Analysis of boiling phenomena associated with liquid jet impingement heat transfer

许多工程系统和制造过程需要在运行过程中进行精确的温度控制，例如，核反应堆中的紧急堆芯冷却系统、电子封装冷却系统以及材料加工中的各种应用，如：钢带热轧、连铸、钢筋硬化、挤压和锻件。在许多这样的应用中，使用液体射流冲击(LJI)进行冷却。当液体射流撞击热表面时，热量就转移到冷却液体上。因此，液体温度上升到液体开始沸腾的沸点。申请人和其他人最近的研究结果表明，与LJI冷却相关的沸腾现象非常复杂，取决于许多变量的相互作用，目前还没有完全了解。这项研究还表明，与其他冷却技术相比，使用LJI冷却具有许多优势。这些优势是：(1)在实现所需冷却速度方面具有极大的灵活性，(2)可以使用白水，取代其他冷却液，如油和聚合物溶液，这些液体(I)更昂贵，(Ii)作为水不能广泛获得，以及(Iii)对环境的影响明显更大。由于我们对与LJI冷却相关的复杂沸腾现象以及它所能提供的显著优势缺乏充分的了解，拟议的研究有两个主流。第一个重点是发现和理解许多尚未被充分研究的参数的影响，如表面曲率、表面粗糙度和多个射流的相互作用对与LJI冷却相关的复杂沸腾现象的物理影响。这篇文章的目的是促进我们对LJI冷却的了解。第二个趋势是关于机械论模型的发展。这一流的主要目标是以最有用的形式介绍第一流产生的知识，以供我们的加拿大工业制定设计指南并实现最佳运行条件。

Many engineering systems and manufacturing processes require accurate temperature control during operation, examples of which are nuclear safety systems, i.e., emergency core cooling systems in nuclear reactors, electronic packaging cooling systems, and various applications in material processing such as: hot rolling of steel strips, continuous casting, hardening of steel bars, and extrusions and forgings. In many of these applications cooling using liquid jet impingement (LJI) is employed. As liquid jets impinge on the hot surface, heat transfers to the cooling liquid. Thereby, liquid temperature increases up to the boiling point at which time liquid starts to boil. Findings of recent research by the applicant and others demonstrated that the boiling phenomena associated with LJI cooling are very complicated, depend on the interaction of many variables, and have not been completely understood yet. This research has also indicated that the use of LJI cooling has many advantages over other cooling techniques. Those advantages are: (1) its significant flexibility in achieving desired cooling rates, (2) The possibility of using plain water, replacing other cooling liquids, such as, oils and polymer solutions, which are (i) more expensive, (ii) not widely available as water, and (iii) have significantly higher impact on the environment. Because of our lack of full understanding of the complicated boiling phenomena associated with LJI cooling and the significant advantages it can offer, the proposed research has two main streams. The first stream focuses on discovering and understanding the effect of many parameters that have not been fully investigated yet, such as, surface curvature, surface roughness, and interaction of multiple jets on the physics of the complicated boiling phenomena associated with LJI cooling. The goal of this stream is to advance our state of knowledge of LJI cooling. The second stream is concerned with the development of mechanistic models. The main objective of this stream is to present knowledge produced by the first stream in the most useful form for our Canadian industry to develop design guidelines and to achieve optimum operating conditions.