Abstract Extensive studies have been conducted on flow boiling heat transfer in mini or micro channels with square and circular configurations. Few investigations, however, have focused on a channel configuration featuring serrated fins. Therefore, the present study experimentally investigated the flow boiling heat transfer characteristics of refrigerant R134a in two mini channels with serrated fins. The equivalent diameters are 1.28 mm with 11 channels and 1.59 mm with 9 channels. Quantitative experiments were conducted under a mass flux of 60–308 kg/(m2.s), heat flux of 6–48 kW/m2, saturation pressure of 0.27–0.45 MPa and vapour quality of 0–1. Flow patterns during flow boiling in the channel were also captured and analysed. Results indicated that in the low vapour quality region, the local heat transfer coefficient increases with both heat flux and saturation pressure. However, the influence of mass flux is related to heat flux. The flow pattern in this region starts with dispersed bubbly flow and develops to vigorous bubbly flow. Slug flow and annular flow are then observed along the flow direction of the refrigerant. In contrast, in the high vapour quality region, the influence of heat flux and saturation pressure seem to vanish and higher refrigerant mass flux corresponds to a greater heat transfer coefficient. The annular flow continues in this region with intermittent dry-out, which leads to a sharp decrease in the heat transfer coefficient. As the existing empirical correlation for calculating flow boiling heat transfer coefficient fails to give a reasonable prediction for the present experimental data, a new correlation was proposed with a mean absolute relation deviation of 15.0% for all 1429 data points. The present experimental data and new proposed correlation can provide meaningful guidance for the design of a mini channel two phase heat exchanger with serrated fins.

中文翻译：

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带锯齿翅片的微型通道中流动沸腾传热：新关联的实验研究与开发

摘要 对方形和圆形结构的微型或微型通道中的流动沸腾传热进行了广泛的研究。然而，很少有研究关注具有锯齿状翅片的通道配置。因此，本研究通过实验研究了制冷剂 R134a 在两个带有锯齿状翅片的微型通道中的流动沸腾传热特性。等效直径为 1.28 mm（11 个通道）和 1.59 mm（9 个通道）。定量实验在质量通量为 60-308 kg/(m2.s)、热通量为 6-48 kW/m2、饱和压力为 0.27-0.45 MPa 和蒸汽质量为 0-1 的条件下进行。通道中流动沸腾期间的流动模式也被捕获和分析。结果表明，在低蒸汽质量区域，局部传热系数随着热通量和饱和压力的增加而增加。然而，质量通量的影响与热通量有关。该区域的流型从分散的气泡流开始，发展为剧烈的气泡流。然后沿制冷剂的流动方向观察到段塞流和环流。相比之下，在高蒸汽质量区域，热通量和饱和压力的影响似乎消失了，更高的制冷剂质量通量对应于更大的传热系数。环流在该区域继续进行，间歇性干涸，导致传热系数急剧下降。由于现有的计算流动沸腾传热系数的经验相关式未能对目前的实验数据给出合理的预测，提出了一个新的相关性，所有 1429 个数据点的平均绝对关系偏差为 15.0%。目前的实验数据和新提出的相关性可以为带有锯齿状翅片的微型通道两相换热器的设计提供有意义的指导。