Abstract Natural convection boiling in channel with Arc-Shaped will be encountered in the IVR-ERVC (In-Vessel Retention measure by External Reactor Vessel Cooling) system in nuclear power plant under severe accident. The flow and heat transfer characters in this situation is simulated by flow boiling of deionized water in an inclined rectangular channel under low flow rates. This paper aims to separate various parameters (such as orientation, mass flow rate and inlet quality, etc.) to investigate their individual effects on heat transfer coefficient (HTC) in a rectangular channel with cross section of 17 mm × 10 mm. By using a preheater at the inlet of the rectangular channel, the inlet quality could be controlled and the two-phase flow situation could be observed before the fluids entering into the main heater region on one side of the channel wall in downstream. Thus the characteristics of HTC on the main heater could be investigated at different flow patterns. The channel orientations vary from 15 to 90°, the mass flow rates vary from 110 to 288 kg/(m2s) and the qualities vary from 0.003 to 0.036, respectively. Experimental results show that the mass flow rate and quality effects on the HTC are very weak in this study. However, the orientation angle effect on HTC shows an transition region within 45°~60°, while it slowly changes when the orientation angle is smaller than 45° and bigger than 60°. Such tendency could be well formulated by the error function. Compared with different empirical formulas of saturated boiling HTC, it is found that the Liu & Winterton correlation can well predict the experimental HTC results in 90° orientation channel. Based on such correlation and coupled with the error function, a new model was developed by considering the orientation effect, which has an error of ±15% comparing with the experimental data.

中文翻译：

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矩形通道低流速下流动沸腾下表面传热系数的取向效应

摘要 核电站严重事故下的IVR-ERVC（In-Vessel Retention measure by External Reactor Vessel Cooling）系统会遇到弧形通道自然对流沸腾。这种情况下的流动和传热特性是通过低流速下去离子水在倾斜矩形通道中的流动沸腾来模拟的。本文旨在分离各种参数（如方向、质量流量和入口质量等），以研究它们对横截面为 17 mm × 10 mm 的矩形通道中传热系数（HTC）的单独影响。通过在矩形通道的入口处使用预热器，在流体进入下游通道壁一侧的主加热器区域之前，可以控制入口质量并观察两相流动情况。因此，可以在不同的流动模式下研究主加热器上 HTC 的特性。通道方向从 15 到 90°不等，质量流量从 110 到 288 kg/(m2s) 不等，质量分别从 0.003 到 0.036 不等。实验结果表明，本研究中质量流量和质量对 HTC 的影响非常微弱。然而，HTC 上的取向角效应在 45°~60° 内呈现一个过渡区域，而当取向角小于 45° 和大于 60° 时，它会缓慢变化。这种趋势可以用误差函数很好地表述出来。与不同的饱和沸腾HTC经验公式相比，发现Liu&Winterton相关性可以很好地预测90°取向通道中的实验HTC结果。基于这种相关性，结合误差函数，建立了一种考虑取向效应的新模型，与实验数据相比误差为±15%。