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。将管束浸入流动的水流中(TOOC)，并研究当管子内部冷却到冰点温度(Tw OOC)以下时，在管子外表面生长的冰层。还将研究移除冷却剂后冰层的后续融化过程。这项研究的主要重点是用新的关联式记录随着冻结和融化过程的进行，系统的随时间变化的传热(Nusselt数)和流体流动(压力降)特性(每行)。我们将在不同的时间通过摄影记录准确的冰形轮廓，并将产生的流过管束的流场可视化。在稳态条件下，得到了局部Nusselt数分布。实验将在低到中等雷诺数范围内进行，并针对一些不同的冷却温度比进行。将考虑串联和交错的管子几何形状。管子的螺距和上游湍流水平的影响将被记录在案。从实际和基本的角度来看，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储能领域具有重要意义。更具体地说，这项研究的结果将对冰蓄冷系统和相变蓄热式换热器的设计具有直接的工程意义。从更广泛的角度来看，所研究的问题是一个高度复杂的相变换热和流体动力学耦合问题，涉及到我们目前缺乏了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.