Research Of New Passive Residual Heat Removal System Projects Of Marine Nuclear Power

Some new passive residual heat removal system projects which are fit for marine nuclear power plants, such as the double-pipe passive residual heat removal system,the U-tube passive residual heat removal system,the separate heat pipe passive residual heat removal and density-lock passive residual heat removal system which is located at the primary loop. The heat exchangers of these new systems are located between the submarine pressure hull and the non-pressure hull, the ocean is their final heat-well, so they don't need much inner space of submarine, and the natural circulation capacity of these systems can be enhanced by increasing the height difference between the heat section and heat exchanger.The heat is transferred by the condensation of steam in heat exchanger of the passive residual heat removal systems and the single-phase natural convection or sub-cooled boiling in the heat exchanger shell. The heat transfer coefficient of seawater-side is less than the heat transfer coefficient of inside of pipe. For enhancing the heat transfer coefficient of sea-water side and the overall heat transfer coefficient of heat exchanger and making the exchanger smaller, the tubes which can enhance heat transfer are used in the heat exchanger.By the experimental investigation and calculation, the heat transfer characteristic of four kind of tubes(integrative pin-fin pipe,porous pipe,low-rib pipe and smooth pipe) was compared and analyzed. The results show that the heat flux and the boiling heat transfer coefficient of integrative pin-fin pipe are about double of the smooth pipe's when the superheat degree changes from the 7℃to 13℃. And the natural convection heat transfer coefficient of integrative pin-fin pipe increases by 40 percent than the smooth pipe, when the temperature difference changers from 30℃to 70℃. Based on this, the overall heat transfer coefficient and overall heat transfer area of residual heat exchanger were calculated. The length and amount of integrative pin-fin pipe were confirmed. The form of pipe collocation was also confirmed. Finally the configuration of the residual heat exchanger was optimized.