Numerical Study On Flow And Heat Transfer Characteristics Of Low Pressure Heaters Hydrophobic Cooling Sections Of CAP1400 Nuclear Power Unit

As the basic resource for human survival and development,energy increasingly presents serious global problems,such as the increasing consumption of traditional fossil energy and increasing environmental pressure,etc.In order to meet the increasing energy needs of mankind,countries around the world have poured a lot of financial resources into the development and utilization of renewable energy,among which nuclear power as a clean energy has been the focus of most countries in the world.Similarly,China’s energy consumption structure based on coal caused by the environmental impact,energy demand and insufficient reserves of resources and other issues are increasingly acute,the development of nuclear energy for China’s sustainable development has an important strategic significance.According to the national medium and long term energy development situation and prospects analysis,by 2050,the total installed capacity should reach 240 GW.In the nuclear power system,the feed water heater is one of the important heat exchangers.As one of the important heat transfer equipment of nuclear power system,the analysis of its technical characteristics is of great value and guiding significance to improve the operation level of the water supply heat recovery system and the safety and economy of the unit.In order to enhance the heat transfer effect,many folding plates are usually arranged in the hydrophobic cooling section to organize the hydrophobic flow trajectory and increase the hydrophobic flow rate.Therefore,a numerical simulation method based on CAP1000 low pressure heater is used to study the heat transfer effect and flow characteristics of submerged and siphon two hydrophobic cooling sections,and the best scheme of two kinds of hydrophobic segments under the optimum comprehensive performance conditions is obtained by comparing and analyzing the numerical simulation results.The results show that,for the submerged hydrophobic section of low-pressure heater,the double bow folding plate can not only reduce the heat transfer effect under the condition of greatly reducing the resistance of the shell,but also effectively optimize the flow pattern of the working medium,so that the comprehensive performance of the bow folding plate is better than that of the single.Because the shell range of the siphon type is short,it is difficult to adjust the folding plate spacing and the selected folding plate,therefore,by changing the notch height of the folding plate to study its effect on the heat transfer effect and flow characteristics of the hydrophobic section.The comparison and analysis results show that with the increase of the notch height of the folding plate,the temperature of the notch position of the bow fold plate is basically,the pressure drop then decreases to a minimum and then increases.The vortex strength and influence range of the gap near the positions on both sides of the shell undergo the same change process.When the notch height is 1/3d,the best flow and heat transfer characteristics are shown by the fluid pressure drop,flow velocity,minimum impact force and relatively uniform flow state.