Abstract Deformed cladding in nuclear power plants can partially block the path of coolant flow and thus alter the heat transfer characteristics between the cladding surface and coolant. In this research, critical heat flux(CHF) in a sudden expansion flow path, was experimentally investigated. Flow boiling CHF experiments were carried out under atmospheric pressure with deionized water for vertical upward flow, with four expansion ratio cases investigated with mass flux ranging from 50 to 250 kg/m2 s. CHF was detected at two different locations. In experiments with either a low expansion ratio(e 1.5) and high mass flux(> 150 kg/m2 s), CHF was detected at the sudden expansion point. Quality at the sudden expansion point was almost zero, which implies that nucleated bubbles under the effect of sudden expansion flow induced CHF at the sudden expansion point. The reason for this transition of CHF location was suggested that local bubble stagnation induced by a balance between drag and buoyancy forces on the bubbles resulted in local flooding in the downward flow.

中文翻译：

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使用突然膨胀管的流动沸腾 CHF 实验

摘要 核电站中变形的包壳会部分阻塞冷却剂流动的路径，从而改变包壳表面与冷却剂之间的传热特性。在这项研究中，对突然膨胀流动路径中的临界热通量（CHF）进行了实验研究。流动沸腾 CHF 实验是在大气压下用去离子水垂直向上流动进行的，研究了四种膨胀比情况，质量通量范围为 50 至 250 kg/m2 s。在两个不同的位置检测到 CHF。在具有低膨胀比 (e 1.5) 和高质量通量 (> 150 kg/m2 s) 的实验中，在突然膨胀点检测到 CHF。突然膨胀点的质量几乎为零，这意味着在突然膨胀流动的影响下，成核气泡在突然膨胀点诱导了 CHF。CHF 位置的这种转变的原因表明，由气泡上的阻力和浮力之间的平衡引起的局部气泡停滞导致向下流动中的局部泛滥。