Abstract The transient freezing/solidification of water subjected to shear flow inside a rectangular cell is investigated under laminar flow conditions. A flow of freezing water is established inside the cell by cooling the top surface of the conductive, copper plate that forms the cell’s top side by contact with boiling liquid nitrogen ( − 197 ∘ C). This heat removal results in an ice layer that forms and grows gradually on the ceiling of the cell, which is subjected to shear from the flow below it inside the channel. The spatiotemporal characteristics of the ice layer are recorded with optical, laser-based measurements and are compared with predictions from a transient freezing model that is developed for this purpose. Furthermore, tracer particles are introduced into the flow to aid the tracking of the ice layer and to allow for measurements based on particle image velocimetry (PIV) of the velocity field inside the flow during the ice-layer evolution. After an initial time-lag/‘buffer’ period (of 5 − 40 s) that depends on the flow conditions, a quasi-linear growth of the ice layer is observed; at longer times the thickness of the ice layer reaches a maximum and then decreases again. The increase in the thickness, and hence thermal resistance, of the ice layer is counter-balanced by a decrease in the temperature of the copper plate and, therefore, a decrease in the temperature difference across the ice layer. Furthermore, it is found that the flow is associated with symmetric velocity profiles, recorded along the vertical spanwise length between the ice layer at the top of the cell and the floor of the cell, while an increase of the velocity maxima is recorded as the ice layer gradually thickens and, consequently, the flow cross-section is reduced. A constant heat flux of 19.7 × 103 W m − 2 is measured on the top side of the channel, while the heat transfer coefficient on the top side of the channel is found to be in the range of 90–110 W m − 2 K − 1 , depending on the wall temperature. Finally, from comparisons against the experimental data, it is concluded that the model developed herein is able to predict the freezing of water and the growth of the ice layer in these flows over a range of water inlet temperatures and Reynolds numbers. This model can be incorporated in thermohydraulic codes for the design of relevant heat-exchange components in the precence of freezing/solidification.

中文翻译：

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两个平行板之间水的瞬态冻结：结合实验和建模研究

摘要 研究了层流条件下矩形单元内受剪切流作用的水的瞬态冻结/凝固。通过冷却导电铜板的顶面，通过与沸腾的液氮 (−197 ∘ C) 接触形成电池的顶面，在电池内建立冷冻水流。这种热量去除导致冰层在细胞顶部形成并逐渐生长，该冰层受到通道内其下方流动的剪切。冰层的时空特征通过光学、激光测量记录下来，并与为此目的开发的瞬态冻结模型的预测进行比较。此外，示踪粒子被引入流中，以帮助跟踪冰层，并允许基于冰层演化过程中流内部速度场的粒子图像测速 (PIV) 进行测量。在取决于流动条件的初始时间滞后/“缓冲”期（5 - 40 秒）之后，观察到冰层的准线性增长；在更长的时间内，冰层的厚度达到最大值，然后再次减小。冰层厚度的增加以及由此产生的热阻的增加与铜板温度的降低以及整个冰层温差的减小相抵消。此外，发现流动与对称速度分布相关，沿单元顶部的冰层和单元底部之间的垂直展向长度记录，而随着冰层逐渐变厚，记录的最大速度增加，因此，流动横截面减小。在通道顶部测得的恒定热通量为 19.7 × 103 W m − 2，而通道顶部的传热系数在 90–110 W m − 2 K 范围内− 1 ，取决于壁温。最后，通过与实验数据的比较，得出的结论是，本文开发的模型能够在进水温度和雷诺数的范围内预测这些流动中水的冻结和冰层的生长。