负的，弯液面中的流动方向都是相反的。因此，马兰戈尼对流预计将在混合物弯液面蒸发中发挥重要作用。

1. Bubble Growth Analysis Based on Meniscus ModelA numerical simulation scheme was developed to analyze the bubble growth in nucleate boiling and the effect of microlayer evaporation on bubble growth. Heat for the bubble growth was assumed as supplied through the bubble cap by convection and the meniscus by conduction. Transient Navier-Stokes and energy equations were solved using a two-dimensional arbitrary Lagrangian-Eulerian finite element method based on quadrilateral elements. It was revealed that the scheme offers a useful mean to investigate the growth process of bubble with no assumption on the bubble shape and it enables a quantitative description of flow and temperature fields around growing bubbles. It was concluded that the microlayer evaporation dominates bubble growth so that it may be substantial in boiling heat transfer.2. Flow and Heat Transfer in Evaporating MeniscusEvaporation from thin film is very important in heat transfer processes associated with phase change. To make it clear, a steady-state temperature distribution of a meniscus film formed on an inclined and heated cooper plate partially submerged into liquid was measured using a Mach-Zehnder laser interferometer. Water, ethanol, ethylene glycol and their mixtures were used as test fluids to investigate the effect of Marangoni convection on heat transfer in the evaporating meniscus. A numerical analysis was also performed to elucidate heat and flow characteristics in the intrinsic meniscus region and the adjacent evaporating thin film region. It was found the flow direction in the meniscus is reversed, whether mixture is positive or negative. Thus Marangoni convection is expected to play an important role in the evaporation of meniscus film for mixtures.