Analysis of boiling phenomena associated with liquid jet impingement heat transfer

许多工程系统和制造工艺在运行过程中需要精确的温度控制，例如核安全系统，即核反应堆中的应急堆芯冷却系统，电子封装冷却系统，以及材料加工中的各种应用，例如：热轧带钢，连铸，钢筋硬化，挤压和锻件。在许多此类应用中，采用液体射流撞击（LJI）进行冷却。当液体射流撞击热表面时，热量传递给冷却液体。因此，液体温度上升到沸点，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冷却有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有许多优点。这些优点是：(1)它在实现所需冷却速率方面具有显著的灵活性；(2)使用普通水替代其他冷却液体（如油和聚合物溶液）的可能性，这些冷却液体(i)更昂贵，（ii）不能作为水广泛使用，（iii）对环境的影响更大。由于我们对与LJI冷却相关的复杂沸腾现象缺乏充分的了解，以及它可以提供的显着优势，因此提出的研究主要有两种。第一个流的重点是发现和理解许多尚未充分研究的参数的影响，如表面曲率、表面粗糙度和多射流对与LJI冷却相关的复杂沸腾现象的物理特性的相互作用。这篇文章的目标是提高我们对LJI冷却的认识。第二种趋势与机械模型的发展有关。这一流程的主要目标是以最有用的形式呈现由第一流程产生的知识，为我们的加拿大工业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.