Under heaving movement conditions, the single phase flow instability in U-tubes is affected by the additional force, which will influence the marine reactor operation. In the present work, one-dimensional thermal-hydraulic model in U-tubes under heaving movement conditions is established, and the critical pressure drop (CPD) and critical mass flow rate (CMFR) which relate to the occurrence of reverse flow in U-tubes are proposed and analyzed. The effects of the heaving period and heaving acceleration amplitude on the flow instability in U-tubes with the different length are discussed. It is shown that (1) the CPD and CMFR are obviously affected by the heaving movement, which means that the reverse flow characteristic in U-tubes will be changed; (2) the fluctuation periods of the CPD and CMFR are the same as the heaving period, but the fluctuation magnitude of them is little affected by the heaving period; (3) the relative changes of CPD and CMFR are the linear function of heaving acceleration amplitude; and (4) the U-tube length has little influence on the relative changes of CPD and CMFR compared with the heaving acceleration amplitude, which means that the heaving movement has little influence on the space distribution of reverse flow in the U-tubes of marine steam generator. 1. Introduction Natural circulation operation is significant for the marine nuclear power plant in terms of passive safety, efficiency, and noise decrease. The operation performance of steam generator (SG) can deeply influence the nuclear power plant safety. Under natural circulation conditions, it is shown that the single phase flow in the parallel U-tubes of SG may be unstable, and reverse flow occurs within some U-tubes [1, 2]. Because of the occurrence of reverse flow, the effective heat transfer area of SG primary side is reduced, and the flow resistance coefficient under the natural circulation is obviously larger than that under the forced circulation. So the actual nature circulation capability of primary loop is lower than the needed value due to the reverse flow in U-tubes, which has negative influence on the operation of the marine nuclear power plant [3]. The flow instability in U-tubes is considered to be a typical Ledinegg-type single phase flow instability [4]. Yang et al. [5] developed a lumped-distribution model to calculate the reverse flow in the inverted U-tubes. Walter and Linzer [6] discussed the influence of the operating pressure on the reverse flow in natural circulation system. They thought that the design procedure for natural circulation systems with
References
[1]
Y. Kukita, H. Nakamura, K. Tasaka, and C. Chauliac, “Nonuniform steam generator U-Tube flow distribution during natural circulation tests in ROSA-IV large scale test facility,” Nuclear Science and Engineering, vol. 99, no. 4, pp. 289–298, 1988.
[2]
F. Wang, W.-B. Zhuo, Z.-J. Xiao, and B.-D. Chen, “Phenomena and analysis of reversal flow in vertically inverted U-tube steam generator,” Atomic Energy Science and Technology, vol. 41, no. 1, pp. 65–68, 2007 (Chinese).
[3]
W. Z. Chen, L. Yu, and J. L. Hao, Thermal Hydraulics of Nuclear Power Plants, Chinese Atomic Energy Press, Bejing, China, 2013, (Chinese).
[4]
I. Babelli and M. Ishii, “Flow excursion instability in downward flow systems: part I. Single-phase instability,” Nuclear Engineering and Design, vol. 206, no. 1, pp. 91–96, 2001.
[5]
R.-C. Yang, J.-G. Liu, Y.-P. Huang, R.-L. Liu, and S.-W. Qin, “Calculation of reverse flow in inverted U-tubes of steam generator during natural circulation,” Hedongli Gongcheng/Nuclear Power Engineering, vol. 31, no. 1, pp. 57–60, 2010 (Chinese).
[6]
H. Walter and W. Linzer, “The influence of the operating pressure on the stability of natural circulation systems,” Applied Thermal Engineering, vol. 26, no. 8-9, pp. 892–897, 2006.
[7]
J. Sanders, “Stability of single-phase natural circulation with inverted U-tube steam generators,” Journal of Heat Transfer, vol. 110, no. 3, pp. 735–742, 1988.
[8]
J. L. Hao, W. Z. Chen, D. Zhang, and S. M. Wang, “Scaling modeling analysis of flow instability in U-tubes of steam generator under natural circulation,” Annals of Nuclear Energy, vol. 64, pp. 169–175, 2014.
[9]
J. L. Hao, W. Z. Chen, and D. Zhang, “Effect of U-tube length on reverse flow in UTSG primary side under natural circulation,” Annals of Nuclear Energy, vol. 56, pp. 66–70, 2013.
[10]
J. L. Hao, W. Z. Chen, and S. M. Wang, “Flow instability analysis of U-tubes in SG based on CFD method,” Progress in Nuclear Energy, vol. 70, pp. 134–139, 2014.
[11]
R. Pendyala, S. Jayanti, and A. R. Balakrishnan, “Flow and pressure drop fluctuations in a vertical tube subject to low frequency oscillations,” Nuclear Engineering and Design, vol. 238, no. 1, pp. 178–187, 2008.
[12]
Z. Y. Chen, J. L. Hao, and W. Z. Chen, “The development of fast simulation program for marine reactor parameters,” Annals of Nuclear Energy, vol. 40, no. 1, pp. 45–52, 2012.
[13]
S.-Y. Jiang, X.-T. Yang, H.-J. Gong et al., “Mechanism of natural circulation taking account into heaving movement,” Atomic Energy Science and Technology, vol. 43, no. 1, pp. 92–96, 2009 (Chinese).
[14]
J. L. Hao, W. Z. Chen, and S. M. Wang, “Investigation on factors affecting reverse flow in inverted U-tubes of steam generator under natural circulation,” Atomic Energy Science and Technology, vol. 47, no. 1, pp. 65–69, 2013 (Chinese).
