超临界水冷堆类三角形子通道传热不均匀性研究

基于类三角形堆芯子通道超临界水传热不均匀性试验,建立棒径为8 mm、栅距比为1.2~1.4的超临界水冷堆（SCWR）类三角形堆芯子通道物理模型,研究通道内超临界水传热不均匀性,分析超临界压力区子通道传热轴向与周向不均匀性。试验研究表明类三角形子通道轴向传热强度不均,沿轴向传热强度存在峰值区,大比热区传热强度大,而远离大比热区传热强度低;试验与数值模拟对比表明 (Spezlale, Sarkar and Gatski Model) 湍流模型可准确预测SCWR类三角形子通道超临界水传热特性;子通道周向传热严重不均,在垂直于主流方向横截面,流体和管壁之间的局部传热系数随着周向角的增大先升高后降低,其值在中心主流区处最大,在窄缝区位置最小,并且在不同的主流焓值区内周向传热不均程度不同;栅距比对子通道传热有影响,随着栅距比的增大,在整个主流焓值区内,平均壁温升高,换热系数降低,周向传热不均匀性显著减小。 

Investigation on Nonuniformity of Heat Transfer in Triangular Subchannels of Supercritical Water Cooled Reactor

A physical model was built to numerically investigate the nonuniform heat transfer characteristics of supercritical water within a triangle sub-channel. The corresponding fuel rod diameter was 8 mm and the pitch-to-diameter ratio was 1.4, respectively. Experimental result shows that the axial heat transfer is uneven and the axial heat transfer intensity has a peak value. The heat transfer coefficient is big when the supercritical water is in the pseudo-critical region and is small when the water is far away from the pseudo-critical region. The comparison between the experimental data and numerical result show that the SSG turbulence model can well predict the heat transfer characteristics of supercritical water in a triangle sub-channel of SCWR. The nonuniform heat transfer of supercritical water is seriously in the sub-channel. In the mainstream direction, the heat transfer from the inner wall to the fluid is enhanced in the great specific heat region and weakened in the high enthalpy region. The local heat transfer coefficient increases first and then decreases with the increasing of the circumferential angle, which reaches a peak in the central region and a trough near the narrow gap. The degree of circumferential heat transfer nonuniformity also differs in different enthalpy regions. Moreover, with the increasing of the pitch-to-diameter ratio, the average wall temperature rises and the heat transfer coefficient decreases, and the circumferential heat transfer nonuniformity reduces significantly.