结构参数对波纹管内液氮流动与能量损失的影响
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摘要
高温超导电缆通常浸泡在采用真空多层绝热保护的双层波纹管内程管的液氮中。液氮在超导电缆内流动的压力损失和冷却效果是其运行系统设计的重要参数。对不同直径的波纹管进行了不同流量下的CFD仿真计算,结果表明流量越大、直径越小,压降越大;波高直径比与波高波距比不变时,波纹管的达西流动阻力系数与波纹管的直径基本无关;波纹管直径对超导电缆的沿程温升几乎没有影响;增大波纹管的直径能够大幅降低超导电缆的沿程能量损耗。该文结果为超导电缆设计过程中波纹管的选取提供了理论依据。
High temperature superconducting cable( HTC) is generally immersed in LN2 coolant flow in pipe-in-pipe casing bellows with high vacuum and multilayer insulation protection. Pressure drop and temperature rise of the LN2 flow in the bellows with high temperature superconducting cable installed are most important parameters for designing the cooling loop system.Simulations by Computational Fluid Dynamics( CFD) were performed on such bellows with different structure geometries. The result shows that the pressure drop rises with the increasing flowrate,while the friction factor goes down. The friction factor is nearly independent on the diameter when the ratio of wave height either over diameter or wave length of the bellows keeps constant. The diameter has little effect on the temperature rise along the distance. To reduce the energy loss,the diameter of the bellows is suggested to be enlarged. The present results can have significance for the optimal design of the circulated cooling system for high temperature superconducting cable.
High temperature superconducting cable( HTC) is generally immersed in LN2 coolant flow in pipe-in-pipe casing bellows with high vacuum and multilayer insulation protection. Pressure drop and temperature rise of the LN2 flow in the bellows with high temperature superconducting cable installed are most important parameters for designing the cooling loop system.Simulations by Computational Fluid Dynamics( CFD) were performed on such bellows with different structure geometries. The result shows that the pressure drop rises with the increasing flowrate,while the friction factor goes down. The friction factor is nearly independent on the diameter when the ratio of wave height either over diameter or wave length of the bellows keeps constant. The diameter has little effect on the temperature rise along the distance. To reduce the energy loss,the diameter of the bellows is suggested to be enlarged. The present results can have significance for the optimal design of the circulated cooling system for high temperature superconducting cable.
引文
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[2]Fuchino S,Tamada N,Ishii I,et al,Hydraulic characteristics in superconducting power transmission cables[J].Physica C:Superconductivity,2001,354(1-4):125-128.
[3]Deukyong K,Hankil Y,Yongju H,et al,Performance tests of high temperature superconducting power cable cooling system[J].IEEE Transactions on Applied Superconductivity,2004,14:1746-1749.
[4]Lee C H,Kim C D,Kim K S,et al.Performance of heat transfer and pressure drop in superconducting cable former[J].Cryogenics,2003,43(10-11):583-588.
[5]Li Z M,Li Y X,Liu W,et al.Comparison of liquid nitrogen flow resistance in corrugated pipe with smooth pipe for HTS cable[J].IEEE Transactions on Applied Superconductivity,2015,25(3):5401304.
[6]孙凤玉,张鹏,波纹管内流动特性的实验研究[J].工程热物理学报,2008,29(10):1725-1727.
[7]李云贤,李振明,方进,等,超导电缆波纹管内过冷液氮流动阻力特性研究[J],低温工程,2013,194(4):29-32.
[8]Sasaki A,Hamabe M,Famakinwa T,et al.Cryogenic fluid dynamics for DC superconducting[J].IEEE Transactions on Applied Superconductivity,2007,17(2):1748-1751.
[9]Kathait P S,Patil A K,Thermo-hydraulic performance of a heat exchanger tube with discrete corrugations[J].Applied Thermal Engineering,2014,66(1):162-170.
[10]Bilen K,Cetin M,Gul H,et al.The investigation of groove geometry effect on heat transfer for internally grooved tubes[J].Applied Thermal Engineering,2009,29(4):753-761.
[11]孙凤玉,张鹏,王如竹,等.高温超导电缆用波纹管内液氮流动特性的数值研究[J].低温与超导,2007,35(5):376-380.
[12]李云贤,李振明,申政,等,波纹管对超导电缆出口液氮温度的影响[J],低温技术,2013,41(1):4-7.
[13]Wilcox D C.Turbulence modeling for CFD[M].2nd edition.La Canada:DCW Industries,Inc.,California,USA,1998.
[14]Barenblatt G I,Chorin A J,Prostokishin V M.Scaling laws for fully developed turbulent flow in pipes:discussion of experimental data[C].Proceedings of the National Academy of Sciences of the USA,1997,94(3):773-776.
[15]Zagarola M,Perry A,Smits A,Log laws or power laws:the scaling in the overlap region[J].Physics of Fluids,1997,9(7):2094-2100.
[16]Maxim P,Bas V D L,Arris T,et al.Friction factor estimation for turbulent flows in corrugated pipes with rough walls[C].International Conference on Ocean,Offshore&Arctic Engineering,2009,79854:1-10.
[17]Schlichting H.Boundary-layer theory[M].7th ed.Springer,1979:639-641.