Abstract Flow transient critical heat flux (CHF) in a narrow rectangular channel has not been studied adequately, and the same is currently predicted using steady-state CHF correlations. To address this gap in research, experiments were performed in this study to investigate the flow transient CHF in a narrow rectangular channel of a research reactor under downward flow. The experiments cover a wide range of flow conditions, including mass fluxes in the 950–4,700 kg/m2s range, inlet temperature of 37 °C, outlet pressure of 170 kPa, and transient time parameters in the 8.7–485 range. Evaluation of previous correlations applicable to flow transient CHF in a tube revealed they could not reasonably predict experimental data obtained in this study. Consequently, the present experimental data and Celata R-12 database were used to deduce a new correlation. The CHF ratio (the ratio of transient CHF to steady-state CHF under same mass flux) was observed to increase up to 1.6 for water and 2.7 for R-12 under the flow transient condition. As observed, the proposed correlation is applicable to both downward flow of water in a narrow rectangular channel and upward flow of R-12 in a tube. The correlation shows average and root-mean-square error values 0.04% and 3.46%, respectively, under a flow reduction rate of 0.1–2.5 s−1.

中文翻译：

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向下流动作用下窄矩形通道中的流动瞬态临界热通量

摘要 窄矩形通道中的流动瞬态临界热通量 (CHF) 尚未得到充分研究，目前使用稳态 CHF 相关性进行预测。为了弥补研究中的这一空白，本研究进行了实验，以研究在向下流动下研究堆的窄矩形通道中的流动瞬态 CHF。实验涵盖了广泛的流动条件，包括 950–4,700 kg/m2s 范围内的质量通量、37 °C 的入口温度、170 kPa 的出口压力以及 8.7–485 范围内的瞬态时间参数。对适用于管中流动瞬态 CHF 的先前相关性的评估表明，他们无法合理地预测在本研究中获得的实验数据。最后，目前的实验数据和 Celata R-12 数据库被用来推导出一个新的相关性。在流动瞬态条件下，观察到 CHF 比（相同质量通量下瞬态 CHF 与稳态 CHF 的比率）增加到 1.6，R-12 增加到 1.6。正如所观察到的，所提出的相关性既适用于窄矩形通道中的向下流动的水，也适用于管中 R-12 的向上流动。相关性显示平均和均方根误差值分别为 0.04% 和 3.46%，流量减少率为 0.1–2.5 s-1。建议的相关性适用于狭窄矩形通道中的水向下流动和管道中的 R-12 向上流动。相关性显示平均和均方根误差值分别为 0.04% 和 3.46%，流量减少率为 0.1–2.5 s-1。建议的相关性适用于狭窄矩形通道中的水向下流动和管道中的 R-12 向上流动。相关性显示平均和均方根误差值分别为 0.04% 和 3.46%，流量减少率为 0.1–2.5 s-1。