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

doi:10.16085/j.issn.1000-6613.2015.06.015

Abstract

Abstract: 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 spacing δ were analyzed. The Rayleigh number ranged from 10³ to 10⁶ and the hot-cold cylinders spacing δ varied 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 spacing δ increased. The results provided a theoretical basis for the performance of nuclear power plant containment passive residual heat removal system.

Key words: natural convection, square enclosure, hot and cold cylinders, vertical location, numerical simulation

摘要： 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。

关键词: 自然对流, 方腔, 冷热圆管, 垂直位置, 数值模拟

CLC Number:

TK124

SHEN Zhongjiang, YU Bin. A numerical study of natural convection with hot and cold cylinders at different horizontal positions vertically aligned in square enclosure[J]. Chemical Industry and Engineering Progree, 2015, 34(06): 1595-1601.

沈中将, 虞斌. 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[J]. 化工进展, 2015, 34(06): 1595-1601.

References

[1] Lee J R, Ha M Y. Numerical simulation of natural convection in a horizontal enclosure with a heat-generating conducting body[J]. International Journal of Heat and Mass Transfer, 2006, 49(15):2684-2702.
[2] Misra D, Sarkar A. Finite element analysis of conjugate natural convection in a square enclosure with a conducting vertical wall[J]. Computer Methods in Applied Mechanics and Engineering, 1997, 141(3):205-219.
[3] Wright J L, Jin H, Hollands K G T, et al. Flow visualization of natural convection in a tall, air-filled vertical cavity[J]. International Journal of Heat and Mass Transfer, 2006, 49(5):889-904.
[4] Tokura I, Saito H, Kishinami K, et al. An experimental study of free convection heat transfer from a horizontal cylinder in a vertical array set in free space between parallel walls[J]. Journal of Heat Transfer, 1983, 105(1):102-107.
[5] Lieberman J, Gebhart B. Interactions in natural convection from an array of heated elements, experimental[J]. International Journal of Heat and Mass Transfer, 1969, 12(11):1385-1396.
[6] Marsters G F. Arrays of heated horizontal cylinders in natural convection[J]. International Journal of Heat and Mass Transfer, 1972, 15(5):921-933.
[7] Sparrow E M, Boessneck D S. Effect of transverse misalignment on natural convection from a pair of parallel, vertically stacked, horizontal cylinders[J]. Journal of Heat Transfer, 1983, 105(2):241-247.
[8] Sadeghipour M S, Asheghi M. Free convection heat transfer from arrays of vertically separated horizontal cylinders at low Rayleigh numbers[J]. International Journal of Heat and Mass Transfer, 1994, 37(1):103-109.
[9] Reymond O, Murray D B, O'Donovan T S. Natural convection heat transfer from two horizontal cylinders[J]. Experimental Thermal and Fluid Science, 2008, 32(8):1702-1709.
[10] Persoons T, O'Gorman I M, Donoghue D B, et al. Natural convection heat transfer and fluid dynamics for a pair of vertically aligned isothermal horizontal cylinders[J]. International Journal of Heat and Mass Transfer, 2011, 54(25):5163-5172.
[11] Park Y G, Yoon H S, Ha M Y. Natural convection in square enclosure with hot and cold cylinders at different vertical locations[J]. International Journal of Heat and Mass Transfer, 2012, 55(25):7911-7925.
[12] Park Y G, Ha M Y, Yoon H S. Study on natural convection in a cold square enclosure with a pair of hot horizontal cylinders positioned at different vertical locations[J]. International Journal of Heat and Mass Transfer, 2013, 65:696-712.
[13] Park Y G, Ha M Y, Choi C, et al. Natural convection in a square enclosure with two inner circular cylinders positioned at different vertical locations[J]. International Journal of Heat and Mass Transfer, 2014, 77:501-518.
[14] Kim B S, Lee D S, Ha M Y, et al. A numerical study of natural convection in a square enclosure with a circular cylinder at different vertical locations[J]. International Journal of Heat and Mass Transfer, 2008, 51(7):1888-1906.
[15] Warrington Jr R O, Powe R E. The transfer of heat by natural convection between bodies and their enclosures[J]. International Journal of Heat and Mass Transfer, 1985, 28(2):319-330.