| AP1000is the third generation nuclear power technology. It was introduced from Westinghouse Electric Corporation of America. Steam generator (SG) is not only an important part of AP1000, but also a connection hub between the primary side and the secondary side. In the primary side, cooling water flows into SG after heated by the reactor core, and then transfers the heat to the second side through the U-tubes’wall, finally is sent back to reactor core by coolant pump. The progress of flow and heat transfer of fluid in the SG primary circuit is generally called the primary side flow and heat transfer. The selection of primary circuit pump, arrangement of U-tubes and heat transfer characteristics of secondary circuit are all related to the primary side flow and heat transfer characteristics. Currently, the traditional research methods are mainly based on experience formulas and experiments. This paper researched the primary side flow and heat transfer characteristics by CFD numerical simulation. The main paper work include flow and heat transfer characteristics numerical simulation study of steam generator parts which are consist of channel head and U-tubes and the whole steam generator.This paper established CFD analysis model of inlet plenum, outlet plenum and single U-tube by studying flow and heat transfer characteristics of component parts in steam generator. This paper not only remained tube-sheet, but also remained10025U-tubes whose height is150mm. The detailed characteristics of flow distribution, pressure drop and flux distribution in U-tubes were gained by numerical simulation of inlet and outlet plenum. Through compared with pressure drop experience formulas results, it could be found that traditional resistance model could not exactly describe resistant characteristics of complex plenum. This paper not only established single U-tube analysis model based on average length, but also gained fitting relation between pressure drop and velocity. The relation gave a basis for simplifying U-tube bundles.The number of U-tubes in the primary side is10025. Average length to diameter ratio reaches1500. The distributed radius of U-tubes is up to2m. If CFD model were based on realistic geometric structure, the number of mesh would reach10billion. This paper simplified U-tubes based on porous media and established CFD analysis model for the whole primary side. Resistance model, heat source model and U shape structure model parameters which were related for building porous media were detailed discussed and analyzed in this paper. This paper proposed two connection approaches between porous media and channel head:porous media was connected with channel head directly and porous media was connected with channel head through heat exchange tubes of150mm height. Through comparing and analyzing results of the two models, it could be found that the difference between two numerical models’ results and Westhouse’s data was not more than5%, but the flux distribution difference of porous media in two numerical models was more than20%. This paper built two porous media heat resource models:average heat source model and distributive heat source model that related to local temperature of the primary side. Based on two heat source models, comparing distributions of U-tube bundles temperature difference between inlet and outlet and cross-section temperature, it could be found that distributions based on distributive heat source model were more uniform and more conform to actual operation results. The studies of this paper indicated that CFD analysis model built by simplifying U-tube bundles into porous media which was connected with channel head through150mm high U-tube bundles brought less prediction deviation on the flow and heat transfer characteristics of the primary side. And the results could present a theoretical base for designing the primary circuit. |
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