压水堆子通道欠热沸腾数值验证及交混翼研究

为改善压水堆交混翼格架在欠热沸腾工况下的热工水力特性，以子通道为研究对象验证了所使用的欠热沸腾数值模型在不同工况下的有效性。基于已验证的数值模型，对含不同偏折角交混翼格架的子通道模型在不同工况下进行了两相流数值模拟，研究交混翼及其偏折角对子通道中两相流动、传热及气泡分布的影响。结果表明：交混翼在增大压降的同时明显强化了冷却剂的交混、降低了近壁面气泡份额、提高了换热效率，且在一定范围内偏折角越大影响越明显。相对较高的气泡份额将导致更大的压力损失、减弱冷却剂的交混、降低传热效率。当交混翼偏折角达25°时，继续增大其偏折角对降低近壁面气泡份额和提高传热效率的作用不再明显，反而造成压降的快速增大，因此建议其偏折角在25°左右。

Numerical Validation of Subcooled Boiling in Subchannel of PWR and Research on Mixing Vane

In order to improve the thermal-hydraulic performance of mixing vane spacer in pressurized water reactor (PWR) under the condition of the subcooled boiling, the effectiveness of the subcooled boiling numerical model currently used was validated. Based on the validated numerical model, a series of two-phase simulations of subchannels with mixing vane spacer grids for different vane slope angles were performed under different working conditions. The influences of mixing vane and its slope angle on subcooled boiling flow, heat transfer and void fraction distribution were investigated. The results show that the mixing vane spacer grid not only causes more pressure loss, but also enhances heat transfer and decreases the void fraction in the near-wall zones. The influence is more obvious with the increase of the slope angle within a certain range. Relatively higher void fraction in rod bundle can lead to more pressure drop, lower mixing performance and lower heat transfer efficiency. While the slope angle of mixing vane reaches to 25°, continuing to increase the angle can not decrease void fraction in near wall zones and increase heat transfer efficiency further, but cause more pressure loss. Therefore, the suggested slope angle of mixing vane is about 25°.