液氮通过受热U型管传热特性的数值模拟

上海交通大学学报（自然版） ›› 2013, Vol. 47 ›› Issue (08): 1292-1299.

液氮通过受热U型管传热特性的数值模拟

邓冬，汪荣顺

（上海交通大学制冷与低温工程研究所，上海 200240）

收稿日期:2012-08-15 出版日期:2013-08-29 发布日期:2013-08-29
基金资助:
国家自然科学青年基金资助项目(50806042)

Numerical Simulation of Heat Transfer of Liquid Nitrogen Through Heated U-Tubes

DENG Dong，WANG Rongshun

(School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China)

Received:2012-08-15 Online:2013-08-29 Published:2013-08-29

摘要/Abstract

摘要：

对单相液氮通过受热竖直U型管的传热特性进行了三维数值模拟.采用结构化网格，并对近壁面处网格加密,对网格无关性和模型有效性进行了验证.将入口速度、出口压力和均匀壁面热流密度作为边界条件及利用标准的k-ε紊流模型和CFX 4.4求解器求解.模拟结果发现：在U型弯头上游直管中，流体温度形成中心低四周高的分布形式；在U型弯头内，流体被二次流重构，温度较低的流体流向管外侧，温度高的流体则流向管内侧；在U型弯头下游直管中，中心低四周高的温度分布逐渐得到恢复.通过分析，曲率比对下游努赛尔数影响明显，其影响区域可用下游努赛尔数达到极小值来衡量；存在一曲率比，使下、上游努赛尔数百分比达到极小值.最后，将模拟得到的平均努赛尔数与不同的经验关联式作了比较.

关键词: 受热U型弯管, 二次流, 曲率比, 液氮

Abstract:

A three-dimensional numerical simulation of the heat transfer characteristics of single-phase liquid nitrogen flowing through heated vertical U-tube was conducted. The structured grid was used and the mesh near the wall was refined. Besides, the grid independence and model availability was verified. The velocity inlet, pressure export and uniform wall heat flux were used as boundary conditions. In addition, the standard k-ε turbulence model was adopted and solved by CFX 4.4. It is found that the fluid temperature is lower in the center and higher near the wall in the U-bend upstream pipe, while the fluid temperature is reconstructed by the secondary flow in the U bend: the cold core is flowing to the concave surface, and the high temperature fluid is close to the convex surface; and in the downstream of the pipe, the temperature distribution is restored. The impact of curvature ratio on the downstream Nu number is significant and the affected area can be measured by the minimum Nu value. There is a curvature ratio which makes the percentage of the downstream to the upstream Nu to be the minimum. Finally, the comparison of simulation results and the correlation was conducted.

Key words: heated U tube, secondary flow, curvature ratio, liquid nitrogen

中图分类号:

TB 75

邓冬，汪荣顺. 液氮通过受热U型管传热特性的数值模拟[J]. 上海交通大学学报（自然版）, 2013, 47(08): 1292-1299.

DENG Dong，WANG Rongshun. Numerical Simulation of Heat Transfer of Liquid Nitrogen Through Heated U-Tubes[J]. Journal of Shanghai Jiaotong University, 2013, 47(08): 1292-1299.

参考文献

［1］Azzola J, Humphrey J A C, lacovides H, et al. Developing turbulent flow in a Ubend of circular crosssection measurement and computation［J］. Journal of Fluids Engineering, 1986, 108(6): 7.

［2］Johnson R W, Launder B R. Local Nusselt number and temperature field in turbulent flow through a heated squaresectioned Ubend［J］. International Journal of Heat and Fluid Flow, 1985, 6(3): 171180.

［3］Hrnjak P S, Hong S H. Effect of return bend and entrance on heat transfer in thermally developing laminar flow in round pipes of some heat transfer fluids with high prandtl numbers［J］. Journal of Heat Transfer, 2010, 132(6): 12.

［4］Sharma M, Ravi P, Ghosh S, et al. Hydrodynamics of lube oilwater flow through 180° return bends［J］. Chemical Engineering Science, 2011, 66(20): 44684476.

［5］Meng M., Peng X F. Influence of Ubend heterogeneous effects on bubble dynamics and local flow boiling heat transfer in hairpin tubes［J］. International Journal of Thermal Sciences, 2011,50(10):20162026.

［6］Meng M, Peng X F, Ye P, et al. Bubble dynamical behavior and thermal nonequilibrium during flow boiling in Uturn bends of hairpin tubes［J］. Chemical Engineering and Processing: Process Intensification, 2009, 48(6): 11771186.

［7］Timité B, Castelain C, Peerhossaini H. Pulsatile viscous flow in a curved pipe: Effects of pulsation on the development of secondary flow［J］. International Journal of Heat and Fluid Flow, 2010, 31(5): 879896.

［8］Lee Xiangdong, Wei Wei, Wang Rongshun, et al. Experimental investigation of boiling twophase flow instability of nitrogen in a vertical tube［J］. Journal of Shanghai Jiaotong Univercity (Sci), 2009, 14(1): 5.

［9］Guo J, Xu M, Cheng L. Second law analysis of curved rectangular channels［J］. International Journal of Thermal Sciences, 2011, 50(5): 760768.

［10］Guo J, Xu M, Cheng L. Numerical investigations of curved square channel from the viewpoint of field synergy principle［J］. International Journal of Heat and Mass Transfer, 2011, 54(1718): 41484151.

［11］Habchi C, Lemenand T, Della Valle D, et al. Entropy production and field synergy principle in turbulent vortical flows［J］. International Journal of Thermal Sciences, 2011, 50(12): 23652376.

［12］Tatsumoto H, Shirai Y, Hata K, et al. Numerical analysis of forced convection heat transfer of subcooled liquid nitrogen［J］. IEEE Transactions on Applied Superconductivity, 2008, 18(2): 14831486.

［13］Tatsumoto H, Shirai Y, Hata K., et al. Forced convection heat transfer of subcooled liquid nitrogen in a vertical tube［J］. Journal of Physics: Conference Series, 2010, 234(3): 032057.

［14］Hong S H. Heat transfer in thermally developing flow of fluids with high prandtl numbers preceding and following Ubend［D］. USA: University of Illinois, 1999.

［15］Clark J A. Cryogenic heat transfer［J］. Advances in Heat Transfer, 1969(5):325517.

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