| The Supercritical Water Cooled Reactor(SCWR) is one of the six Gereration-nuclear reacters, which is the only one cooled with water. In addition, the fuel rod sustains megawatt heat flow and strong neutronic thermo hydraulic in the special and complicated flow channel of SCWR. Due to the limited of experimental technology under high temperature and pressure conditions, the numerical simulation methods make it possible to analysis heat transfer characteristics of supercritical pressure water in the sub-cannel of reactor.With the range of pressure from 23 to 28 MPa, mass flux of 700 to 1300 kg/(m2·s), heat flux from 200 to 1000 k W/m2, the diameter of the heat tubes was 8 mm and the pitch-to-diameter ratio P/D from 1.2 to 1.4, numerical simulation have been performered to investigate the heat transfer of supercritical presusure water in the sub-channel and the secondary flows in the narrow gap of the region using computational fluid dynamics software CFX 14.0. By the analysis of simulation results, it confirms that the physical model and numerical method are reasonable. And the numerical simulation was compared with experimental data and correlations.The choices of turbulence models and the analysis of mesh sensitivity were investigated. It can accurately pridict heat transfer characteristics of supercritical water in sub-channle and the secondary flows in the narrow gap of the region by using SSG model.The heat transfer characteristics on supercritical water were investigated. The effects of mass flow, pressure, heat flux and P/D on heat transfer were discussed in detail. And the nonuniformity of heat transfer between narrow gap and the central region of sub-channel were investigated. The results show the heat transfer enhance as the mass flow rate increase. The drastic changes in thermophysical properities near the pseudo-critical points cause heat transfer enhancement. Heat transfer enhancement becomes weaken away from critical pressure. The difference of heat transfer cofficients between central region and narrow gap region decreases as the mass flow rate decrease. As the pitch-to-diameter ratio P/D increase, the wall temperature becomes more uniformity, and the difference of heat transfer cofficient between central region and narrow gap region decrease.The secondary flow characteristics in the narrow gap of the region were investigated. The results show the secondary flows appear in vertical direction of the mainstream velocity. Four symmetrical vortexs between central region and narrow gap region compose the secondary flow. The system parameters have a little influence on the structure of the secondary flow. But it has a vital effct on the intensity of the secondary flow. The increase of pressure and mass flow rate, and the decrease of heat flux can make the ratio of the largest secondary flow velocity and mainstream velocity increase.Comparative analysis of the results come from the experiment and the results of numerical calculation was carried out.According to the results, the wall temperature and heat transfer coefficient trends along with water enthalpy well, but the numerical value of the heat transfer is high than experimental data in whole enthalpy region. Futhermore, the numerical simulation were also compared with correlations. The reasearches show that the numerical simulation can pridict the heat transfer of supercritical pressure water in the regions away from pseudo-critical region. Own to the thermoplysical properities of water vary greatly, numerical simulation can not catch the character of heat transfer in the pseudo-critical region.The support of the national natural science foundation of China(NO.51406026) and the plan of innovative talents in universities of Henan Province(NO.2012HASTIT018) is gratefully acknowledged. KEY WORDS: Supercritical pressure water; Sub-channel; Heat transfer; Narrow gap of the... |
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