反应堆矩形强化流道内超临界水流动传热特性数值研究

Numerical Study on the Flow and Heat Transfer Characteristics of Supercritical Water in Rectangular Enhanced Flow Channels in Reactors

反应堆堆芯超临界水流动传热特性复杂,为优化其传热特性,针对反应堆堆芯矩形强化通道的超临界水传热特性进行数值研究,采用雷诺应力湍流模型,研究了25 MPa超临界压力下,单根燃料棒在无肋、带长条肋和等距短肋布置的三种矩形流道内的流动传热特征.研究结果表明:堆芯矩形通道内设置肋片可强化传热,不同肋片布置方式的传热强化效果显著不同;强化通道内角部超临界水温度比无肋流道内角部温度高,强化流道径向截面内不同位置温差小;无肋流道最窄处超临界水存在流动死区,且死区随轴向高度变化较小,带长条肋布置流道最窄处超临界水流动死区范围减小,在近肋片区域出现流动死区,等距短肋流道内无明显流动死区;三种流道中,带等距短肋布置的流道相对合理.

The flow and heat transfer characteristics of supercritical water in reactor core is complex,there is a big deficiency in the study of enhanced fluid channels in reactors.Numerical simulations were carried out in three kinds of rectangular channels around one fuel rod for study the flow and heat transfer characteristics of supercritical water flowing in ribbed channels.The turbulence model of Reynolds stress model was used in simulations.At the supercritical pressure of 25 MPa,the flow and heat transfer characteristics were studied and comparatively analyzed in the three different kinds of fin arrangements around the fuel rod,which were no fins,long strip fins and equal-distance-short fins.The results show that the rectangular channels with fins in the core can enhance the heat transfer of supercritical water.The effect of different fin arrangements on the heat transfer enhancement is notably different.The temperatures of supercritical water are higher in the corners of enhanced flow channel than in the channel without fins.The temperature difference is small at different positions in the same radial section in the enhanced flow channels.There exists a flow dead zone of supercritical water in the narrowest position in the channel without fins,and the change of flow dead zone is small with the increase of the axial height.The flow dead zone shrinks in the narrowest position in the channel with long strip fins arrangement,but near the region of the fin,there exists flow dead zone.There is no obvious flow dead zone in the channel with equal-distance-short fins.So the channel with equal-distance-short fins is a reasonable type of the channels of heat transfer enhancement.