冷热圆管在封闭方腔内不同垂直位置的自然对流数值研究

A numerical study of natural convection with hot and cold cylinders at different horizontal positions vertically aligned in square enclosure

利用有限体积法对冷热圆管在封闭方腔内不同垂直位置的自然对流现象进行了数值研究。讨论了瑞利数Ra和冷热圆管间距δ对方腔内自然对流流动与换热的影响，其中瑞利数的变化范围为103～106，圆管间距变化范围为0.3～0.6。为了揭示冷热圆管间的相互作用和圆管与方腔间的相互作用对自然对流换热与流动的影响规律，比较分析了热圆管在上、冷圆管在下和热圆管在下、冷圆管在上两种情形下冷热圆管、方腔的自然对流换热能力的差异。研究表明：瑞利数的改变，对方腔内温度场分布和涡流结构有显著影响；热圆管在下、冷圆管在上这种情形更有利于自然对流换热的进行；增加圆管间距δ，热圆管和方腔的换热能力增强，但冷圆管的换热能力却有所减弱。研究结果为核电站安全壳非能动余热排出系统的性能研究提供了理论依据。

A numerical simulation of natural convection with a pair of hot and cold cylinders at different horizontal positions vertically aligned in square enclosure was obtained using finite volume method. The main affecting factors natural convective flow and heat transfer,including the Rayleigh number Ra and hot-cold cylinders spacingδwere analyzed. The Rayleigh number ranged from 103 to 106 and the hot-cold cylinders spacingδvaried from 0.3 to 0.6. In order to investigate the interaction between the two cylinders and the interaction between the inner cylinders and the cold enclosure,two different cases were considered,including the case of the hot cylinder upper section and the cold cylinder lower section and the case of the hot cylinder lower section and the cold cylinder upper section. The results showed that the intensity of natural convection had a significant impact on distribution of temperature and vortex structure in the enclosure. The situation of the hot cylinder lower section and the cold cylinder upper section was more favorable to natural convection. Heat capacity of hot cylinder and square enclosure increased and that of cold cylinder decreased when cylinder spacingδincreased. The results provided a theoretical basis for the performance of nuclear power plant containment passive residual heat removal system.