| Steam generator is a critical heat exchange equipment in nuclear power plant.The thousands of tubes in the steam generator are relatively weak parts,once the tubes are broken,it may lead to the safety accident of radioactive fluid leakage,which causing serious environmental damage and economic loss.Flow-induced vibration is one of the main factors of the tube damage,the vibration amplitude is proportional to cross flow energy.Thermal hydraulic characteristics such as secondary side temperature and void fraction are closely related to cross flow energy.Therefore,in this paper,the flow and heat transfer characteristics,such as cross flow energy in the secondary side of the steam generator under different working conditions,support plate type and height of the central plate,were numerically simulated and studied,to reveal the rules between these influencing factors and the failure of tube,and to provide some reference for improving the thermal hydraulic design of the steam generator.According to the structure and operating parameters of the steam generator in first phase of Qinshan nuclear power plant,the geometric model of the secondary side including the whole bundle area,support plates and separators was established by Gambit.The resistances of the tube bundle,separators and support plates were simulated by the porous media model of Fluent,heat transfer from primary to secondary side was loaded to the model in the form of internal heat source,mass transfer rate were calculated by Lee model,the flow and heat as well as mass transfer characteristics of the secondary side were numerically calculated based on the k-ε turbulence model and the two-phase drift flow model.Under the design condition,the variations of temperature,void fraction,velocity and pressure of the secondary side fluid along the axial height were studied,at the same time,the cross flow velocity and cross flow energy of the secondary side fluid in straight and bend region were analyzed.Under the off-design condition,the influence of different inlet temperature and velocity of computational domain on the flow and heat transfer characteristics such as fluid void fraction,cross flow velocity and cross flow energy in secondary side were revealed.The influence of three support plate types and different central plate heights on flow and heat transfer properties such as cross flow velocity and cross flow energy in secondary side were analyzed.The results show that,under the design condition,the distribution of temperature,void fraction and velocity were obviously different between hot and cold side in secondary side,which affects the stable operation of the steam generator in some degree,cross flow energy was larger at 2.3 m of the straight region,cross flow energy was also larger around 80° and 100° of the circumference from the hot to cold side,and the failure rate of tube was larger.When the inlet temperature was increased,the void fraction and velocity were increased in secondary side,and the maximum of cross flow energy was decreased in the straight region,while the maximum of cross flow energy was increased in the bend region.When inlet velocity was increased,the temperature and void fraction were decreased in the secondary side,the maximum of cross flow energy was increased in the straight region,and the maximum of cross flow energy was decreased in bend region.The type of support plate had a great influence on cross flow energy in straight region,but it’s influence of cross flow energy in bend region was small.The cross flow energy in straight region with grid support plate was minimum.The higher central plate,the greater hot side flow velocity and the void fraction,the smaller cold side flow velocity and void fraction at entrance of the separators,the lower maximum of cross flow energy in straight region,and the greater maximum of cross flow energy in bend region.Compared with the non-central plate,the maximum cross flow energy in the straight region was reduced by 76% and the maximum cross flow energy in the bend region was increased by 8.9% after installing the 5.65 m high central plate. |
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