Analysis of boiling phenomena associated with liquid jet impingement heat transfer

许多工程系统和制造工艺在操作期间需要精确的温度控制，其示例是核安全系统，即，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，例如：钢带的热轧、连续铸造、钢棒的硬化以及挤压和锻造。在这些应用中的许多应用中，使用液体射流冲击（LJI）进行冷却。当液体射流冲击热表面时，热量传递到冷却液体。因此，液体温度升高到沸点，此时液体开始沸腾。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，并且尚未完全理解。这项研究还表明，使用LJI冷却比其他冷却技术具有许多优势。这些优势是：（1）其在实现所需冷却速率方面的显著灵活性，（2）使用淡水代替其它冷却液体（例如油和聚合物溶液）的可能性，所述其它冷却液体（i）更昂贵，（ii）不能作为水广泛获得，和（iii）对环境具有显著更高的影响。由于我们对LJI冷却相关的复杂沸腾现象及其所能提供的显著优势缺乏充分的了解，因此拟议的研究有两个主流。第一个流的重点是发现和理解尚未充分研究的许多参数的影响，例如，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学。这个流的目标是推进我们对LJI冷却的了解。第二个方面是关于机械模型的发展。该流程的主要目标是以最有用的形式为我们的加拿大工业提供第一流程产生的知识，以制定设计指南并实现最佳操作条件。

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.