Research Initiation Awards: Experimental Investigation of Transient Convective Freezing and Melting of Ice on a Cold Tube Bank in a Crossflow of Water

本研究是对冷管束上冰的冻结和融化现象的研究。将管群浸入流动的水流中，研究当管内部冷却到冰点温度以下时，管外表面生长的冰层。当冷却剂被移除后，冰的后续融化过程也将被研究。本研究的主要重点是记录新的相关性，随着冻结和融化过程的进行，系统的时间依赖性传热（努塞尔数）和流体流动（压降）特性（每排）。我们将在不同的时间以摄影方式记录精确的冰形轮廓，并将通过管库产生的流场可视化。在稳态条件下，得到了局部努塞尔数分布。实验将在低到中等雷诺数范围和许多不同的冷却温度比下进行。将考虑直列管和交错管的几何形状。管的节距和上游湍流水平的影响将被记录下来。无论从实践角度还是从基本观点来看，对这项研究的兴趣都是合理的。本文的研究结果对相变材料蓄热领域具有重要意义。更具体地说，本研究获得的发现将对冰蓄冷系统和相变蓄热换热器的设计产生直接的工程影响。从更广泛的角度来看，正在研究的问题是一个高度复杂的耦合相变传热和流体动力学问题，它解决了我们目前缺乏理解和需要改进的新领域。

This research is an investigation of the phenomena of freezing and melting of ice on a cold tube bundle. The tube bank is immersed in a flowing stream of water (T OoC) and the ice layer is studied that grows on the outside surface of the tubes, when the tubes are internally cooled below the freezing temperature (Tw OoC). The subsequent melting process of the ice formations when the coolant is removed will also be studied. The main focus of this research is to document in terms of new correlations, the time-dependent heat transfer (Nusselt number) and fluid flow (pressure drop) characteristics (per row) of the systems as the freezing and melting process proceeds. We will photographically record, at various times, the exact ice shape profiles and will visualize the resulting flow field through the tube bank. Under the steady state condition, the local Nusselt number distribution will be obtained. Experiments will be conducted in the low to moderate Reynolds number range and for a number of different cooling temperature ratios. Both in-line and staggered tube geometries will be considered. The effect of the tube's pitch and the upstream turbulence level will be documented. The interest in this research is justified from both a practical and from a fundamental view-point. The results of the proposed study is important to the field of thermal energy storage involving phase change materials. To be more specific, the findings obtained in this study would have direct engineering consequence in the design of ice storage systems and in phase change storage heat exchangers. From the broader perspective, the problem under investigation is a highly complex coupled phase change heat transfer and fluid dynamic problem that addresses new areas in which our current understanding is lacking and needs improvement.